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Forced convection heat transfer from a cylinder in supercritical carbon dioxide Green, John Richard 1970

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FORCED CONVECTION HEAT TRANSFER FROM A CYLINDER SUPERCRITICAL CARBON DIOXIDE  BY JOHN RICHARD GREEN B . A . S c , University of B r i t i s h Columbia, 1966  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE in the Department of Mechanical Engineering  We accept this thesis as conforming to the required standard  THE UNIVERSITY OF BRITISH COLUMBIA February,  1970  In p r e s e n t i n g  t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the  r e q u i r e m e n t s f o r an advanced degree a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a , I agree t h a t t h e L i b r a r y s h a l l make i t freely  a v a i l a b l e f o r r e f e r e n c e and s t u d y .  that permission f o r extensive  I f u r t h e r agree  copying of t h i s t h e s i s f o r  s c h o l a r l y purposes may be g r a n t e d by t h e Head o f my D e p a r t ment o r by h i s r e p r e s e n t a t i v e s .  I t i s understood  that  copying o r p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l s h a l l n o t be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n .  JOHN RICHARD GREEN  Department o f M e c h a n i c a l E n g i n e e r i n g The U n i v e r s i t y o f B r i t i s h Columbia Vancouver 8, Canada Date  jQ-jOr", I  )°)lO  gain  ABSTRACT  Heat transfer rates have been measured for forced flow of s u p e r c r i t i c a l carbon dioxide normal to a horizontal heated c y l i n d e r .  The 0.006 inch diameter cylinder was held  at various constant temperatures by a feed-back bridge circuit.  Free convection results are also included. The effects of bulk' f l u i d temperature, bulk f l u i d  pressure, and surface temperature were studied for a range of bulk f l u i d temperature and pressure of from 0.8 to  1.4  times the c r i t i c a l temperature and pressure f o r . s e v e r a l free stream v e l o c i t i e s  from zero to three feet per second.  The temperature difference between the heated cylinder and the bulk f l u i d was varied from 1 deg F to 320 deg F . Flow f i e l d s of a l l data runs were observed.  Still  photographs and high speed movies have been taken at operating conditions of  interest.  In a s u p e r c r i t i c a l f l u i d the heat transfer rate increases smoothly and monotonically with increasing temperature difference, pressure.  increasing v e l o c i t y , and increasing  In f l u i d with the bulk temperature below the  p s e u d o - c r i t i c a l temperature the..heat transfer  coefficient  shows large peaks when the cylinder temperature i s near the pseudocritical  temperature.  Peaks are largest when  the bulk f l u i d pressure i s near the c r i t i c a l pressure. heat transfer c o e f f i c i e n t  The  decreases with increasing tempera-  ture difference when the bulk f l u i d temperature i s above the p s e u d o - c r i t i c a l temperature.  The heat transfer rate  noteably increases with increasing pressure only when vaporl i k e f l u i d i s i n contact with the heated c y l i n d e r . S u p e r c r i t i c a l forced flow has been compared to forced flow b o i l i n g .  The s u p e r c r i t i c a l case does not exhibit the  c h a r a c t e r i s t i c strong maxima in heat transfer rate shown in forced flow nucleate b o i l i n g . temperature differences  Heat transfer rates at larger  are very similar in forced flow film  b o i l i n g and s u p e r c r i t i c a l forced flow heat transfer. With t h i s h o r i z o n t a l , constant temperature c y l i n d e r , no "bubble-like" or "boiling-like" mechanisms of heat transfer were observed in s u p e r c r i t i c a l free or forced convection. The flow f i e l d and heat transfer rate in free convection were found to be very unstable and sensitive to small temperature disturbances in the bulk f l u i d .  TABLE OF CONTENTS Chapter 1  Page INTRODUCTION  1  1.1  Preliminary Remarks  1  1.2  Review of C r i t i c a l Region Terminology . . .  2  1.3  C r i t i c a l Region Heat Transfer General  2  5  1.4  Free Convection Studies  10  1.5  Forced Convection Studies  23  1.6  Scope of Present Investigation  26  EXPERIMENTAL APPARATUS 2.1 General Concept of the Experimental Apparatus  28  2.2  Details of Apparatus Components  31  2.2.1  Main test section  31  2.2.2  Flow loop tubing and valves  2.2.3  Flow conditioning and t r a n s i t i o n section  34  2.2.4  C i r c u l a t i n g pump  36  2.2.5  Heat exchangers  37  2.2.6  Transducer glands  40  2.2.7  Velocity measurement . . . . . . . .  40  2.2.8  Temperature measurement  42  2.2.9  Pressure measurement  43  2.2.10 Hot wire anemometer power supply  28  . . . .  33  44  V  Chapter  Page 2.2.11  Probes and heated cylinders  2.2.12  Photographic equipment and  . . .  Schlieren system 3  48  EXPERIMENTAL PROCEDURE . . . 3.1 3.2 3.3  50  I n i t i a l Preparation and C a l i b r a t i o n of the Apparatus Procedure i n Free Convection Measurements  .  5  6  50 55  Procedure in Forced Convection Measurements  4  46  59  EXPERIMENTAL RESULTS  62  4.1  Effect of Free-stream Velocity  62  4.2  Effect of Bulk Temperature  69  4.3  Effect of Bulk Pressure  72  4.4  Interpretation of Photographs  74  DISCUSSION OF RESULTS  . .  77  5.1  Free Convection Results  77  5.2  Forced Convection Results  81  CONCLUSIONS  87  6.1  General .  87  6.2  Free Convection Heat Transfer  87  6.3  Forced Convection Heat Transfer  88  6.3.1  Forced convection - general  6.3.2  Effects of v e l o c i t y  6.3.3  Effects of bulk temperature  6.3.4 6.3.5  Effects of bulk pressure Heat Transfer Mechanisms  . . .  88 89  . . .  89 90 90  vi Chapter  Page  REFERENCES  135  APPENDIX APPENDIX  I - Properties of n e a r - c r i t i c a l carbon dioxide II - L i s t i n g and summary of taken  140  Photographs  APPENDIX III - Calculations and error analysis .•. . .  145 149  LIST OF FIGURES Figure  Page  1  Summary of N e a r - C r i t i c a l Region Terminology . .  92  2  Typical Property Variations in N e a r - C r i t i c a l Carbon Dioxide  93  Property Variations which would occur in S u p e r c r i t i c a l CO2 for the Free Convection Temperature D i s t r i b u t i o n Developed in A i r . . .  94  4  Bubble-Like Heat Transfer Mechanism Previously Observed by Knapp  95  5  Summary of Previous Work with Heated Cylinders in S u p e r c r i t i c a l Fluids  96  3  6  Schematic of N e a r - C r i t i c a l Carbon Dioxide Forced Flow Loop  97  7  Cutaway View of Test Section Arrangement  8  Section View.of-Test Section Block'  9  General Layout of Experimental Equipment  . . .  98 99  . . .  10  Thermocouple Measuring C i r c u i t  11  Reproducibility of Data  102  12  Dimensions and Surface Condition of Heated Probe Flow F i e l d Around Probe and Supports i n  103  Free Convection  104  14  Arrangement of Schlieren System  105  15  Effect of Velocity on Heat Transfer Rate  16  in C 0 at 80 deg F and 1100 psia . . . . . . . Effect of Velocity on Heat Transfer Coefficient in CO„ at 8 0 deg F and 1100 psia . . .  13  2  . . . . . . . .  100 101  106 107  viii Figure 17  Page Effect of Velocity on Heat Transfer Rate in C 0 at 87 deg F and 1100 psia  108  Effect of Velocity on Heat Transfer Coefficient i n CCu at 87 deg F and 1100 psia : . . .  109  Effect of Velocity on Heat Transfer Rate in C 0 at 91 deg F and 1100 psia  110  Effect of Velocity on Heat Transfer Coefficient in CO„ at 91 deg F and 1100 psia  Ill  Effect of Velocity on Heat Transfer Rate in C 0 at 80 deg F and 1300 psia  112  Effect of Velocity on Heat Transfer Coefficient in CO„ at 80 deg F and 1300 psia  113  Effect of Velocity on Heat Transfer Rate in C 0 at 86 deg F and 1300 psia . . . . . . . .  114  2  18  19  2  20  21  2  22  23  2  24  25  Effect of Velocity on Heat Transfer Coefficient i n CC) at 86 deg F and 1300 psia  115  Effect of Velocity on Heat Transfer Rate in C 0 at 80 deg F and 1500 psia . .  116  Effect of Velocity on Heat Transfer Coefficient i n CO- at 80 deg F and 1500 psia .  117  Effect of Bulk Temperature on Heat Transfer Rate at 1100 psia (Re*=300)  118  28  Effect of Bulk Temperature on Heat Transfer Coefficient at 1000 psia (Re* = 300)  119  29  Effect of Bulk Temperature on Heat Transfer Rate at 1100 psia (Re*=600)  120  30  Effect of Bulk Temperature on Heat Transfer Coefficient at 1100 psia (Re*=600)  121  31  Effect of Bulk Temperature on Heat Transfer Rate at 1300 psia (Re* = 600)  122  2  26  27  ix Figure  Page  32  Effect of Bulk Temperature on Heat Transfer Coefficient at 1300 psia (Re*=600)  123  33  Effect of Bulk Pressure on Heat Transfer Rate at 80 deg F (Re* = 600)  124  34  Effect of Bulk Pressure on Heat Transfer Coefficient at 80 deg F (Re*=600)  ] 25  35  Flow F i e l d V a r i a t i o n with Velocity at 80 deg F and 1100 psia  126  Flow F i e l d Variation with Velocity at 80 deg F and 1300, 1500 psia  127  Flow F i e l d Variation with C i r c u l a t i o n and Pump Vibration - Free Convection  128  Flow F i e l d V a r i a t i o n with Cylinder Temperature Increase i n S u b c r i t i c a l and Superc r i t i c a l Free Convection  129  39  Flow F i e l d Variation with Velocity i n S u b c r i t i c a l Film Boiling  130  40  Flow F i e l d V a r i a t i o n with Pressure and Cylinder Temperature Variation i n Forced Convection  131  Comparison, of Experimental Free Convection Data with Other Workers  132  Comparison of Experimental Free Convection Data with Other Workers  133  E l e c t r i c a l Resistance Change of Nichrome V with Temperature (Minimum Curve for Annealed Nichrome Wire From [40] . . . . . . .  134  36 37 38  41A 41B 42  NOMENCLATURE A  surface area of the probe  Ap  flow channel area at the probe location  A ^  area of the venturi meter throat  Gr  Grashof number  I  current dissipated by the heated cylinder  L  effective length of the heated cylinder  Nu  Nusselt number  P  power dissipated by the heated cylinder (watts)  P^  f l u i d bulk pressure  Pr  Prantl number  (amperes)  (psia) 2  Q  heat transfer rate  (BTU/hr-ft )  Ra  Rayleigh number  Rc  probe resistance  at the bulk f l u i d temperature (ohm)  Re  Reynolds number  (~  Re*  Reynolds number based on mean properties  Rop  probe resistance  T^  f l u i d bulk temperature  T^ AT  cylinder temperature (deg F) temperature difference between heated probe and bulk f l u i d (deg F)  (—)  at temperature (ohm) (deg F)  f l u i d v e l o c i t y past probe V.^  f l u i d v e l o c i t y through venturi meter throat  c,  venturi meter discharge  coefficient  specific  heat  diameter  of the  heat  at constant probe  transfer coefficient  thermal  conductivity  differential  pressure  2  ( B T U / h r - f t -deg  of the bulk  pressure  fluid  across venturi  e x p e r i m e n t a l l y measured c o e f f i c i e n t change w i t h temperature ^ (deg r a t i o of v e n t u r i diameter change i n  threat  diameter  ( )  viscosity  (lb/ft  dynamic v i s c o s i t y  )  (lb/ft-hr)  2 kinematic  viscosity  meter of  resistance  F)  3  fluid  F)  ( f t /sec)  to upstream  tube  ACKNOWLEDGEMENTS  The author wishes to express his deep gratitude to his thesis supervisor, Dr. E . G . Hauptmann, for the amount and quality of guidance throughout the project.  Additional  thanks are due to Dr. Z. Rotem and Dr. I . S . Gartshore for invaluable comments on phases of the research.  The author  would also l i k e to thank Mr. D. Workman and the members of the technical staff of the Mechanical Engineering Department for  their assistance in the actual construction of the  apparatus. Support for this research from the National Research Council of Canada i s gratefully acknowledged. puting f a c i l i t i e s Centre.  Com-  were provided by the University Computing  1. 1.1  INTRODUCTION  Preliminary Remarks Heat transfer to f l u i d s i n the region of the  thermodynamic c r i t i c a l point has become of great importance i n the l a s t 15 years due to the very high heat transfer rates possible i n this region.  Current applications involving  heat transfer to f l u i d s above t h e i r c r i t i c a l pressure include s u p e r c r i t i c a l water i n power station b o i l e r s , s u p e r c r i t i c a l water as the working f l u i d in thermal power stations,  and  s u p e r c r i t i c a l hydrogen as the fuel and coolant for the combustion chamber i n large regeneratively-cooled rocket engines. Proposed applications include:  s u p e r c r i t i c a l methane as the  fuel in the SST as well as an aerodynamic and engine heat sink: n e a r - c r i t i c a l helium to cool the c o i l s of superconducting electromagnets:  and limited applications i n the  cation of hydrocarbons from natural gases.  liquifi-  An e n t i r e l y  s u p e r c r i t i c a l turbine power cycle using s u p e r c r i t i c a l carbon dioxide has been devised. would offer many advantages  Such a turbine i s now feasible and for such applications as e l e c t r i c  power generation for t e r r e s t i a l or space applications and shaft power for surface or sub-surface marine propulsion. An e n t i r e l y s u p e r c r i t i c a l turbine would have high thermal efficiency,  low volume to power r a t i o , no blade erosion i n  the turbine, no cavitation i n the pump, and use a single stage  2 turbine  and  pump.  engineering has  been  i n the Of  by  lack  fluid  i s an  variations  severe  critical  that  has  This  date  been  of  methods  few  obtained which  posed.  To  sections of  these  of  large  near  other pressure fluid  transfer  of  heat  property  the  mechanisms,  a  transfer  point  similar  f o r the  in  in  variations.  critical  can to  be sub-  supercritical  the  in supercritical flow  related  transfer  correlations  are  valid  over  heat  predictions  heat  inside  equipment  of  heated  tubes.  and  required  experimental  limited  o n l y been  heat  data  ranges,  rates  r e g i o n and  predictable  trans-  rates.  transfer  have  near-critical  regions of  situations  fluid  engineering importance  and  heat  predicting  date  of  critical  heat  example  proposed  with  exchangers  predicting  methods  very  immediate  Engineering been  the  i n f o r m a t i o n about  interest,  extreme  most work  i s of  heat  of  t u r b i n e and  region.  been  concerned  geometry  design  above  basic  secondary  have  this  fluid.  To fer  of  in fluid  unusual  boiling,  single-phase  with  of  fluids  fundamental  single-phase f l u i d  so  of  critical  more  near-critical  Property  development  applications  hampered  behaviour  a  The  have  valid  even  transfer  and been  in  the  have a  very pro-  certain  boundaries  have  not  been  fixed.  1.2  Review  of  Critical  Problems region  are  of  more  Point  involving than  Definitions heat  academic  transfer interest.  i n the Design  near-critical for greater  3 efficiency  i n b o i l e r s and regeneratively-cooled rocket com-  bustion chambers has forced operating temperatures and pressures into the c r i t i c a l region.  The c r i t i c a l region i s  considered to include those thermodynamic states within 0.8 to 1.5 times the c r i t i c a l temperature and pressure.  The  c r i t i c a l pressure i s defined as that pressure above which the f l u i d can not exist as two d i s t i n c t phases, while the c r i t i c a l temperature i s the highest temperature at which the f l u i d can exist as two d i s t i n c t phases.  For engineering purposes these  l i m i t i n g values define a c r i t i c a l point.  At the c r i t i c a l  point the physical properties of the l i q u i d and vapor  phases  are i d e n t i c a l and the c h a r a c t e r i s t i c surface tension between the l i q u i d and vapor phases has disappeared. the c r i t i c a l pressure i s therefore a continuous medium.  F l u i d above single-phase  Properties vary extremely rapidly with both tempera-  ture and pressure in.the c r i t i c a l region, and change continuously from those of a l i q u i d to those of a vapor with bulk temperature increase.  F l u i d above the c r i t i c a l pressure  termed s u p e r c r i t i c a l ,  while f l u i d below the c r i t i c a l pressure  i s termed s u b c r i t i c a l .  is  For a given s u p e r c r i t i c a l pressure  the temperature at which the maximum s p e c i f i c heat occurs  is  known as the p s e u d o - c r i t i c a l or transposed c r i t i c a l temperature for that pressure. the l i t e r a t u r e .  Both terms are i n common usage i n  The p s e u d o - c r i t i c a l temperature may equiya-  l e n t l y be defined as the temperature at which the maximum rate of change of enthalpy with temperature at that  constant  4 pressure  occurs.  variation the  with  locus  pressure  subcritical  summary  The  may  saturation  temperature much  dynamic  i s termed  like  critical  temperature  thermal  affected  by  by  a small  a t 1100  pressure  on d e n s i t y ,  and  Prandtl  the  properties  like  number  with  critical  respect  fluid  a  graphical  with  begin  temperature to increase ' above  as v a p o r - l i k e  dynamic  showing  conductivity,  the free  ( I ).  t h e maximum  pressure.  carbon  the e f f e c t of  v a r i a t i o n from  f o r that  -  dynamic v i s c o s i t y  i n Appendix  and t h a t  -  fluid.  for supercritical  continuous  the  v i s c o s i t y , and P r a n d t l  figures  horizontal  a normal gas.  the v i s c o s i t y  increasing  occurs  a heated  the pseudo-  like  Initially  to pressure  ( 3 ) shows  above  as i n  v i s c o s i t y are not greatly  i s known  fluid  properties and the  Supercritical fluid  Further  show  has  temperature  somewhat  properties  are reproduced  temperature  around  these  thermal  cited  Figure field  decrease  temperature  to the vapor-like  change  increasing  temperature.  the density,  psia.  fluid  conductivity  and dynamic  and t h e n  variation with  dioxide  with  temperature  (2) s h o w s  The  the thermal  temperature.  pseudo-critical  number  (1) s h o w s  of  the pseudo-critical  supercritical  conductivity amount  below  has p r o p e r t i e s  increasing  increasing  Figure  The  conductivity  thermal  with  as an e x t e n s i o n  Figure  liquid-like.  v i s c o s i t y decrease liquids.  and  considered  curve.  fluid  a liquid,  ordinary  The  be  temperature  of these d e f i n i t i o n s . Supercritical  very  of the p s e u d o - c r i t i c a l  roughly  convection  Note the  rate  that  liquid-  of  a t the pseudo-  temperature  c y l i n d e r ; i n a i r . .The  cylinder  5 temperature of  80  deg•F.  property in  i s 130  Plotted  variations  supercritical  bulk  temperature  flow  field  ent  from  the wall  that  function  of  of  the  the  and  i n the  thermal  same  dimensions  animonia tivity that of  must and  work  across the  1100  of  psia  bulk  80  field.  course  in a  fluid  boundary  and  be  f l o w does  occur  temperature  representative  deg  The  actual  vastly  show  the  temperature  layer  F  differtremendous  supercritical  in near-critical  [1]  i n the  Nusselt  Grashof  transfer  (the  are  temperature would  a bulk  fluid  span  the  Heat T r a n s f e r - G e n e r a l  the  variations  presented  at  the model  which  Schmidt  as  Grashof  imentally  same  scale  occur  dioxide  dioxide  Region  property  were  same  would  a i r i s at  temperature.  by  reasoned  the  f o r the  earliest  reported  to  temperature  Critical  was  the  carbon  variations  The  and  i n a i r but  pseudo-critical  1.3  F  which  i n carbon  that  property when  deg  and  Prandtl  number Prandtl  numbers  should produce  near-critical i n terms  of  conductivity as  observed  Schmidt  the  [15]  this  large  value extended  temperatures.  4000  numbers, expected very  times  fluids the  due  to  effective  to  an  that only  a  solid  heat  pure  over  results  bar  of  the  the exper-  supercritical  apparent of  large  conductivity  transfer For  a  values  the  thermal  of  is  high  apparent  found  as  Schmidt  i n normal  of heat).  large  1930"s.  Experimental  chamber  as  transfer  region.  required  test  amount  later  an  early  heat  thermal  copper  a very  but  narrow  conducnoted range  6 L i t t l e further investigation into s u p e r c r i t i c a l heat transfer was done u n t i l the mid-1950's when studies were begun to provide engineering design data for superc r i t i c a l b o i l e r s and regeneratively-cooled rocket engines. Notable i s the work of Powell [2] i n s u p e r c r i t i c a l hydrogen, oxygen, and nitrogen, the work of Goldmann [3] i n superc r i t i c a l water, and the work of Deissler water.  [4] i n s u p e r c r i t i c a l  These studies were primarily interested i n obtaining  experimental pressure drop and heat transfer  characteristics  for s u p e r c r i t i c a l and n e a r - c r i t i c a l fluids i n heated  tubes.  Controversy about the heat transfer rates, the f l u i d behaviour, and even the fundamental mechanisms of n e a r - c r i t i c a l heat transfer immediately arose.  B o i l i n g - l i k e mechanisms were  proposed by some [3, 5, 6] but other workers [4, 1, 8] maintained that property variations alone would explain the heat transfer rates.  In attempts to resolve the controversy, a  large number of experimental studies were done i n a variety of fluids with extremely varied r e s u l t s .  Some investigators  observed large peaks in surface temperature along the heated tubes, others observed minimums in surface temperature along the heated tube, while s t i l l others observed conventional temperature d i s t r i b u t i o n s . drops, pressure o s c i l l a t i o n s  Some workers noted large pressure as high as 0.3 of test pressure,  singing noises i n the heated tubes, the test section.  and even destruction of  Others observed only some or none of these  unusual heat transfer c h a r a c t e r i s t i c s .  '  7 Workers have ing a  been  able  i n the  to correlate  or not assuming  correlation  sections  field  been  their  obtained which  have  pointed to the  same  that  a boiling-like  phenomena  heat  transfer  most  sophisticated  beginning  transfer  from  heat  by  able  ±  transfer  i n the c r i t i c a l  contained progress been known  a r e so  in internal  Russian  flow  heat  [10].  but  s t i l l  in  single-phase c r i t i c a l  of  heat  and  Simoneau  transfer  are  critically  all  facets  complex  reviewed  of n e a r - c r i t i c a l  i n which  from  with  moderate  model  of  the  situations  to  1968  that  As  some  some  a very  as  are  transfer mid-1969 survey  publications  of progress  transfer  has  attention  complete 196  i s"  little  of heat  recently  heat  accepted.  of  fluids.  summaries  unusual  survey  mechanisms  region.  now  1965  includes  concludes  the  to  A  short,  differences  literature  [ 9 ].  Petukov  heat  In  that  differ  not y e t been  [11] c o m p i l e d  and  can  a physical  transfer  to near-critical  selected  not exist.  fluids  transfer  to the actual  in  has  concluded  observed  that  r e g i o n has  now  Hendricks  given  severe  should the  be  The  o f Hauptmann  Petukov work  the areas  assum-  case  researchers are only  involving  of the heat  i n t h e work  g i v e n by  and  well  researchers  and  o r does  likely.  situations  variations  review  Various data  transfer  I n no  except  r e g i o n i s so  100%  are  property  A  is valid  does  to predict  results  transfer  mechanism.  experimental  heat  equally  engineering predictions  results  heat  data  region.  i n the c r i t i c a l  t o be  own  a boiling-like  of the n e a r - c r i t i c a l  experimental  of supercritical  to date  included.  on  8 Only vent  has  to  special  study  will  As  noted  above most  done  tube; f i l l e d immediate  transfer  i n the  with  be  reviewed work  geometry  of  supercritical  work  has  mechanism  been  by  direct  The  on  very  sures  with  deg  (water  Tcr  =  moderate  pressures  and  -400  F  =  Per  ties  =  and 730  psia)  become  and  difficult  large  pressure  could  also  safety  or  one  basic fluid.  and  mechanisms  region  fluid  can  mechanism  have not  high F  should  and  and  or  the  fluid  of  in  Per  =  3206  with  Tcr  (methane). equipment of  errors  and  =  These  to  be  be  be  concerned of  heat  although  dependent  on  The  experimentally  another  for  the  transfer  the  F  variables  large.  measurements  applied to  deg  proper-  fundamental  can  =  very  with  variables  Tcr  -182  Most  workers  or  with  design  not  heat  pres-  psia)  (hydrogen  p r e v i o u s l y observed  directly  the  engineering  temperatures  Measurements  that  of  transfer  c o n s e r v a t i v e equipment  and  heated  oxygen.  i n heat  used  oxygen  experimental  agreed be  now  explosive  oscillations  region  situations.  experimental  considerations.  critical  are  with  determination  temperatures  psia  costly.  require very  fundamental  low  188  severely restrict  sophisticated  in  Per  705  rele-  interest—the  n i t r o g e n , and  the  fluids  involve either  directly  near-critical  and  observation  applications  and  i n the  immediate  flow  supercritical  or  here.  fluid,  done  external supercritical  deg  interest  i n t e r e s t — w a t e r , hydrogen,  little  with  of  this  been  Very  papers  in  the  made  fluid,  individual  the test  9 It  i s not  transfer  and  fluid  another  to  erties  to  properties  a  critical  or  more.  ponding  can  has  f o r many  property variation  more d e v i a t i o n  change  with  temperature  of  primary  fluid-flow  as  any ized  with  mentals chosen working  having  near  the  i n the of  there  of  from  and  to  when  not  Near  occur;  the  by  25%  or  of  corres-  law  of  fluid  transport the  to  pressure of  transport  fluid. such  density,  in a near-critical  the  differ  the  change  conductivity,  are  with  a  fluid.  s t i l l  and  The  transviscosity  heat-transfer  region  fluid  laboratory.  carbon The  formidable problems  transfer  critical  supercritical  either  the  rates  apply  prop-  situation.  working  obtained  thermal  determining heat  fluid by  the  importance  Although ated  and  to  even  are  fluid  g e n e r a l i z e d , may  show  properties  fluids  does  found  one  considered to  collapse  properties  port  be  however,this  been  heat  from  constants.  not  of  Thermodynamic  sometimes  of  of  possible  region.  properties  rates  a  be  critical  generalized  states  will  comparisons  the  properties,when  This  direct  relationship  n o r m a l i z e d by  region  thermodynamic  critical  substance  single  are  that  flow behaviour  i n the  f o r a pure  collapse  the  fluid  expected  heat  dioxide critical  rates these  and  critical  Most  workers  transfer or  one  of  mechanisms  problems  with  are  values  fluid  the  Freons carbon  Freons - the s e r i e s of f l u o r o - c h l o r o g e n e r a l s t r u c t u r e C,H,C1 F (k,l,m,n  in  minim-  easily  studying the  and  constants of  associ-  flow as  fundahave the  dioxide  are  hydrocarbons variable).  10 T c r = 89 deg F and Pc ~ 1071 psia while those, of a t y p i c a l Freon, Freon 114A and Tcr = 2 94 deg F and Per = 4 73 p s i a . 1. 4  Free Convection Studies Perhaps the e a r l i e s t work directed at i s o l a t i n g  the mechanism in s u p e r c r i t i c a l heat transfer was that of G r i f f i t h and Sabersky [12]. from a 0.010  Heat transfer rates were measured  inch diameter horizontal wire in Freon 114A.  Free convection was studied at both s u b c r i t i c a l and superc r i t i c a l pressures.  Heat transfer rates were observed to be  smooth functions of wire temperature but bubble-like formations were photographed in the s u p e r c r i t i c a l f l u i d .  The super-  c r i t i c a l photographs show great s i m i l a r i t y to photographs presented of s u b c r i t i c a l nucleate b o i l i n g but the heat transfer rate in the s u p e r c r i t i c a l f l u i d does not show the char ester i s t i c s u b c r i t i c a l departure from nucleate b o i l i n g peak. G r i f f i t h and Sabersky concluded that an unusual b o i l i n g - l i k e heat transfer mechanism  r  as proposed by Goldmann [ 3 ], was  present in the single phase f l u i d above the c r i t i c a l pressure. Doughty and Drake [13] also used a 0.010 diameter horizontal heated cylinder to study free heat transfer i n s u p e r c r i t i c a l Freon 12. and heat transfer coefficients  inch convection  Heat transfer rates  were presented as functions of  wire temperature but no flow v i s u a l i z a t i o n was attempted. data presented were reasonably correlated by the McAdams formulation that the Nusselt number was a function of the f l u i d Grashop  and  Prandtl  numbers  but the  peaks  in  The [14]  heat transfer coefficient  were not explained.  It was noted  that the heat transfer rates obtained i n the s u p e r c r i t i c a l f l u i d are up to 10 times those observed i n the s u b c r i t i c a l vapor at the same bulk temperature.  An elusive  which increased the heat transfer coefficient  phenomenon  by 100% was  also noted occasionally at some bulk conditions.  Doughty  and Drake concluded that the heat transfer behaviour observed could be accounted for by the f l u i d property variations and that the agreement with the c o r r e l a t i o n proposed by McAdams would be improved i f more accurate property data were available for s u p e r c r i t i c a l Freon 12. An interesting series of experiments directed at c l a r i f y i n g the heat transfer mechanism from a horizontal s t r i p in n e a r - c r i t i c a l hydrogen was performed by Graham et a l .  [16].  Heat transfer rates were measured as a function of temperature difference between heater surface and bulk f l u i d temperature for s u b c r i t i c a l and s u p e r c r i t i c a l hydrogen (Tcr = -400 deg F and Per = 188 psia)  for a variety of accelerations  Earth g r a v i t i e s .  from 1 to,10  The induced gravity effect was produced  in a centrifuge arrangement.  The hydrogen-filled tank was  mounted on a trunnion arrangement which automatically oriented the heater s t r i p so that the resolved acceleration vector was perpendicular  to the heater surface.  The heated s t r i p was  0.062 inches wide and mounted flush on the face of a large bakelite block.  The heater geometry could be considered as  a horizontal heated patch under various gravity conditions.  12 Graham noted that i n both the s u b c r i t i c a l and s u p e r c r i t i c a l f l u i d the heat flux v a r i a t i o n with temperature difference was smooth and was similar to that obtained by previous workers i n different n e a r - c r i t i c a l fluids and with other heater  geometries.  The established film b o i l i n g region i n a s u b c r i t i c a l f l u i d and the s u p e r c r i t i c a l heat transfer process were sensitive to an enhancement due to the induced multi-gravity e f f e c t . The established nucleate b o i l i n g region i n s u b c r i t i c a l hydrogen was not influenced by an induced gravity effect of 7 g.  The  nucleate b o i l i n g region and the t r a n s i t i o n zone from nucleate to film b o i l i n g were influenced by the past history of the test f l u i d but this effect was absent i n established b o i l i n g and in s u p e r c r i t i c a l heat transfer.  film  Graham suggested  that the observations of heat transfer rates, the effect of m u l t i - g r a v i t y , and the high speed movies taken, a l l indicate that s u p e r c r i t i c a l  heat transfer resembles established  b o i l i n g in a s u b c r i t i c a l f l u i d .  film  Graham concluded that while  suitable selection of the constants can make the  existing  b o i l i n g correlations f i t the experimental data, no accurate predictions of heat transfer rate can be made. An early experimental study of free convection from a horizontal cylinder in s u p e r c r i t i c a l water was done by Holt [17].  Holt's study was an extension of a s u b c r i t i c a l  b o i l i n g investigation to s u p e r c r i t i c a l pressures. 0.010  inch diameter horizontal cylinder and a short  Both a (1/8 th  inch high) v e r t i c a l wall were manufactured of platinum and  mounted  i n a high  transfer various found a  rate  pressures, both  smooth  of  critical  disappeared  vs temperature  This  effect.^occurred  vertical  as o b s e r v e d  wall.  the heat  same  shape  gross and  f o r each  film  transfer  rate  as from  geometry.  that  circulation  of sheets  of fluid  at supercritical  ature  corresponding  influence small.  of bulk  Holt  resembled  property  fluid  film  cylinder  that  that  remained  boiling.  heat  transfer  very  Holt's  close  rate  was  assumed  the c r i t i c a l constant  region  vanished to that  temper-  and t h e  convection to a  boiling  due t o chamber  a t the bulk  the deteriorated  film  fluid  the test  c o n v e c t i o n above  single-phase free  transition  rate  free  done  have t h e  visible.  specific  t e m p e r a t u r e on h e a t  and noted  with  transfer  p r e s s u r e were  t o t h e maximum  concluded  pressure  associated  through  wall  the flow  i n the n e a r - c r i t i c a l  was  and the  the v e r t i c a l  obscurred  b u b b l e - l i k e mechanism  existed.  cylinder  the horizontal  Holt noted  portion,  had  boiling  from  At  transfer  was  no s e c o n d a r y  stable  curve  vs t e m p e r a t u r e - d i f f e r e n c e curves  tests  heat  flux  region of heat  transient  t o be  difference.  f o r the horizontal  t h e same  flux  visualization  both  The h e a t  was a p p r o x i m a t e l y and  during  and  pressures  nucleate heat  difference  and no d e t e r i o r a t e d  such  and s u p e r c r i t i c a l ,  o f temperature  t h e peak  heat  difference for  at supercritical  function  rate  H o l t measured  o f temperature  rate  pressures  flux  section.  subcritical  transfer  increasing  the heat  test  as a f u n c t i o n  the heat  super  pressure  while the  observed  i n  14 In investigate mechanism studied  an e x p e r i m e n t a l  free  by G r i f f i t h  convection heat  cylinder  i n supercritical  constant  c u r r e n t power  nichrome  cylinder  the  heat  thermal and  which  carbon  constant  must  equilibrium.  difference  (less  than  to a turbulent  cylinder.  A t much  plume  existed  seen  by G r i f f i t h  flow  and Sabersky, observed  must  over  vary  to reach resistance  temperature  type  of  very  r e g i o n a t intermediate temperature  flow  the entire  differences  existed  similar  under  heated (greater  to  that  the heated  an  oscillating  differences  (from  150  t o 250 d e g F )  the  low-temperature-difference laminar  the  h i g h - t e m p e r a t u r e - d i f f e r e n c e b u b b l e - l i k e mechanism.  oscillating and  heat-flux  averaged taken as  r e g i o n was  heat  from  Figure  marked  oscillations transfer  a high (4 ) .  speed  the flow  fixes  by t h e heated  and photographed  i n which  diameter  supply  A t low  temperature  300 d e g F ) a b u b b l e - l i k e f l o w ,  Knapp  inch  a  as one l e g o f a  100 d e g F ) a l a m i n a r  higher  used  measured the c y l i n d e r  temperature.  changed r e p e a t e d l y  by l a r g e  from  convection to The  temperature-difference  Photographs  movie produced  The o n s e t  free  and by a sharp  rate.  [18]  horizontal  c u r r e n t power  than  cylinder.  a  to  transfer  Knapp  connected  temperature  designed  [ 1 2 ] ,Knapp  a 0.010  be d i s s i p a t e d  Knapp  the wire  from  dioxide.  t o heat  i s also  and the c y l i n d e r  calculated  rising  A  heat  and Sabersky  transfer  supply  which  bridge.  flux  cylinder  specifically  the bubble-like supercritical  observed  Wheatstone  study  increase i n the o f these  b y Knapp  of the o s c i l l a t i n g  two  modes  are reproduced region  was  noted  to  be  concluded by  the  bulk  that  temperature  the  bubble-like  trigger  the  wire  cooling  the  heated  Knapp vertical  wall  strip  the  in  laminar  free  ences.  The  heat  times  that  from  temperature concluded ism,  that  boiling,  can  and  this  on  heat  from  a  bulk  this  short  Knapp  increased  increase  by  a  inch  even  smooth rate  (0.125  could  suddenly  at  for  the  of  from  heated  heated  bulk  to  general  in  the  a  a  phenomena  single-phase mechanism  or  be  as at  much the  have  five  same Knapp mechan  subcritical  supercritical  can  with  as  bubble-like as  differ  cylinder  conditions.  certain conditions  as  wall  a  differ  temperature  strips  fluid  only  temperature  function  the  and  observed  vertical  the  high)  horizontal  but  high  either  of  inch  wide)  apparatus  rate  bubble-like  a  fluid,  strong  effect  rate. the  also  work  cylinder  used  as  of  K n a p p was  studied  free in  constant  a  0.015  Knapp  convection  current  inch  studied and  i n progress,  supercritical  a  independently  conditions  that  observed  c y l i n d e r was  Goldstein  greatly  was  exist  also  was  mechanism  horizontal  Goldstein heated  was  not  [20]  rate  (0.125  flow  transfer  transfer  Aung  a  experimental  under  While and  narrow  difference  although  that  a  transfer  bubble-like  dependent.  oscillation  studied  convection heat  pressure  wire.  same  ence.  and  temperature  and  strip  The  transfer  mechanism  also  horizontal  the  heat  and  power  diameter very  observed  transfer  carbon  dioxide.  supply  platinum  nearly a  heat  Goldstein  the  but wire.  same  bubble-like  the  fluid flow  at  16 high  wire  temperatures  bulk  temperature  was  Goldstein  also  and  the heat  of  found  occurrence  the  sharp  at  by.Knapp (400 by  t h e same h e a t  cylinder  fluid  that  n u m b e r was  as given  numbers  should  could  be e v a l u a t e d  o f any s t r o n g  due  to the bubble-like  The greatly  transfer  rate  heat  idea  that  that  effect  was  observed  convection  from  selected  the Nusselt  (Nu) (Pr)  t h e Gr and Pr  dioxide  on t h e h e a t  mean  temper-  mechanism  but noted  that  transfer  rate  be e x p l a i n e d  by t h e abrupt  varied.  the rate  o f change  influences  the heat  transfer  with  found  conditions.  arithmetic  that  originated  that  a bubble-like  carbon  occurred  measured  (Gr) and P r a n d t l  [14] b u t t h a t at the  Knapp.  flow he  of suitably  proposed  flow might  flux  than  i n free  i n terms  in supercritical  i n which  larger  by  by  he o b s e r v e d  f o r t h e same b u l k  concluded  absence  n o t marked  temperature  his results  b y Mcadams  investigated.  observed  flow  of the Grashof  the  rate  much  Goldstein  Goldstein exist  manner  very  that  a function  numbers  rate  function  as t h e b u b b l e - l i k e  the wire  c a n be e x p l a i n e d  properties.  ature.  flux  range  f l o w was  transfer  ( 1 5 0 t o 200 d e g F ) concluded  t o be a smooth  the bubble-like  t o 500 d e g F ) w a s  Knapp  rate  temperature.  u p t o 1500 d e g F  f o r the entire  i n heat  but stressed  Goldstein a  transfer  that  500 d e g F ) w h e n t h e  temperatures  of the bubble-like  noted  roughly  than  the pseudo-critical  wire  difference  increase  Goldstein  below  studied  temperature  The  (greater  Yamagata  o f heat mechanism  e t a l .[21].  transfer and  heat  17 Yamagata zontal  cylinder  mental  data  in  0.008 w  inch  by Yamagata  by Nishikawa diameter  heatstone  bridge  studied  [19]  and G o l d s t e i n  isis  effect  rate the to  platinum  very  nearly  heat  rate  a smooth  by  and G o l d s t e i n  necessary  of  the heat  Miyabe  mean  between  The d a t a  boiling  by Yamagata  [23],  and f i l m  o f Yamagata"s  data  taken  the heated  20 d e g F ) (up  difference. reported  experimental  greater than  assuming the p h y s i c a l  fluid.  than  observed The  o f the bubble-like flow  part  relations  temperature  nucleate  however  transfer  differences  Goldstein  flux-temperature o s c i l l a t i o n .  correlate  property  were  a  temperature  the bubble-like flow.  differences  for initiation  than  a hyster-  t o be  o f temperature  but the experimental less  Knapp  of the heat  t h e b u b b l e - l i k e mechanism  slightly  to initiate  temperature Knapp  were  function  Yamagata  rate- seemed  temperature  a  i n a  observed  (less  experi-  used  c o n d i t i o n s as  time  hori-  correlated  current.  differences  at higher  d i d not observe  differences  transfer  and  located  Yamagata  o f change w i t h  Yamagata Knapp  t h e same b u l k  a  The  Yamagata  also  by c o n s t a n t  a t low temperature  400 d e g F ) was  [22],  cylinder,  from  dioxide.  are reproduced  i n which the heat  transfer  convection  carbon  [20]. Although  of the rate  itself  free  and Miyabe  and heated  also  function  studied  i n supercritical  taken  a report  also  noted  and t h e onset  Nishikawa using  and  the constant  properties  cylinder  by  at the  and the bulk  i n t h e r e g i o n d e s c r i b e d as pseudo-  are correlated  boiling  model  by ah e x t e n s i o n o f a  proposed  Agreement o f the experimental  data  earlier with  by  the  Nishikawa proposed  18 expression  i s reasonable but again  expressions mental heat  have  data.  however,and  transfer  dioxide.  at  very  therms that  wire low  workers  from  have  to investigate  heat  transfer  difference  i n bulk  temperature  heat (up bulk  transfer  smooth heat  with  function  transfer  temperature  and heat  Increasing  affected  heat  isonoted  small heat  temperature i s and t h e peak  bulk  temperature.  o f p r e s s u r e on  coefficient f o r larger for fluid  transfer  difference  c o e f f i c i e n t showed  large  an i n c r e a s e  rate  even  peaks  the pseudo-critical  pressure caused  The peak  the e f f e c t  differences  o f temperature  by v e r y  temperature  transfer  The o b s e r v e d  exceeded  along  and S k r i p o v  increasing  showed  t o 20 d e g F ) t e m p e r a t u r e temperature.  inch  mechanism  differences  the bulk  the pseudo-critical  rate  transfer  or pressure.  above  and S k r i p o v a l s o  convection  coefficient at a particular  slightly  Dubrovina  required.  a 0.0012  Dubrovina  i s strongly  and s h i f t s  correlated  i n s u p e r c r i t i c a l carbon  the heat  c o e f f i c i e n t o c c u r s when  decreases  i s  free  [24] u s e d  region.  experi-  regions of  c a n n o t be  studied  cylinder  and S k r i p o v  certain  investigation  also  transfer  value  that  (0.9 d e g F) t e m p e r a t u r e  t h e peak  changes  further  a heated  i n the c r i t i c a l  temperature  concludes  that  Dubrovina  diameter  to f i tthe p a r t i c u l a r  in a supercritical fluid  Other heat  chosen  Nishikawa  transfer  readily  been  the constants i n the  a t one was  though  a the  as t h e w a l l  temperature.  i n heat  transfer  rate  except  a t temperature  Dubrovina  and  Skripov also  same e x p e r i m e n t a l of  heat  transfer  transfer  apparatus  coefficient  from  1.2  from  the c r i t i c a l  t o 1.5,  rate  less  studied and  coefficient  heat  transfer  differences  was  pressure. a smooth  unusual  For both function  observed.  free  convection i n a supercritical  Dubrovina  c a n be  but that  used  wire  the  heat  differ-  mechanisms  Skripov concluded t h e Nu  further  the  transfer  fluid  to the  varied  of temperature  to correlate  the form  that f o r =  f(Gr,Pr)  experimental  o f f ( G r , P r ) must  be  determined  experiment. Daniels  convection carbon  from  difference  and B r a m a l l  Both  were  f o r both of bulk  and  Daniels concluded  1100  psia.  flux  observed  fluid  and  by  Knapp  the heat  pressure  at roughly  of the data  the s u p e r c r i t i c a l  heat  i s  and h e a t  were  free  supercritical transfer  temperature  supercritical  temperature  that  increasing  rate  in  functions of  Daniels d i d not note  correlation  that  as  investigated  cylinder  transfer  subgritical  effects  with  heat  presented  The  constant  [25] a l s o  a small horizontal  dioxide.  coefficient  No  and  ratio  wire  geometries  or b u b b l e - l i k e heat  i n the  the  d e c r e a s i n g as t h e p r e s s u r e became  were  by  that  f o r the v e r t i c a l  F.  wire  of the horizontal  and no  results  3 deg  a vertical  concluded  ence  relationship  than  assumed  transfer  rate  pressures. small was  almost  at pressures greater the sharp  increase i n heat  t h e same b u l k  presented  transfer  than  conditions.  but Daniels  m e c h a n i s m was  conclud  normal  20 free  c o n v e c t i o n and t h i s  caused  b y t h e movement  i s augmented  of clusters  by a s t i r r i n g  action  of differing-density  i fluid. Recently from  a 0.080  dioxide. deg  inch  Only  F) were  Kato  e t a l . [26] s t u d i e d  diameter  cylinder  low temperature  attained  transfer  c o e f f i c i e n t d i d n o t show  observed  by Yamagata  bubble-like [20]  was  not observed  function by  Kato  workers  expect  to  those  observed  expected studied wall was  because free  just  same b u l k of and  again  functions the  difference. larger  Heat  obtained  than Kato  forced heat  o f temperature Nu =  used  were  transfer  diameter  a short  also flow  past  not high  used  enough  were  as  Kato high)  also vertical  f o r the wall  cylinder  at the  a limited  series  which  were  expression f o r free  cylinder  smooth  concluded  ;  similar  but lower,  rate  Kato  smooth  other  the horizontal  rates  difference.  by  (0.090 i n c h  performed  a  cylinder  cylinder.  transfer  Goldstein  was  rates  f o r the heated  transfer  f(Gr,Pr)  those  and G o l d s t e i n  the heat  lower  conditions.  familiar  than  The h e a t e d  differences  flow.  that  with  The  rate  c o n v e c t i o n from  experiments  conditions.  transfer  of the larger  slightly  effects  and t h e heat  by Yamagata  and o b s e r v e d  the h y s t e r i s i s  90  heat  [19] a n d  much  bubble-like  and  by Knapp  and t h e temperature  to  rate  than  photographed  o f temperature e t a l . was  (less  transfer  f o r t h e same b u l k  mechanism  convection  i n s u p e r c r i t i c a l carbon  differences  but the heat  free  that  convection  and  the  could if  be  used  to  integrated  the  mean  between  the  the  a heated  dioxide inch 1.0  and  the  liquid  at  rate  wire  the  and  convection, and  only  lack  of a  are  wire  Heat  were  was  vs  used  unable  also  studied  in near-critical  at The  results  results property  rates  were  and  and  similar  0.75  heated  regions of  i n the  two  similar  to  that  free  observed  that  fluids  information for near-critical  correlation  presented  the  heat  the  concluded  the  near  as  were  to  of  very  between  boiling  Abadzic  transfer  0.0004  from  presented  The  film  a  temperature  difference  temperature.  coefficient.  carbon  maintained are  correl  columns  heat  from  pressures bulk  any  thread-like  [27]  pressure.  Grigull  note  transfer  transfer  temperature  to  evaluate  heat  studied  and  to  the  v a r i o u s p r e s s u r e s was  photographed.  prevented  Abadzic  13.  wire  and  nucleate boiling  transfer  coefficients  properties  fluid  saturation  heat  transfer  heat  generation of  temperature  transfer  convection  observed  critical  saturation  the  for forced  Kato  and  Freon  the  F(Re,Pr)  groups.  horizontal  diameter of  =  fluid  supercritical Grigull  from  Nu  correlate  dimensionless  ation in  expression  the and  that  Freon  13  as  Nu  =  0.  1/8 (Gr*Pr)  '  conclude lower raised  f o r carbon that  the  temperature near  observed  to  region of  vapor  subcritical clusters  G r i g u l l . and  stable  differences  the. c r i t i c a l  i n the  containing  dioxide.  as  film  the  fluid, and  boiling  bulk  pressure.  fluid  The  such  sheets  Abadzic  of  as  occurs  vapor  at  pressure  various vapor  also  is  mechanisms columns  were  con-  22 eluded  not  transfer  to  have  contained  Baumeister  in a  and  inch  diameter  0.03  to  0.99  observed in  which  at  low  to  f i t the  boiling axial with  at  to the  to  actual  data  by  a  heat  fluid  heated  expression  can  be  the  heat  film  simple data.  rate  and  that  flow  problem  cylinder  small  has  the  of  mechanism  the  wire  and  been  by  done  on  for film  and  boiling  coefficient Simoneau  con-  the  change  is in  '  from  accordance  models. from  fluid  property  constant to  but  for film  convection  modified  the  near-critical,  wire  therefore a  the  well  observed  when  resulting  very  supercritical  except  was  about  developed  free  from  pressure  theoretical  in a  empirically  L i m i t e d work  on  0.001  The  flow  [28].  bulk  in a  the  a  pressures  i n the  trend  pressure  the  Baumeister  transfer  trans-  Simoneau  from  Baumiester  increase  follows the  the  at  as  correlated by  and  boiling  along  of. h e a t  critical  Baumeister  flow  earlier  theoretically  considered  to  columns  were  pressures  date  by  mechanism  circumferential  p r e v i o u s l y developed  solved  data.  axial  circumferential  horizontal  be  the  pressure.  i n vapor  developed  low  To  been  from  The  the  paper  critical  experimental  that  the  near  studied  bubbles  pressures  subcritical,  can  the  resulted  relationship  cluded  on  in saturated nitrogen  change  increased.  very  recent  wire of  to  fluid  Simoneau  l a r g e vapor  wire is  i n f o r m a t i o n on  in subcritical  is  strong effect  rate. Further  fer  a  a  has  not  variations  property  f i t experimental  predicting  heat  transfer  j rates  with  the simpler  supercritical and  Yoshioka  approach terms to  fluid  t o account  heat that  enthalpy  i s likely  free  differences  used  variation  variation.  The  by  Hasegawa  a perturbation  i s restricted  not consider  Hasegawa  and  t h e p e r t a b a t i o n method u s i n g t o be  i n v'  evaluated i n  approach  and does  mechanism.  plate  convection  and Y o s h i o k a  f o r property  transfer  conclude  of a vertical  laminar  Hasegawa  o f an e n t h a l p y  unusual  is  with  [29].  low t e m p e r a t u r e  geometry  a  any  Yoshioka  reference  s u c c e s s f u l b u t much  further  work  required. In  tion  from  fluid has ment  no  summary,  a heated  f o r the s p e c i f i c  horizontal  satisfactory  y e t been about  cylinder  case in a  method o f p r e d i c t i n g  developed  and t h e r e  the experimental  heat  of free  convec-  supercritical heat  transfer  i s still  no  general  transfer  r a t e s and  rate  agree-  mechanisms.  1.5  Forced  Convection  Studies  Experimental flow  forced convection  experimentally over  results  illustrating  heat  and  transfer  transfer  are extremely  studied forced  dioxide  pressure,  or theoretical  a heated  flat  flow  plate.  the effects  free-stream coefficient.  mechanisms u s i n g  studies of external  limited.  of supercritical Hauptmann  of bulk  velocity Visual  Hauptmann  presented  transfer  studies of the  a modified  carbon  temperature,  on h e a t  [30,  semi-focusing  bulk  r a t e and  heat schlieren  24 color  system  values due  are presented.  i n observed  heat  Hauptmann  transfer  to the large property  concluded  coefficient  variations  that  were  peak  primarily  i n the near-critical  fluid. Kato convection one of  bulk  i n an e x t e r n a l f l o w .  pressure,  free-stream  crossflow Kato  e t a l . 126] a l s o  bulk  Reynolds  a t low  concluded  five  (less  that  studied  forced  Kato  results  at  an e x p r e s s i o n  properties  transfer  was  able  comment  Nu = 0 . 2 7 Re  to correlate on t h e heat  experimental  the  calculated  the  forced convection  sensitive  fluid  Simoneau laminar case  correlated  a l l fluid properties.  coefficient  transfer  unable  was  always  and t h a t  coefficient  variation  than  that above  Kato  was  Kato  to  I t i s notable  coefficient  temperature  general over  studies  couette  of external flow  illustrate  flow  involves only  case  any geometry  and W i l l i a m s  ductivity  heat  be  found  less  the free  coefficient. The  analytical  mechanism.  transfer  to cylinder  convection  critical  heat  where  t o ± 2 5 % b u t was  transfer  differences.  33  ' Pr*  h i s data  heat  could  a s i n t e g r a t e d mean  transfer  the  rate  range  cylinder i n  2 5 d e g F) t e m p e r a t u r e  the heat  are evaluated  and a narrow  (Re) f o r a h e a t e d  0 6 by  presented  temperatures,  number than  experimentally  has n o t been  the progress  [31] have  of a  recently  i n a near-critical  solved  made  solved fluid.  with  temperature.  Simoneau  b u t two  t o date. the case This  the influence of the viscosity  variations  super-  and  of  simple con-  and W i l l i a m s  concluded reduced  that  the  heat  para-hydrogen adequately ships. flow  boundary  but  the  layer  plates  augmented  by  taken  water heat  fluid  cases  the  closer work  but  with  into  critical  transfer  be  is  summary,  mechanisms  a  and  [32]  the  has  heat  which  a  the  similarity property  couette with  variations  transfer  He  Graham a  model carbon  concluded  techniques sub-layer  to to the  explain  dioxide,  and  pipe-flow  that  that  be  typical  to  model  but  a  from  turbulent  penetration  the  process  presented  a  model  similar  directly  hydrogen, by  a  involving  somewhat  penetration  predicted  of  be  relation-  suggested  spring  stream.  than, c l a s s i c a l  flow  no  mechanism,  using  influence  the  that  could  that  t r a n s f e r mechanism  correlation.  forced In  Graham  enabled  not  of  liquid-like  property  concluded  greatly  included.  fluid  predictions  the  been  near-critical  could  values  also  stressed  heat  the  constant  because  packets  which  transfer  assuming  considered  into  which  para-hydrogen  penetration  Graham  correlations  vapor-like  useful  have  properties  near-critical  Williams  supercritical  region  rate  transport in  recently  boiling.  data  and  flow  time-dependent  wall  by  prove  Very of  that  treated  may  the  variation in  transfer  Simoneau  case  along  the  in  some  gave  much  much  structure  in  further near-  required. study heat  of  forced  transfer  convection  rates  in  heat  external  flow  26 situations the  has  not  near-critical  transfer  1.6  been  done  region  to  correlations  Scope  of  This  which with  had  peak  effects  on  heat  and  had  current  actual could  probe,  rate  heat  cylinder.  rate  accompanied and  this  rate Other  transfer  might  region be  heat  by  and  possible [13,  could that  mechanism  20]  show  had  large  unusual  possible.  transfer  large  previously  cylinder  t h e r e was improved  be  results  coefficient  might  mode o f  heat  heat  temperature  some d o u b t  regime  of  as  heat  to  the  transfer  expected. the  present  held at constant be  under  It  stream  of  in near-critical  secondary  near-critical  i n which  heat  study  an  was  tool  oscillating would also  transfer  v e l o c i t y might  i t was  temperature,  a very, u s e f u l  oscillations  improved  21]  transfer  oscillations  would  behaviour  heat  enhanced  For cylinder  heated  transfer  been  region be  [18,  transfer  The observed  results  heat  i n the  development  in  i  affected  the  for fluids  applications.  a  that  values  for technical  that  horizontal  indicated  i n the  indicated  greatly a  aid  i s required  Investigation  Previous transfer  and  only felt  as  i f a  in free the  that  i s an  indicate  mechanism  that  improve  as  to  show up  existed  felt  heat  as  region  of  heat  transfer  transfer fluctuations. vastly  convection a transfer  heated  anemometer  heat  current  a  rate  1  frees t i l l  27 further  and be  very  also  felt  from  the simple  might  that  geometry what  reported  i n most  designed  with  cylinder  to f i r s t l y the factors  secondly on  any  [18,  26,  20]  were most bulk  affecting  fluid  temperature  was was  near  the c r i t i c a l  well  operating  effects  of bulk  temperature,  and v a p o r - l i k e  heated  effects rate  and  and velocity  Previous  studies  heat  transfer  effects  pressure,  a n d when  the  condition,  and  above the p s e u d o - c r i t i c a l  c o n d i t i o n s were  was  temperature  free-stream  unusual  i n the l i q u i d - l i k e  Present  liquid-like  that  studies.  study  transfer  transfer.  discrep-  transfer  convection  of a  mechanism  cylinder  experimental  free  I t was  the large  heat  the heat  of heat  heated  a constant  the e f f e c t  indicated  likely  transfer  causing  near-critical  investigate  regions  had  were  of using  to investigate  improved  of the heat  the present  the idea  applications.  of a horizontal  factors  Accordingly  isolate  i n modern  investigation  indicate  ancies  useful  chosen  and b u l k free-stream  i f the  temperature.  to investigate  pressure fluid.  cylinder  with  both  the  28  2.  2.1  General  Concept  The transfer stream that  the  bulk  Experimental  study  i s concerned  heated  of  region  necessary  that  the was  the  carbon  through  flow  with  fluid  the  test of  fields  in a  I t was bulk  required  be  produced  study could  and  the  variable.  transfer  this  heat  uniform  pressure  section  heat  goal of  measuring  mounted  dioxide.  mechanisms a prime  Apparatus  in  so be  the  i t  was  observed  photographed. Carbon  because  the  dioxide  state  Carbon  dioxide  n o n - t o x i c , does  readily  available,  critical  was  critical  laboratory.  region . The  and  the  heated  been  a  constant-rpm  through  the  system  hydraulic pressure  test  loop.  or  The  the  studied  controlled by  a  bulk  fluid  in  the documented.  closed  circuit,  circulated  pump by  that i t  is  and  in a  f l u i d was  canned-rotor  the  easily,  properties  u s i n g compressed  system  in  fluid  advantages  mounted  test  p r e s s u r e was m a i n t a i n e d  fluid.  reached  extensively  The  the working  decompose  physical  s e c t i o n was  accumulators  as  has  c y l i n d e r was  flow  centrifugal  also  react  have  chosen  is easily  not  recirculating  The  cylinder  temperature,  velocity  Determination  is  a  APPARATUS  the  supercritical  free-stream  and  from  fluid  critical  of  present  rates  of  EXPERIMENTAL  and  flow  a bypass  set of a i r as  by velocity  arrangement.  free-piston the  high  t e m p e r a t u r e was  lowered  29 by  cold  from is  water  the  able  The  in Figure  test  inches  section  the  the  very  fine  and  3  feet  the  located with  was  upstream the  heated the  the  removed  nichrome  probes. wire  a  section  was  was  more  heated wires  the of  Figure  determined  Overheat  2 x by  ratio  10 the  the  to  factory  test ports. to  insert tube  found  into  to  be  free-stream the  caused  smooth  (7). consisted  i n the The  and  a  main  general  section  of  a  series test  packed of  section  arrangement  components  is  of  shown  (8).  used  in this  specially modified  supplied  set,  to  remov-  chamber  round  was  section,  test  cylinders or  and  section  cylinder.  and  section  P o w e r was  than  loop  a  viewing  illustrating  located  The  section  the  in Figure  honeycomb  and  from  section,  fi of  flow  with  pressure  test  disturbances A  long  pyrex  high  The  free-stream  heated  anemometer  a  conditioning  cylinder  The fine  flow  tempered  also  i s shown  matrix,  of  heating  stainless  at mid-height.  insert.  ports.  screens  the  i n diameter  fitted  section  teflpn-wool  of  vertical  eliminate  The  schematic  friction  a  section  viewing  by  was  p a r a l l e l - s i d e d viewing to  A  raised  section  block  changed  transition  in  test  block  was  test  necessary by  2  section  smoothly the  main  block  test  house  and  (6).  The tube  section  exchangers  r e c i r c u l a t i n g pump.  shown  steel  heat  the  hot  heated  modified  to  study  were  film  cylinder provide  either  anemometer by  power  a  hot levels  2 BTU/ft  hr.  overheat  Probe Probe  The ratio  cylinder  *  used  on  temperature the  anemometer  operating resistance . resistance at bulk f l u i d temperature  set.  Power d i s s i p a t e d  from  the  current  resistance.  back  which  cylinder  the  supplied to  operating loop  by  kept  The the  temperature  at  heated the  cylinder  cylinder  anemometer  cylinder the  and  was  determined  the  cylinder  set contained a  r e s i s t a n c e and  set value  by  feed-  hence  varying  the  the  current  supplied. The system  was  pps  as  were Bulk  thermocouples played  on  a  block  type  calibrated  high-speed  taken  at  a l l operating  fluid  the and  i n the  and  test  bulk  the  meter was of  l o c a t e d i n the  5000  psia.  0  to  a  was  The  35  mm  pictures  at  conditions of  interest.  measured  sheathed  test  by  2  fluid  and  dis-  galvanometer. both  i n the  test  v e n t u r i meter. measured to  bulk  between  1500  by  Heise  psia  pressure the  a  test  and tap  factory was  section  insert  block. the  pressure main  Barton 10  the  Schlieren  s t i l l  motion  measured  reading  fluid  through  differential  measuring  gauge  accuracy.  section  d i s p l a y e d on  of  mm  and  ballistic  was  pressure  stagnant  Velocity from  fluid  16  i n the  calibrated  i n the  runs  was  directly  downstream  0.1%  located the  temperature  bulk  pressure  to  a l l data  as  System bourdon  produced  well  immersed  of  field  during  specially  Temperature section  flow  monitored  photographs 5000  heated  flow  test  section  developed loop.  differential  p s i at  a working  was  across  determined a venturi  Differential pressure pressure  pressure  meter up  to  capable  Additional struction,  and  special  used  in  2.2  D e t a i l s of  2.2.1  this  Main  study  Mechanical o.d. Two  obtained. and  were  drilled  the  The  The  and  adaptors  as  were to  the  test  the  flanges  was  designed  block  can  be  required.  slipped  over  to  and  for  the  to  section.  the  the  be  The  Copper each  were  to The  accept  optical  section block 3  inches  section.  The  1/2  inch  the  to  act  path can  NPT  fitof  the  flange supports  square are  used  entire  test  each  flanges  as  and  were  The the  of  i.d.  in  The  tubing.  were  inch  holes  section block.  the  2  end  milled  O-rings  that  UBC  circular  tubing.  mounting  so  one  to  designed  Teflon  the  steel  long  1/2  bored  groove  loop  four  tubes  tube  to  O-ring  with  test  inches  been  symmetrical  mounted  stainless  other.  had  flow  test  18  in  section of  were welded  tapped  with  a  316  tubing  section block. and  con-  components  manufactured  from  type  flanges  through  orientations. if  of  flanges  circular  drilled  inch)  concentric  face.  design,  various  next  s e c t i o n was  flanges  square a  the  the  Components  flanges  through  and  the  in  Workship  sections  square  tube  (0.25  Circular  tube  given  test  Engineering  identical  of  on  Section  main  thick wall  tings.  are  details  features  Apparatus  Test  The  specific  flanges bolted  between assembly  section  i n e i t h e r of also  i n diameter annulus  be  two  inverted  were  formed  also was  sealed with s p l i t rubber bushings and was o r i g i n a l l y to be used as a system heat exchanger.  intended  These heat exchangers  were only used during f i l l i n g of the test loop as coolers but were used to insulate the test section i n some data runs. The test section block is a rectangular block of type 3 0 4 stainless s t e e l 3 inches by 4 inches by 7 inches high.  The 7 inch length was bored to match the i . d . of the  main test section tubes.  The upper and lower faces were  d r i l l e d and taped 5/8 NC to accept the four mounting b o l t s . A 1 inch diameter o p t i c a l path is bored through the 4 inch width at mid-height of the test section block.  The viewing  path is counterbored to accept the 1 1/2 inch diameter by 3/4 inch thick viewing ports. quality tempered glass.  The viewing ports are o p t i c a l  A circumferential O-ring groove  cut at mid-depth of the window boss.  is  This design results i n  more uniform stress d i s t r i b u t i o n i n the glass window.  The  window is a press f i t into the test block past the Teflon O-ring and is held i n place by a threaded plug bored with a 1 inch diameter  o p t i c a l path.  The stress produced by the  mounting plug is distributed more evenly over the glass surface by a soft fibre washer.  Details of the porthole  assembly are shown in Figure ( 8 ).  The test section block  is also bored through the 3 inch face into the main flow passage.  The holes are tapped 1/2 inch NPT for the Conax  transducer  glands.  33 2.2.2  Flow  loop  All stainless used  tubing  steel.  flow  inch  loop  t o connect  a l l 1/2  inch  o.d. t u b i n g  for  the parts  thin  wall  t o 0.035  fittings.  No  auxiliary  apparatus  use  completely  taken  wall  was  apart  with  Initial-  required  as t h e  i n the ferrule  occurred  was  thickness  tubing  type  the smaller  o.d.  stainless  fittings i n stainless  steel  steel  bulk  work  during  used with  even  were  forced  fittings.  the  ;  Cadmium  f o r the frequently was  easily  flow  when  ball  These  fully  open  a very  spalled o f f  system  of the valve  leakage  was  any l a r g e  body by  type  featured  and easy  in-line  leakage  rate fluid  Compression  pressure  minimized system  valves  of  supercritical  a s 105 d e g F .  i n bulk  valves  small  the vapor-like  as h i g h  d i f f e r e n t i a l heating  during  seats.  had only  r a p i d changes  This  Worchester  Delrin  with  temperatures  fluid  of avail-  steel.  The v a l v e s  atmosphere.  steel  as t h e p l a t i n g  unobstructed  with  mild  not acceptable  valves  the seat  f i t t i n g s i n the Lack  the mild  disassembly.  test  wall  steel.  sections  stainless  through  tubing  equipment.  inch  disassembled  cadmium-plated  All  cause  316  f i t t i n g s were  exposed  316  type  of special  disassembled and  well  316  o.d. t h i n  thickness  frequently  type  wall  inch  0.027  wall  problems  frequently  were  o f some  plated  was  was  tubing. All  ability  o.d. t h i n  a n d 0.25  d i d not seal  leakage  loop  a l l auxiliary  inch  of the loop  tubing  Valves  i n the test  used  a change  the  used  was  but  to  and  One-half  f o r t h e main  tubing ly  tubing  could  and a l l o w  leakage  circulating  pressure  changes.  34 2.2.3  Flow  C o n d i t i o n i n g and  One  of  investigation of  heat  fore  felt  that  necessary. also The  connecting  organized  the  provide  an  flow be  jet.  The  flow  flow  of  section.  approximately of  1/16  The  was  again  passed  steel  only  minor  the  which  wire  shaped  cutaway  and  of  flow  remove  settle  separated  by  1/2  flow  the  from  and  10  to  velocity  led directly from to  the  flow  the  jet  4  10  mean  inch  length motion. and  stainless Re  75  the  flow  disturbances. the  for  cross  The  into  inches  inch  inch. and  section section  settle  1000-mesh  well  packed  first  a  a and  test  tightly  the  as  test  f o r another  three  was  square  through  velocity.  diameter  this  to  was  was  as  section  up  allowed  passed  to  inch  j e t i n the  was  to  of  there-  fields  well  inch diameter  series  the  flow  as  test  inch  of  section  view  2  a  then  one  mechanisms  cylinder  1/2  break  series  section the  the  allowed a  heated  larger to  the  I t was  resultant  the  the  honeycomb  temperature  screen  the  up  The  diameter  conditioning A  each  the  necessary  break  through  screens  screen  of  square  of  through  inch  inch  flow  then  1  to  experimental  region.  the- pump was  entered  pads  test  critical  through  passed  this  i n temperature  entered  teflon-wool the  from  of  Section  explanation of  approaching  I t was  insert.  first  near  uniform  flow  uniform  was  to  tubing  provide  and  goals  visualization  The  and  primary  i n the  required to  tubing  the  was  transfer  Transition  based  on  contained The  outlet  transition  insert  circular cross-section  parallel-sided c o n d i t i o n i n g and  viewing  region.  transition  sections  is  shown  very  as F i g u r e  light  (7 ).  aluminum  the  tubing  was  has  optical-quality  approaching  between  the t e s t  the pressure through  problem the  rigidly test the to  section  flow  insert  block  transition  in  fluid  could  density The  flow  allowed  quality  of the f l u i d  section  was  of the flow  of the schlieren  was  ity  of the f l u i d  easily  a  was  evolved  satisfactory  and  a  due  accel-  by  test  cementing  section  does n o t  fine  pressure  large  insert  cured  pressed  very  level  present  harden  out of the groove  around  scratch  extending  equalization of carbon  circulation  without  dioxide  due  to  very  differences.  image  was  A  be  port-  circulation  cement  low v i s c o s i t y  ity  section  still  allowed  The  region  conditioning  schlieren  RTV-5  a t window  movement.  This  pressure  the  pressure was  of  insert  with  as t h e f l u i d  into  the high  made o f side  the t r a n s i t i o n  b u t was  i f required.  insert  the c r i t i c a l  small  set flush  section.  The  each  of circulation  and  was  transition  visualization  the top of the i n s e r t  gross  block  on  to the high  amount  RTV-5.  the i n s e r t  section  The  windows  and p a r a l l e l  Silicone  and  t h e same.  glass  a large  insert  as t h e p r e s s u r e  d i f f e r e n t i a l developed  hampered  with  transition  the t r a n s i t i o n  transition  block  flat  contour  Initially  erated  tubing  essentially  holes.  to  The  by  quality  after  monitored  past  by  and an  obtained. tests  o f f l o w was  idea  The  through  viewing  the cylinder.  variable  repeated  passing  the  The of the  sensitivuniform-  conditioning  and m o d i f i c a t i o n s  reached.  the  The  until  available  design [34]  criteria  apply  clumps  quality  that  fluid  entering  modifications  o f the free-stream  A  fluid  of the supply  rms c o m p o n e n t  was  fluids  a l l final  disturbances voltage index  remained  second  voltage  attributed existing  than  film  The  constant  tests  circulating  CO.  and i s a unique  design  and f o r ;  one moving  fluid  with  cylinde  effect  temperature.  of the turbulent  rms o n a  signal  T h e rms s i g n a l cylinder  or quality  temperature  u p t o 0.04 v o l t s  rms o n a  o c c a s i o n a l l y observed  b u t these  disturbances  conditions  during  i nt h e  were theco-  boiling.  pump  canned-rotor  pump was m a n u f a c t u r e d  contamination  measuring  Pump  The  only  were  and nucleate  steel  by  of the  t o the heated  effect  0.002 v o l t s  to the oscillating  Circulating  stainless  t h e combined  o f 4.5 v o l t s boiling  indication  was o b t a i n e d  1.0 t o 5.0 v o l t s . almost  conditioning  i n t e r p e r t e d as t h e combined  runs  less  and t h e d i s t i n c t  b e made t o t h e c o n s t a n t  voltage  Isolated disturbances  subcritical  2.2.4  was  o f from  increase. base  data  [33] and  the flow  V e l o c i t y f l u c t u a t i o n s and non-uniform  For  has  property  specifications.  rms c o m p o n e n t  This of  density  fluid  conditioning sections  t o constant  required  property  the  only  of high  section  f o r flow  used  fixed  study  rpm i m p e l l e r  developed  pump.  o f CRANE  to eliminate  applications.  a combined  was a  type  b y t h e CHEMPUMP d i v i s i o n  leakproof  part,  i n this  T h e pump  rotor-impeller  assembly  37 driven  by t h e magnetic  lubricant  i s used  circulation operating 49.5  of the test  a t a base  the flow  bypass  and  steel the  were  connectors  enough any  friction  heating  desired value No  operating  problems  this  2.2.5  the present  to raise  1/2 test  fluid  with  by a  discharge r e operates  T h e pump  inlet  i n c h NPT  stainless  facility.  Due t o  the fluid  vibration,  noted  was v a r i e d  t h e pump  and e l i m i n a t e d any need  were  In the present  T h e pump  rpm.  of  supplied  bulk  temperature  f o rbulk or other  t h e pumping  to  fluid common  circuit  used  '  Exchangers  As temperature  i t was n e c e s s a r y within  was  required.  the  pump  the  loop.  secondary  and i s r a t e d  o f t h e pump  t o accept  leaks, excessive  by a  study.  Heat  raise  section  a t 3450  of recirculated  heaters.  in  modified  psia  o f water.  the test  i n a bypass  to suit  l a r g e volume  o f up t o 2500  a c power  No e x t e r n a l  T h e pump w a s c a p a b l e  and t h e remainder  3 phase  discharge  are lubricated  o f 138 f e e t  through  and c o o l e d  440 v o l t  fluid.  pressure  rate  arrangement  circulated  o f an i n d u c t i o n motor.  as t h e bearings  U . S . gpm a t a h e a d  study  on  field  I t was  temperature  exchanger  convection  data  limits  found  running, a t f i x e d  the bulk  heat  close  the fluid  a variable  f o r forced  flow  flow  no h e a t  for.cooling  exchangers  could  runs  exchanger" that  heating to  t o any r e q u i r e d v a l u e . was  bulk  heat  data  rpm s u p p l i e d enough  application  runs  to control  In  only. be used  fact, In  free  a t any  point flow was  i n the  apparatus  disturbances. below  the  the  fluid  provide  sufficient  critical  The  critical  cooling  the  as  and  to  a  was  using  domestic  cold  very  wall the  simple  aluminum 1/2  design;  resulting  annulus  flow  tubing.  and  inch  The  pipe  RTV-5, valve. the  varied  most and loop  data a  to  water  of  the  A  a  heat  t u b i n g was  main  flow  to  the  common  drain.  exchangers heat  section  thin  as  section ends  of the  suit  into  the  place  to  prevent  bored  to  accept  of  this  on  was  on  the piped  in  therefore  combination. was  on  the  two  necessary the  1/4  flow  design  one  could  through  any  silicone  variable  and  Flow  otherwise  of  to  exchangers  was  of  used  exchanger  balance  cooling  were  bored  loop  i n any  adjusted  The  exchangers  the  via a  exchangers  would  exchangers  sealed with  supply  exchangers  and  that  influence of  straight  plugs  delivered  sensitive  heat  c e m e n t was  again  r a t e was  the  These  tubing  RTV-5  the  felt  p l u g s were f o r c e d  bypass-loop  flow  main-loop  a  over  laboratory  ambient  diameter  rubber  aluminum  on  near  water  inch  loop  rubber  three  the  exchangers.  flow  i t was  temperatures.  supply.  slipped  convective  i n the  illustrate  flow  1/2  supply  a l l used  runs  1  connectors,  The  suitable  two  wall  two  any  to  water  silicon  were  loop. and  very  a  The  water  apparatus;  parallel  the  the  There  bypass  be  thin  thread  and  temperature  sealed with  non-hardening  leaks.  and  t u b i n g was  inch diameter  loop  temperature  forced  strong  temperature  pseudo-critical  selected  of  generated  ambient  subcooling  mechanism the  they  fluid  For full main-  between approach-  39  ing  the probe  tubing  wall  would  contain  i n the exchangers.  on  t h e main  as  insulators  flow  loop  o r thermal  cushions  The l a r g e  section  n o t b e "used  could  either  heat  free  exchanger  section  in  are to  section.  that  test  cold  down  section  fluid  sank  data  runs.  the wall  lighter fluid was  easily  the flow  the heat  of colder  large  noted  only  o f the honey-  cylinder  section.  begins  on t h e s c h l i e r e n  Cold  clumps  fluid and  section. image  an sank  forced  This  circu-  o f the test  section. The  heat  exchangers  constant  property  expected  as i t i s one o f t h e p r o b l e m s  cations  using  fluid  d i d not perform  calculations  a supercritical fluid.  as w e l l  predicted  -J  on t h e u p p e r  and caused  section  the center  carried  generated  section  Cooling  down  when  currents  test  o f the test  up t h r o u g h  was  h a d t h e same e f f e c t ,  the heated  region  lower  d i d not break  The c o n v e c t i v e  exchanger  test  The  fluctuations  vertical  loop  conditioning  passages  fluid  only  temperature  exchanger  c i r c u l a t i o n loop.  past  on t h e main  convection around  used  the flow  fluid  c i r c u l a t i o n i n the test  along  lation  exchangers  and cause  heat  were  to maintain  from the  exchangers  bulk  the entire  a c t as a n a t u r a l  heat  section  i n the outer  cylinder.  fluid  to control  from  The lumps  the heated  induced  the  located  screens,  so strong  main of  was  to the f l u i d  the fine  past  or forced  and any c o o l i n g  transferred comb  heat  of colder  The l a r g e  conditioning  temperature.  for  clumps  as  but this  associated  with  The s i m p l e  design  was  appligave  40 no  operating problems  more h e a t if  exchanger  would  permit  c a p a c i t y on  any  easy  addition  straight  run  of  of tubing  required.  2.2.6  Transducer  Glands  Electrical pressure was  test  provided  transducer diameter forcing teflon were  one  by  two  steel  plug  had  rod  around  to  transducer  the  the  other  tubing,  and  the  diameter and were  2.2.7  and  temperature noted  at  Flow from  the  of  bored  teflon  transducer port  probe  gland.  time  a  one The  leads  by  of  and  while  were  seal  tap  Each l/16th  copper gland  was  fed  rods, were  the  from  rods to  through was  ±  fed tap  inch  the  pressure  insulators.  instrument  the  pressure  a l l 1/16th  inch  by  deforming  thermocouple  isolated  these  on  transducer  ceramic  cylinder  glands.  Solid  pressure  sheath  heated  thus  leads.  each  high  accomplished  plug  copper  around  to  sheathed  2-port  the  the  No  leaks  fittings.  Measurement velocity  differential  downstream  passages  a  one  of  transducer  against  taps  Velocity  to  S e a l i n g was  power  any  interior  power  Conax  thermocouple  the  the  leads.  gland  through  to  supply  two  the  through  power  to  2-port  electrical a  access  chamber  gland  passed  supply  The  and  the  differential  test  through  pressure section  pressure  was  the  test  developed  section across  i n the  main  measured  on  flow a  was a  venturi  loop  Barton  calculated meter  tubing.  model  200  Differential ential up  Pressure  pressure  t o 3000  ranges.  A l l parts  type  used  t o connect  at  3.6  curve  o f t h e meter  base  obtained  a mercury  was  assumed  to  the standard  ASME  The  v e n t u r i meter  and  an o u t e r  throat diameter  diameter taken  was  diameter, stalled  with  upstream located  distances venturi  diameters  exceed  meter  calibration run pressures.  a n d was  as d e s c r i b e d  diameter  numbers,  runs.  was  downstream quoted  The  ' • •  section ratio  0.5, t h e t h r o a t coefficient  based  was  on t h r o a t was i n -  tubing  temperature  of the throat. by  designed  flow  taps.  of straight  fluid  workship  i n [35].  The v e n t u r i meter  diameters  t h e minimum  calibrated  i n the  Department  and the d i s c h a r g e  100 t u b e  probe  was  These  [36] f o r a c c u r a t e  measurements.  Velocity constant  was m a n u f a c t u r e d  t o upstream  was  d i o x i d e gas i n  at a l l data  o f the t h r o a t and a bulk 10 t u b e  was  i n two p a r t s ; a n i n n e r  i n the data  over  tubing  fluid  valves, to the  to hold  f o r the Reynolds  used  the test  meter  containing the pressure  0.25 i n c h e s  a s 0.9 6  carbon  specifications  was made  sleeve  isolating  pressure  pressure  steel  The l i n e a r  Engineering  differ-  pressure  differential  and s t a i n l e s s  using  a  bellows-type  column.  v e n t u r i meter  t h e UBC M e c h a n i c a l  on a working  i n contact with  through  pressure  at  of  steel  t o measure  i s a  interchangeable  t h e meter,  with  The  Meter  The d i f f e r e n t i a l  atmospheric  equilibrium  0 t o 10 p s i a  stainless  meter.  calibrated  The B a r t o n  featuring  were  venturi  o f from  psia.  instrument  Meter,  property  was c a l c u l a t e d flow  through  assuming  incompressible,  the v e n t u r i meter  and t h e flow  42 loop.  The  maximum  throat  was  calculated  in  fluid  the  the  at  velocity  Appendix  2.2.8  the  sheaths,  and  i n one  port  was  electrically  and  the  from  main  the  fluid  the  test  circuit  and  switching  and  Northrup  run to  was read  of  shown  a Conax  insulated  the  speed  Probable below  in  measured  by  of  sound  accuracy  consisted  of  measured  on  temperature  K-5  a  the  s h e a t h by  One  one  inch  not  i n the 10  The of  above  The  tube  heated  remainder  a  of  small  The  temperature  Scalamp  difference  located  cylinder, The  slight  in  in  second of  the measur-  junction  potential  galvanometer  directly.  ceramic  temperature  changes  to  sealed  downstream  the  thermocouple  as  was  copper-constantan cold  potentiometer.  Pye  wake.  diameters  (10).  thermocouple  powdered  heated  two  steel Figure  purchased  the  of  selected  transducer gland.  to read either  to  o.d.  thermocouple  located  due  inch  of  Company.  throat.  circuit  l/16th  circuit  were  but  Model  i n the  from  either  set i n stainless  thermocouples  section  meter  ing  as  sheaths were  Conax  was  was  thermocouples,  stream,  thermocouple  the  of  tested.  temperature  sheaths with  the  of  30%  meter  Measurement  arranged  thermocouple  venturi  than  conditions  bulk  copper-constantan  units  less  the  (III).  Temperature  seal  at  obtained through  determination i s discussed  Fluid  The  flow v e l o c i t y  on  a  Leeds  imbalance  during  a  calibrated  test  The a  PYE  Cadmium  obtain cell  of  a  of  brated  6 volt was  Precision  18  calibrated  in a  water  Calora  water.  to  for reference  The the  thermal  and  ice.  constant  was  a  circuit  by  The  one  cold a  mix-  were  filled  comparison  cali  with  with  thermometers  Dymec M o d e l  to  was  thermocouples bath  was  used  containing  temperature  Calibration  against  flask  voltage  source  battery.  The  inch mercury-in-glass  [37]  voltage  measuring  lead-acid storage  distilled  distilled  used  cell.  power  immersed  in a  cell  reference  stable input  junction ture  standard  two  previously  2801A q u a r t z - c r y s t a l  -4 digital-thermometer separate that  accurate  calibrations  both  thermocouple  standard  tabulated  standard  calibration  2.2.9  Pressure  Heise  against full to  tube  tube  pressure  port  probe  inches  After  period  used  f o r temperature  two  i t was  1%  of  f o r copper-constantan  The  of  was  above  out a  was  pressure  tester  gauge  passing  one  C.  e i g h t month  pressure  weight  pressure  through  three  was  bulk  Bourdon dead  deg  p o t e n t i a l s were w i t h i n  values  scale reading.  the  steel  a  an  10  and  found  the this  determination.  Measurement  System psia  over  to  by of  to  bulk a  gauge, be  Canax  high  the  heated  a  to  signal  pressure  0.1% was  test  cylinder  section but  to  1500  of  the  transferred stainless  test  gland.  0  certified  inch diameter  transducer  l o c a t e d i n the  by  factory  accurate  pressure  l/16th the  measured  block  The  system  approximately  extended  only  44 to  the  edge  immersed  of  in  the  test  stagnant  section  fluid  and  i n s e r t so measured  that  only  i t  was  static  pressure.  2.2.10  Hot  Wire  The maintained a  experimental  at  constant  ThermoSystems  modified wire  to  tain  the  power  Inc.  provide  operating  operations  Anemometer  area  of  coefficients  heated  Model 100  1010-A  watts  require  in  the  at  the  attained  in  and  ment w h i c h  had  test  resistance  a  feedback  the  heated  balance. heated  Varying  experimentally the  the  which  the  decade  for  using  anemometer  1 watt  was  so  high  variable  that  the  rate  of  the  test  cylinders  decade  power but to  to  the the  heat  leg  leg.  resistance resistance  large  The  arrange-  and  a  The  bridge  to  was  raise in  varied  therefore  was  large  transfer  power  bridge  resistance  hot  main-  dioxide.  therefore  and  factory  film  bridge  sufficient  resistance  The  due  variable  resistance  built-in  hot  of  carbon  The  the  set.  one  other  resistance  or  a wheatstone  as  Set  from  r e t a i n normal  wire  very  was  supplied  temperature  the  supplied  operating  change  of  probe  as  temperature.  temperature  of  loop  cylinder  cylinder  cylinder  box  and  study  to  probe,  Anemometer  near-critical  consisted  the  Hot than  or  current  power  present  probe  by Wire  constant  circuit  had  of  less  anemometer  decade  cylinder,  temperature  probes  requirement  surface  Supply  characteristics.  usually  heated  Power  the  change  the  heated  with  determined measuring of  the  circuit  Thermo-  45 Systems  I n c . anemometer  ing  resistance  use  with  ohms.. range  directly.  probes  a probe  at  low temperature  tions at  steps.  temperature  normal  overheat,  variation  hot wire ratio  a t temperature  ations  i n t h e mean p o w e r  varied power  with  level  t h e probe t o keep  on t h e b u i l t - i n  to  s e t and t h e power  calculate  tored  coefficient  3400A rms  full  scale  with  applica-  calibration the heated  as a v e l o c i t y . as  the overheat velocity  cylinder  dissipated  Fluctu-  turbulent  ratio  stream  was  and t h e  !  at the elevated  using change  supply  as t h e combined  capable  was  effect  using  was  used  the experimentally with  of  temperature. also  moni- -  turbulent  i n the bulk  a Hewlett  o f measuring  a time- c o n s t a n t  ratio  v o l t a g e was  temperature using  o f the  calculated  The o v e r h e a t  of resistance  was m e a s u r e d  rms v o l t m e t e r  to maintain  temperature  and non-uniform  rms c o m p o n e n t  probe  d.c. c u r r e n t meters  o f t h e probe  and i n t e r p r e t e d  fluctuations The  the cylinder  rms c o m p o n e n t  2 deg F  The c u r r e n t f l o w i n g t o t h e probe  operating resistance.  determined The  study  the heated  was m e a s u r e d  probe  correspond  anemometry  are interpreted  i n a constant  was m e a s u r e d .  the  the entire  o f 0.01 ohms  and a f t e r  i s interpreted  temperatures  anemometer  over  0.10 a n d 3 9 . 9 9  of approximately  required  In the present  required  between  or hot film  i s fixed  t h e power  sensor  disturbances.  steps  operat-  s e t was d e s i g n e d f o r  was v a r i a b l e  These  probe  differences.  the overheat  this  to read  The anemometer  resistance  ohm  to  In  designed  of operating resistance  Operating i n 0.01  s e t was  Packard  t o 0.001  o f 2 seconds.  fluid. Model  volts :  46 The heat  a test  use o f a hot wire  probe  advantages.  The t e s t  accurately  from  dissipated  Sharp  changes  power  probe  heat  i n heat  cylinder  transfer  rate,  b o i l i n g , were  indicated  supplied  t o the probe.  Regions  heating  would  have  destroyed  could  to  h a d many quite instantaneous  be  monitored.  as encountered  only  in  by a d e c r e a s e  i n which  the test  supply  known  and t h e  such  film  data  was  resistance  by t h e heated  power  transfer  temperature  the operating  power  transient  and p r o v i d e  anemometer  probe  constant  were  i n flux  investigated  successfully.  2.2.11  Probes It  film  probe  film  probes  (selected  and Heated  was  originally  as t h e heated usually  deposited  an  electrically  of  the reasonable  conductivity).  Usual  long.  The r e q u i r e d inches  resistance by  apparatus.  f o r the present  of a thin  on a q u a r t z film  of  cylinder  of quartz  probes  and t h e c y l i n d e r heated  cylinder  a n d 0.6  o f 6 t o 10 o h m n s .  Two  data  was  and low  long  such  probes  i n the  taken  change  with with  because  electrical  are approximately  t o be  Hot *  platinum  (selected  i s about was  study.  and coated  inches  I n c . and i n s t a l l e d  Qualitative  layer  conductivity  hot film  i n diameter  ThermoSystems  t o use a m o d i f i e d h o t  coefficient of resistance  thermal  i n diameter  0.010  cylinder  insulating  inches  intended  consist  f o r the high  temperature)  Cylinders  0.10  0.010  inches  approximately and have were  a  cold  produced  experimental  and probe  calibration  47 was  completed  probe  failed  during  differential shield  and  platinum  f o r one  to  ThermoSystems  this  period a  author  and  but  to  were  far apart.  platinum  with  A  initial  data  trigger  an  A  second  used  the  data  of  and  an  and  ing  circuit,  The  best  areas  gold  the  to  of  with  obtained  and  coated  the  but  was  calora  was  assumed  of to  the  from  platinum  two  and  shows  different  the  to  •  were  (11)  data. by  immersion water  anemometer  over  to  repaired.  temperature  23  and  supplied  98  deg  r e s i s t a n c e change hold  with  presented  of  the  points  attempt  calibrated  using  low  probe  Figure  with  constant  temperatures  data  was  but  reproducibility  the  the  easily  Data  runs  During  by  of  a  an  probe  probe  used  built  calibrated  during  data.  data  coefficient was  developed  pyrex  r e s i s t a n c e measured, various  Because  temperature  failed  on  and  calibration.  data.  coated  cylinder the  designed  manufactured  situation  different  inside  f i t linear  temperature  large  was  experimental  heated  at  caused  c o n s t r u c t i o n was  platinum  illustrates  the  due  quartz  during  probe  probe  flow  second  three  o i l bath  were  second  outer  were  cylinder  this  The  gold-coated  from  probes  initial  pyrex  taken.  The  bath  a  probe  the  The  the  ThermoSystems  oscillating  using  probes  in  on  for a l l further  taken  which  failed.  failures  between  r e s i s t a n c e change  film  gold.  wire  obtain  of  a  probe  Both  a l l failed  coefficient rather  layer  additional  nichrome  used  the  off.  Several by  expansion  platinum  spall  and  calibration.  thermal  the  probe  the  measurC,  with  entire  48 range  of  cylinder  The.heated probe  meter was  cylinder  diameter  vernier  stage  micrograph  along of  2.2.12  as  Figure  using  The  and  the  by  and  error  immediately was  e d g e was  tivity were a  of of  with  this the  the  any  a  second  system both  was  cutoff,  up  to  produced 1000  x  and  as  image  micro-  The a  a  diameter photo(12).  of  the  System study  the  slide beam. be  of  and  white be  size.  in edge  were  determined  fluid  only  The  The  second  one  knife  amount and  of  the  variable.  vertical  and  shown  the  lens  and  knife  varied  easily  a  source  as  the  was  cylinder.  clearest  could  full  the  Figure  orientation  could  the  this  width,  light  black  both  midpoint  arranged  horizontal  horizontal  vertical  scale  was  therefore  but  in  edges  and  cutoff  system  image  used  clear  the  The  and  Schlieren  horizontal  deflect  as  C ) .  using  and  length  from  deg  (12).  locations  shown  and  slit  a  the  schlieren  The at  to  made w i t h  color  edge  200  (12).  knife  give  on  is  Figure  spacing  to  to  microscope.  assumed  system  surrounding  used  ference  lens  (0.  Figure  cylinder  system  The  mounted  four  Equipment  knife  spacing, trial  was in  in  another  vertical  cutoffs.  in  surface  schlieren  (14).  shown  heated  length  studied  power m i c r o s c o p e  on  probe  Photographic  schlieren  low  indicated  system  cutoff  a  the  the  The  is  measured on  cylinder  supports  used  adjustment  uniform  type  was  eyepiece  Heated  temperatures  sensiTests  cutoffs  images  inter-  and  were  with obtained  system.  projected  on  a  screen  A l l s t i l l  photographs  were the  taken film  shutter ient  plane speed  to give  given  clear  prism  filming  possible  the  shutter.  ing  speed  had  a built-in  roll  because  timing  camera.  lag  b u t t h e t i m i n g marks motion were  1/1000  to film taken  were  sec.  provided  viewing  a t 5000 p p s .  HYCAM.  c a m e r a was filming  voltage.  a pulse  capable  speed  and  had an  as film-  The camera  on t h e f i l m  contained  t i m i n g marks  an easy  speed.  pro-  p r i s m was u s e d  by a s e l f  T h e HYCAM  suffic-  by  by a d.c. motor  marks  study  was  of a  large  of applied  which  Maximum  taken  plane  16 s i d e d  on  p a t t e r n a t any  also  This  i s driven  and f o r t h e p r e s e n t every  s e c and t h i s  T h e HYCAM  pps.  directly  35mm c a m e r a .  on t h e f i l m  was t r i g g e r e d  film  project  movies  light  image  o f the flow  i s a direct'function  the  actual  1/1000  a rotating  The camera  The l i g h t  generator  speed  a t up t o 10,000  was  margin.  was  directly  16mm  field  Spotmatic  indication  High  t h e image  rotating  the flow  o f a Pentax available  instant.  jecting  of  by p r o j e c t i n g  were  signal p u t on  acceleration  reference to relate  A l l films  taken  f o r this  3.  3.1  I n i t i a l Preparation The  the  loop  tested  components  filled  entire  apparatus  t h e main  The  components  plastic  bags.  solutions  was  a pressure  with and  liquid filled  compressed  pump w a s d e g r e a s e d  under  t o any data 4 psia  were  a i r was  under  flow  loop.  This  the c r i t i c a l value  using  i n sealed  trichlor  with  a n d t h e pump  The flow  loop with  contamination. the flow  The system dioxide.  into  loop  The f r e e  the other  fillings evacuated piston  dioxide,  side o f the pis-  forced  loop  so t h e pressure  evacuated  was a g a i n  by t h e carbon  the flow  was  by repeated  o f the accumulators raised  The  shop.  plating  c o n d i t i o n s and f i l l e d  extended  introduced  was  except  plating  i n place  stream.  and purged  carbon  fully  ethylene  runs  dioxide.  liquid  tightened.  and r e t u r n e d  dioxide  sterile  pressure  Pressure  as f o r chromium  The main  a carbon  was  and a l l components  solution  and t h e c o n t e n t s  main  psia.  Apparatus  assembled and  The loop  trichlor  carbon  accumulators  ton  degreased  below  with  were  t o a commercial  d i o x i d e gas t o prevent Prior  to  taken  o f a l c o h o l and c o o l  reassembled  loop  up t o 2000  was d i s a s s e m b l e d  flushed with  carbon  o f the flow  of the  and l e a k i n g f i t t i n g s  pump w e r e  hot ethylene  and C a l i b r a t i o n  pressures  were  PROCEDURE  d i s t i l l e d water.  at intervals  for  body  with  at various  released  a  EXPERIMENTAL  into the  pressure  would  to just  be b l o c k e d i n  51 the  main  flow  with  liquid  loop  and  flow to  repeating  loop  could  psia.  exchangers the  flow  loop  accumulators with  a  vary  the  sterile  would heat  be  allowing  oil  would  could method  be  the  left  vicinity  but  heat  flow a  out  the  from  carbon  that  of  solution  the  the  to  from  the  source which  critical  on  under  found  changing  that  a  The  dioxide This  o i l was  each  the  i n the  was  after  system.  It  o i l in solution  was  the  and  re-  was that  organic solvent  leaching  the  fitting  tubing.  carbon  used  i  the o i l  opening  the  t o be  This o i l  greatly  solid  i s a powerful point,  dioxide.  assembled  found  and  easily  tubing exterior.  noted of  to  carbon  slightly  i n the  through  dioxide  piston,  o i l was  probe  up  The  dioxide.  solidify  dissolved  o i l was  been  carbon  by  pressure  carbon  the  of  main  circulated  of  flow  a l l heat  releasing  I t was  system  dioxide  removed  dioxide, the  the  was  a i r behind  characteristics.  and  i n the  test  f i l l  flow  pressure i n the  full  heated  The  compression.  l o o p had  to  equalize  pressure  fluid  s m a l l amount  on  to  procedure  of  allowed  tanks.  required  nearly  supercritical  o r whenever  of  very  the  any  the  supply  the  pressure without  removing  carbon  and the  degreased  easily  found  to  again  allowed  filling  compressed  come o u t  of  assembly later  were  removed  and  the  to build  up  on  remove  precipitate  could  from  procedure  the  fully  i n the  transfer  the built  conditions  solution  used  to  system  accumulators  p r e s s u r e was  During  cushion of  The  in  be  were  the  dioxide  a i r again  By  1500  carbon  accumulator  compressed loop.  l o o p and  o i l out  in of  the  52 the  micarta  supply  wires.  installed changed the  probe  in  to  support small  When the  the  test  solid  micarta  support  amounts  periods  of  of  time  rod  the  the  o i l s t i l l but  power  probe  was  supply  wires  with  Teflon  spaggetti  replaced  i n s u l a t i o n was  Inc.  the  power  covered  was  i n s u l a t i o n on  Thermo-systems  section,  support  (electrical  from  proper  copper  probe  and  with  not  appeared  an  the  the  Very  system  were  removed  by  the  initial  preparation  and  aluminum  necessary).  in  were  method  over  long  described  above. As  part  of  the  optical  and  o r i e n t a t i o n of  were on  found  the  by  sharply checking  the  the  that  slit  that  the  test  section  schlieren  the and  plane  was of was  lens  light  screen.  The  optical  bench  that  the  varied so  that  slit  second by  lens.  moving  more  of  completely  the the  aligned.  edges  schlieren focal  entering and  and  the  resulted, i n  came a  was  edge,  located  therefore  so  that  slit  the  into  was  plane of  the to  use.  shadowgraph  image  on  the  focal  system the  type  optical  of  on  the  point  could  Removing  the  the  positioned  of  the  ensuring  second  sharp  >  then  The  a  of  located  horizontal.  perpendicular  cutoff  consisted  through  sensitivity  slit  was  obtained  path  obtain  in  knife  was  optical  cutoff  i t was The  lens  point  to  procedure  cutoff  size  Schlieren  image  source  apparatus •  proper  the  best  filament  first  the  The  in  the  alignment  the  second  used  until  the  located  viewing  of  of  collimated  was  so  The  of  the  and  error  first  at  up  knife  image  the  beam  set  screen.  that on  was  trial  viewing  ensuring  cutoff  bench  of  be  axis  the  optical  second  set-up flow  which  teardown  was of  carried  the  components  light.  The  filled  with  to  minimize  in  the  initial  initial  the  author.  were  diameter  an was  heated  cylinders  a  slight  carbon  hot  of  the  ture  every  above at  the  major  i n the  large  with  refraction  stretched on  an  first  amount  the  set  of  optical  path  the  critical  the  various surfaces  could not  be  same  change  differences  across  of  two  used  point,  being  low,  500  the flow  rods  power  this  only  lower  supplies be  Nichrome  i n probe  i n steps  near  nichrome  non-linear, coefficient resulted  by  which  fields  could not  requirement.  do  cylinder  diameter  resulting  the  to  Although  the  nichrome  temperature variable  the  this  diameter  support  Larger  with  than  of  at  great  manufactured  0.00 3 i n c h  g r e a t e r than  because  having  decided  probe  micarta base.  resistance the  i t was  copper  difficult.  other  with  of  was  cylinder  cylinder  compatible  that  work  interpretation  was  not  disadvantage  heated  consisted  ratio  s m a l l and  cylinder  manufacturer  stable  insulating  aspect  this  a  probe  a heated  probe  Materials  resistance  a  into  initial  change  of  dioxide,  This  after  out  experimental  available.  the  loss  carried  of  film  were  of  the  insight  path.  resistances  because  was  effects  This  wire  has  as  work w i t h  mounted  probe  apparatus  i n producing  the  nichrome  check  the  stage  screen.  a  liquid any  the as  c o u l d cause  optical  difficulty  on  more  out  alignment  As  the  i n s t a n c e s gave  patterns appearing  alignment  of  i n some  larger  used had of  temperathan  5  54 deg.F  and  raised  some q u e s t i o n  ature.  Even  so,the  initial  data  runs  requirements pressure  and  air as  be  a l l data  obtained  side a  of  the  were  determine  the and  limits i n the  actual very  the of  wire  temper-  valuable  heat  in  exchanger  temperature  development  and  of  techniques.  system .pressure  could  probes  to  possible,  During the  designed positions,  control  photographic  nichrome  about  the  cushion  as  by  runs  i t was  the found  varying only  accumulators.  to  absorb  small  accumulators that  the  The  good  were  pressure  pressure  on  accumulators  volume  changes  open  the  control compressed  also,  i n the  to  acted  main  system. Steady were  defined  and  a bulk  any  data  30  psia  a  pressure  Except  temperature  state and  5  deg  F  of  and  full  allowable  of- d a t a is  so  i s due close  taking  described  of  of  critical  ±0.5  one  por.it  to  to  the  the  widely  critical  to minimize  below.  these  range  variable point. bulk  ±2  deg of  hour  was  The  during  maintain  more state  one-half used.  fluid  within con-  hour  This  properties  devised  condition  '  :  the  or  steady  work  psia  F  possible to  possible for approximately temperature  than  vicinity  i t was of  experimental  more  than  immediate  pressure  the  not  less  conditions for periods  only  states  change  and  were  difficulty  change  i n the  ditions the  conditions for this  temperature  run.  critical steady  as  state  at  manner  fluctuations  Bulk the  flow  fluid  dioxide heat  Steady  state  required  walls in  study  that  clumps  give  differences from  mate when was  3.2  temperature  0.5  Procedure  deg F  Following property fluid  situations  the standard i t was  a t the required bulk  by  heat  it  was  exchangers found  that  adjacent this  from  was  used  obserto  required thermoorganized  schlieren  temperature  i t was  resulting  possible to  i n the flowing  estifluid  temperature.  Measurements techniques  used  i n constant  originally  intended  temperature  and p r e s s u r e  to the test  procedure  the  used  of light  fluid  was  system  be no w e l l  At best  distribution  Convection  which  I t was  of the  difference  rates to  b y t h e two  the shading  of the bulk  i n Free  cylinder  and t h e r e  picture  runs  for sensitivity  i n the flow.  temperature  directly  as i n d i c a t e d  a qualitative  loop.  flow  flow  of the flow.  be u n i f o r m  fluid  water t o  As t h e s c h l i e r e n  the unheated  the temperature  within  fluid  past  b u t by o b s e r v i n g  a known  a uniform  adjustable  i n the flow  systems  cooled  quality  varying  data  the water  easily  the thermal  of colder  between  exchangers.  was  the f l u i d  couples  counter-flow  by  located i n the flow  t o produce  o f unmixed  o f the flow  determine  balance  exchangers  of the heat  vation  controlled  conditions f o r forced convection  clumps  this  exchangers  a delicate  heat  without  was  r a t e t o any o f t h e t h r e e  carbon  these  temperature  to hold the  section.  resulted  i n large  condition However, measurement  errors  because  regions test  o r g a n i z e d clumps  o f the heat  section  exchangers  greatly I n some  a  i n the monitored  variation  heated These only  probe  would  5 t o 10 d e g F  temperature.  observed the  fluid  free  bulk  and p a s s i n g  i n the entire  was  found  that  heat  would  the entire  temperature. current 77 deg  F  could  and a w e l l  oscillate  operating  l o o p was  that  fluid  heat  result  with  bulk  a two m i n u t e a clump  of the test transfer  control  results  was t o  bulk  fluid  i n large temperature  of  o f 80.5  by t h e  probe  a t t h e same  period.  The  of fluid  a t room  chamber w o u l d both  until  temperature, i t  dissipated  over  control  exchanger  a room  amps  to  as m i x i n g t h e  temperature  t o 0.48  break-  easily  temperature  would  the current  more h e a t  fluid  be  to the desired  resistance  the side  fluid  attempts  and c o n s i s t e n t  f o r example, mixed  could  at a uniform  amps  and cause  from t h e  the bulk  many  of bulk  t o do t h i s  r e a d i n g s o c c u r r e d when  probe  be t o i n d u c e  exchanger  techniques  0.35  from  flow  and t h e subsequent  from  temperature the  found  than  an e x t e r n a l  and apparatus  Failure  i t was  current  room  would  the heat  After  by such  reproducible  fluctuations;  deg F  screen.  t h e o n l y method  yield  convection  convection flow  i t through  fluid  through the  dissipation  or colder of fluid  temperature  the  which  occur with  The clumps  on t h e v i e w i n g  fluid  circulate  the free  power  the near-wall  as 75% o f t h e u n d i s t u r b e d r e a d i n g .  hotter  down o f t h e o r d e r e d  from  instances the effect  o f a s much  differences  would  affecting  patterns.  of fluid  by i t s  larger  sink  past  motion  1  and  by t h e l a r g e r  and  the heated  in  this  work  fluid  equal  noted  that  clumps for  the  probe.  clumps  near  by  t h e pump  here  data  runs  exchangers then  fluid to  taken  t h e pump  A l l free  a minimum  to  circulate  had been  shut  on t h e s e c t i o n s o f  and c o n t i n u e d  to circulate motion  convection data  o f 1/2 h o u r  standardized procedure  caused  runs  after the  filled  operated  with  fluid  circulated  water  i n the heat  the  proper  the fluid  Final  out during this  T h e pump  and t o heat t h e  p r e s s u r e and t h e  apparatus,  including the  was a t t h e r e q u i r e d allowed  and p r e s s u r e u n t i l adjustments time  and the heat  T h e p r e s s u r e was a d j u s t e d  and t h e apparatus  temperature  the laboratory  closed.  the desired  the entire  convection  temperature  and b l o c k e d  above  exchangers,  Initially  fluid  temperature.  until  pump w a s s t o p p e d  carried  water  10 p s i a  The  had passed.  bulk  to circulate  to the required  f o ra l l free  developed.  to the required  approximately  hour  continue  formed  also  temperature  any o r g a n i z e d f l u i d  out.  was e v e n t u a l l y  raised  was  were  after  probably  after  would  o f the bulk  I t was  a t room  reported  shutdown. A  was  well  had died  fluid  fluid  t h e warm b e a r i n g s  odd i n t e r v a l s  reported  mixed  t h e clump  runs  temperature  temperature.  15 m i n u t e s  were  between  convection data  the bulk  density  o f about  at  pump  with well  of different  pump  with  t o t h e environment even  There  differential  A l l free  are taken  a period  off.  temperature  temperature.  t o stand a t  at least  of less  than  by v e n t i n g compressed  one  5 psia air  half were from  58  the accumulators.  The Thermo-System power supply had been on ;  in the standby mode at least one hour before the test was to begin to allow the components to reach operating temperature. It had been noted that i n i t i a l s h i f t s observed i n the probe cold resistance were due to shifts in the power supply.  in the decade  resistances  The probe cold resistance was checked  using the b u i l t - i n c i r c u i t i n the power supply.  An overheat  of approximately 10% was set on the resistance decade and the probe turned on.  The balance of the wheatstone bridge  was adjusted using the n u l l meter i n t e g r a l with the power supply and the feedback c i r c u i t tuned for maximum frequency response by adjusting the variable capacitance i n the power supply.  The power supply was returned to the standby position  and the cold resistance checked again.  Assuming that the two '  determinations of cold resistance agreed, the power supply resistance decade was set to an overheat of 0.01 ohms and the power supplied to the probe.  The n u l l balance was adjusted  so that the current indicated by the panel meter was just that required to keep the heated cylinder at the resistance on the resistance decade.  selected  The probe operating resistance,  current, the output voltage of the bridge, and the rms voltage fluctuation level, were a l l recorded for each data point. The temperature of the bulk was monitored continuously on the galvanometer.  The system bulk pressure was checked to ensure  that i t did not vary by more than +2 psia during the data run. The probe overheat was increased i n 0.01 ohm steps (correspond-  59 i n g t o a p p r o x i m a t e l y 2 deg F  probe temperature s t e p s ) and  the b r i d g e b a l a n c e checked and a d j u s t e d a t each d a t a p o i n t . I f a 0.01 ohm o v e r h e a t change d i d n o t r e s u l t i n a d i s c e r n a b l e change i n probe c u r r e n t l a r g e r s t e p s were used. r a t i o was i n c r e a s e d u n t i l t h e maximum p e r m i s s i b l e  The o v e r h e a t probe  temperature t o p r e v e n t probe damage (400 deg F) was reached. A d d i t i o n a l d a t a p o i n t s were then t a k e n i n random o r d e r t h r o u g h out t h e range p r e v i o u s l y covered as a r e p r o d u c i b i l i t y  check.  Photographs were t a k e n a t o p e r a t i n g p o i n t s o f i n t e r e s t and the d a t a was a l s o i n c l u d e d " f o r these o p e r a t i n g c o n d i t i o n s . A computer program was w r i t t e n t o o b t a i n heat t r a n s f e r r a t e , heat t r a n s f e r c o e f f i c i e n t , and temperature d i f f e r e n c e d i r e c t l y from t h e raw d a t a o f o v e r h e a t r a t i o and probe c u r r e n t .  Both t a b u l a t e d and p l o t t e d r e s u l t s o f heat  t r a n s f e r r a t e and heat t r a n s f e r c o e f f i c i e n t vs temperature d i f f e r e n c e were o b t a i n e d d i r e c t l y .  3.3  Procedure I n F o r c e d C o n v e c t i o n Measurements An e x p e r i m e n t a l t e c h n i q u e , d e s i g n e d t o m i n i m i z e ex-  p e r i m e n t a l e r r o r s , was a l s o developed f o r t h e f o r c e d c o n v e c t i o n data runs.  F l u i d b u l k p r e s s u r e was a d j u s t e d t o s l i g h t l y under  the r e q u i r e d t e s t p r e s s u r e , t h e pump was s t a r t e d and t h e f l o w r a t e through t h e t e s t s e c t i o n a d j u s t e d t o t h e d e s i r e d v a l u e . The heat exchangers were a d j u s t e d u n t i l t h e b u l k f l u i d was b e i n g v e r y s l o w l y heated  ( l e s s than 1 deg F p e r hour) and t h e  loop allowed t o s t a b i l i z e .  M i n o r c o r r e c t i o n s were made t o b u l k  pressure 5%  bulk  fluid  the test  Data  was  just  over  taken  5 psia)  and t o t h e flow  pressure).  temperature  value  A  and t h e probe  until  the bulk  typical  s a y 80.5 d e g F  temperature  The l o o p  reached  the required value  increased. of  than  of differential  the of  (less  data  would  reached  slightly  when  80.5  d e g F.  The b u l k  temperature  data  would  deg  F.  would In 0.5  The b u l k be t a k e n  some d a t a deg F  first  during  cylinder points  steps  during  i n either a data  a data bulk  run.  steps,  and f i n a l l y  run.  No  cold  rise  i n decreasing  or differential  allowed  during  a data  run.  Flow  fields  Photographs  were  taken  taken  then i n  order.  was than  were during  Data  i n bulk  d i s c e r n a b l e change  greater  by  p o i n t s were  variation  and no v a r i a t i o n  runs.  only  i n random  points  data  80.2 d e g F .  then  resistance  80.9  reached  steps,  data  all  reached  and  and the data  Data  the entire  pressure  Probe  run.  to rise  t o drop  would  temperature  temperature  shown t h e r e f o r e c o v e r  allowed during  cylinder  cylinder  data  flow  reached  continue  temperature  temperature  the entire  temperature  temperature  10  the bulk  i n increasing  decreasing  the bulk  temperature  begin  rate  fluid  exchanger  temperature  would  flow  temperature  the bulk  would  the bulk  temperature  until  runs  the bulk  limit  checked.  bulk  and t h e heat  modified  until  lower  exchanger  run at a design when  than  had increased t o  and the heat  be s t a r t e d  until  operated  resistance  temperature  rate  be t a k e n  was  (less  the allowable  cold  80.0 d e g F  rate  was  pressure  checked 0.005  every  ohm  monitored some  data  was during runs  and  special  graphs. graphs A  duplicate data  In a l l cases have  typical  been  data  0.05 ohms  temperature over  runs  r u n would  data  extending  were  consist  o f 0.02 ohms  was r e a c h e d  runs  data  over were  completely  runs  at least  f o rother  during  photo-  the  photo-  on t h e o r i g i n a l  o f 20 s t e p s  t h e maximum  range  presented one hour.  points  taken  order. A l l  are continuous Typical  data  forced  d u p l i c a t e d on s u c c e s s i v e days reproducible.  steps  cylinder  30 d a t a  i n random  data.  o f 0.01 ohms'  (4 t o 5 d e g F ) , 20  and a f u r t h e r  temperature  convection  convection  obtained  (10-12 d e g F) u n t i l  the entire  forced  the data  w e r e made  i n c l u d e d as a check  (2 d e g F ) , 30 s t e p s of  runs  and t h e  62  EXPERIMENTAL  4.1  Effect  of Free-stream  Typical of  the  heated  rized  and  cylinder  with  heated  bulk  (26).  have  venience,  been  both  between  are graphically  above  states,  summa-  free-stream fluid  number  properties  temperature,  cover  a  variety  convection  purposes.  i s expressed  were  and below t h e  and f r e e  f o r comparison  constant property Reynolds  constant  difference  Results presented  free-stream velocity  equivalent  transfer  the pseudo-critical  temperatures  included  effects  The m a j o r i t y o f r e s u l t s  below  temperature.  fluid  the  and heat  of temperature  s u p e r c r i t i c a l thermodynamic  studies  the  fluid  illustrating  transfer  and t h e b u l k  cylinder  pseudo-critical of  on heat  as a f u n c t i o n  i n F i g u r e s (15) t o  obtained  Velocity  experimental results  free-stream velocity  coefficient  RESULTS  F o r con-  i n terms  o f an  (Re*) b a s e d  and t h e  on  cylinder  diameter. Figures fluid of  with  a bulk  1100 p s i a  whenever fluid  shows  near  the heat  which  cylinder  and have  effects in  o f 80 d e g F a n d b u l k  difference  the heated  tested  a peak,  the velocity  (supercritical liquid-like  temperature  velocities  ( 1 6 ) show  temperature  the temperature  very  critical  (15) a n d  i s above will  vapor-like  transfer  i s slightly  region).  be  Note  that  10 d e g F t h e above  the pseudo-  properties.  coefficient  velocity  pressure  Fora l l  ( F i g . 16)  dependent  i n both  magnitude exceeds  the  slightly higher width  and  shifts  and  the  though  heat  Further  the  behaviour,  At  increase  in  free-stream  the  approach  The  the of  fluid  lent  plume  flow  with flow  changes  and  field  At  over  causes  larger  coeffic  definite  remains  a  and  difference the  free-stream  velocity  ordered  free  velocity.  less  of  an  temperature  for various  i n columns  of  even  due  to  a very density  shown  in Figure  (36).  the  small  effect  the  circulating  pump.  resulting  (35) . T h e  Re*  of  photographs with  a  hotter  fluid  to  turbu-  of  shown due  this The  velocity  gradients  field  series  field  velocity.  small  i n the  from  flow  breakdown  Also  flow  field  illustrated  Figure  progressive  on  flow  free convection  rising the  are  increasing free-stream  circulation  the  small  i n the  of  are  by  very  changes  photographs  well  this  temperature  transfer coefficients  velocity  schlieren  transfer  shows  increased  a  values.  marked  free-stream  given  transfer rate.  heat  constant  a  to  effective  transfer rate  i s sharply  even  velocity  increasing velocity  any  by  differences  by  heat  peak  the  heat  coefficient  just  Increasing  increases improved  value  i n heat  the  the  the  difference.  improvement  sheet  of  and  film  transfer rate  convection  c y l i n d e r temperature  transfer coefficient  i n c r e a s i n g f u n c t i o n of  temperature  show  heat  maximum v a l u e  Even  smoothly  the  p s e u d o - c r i t i c a l temperature.  non-constant  of  when  c y l i n d e r temperature  ient.  the  position,  in Figure to  well  ordered  effects  such  i n the  a  as  test (36)  vibration  hot  on  caused section is induced  64 (17)  Figures velocity  when  the bulk  pseudo-critical the  heat  maximum the  fluid  illustrate  temperature A t 87  temperature.  transfer when  (18)  and  pseudo-critical  temperature  temperature.  attained  temperature  of 8 0 deg F but the heat  remains ature  difference  same a p p e a r a n c e resemble between is  to  break  ature  f o r either  the well  and even  down  i s raised  temperature  and  bulk  (20)  pressure deg F  transfer  rate  i s almost  difference  of velocity  The h e a t  of increasing fields  temper-  have t h e  and  strongly  convection  disturbance  when  convection  the bulk  (just over psia).  the  rate  flow  pattern  (36)) . of velocity  fluid  temper-  pseudo-critical  Now  a decrease  patterns *  i n the test  show t h e e f f e c t s  transfer  rate  ( 3 5 ) . The d i s t i n c t i o n  f o r any v e l o c i t y  on heat  bulk  transfer  shown i n F i g u r e  f o r 1100  deg F  transfer a  the free  c o e f f i c i e n t shows o n l y  temperature ence  (19)  heat  above  with  and f o r c e d  to that  velocity-influenced  temperature  thermal  t o cause  t o 91  o f 90  free  less  (similar  psia  bulk  psia  than  The f l o w  of Figure  ordered  i s required  a t 1100  transfer  larger  function  and v e l o c i t y .  Figures also  increasing  the photographs  retained  section  slightly  of  under the  i s slightly  f o r a l l v e l o c i t i e s tested.  a smoothly  a  The peak  coefficient  identical  was  i s just  d e g F a n d 1100  coefficient exhibits  the cylinder  the effects  the heat  with  tested.  increasing The  influ-  i s n o t as s t r o n g  as  65 with any  lower  bulk  typical  half  that  temperature  temperature  observed  with  the  same b u l k  the  pseudo-critical  and t h e heat  difference  a n d Re*  fluid  4 deg F c o o l e r  pressure.  only  The e n t i r e  temperature  properties  but the q u a l i t a t i v e  the  Relatively  same.  property' v a r i a t i o n s the  cylinder  appear not  strong  s t i l l  to the bulk  but.the  The heat  but the dependence  difference  i s not nearly  vapor-like  the heated  fields i s  flow  on v e l o c i t y  a  and  near  patterns fluid  i s again  velocity  standards)  fluid  h o t and c o l d  i s  smoothly  temperature  and  as s t r o n g as w i t h  order  t o i s o l a t e whether  coefficient  were  temperature  a series  of data  pressures.  Figures  (21,) a n d  heat  temperature  the l i q u i d - l i k e  transfer  connected  rate  with  t h e peaks  the c r i t i c a l  runs  was  and f i l m  '  a bulk  heat  transfer  coefficient i s velocity  when  the cylinder  critical  temperature  transfer  increased  temperature  pseudo-critical  at other  o f 8 0 deg F.  just  f o r 1300 p s i a  c o e f f i c i e n t occurs  pressure  or  transfer  bulk of velocity  coefficient for fluid  and w i t h  temperature  done  i n heat  (22) show t h e e f f e c t s  psia  heat  i s above  property  a n d t h e same  of increasing  and a t  of the flow  rate  than  fluid. In  on  from  transfer  difference  fluid  (by c o n s t a n t  fluid  function  bulk  nature  exist  increasing  bulk  rate f o r  i s less  and t h e r e f o r e  d i s t i n c t i o n between  as marked.  transfer  but the heat  The  influenced  exceeds  a broader  transfer  peak  and  appears  the pseudo-  (105 d e g F ) .  over  a t 1300  rate  The range  remains  peak at this a  smoothly  increasing  difference. 1300 deg  psia F  rate  as  Similar  when  the  shown  remains  velocity  a  and  just  forced  the  with  convection  increased  by  The  series  the  free  induced  very  shown  similar  the  and  fluid  in Figures  psia  bulk  pressure  1300  psia  bulk  pressure.  cases  hotter The  vertical  spacing  cylinder it  consists  and  (21)  86  The  cylinder  temperature.  very  free  (36-A)  (22).  The  a  fluid  illustrates  and  change  bulk  flow  fields  cylinder bulk  fields  at  those  at  to  flow  field  divided  turbulent  cylinder  bulk  fluid.  warmer  flow  similar  t u r b u l e n t plume  by  the  f o r the  identical  heated  increasing  but  very  strongly  convection  to  are  characteristic  (24).  rise  affected  the  The  also  increasing  F,  velocity  by  transfer  colder bulk  Figure  86  transfer  i s more  the  to  heat  rates  deg  of  heat  and  which  slightly  the  i n the  columns  with  The  velocities  of  the  is raised  transfer  and  sheet  decreases  i s only  as  a  between  of  are  pressure  p e a k when  i n the  produced  (23)  and  rate  shown  free-stream  bulk  f u n c t i o n of  or  free-stream  1100  all  80  field  those  temperature shown  at  in Figures to  heat  velocity  flow  temperature  pseudo-critical  transfer  photographs  varying  conditions are  heat  convection by  sharp  the  fluid  increasing  of  a  a  (24) .  difference  convection  bulk  and  increasing  exceeds  the  at  and  temperature  (23)  exhibits  free  velocity  occur  fluid  temperature  temperature  similar  bulk  smoothly  s t i l l  that  trends  in Figures  coefficient  Note  f u n c t i o n of  the  in  into  plume.  heated  temperature,  temperature  and  pres-  sure  changes  intensity the  i n the s u p e r c r i t i c a l f l u i d .  of the v e r t i c a l  nearness  of the bulk  critical  temperature.  and  distinct  more  pseudo-critical show  fluid  as t h e b u l k  temperature.  bulk  temperature  states.  definite  fluid.  The  of f l u i d from  i s a complicated function  ature,  system  seem  t o be d e p e n d e n t  further  smoothly  by  rate  and h e a t  on  the  difference  approachfree-  of the heated and b u l k The  (25) a n d increasing  but the  horizon-  temperature.  s h a l l o w p e a k when the pseudo-critical  on  c o e f f i c i e n t as a  transfer  of increasing  The h e a t  vertical'  of velocity  are included  The h e a t  function  difference.  a broad exceeds  (26).  temper-  roughly to  cylinder  the e f f e c t s  transfer  at  for a  o f 80 d e g F a n d a b u l k p r e s s u r e o f 1 5 0 0  temperature shows  torn  increasing  vortex analysis,  comparison,  of temperature  Figures  at different  corresponds  variations  temperature  just  layers  Karmen  function  increasing  of cylinder  from  transfer  to  and o r i e n t a t i o n  indicated  heat  a  the heated  the  convection flows  p r e s s u r e and t h e f r e e - s t r e a m Re*.  between  For  in  shape  to  together  approaches  cylinder  i n t e r v a l decreases with The  closer  velocity  the heated  layers  tal  due  related  to the pseudo-  are repeatedly  velocity.  that  forced  effects  stream  spacing  become  temperature The  s p a c i n g and  t o be  temperature  and i n c r e a s i n g  Sheets  intervals  appears  The columns  q u a l i t a t i v e l y t h e same  cylinder  ing  columns  The  transfer  rate  bulk  psia  i s  s t i l l  velocity  and  coefficient  the cylinder temperature.  s t i l l  temperature The  free  convection only to  heat  slightly  transfer  increased  1300 t o 1500 p s i a .  rate The  i s strongly effect  of increasing  and  (36-B).  all  s u p e r c r i t i c a l flow  will  show  increase  temperature the both  bulk  fluid  below  the  fluid  i s  with  near  beyond  velocity. with  The i n f l u e n c e  on t h e f i l m  convection  increasing  When t h e i s above  with  decrease  pressure  the c r i t i c a l  any sharp through  change as  t h e pseudo-  of the pseudo-critical  increasing  i n heat  i s small  fluid  coefficient  coefficient i s not discernable  but increases  The i n i t i a l  passes  When  transfer  vapor-like  pressure  temperature  the cylinder  cylinder  transfer  cylinder  on  i sto  pressure.  (therefore  d o n o t show  effect  the heat  the heat  the  free  ( 3 5 ) , (36-A)  the cylinder are  and t h e h e a t e d  temperature  increasing  near  temperature  fields  temperature  fields i s  temperature.  the c r i t i c a l  liquid-like  temperature.  pressures.  pressure  the pseudo-critical  The f l o w  critical  transfer  ( 1 6 ) , (22) a n d (26)  c o e f f i c i e n t when  fluid  1100  i s evident.  of Figures  pressure. heated  bulk  of Figures  of increasing  to the cylinder)  increases  heat  on t h e f l o w  examined  and t h e heated  pseudo-critical  adjacent  fields  transfer  i s highest  from  similarity of the velocity  the pseudo-critical  coefficient bulk  velocity  comparison  i s above  increase  by t h e d i f f e r e n t  the effect  the heat  a t 80 d e g F i s  convection  comparison  The s t r o n g  that  fluid  by t h e p r e s s u r e  affected  detailed  i n bulk  The f o r c e d  shown b y a q u a l i t i t i v e  A  rate  free-stream  transfer  and does  i n  coefficient  n o t appear t o  69 affect Re*  the o v e r a l l  heat  tested.  The f a c t  like  fluid  i s increased  when  the f l u i d  vapor-like heat the  heated  The  secondary  and  appears  heat  indicated  the heated  The  of Bulk effects  fer  rate  and h e a t  are  graphically  temperature rate  uniform,  comparison  ature psia  variation f o r a Re*  decrease fluid  dispersion  the l i q u i d - l i k e  of  free-stream.  i s velocity  dependent  t o 20,000 c p s )  i n the high  speed  zone  has  motion  been  (36-B).  -  temperature  variation  on h e a t  transfer  coefficient  i n forced  convection  i n Figures  cause  f o r the free This  effect  from  very  convection  minor case  c a n be n o t e d  (28) show  (32).  heat in  by a  the effect  80 t o 105 d e g F  o f 300.  f o r a given  only  (27) t o  trans-  Bulk  transfer  s t i l l , detailed  ( 1 5 ) , ( 1 7 ) , and ( 1 9 ) .  (27) a n d  temperature  convection  of bulk  of Figures  Figures  only  i s i n the  by t h e r a p i d  (5,000  liquid-  Temperature  summarized  fluid.  in  increase  the forced  oscillating cylinder  rate  cylinder  mechanism  (35) a n d  variations  variations  at the highest  transfer  of the o s c i l l a t i n g  i n Figures  Effect  into  transfer  The e x t e n t  that  i s aided  as a r a p i d l y  behind  the heated  fluid  even  by a v e l o c i t y  suggests  mechanism  rate  the heat  more  near  vapor-like  pictures.  4.2  that  condition,  transfer  region  very  transfer  The h e a t  temperature  just  exceeds  i n bulk  transfer  of bulk fluid  rate  difference  temper-  a t 1100  shows a  when  large  the bulk  the pseudo-critical  temperature  and  the free  temperature less deg  than F  stream  fluid  difference  5%  the heat  f o r a bulk  (liquid-like  like  free-stream fluid).  and  i n the vapor-like rate  86 d e g F )  when  temperature  by  the cylinder  temperature. like  fluid  peak  value with  bulk  temperature  A  increase  further  transfer  exceeds  shows  increasing  the  i s raised  i s very nearly  independent  50%  deg F  the heat  shows  a maximum  i n the vaporfrom  the heat of  by  (a v a p o r -  the  difference.  t o 105 d e g F  t o 86  f r e e - s t r e a m (80  a decrease  temperature  by  pseduocritical  coefficient  only  80  t o 105  decreases  coefficient  transfer  a t 90 d e g F  coefficient  t o 90 d e g F  temperature  The h e a t  from  but decreases  For the l i q u i d - l i k e  the heat  changes  i s raised  region) only  10%.  A t any g i v e n  rate  increase  free-stream fluid)  the bulk  transfer  transfer  temperature  when  (also  becomes v a p o r - l i k e .  initial  When t h e  transfer  temperature  difference. The Re*  i s even  Figure  that  (30)  more  rate  clearly  fluid  very clearly  cylinder ature.  with  shows  shown  The h e a t  the bulk  t h e peak  just  heat  (40 t o 50%) temperature  coefficient  region.  i s raised Figure  coefficient  when t h e  the pseudo-critical again  a maximum v a l u e w h e n  i s i n the vapor-like  i n heat  region.  transfer  free-stream fluid exceeds  at a higher  (29) a n d ( 3 0 ) .  i s i n the vapor-like  transfer  from  variation  i n Figures  decrease  when  liquid-like  temperature  deterioration  temperature  the sharp  occurring  the bulk  occurring  fluid  of bulk  (29) s h o w s  transfer so  effect  shows  only  tempera  the bulk free-stream  71 Figures bulk  temperature  coefficient of  1300  (31) a n d  variation  i n forced  psia.  The  fluid  like  region  psia  i s approximately  in  heat  be  noted  deg by  transfer  f o r 1300  psia.  temperature  the  by t h e f a c t  fluid  bulk  layers  with  bulk  that  the bulk  and p r o p e r t y  fluid  can  increasing  the  pseudo-critical  rate  a t 105 i s aided  fluid  i s very  but i s  nearly i n  through  as w i t h  bulk  occurs  pressure  variations  a r e n o t as s t r o n g  liquid-  (32) s h o w s t h e  transfer  psia  pressure  decrease  coefficient  exceeds  The h e a t  film  temperature  Figure  of  f o r 1300  gradual  conductivity of the bulk  vapor-like state  heated  A more  just  and  i n the  temperature  transfer  a n d 1300  rate  i s s t i l l  coefficient  heat  the effect  but f o r a bulk  increasing  temperature  the large thermal  decreased  (Re*=600)  105 d e g F .  and t h e peak  the cylinder  F bulk  transfer  increased pressure.  i n heat  temperature  summarize  i n a l l cases  rate with  at this  temperature when  on heat  as t h e p s e u d o - c r i t i c a l  transfer  variation  flow  (32) a l s o  the  colder  bulk  fluid. A that  detailed  the relationship  pseudo-critical peak  heat  coefficient  the  critical  vapor-like  with  temperature.  bulk  fluid  fluid  determines  coefficient.  occur  of Figures  of the bulk  temperature  transfer  fer  comparison  Heat  rapidly  temperature  peaks  bulk  transfer  decrease  (32) s h o w s to the  the magnitude  Sharpest  liquid-like  (27) t o  of the  i n heat  fluid  trans-  close to  coefficients  to a constant  in value.  72 Heat  transfer  increasing  4.3  rates  free-stream  Effect  o f Bulk The  free  detailed  comparison  bulk  temperature. increase  Re*  transfer with  Maximum  improvement noted  rate  f o r a pressure  than  25%. Figure transfer  nucleate 5 deg F  critical  cylinder  less  the entire  temperature  than  locations  covers  a variable  cylinder  transfer i n film  (Fig.  results  on t h e heated amount rate,  heat  (1000 p s i a )  fields.  38-a), i n some  further  cylinder.  including  t h e peak of  the effect of  temperature observed  increase  in  boiling at  Film  boiling  and s m a l l  on t h e percentage  observed.  pressure  difference  b o i l i n g was  film  less  convection sub-  At a  of the cylinder  b o i l i n g , were  was  (Re*=600)  on t h e f r e e  dependent  transfer  of increasing  (38) s h o w s  6 deg F n u c l e a t e  difference  random  heat  Figure  temperature  cylinder  difference.  a t a temperature  and s u p e r c r i t i c a l flow  difference  in  occurring  effect  1100 t o 1500 p s i a  convection  bulk  was t o  and t h i s  convection  the effect  i n forced  i s clearly visible.  increasing  over  rate  from  by a  ( 2 5 ) a t 80 d e g  pressure  temperature  i n free  i n super-  (23) a t 86 d e g F  slightly  increasing  increase  variation  (17) a n d  rate  (33) s h o w s  flux  of  difference.  (15), (21), and  and s u p e r c r i t i c a l p r e s s u r e  heat  functions  and c a n be o b t a i n e d  The e f f e c t o f i n c r e a s i n g  the heat  subcritical  are small  and F i g u r e s  stronger  heat  pressure  of Figures  becomes  on  increasing  and temperature  of bulk  convection  temperature  smoothly  Pressure  effects  critical  F  remain  Film  changes of the  boiling  showed  73 no  preference  photographed (Fig.  f o r any p a r t at various  38-b)  boiling until  with  a temperature  Stable  film  increasing  difference  corresponding temperature  (38-d),  free  the effect  pressure  attained  i n the present Figure  is  nearly  fluid  given  very  near  creasing  fields  film  attained. temperature  show t h e  f o r increasing (1100 p s i a ) .  velocity  temperature  that  a t sub-  difference  o f pressure  i s small  the pseudo-critical the heat  cylinder  (34) w h e r e  This  tempera-  transfer  rate  and i n t h e f r e e s t r e a m i s shown  i t c a n be noted  difference,  less  transfer  than  even  that  When  the pseudo-critical  the cylinder  temperature cylinder  i s to increase  more  fora  c o e f f i c i e n t decreases  and t h e e f f e c t  the heat  slightly  temperature  vapor-like  transfer  fluid i s of  '  until  o f t h e s u p e r c r i t i c a l p r e s s u r e and  condition.  the heated  the effect  convection  differences  the heated  pressure.  pressure  (38-f)  of increasing  exceeds  the pseudo-critical with  and  flow  f o r forced  independent  the heat  increasing  contact  with  difference  at a l l higher  shows  temperature  temperature  exceeds in  rate  i n Figure  temperature, with  length.  work.  (33) a l s o  i n the liquid-like  clearly  covered  o f 50 d e g F was  a t t h e maximum  temperature  A t lower  very  the is  transfer  cylinder  ture.  area  at s u p e r c r i t i c a l pressure  critical  the  the cylinder  temperature  (38-e),  convection  difference  (39) s h o w s  heat  and has been  ( F i g . 38-c) Figures  on  along  of cylinder  b o i l i n g was o b s e r v e d  differences  Figure  locations  The amount  increased  of the cylinder  i n -  rate.  In  short,  heat  transfer rate  cylinder the  increasing supercritical significantly  i s in contact  with  pressure  only  when  vapor-like  p s e u d o c r i t i c a l temperature)  and  increases the  fluid  is in a  the  heated  (that  is,above  liquid-like  free-  stream. Figure coefficient value,  in  nearly  difference  (34)  also  shows  forced  flow  rapidly  independent  exceeds Figure  temperature  (40)  above  variations visual  noted.  bulk  mm  in  order  high  field  transfer a  constant  the  temperature  variation  variation  for  with  forced  to  35  40)  mm  to  photographs  illustrate  gain  the  of  velocity motion  into  time  of  each  conditions  taken  film  are  A  a  direct  at  5000 of  were  brief  contained  temperature series  dependence  and  field  on  cylinder  t r a n s f e r mechansims which  operating  observations  the  repro-  systematically  below.  also  been  flow  based  while  described  p i c t u r e s was  insight heat  are  have  the  Additional observations  pressure,  speed  to  Photographs  bulk  of  (II) .  flow  temperature,  A  the  the  fields  rapid  of  when  flow  extremely listing  pressure,  the  free-stream  16  approaches  pressure  typical  ( F i g . 35  observation  varying  heat  F.  shows  I n t e r p r e t a t i o n of  duced  the  (Re*=650).  Selected  and  deg  d i f f e r e n c e and  convection  4 .4  100  of  that  in  of pps  the noted.  summary Appendix  75 The were  observed  s t i l l the  flow  fields  photographed  t o be e s s e n t i a l l y  photographs  various heat  reproduced transfer  t h e same  above.  the high  speed  by  by frame  examination.  movies in  was  slow  have for  motion.  been  viewing  cylinder rapidly  transfer  repeated  tearing  value  rate  film  by  or  of the  mechanisms p r o j e c t e d  of the sixteen  of heated  region behind  identified  obtained.  which  films  i s available  dependent  and o c c u r s  of fluid  are torn  can  follow  and o n l y  the secondary  o f f much  clumps  from  cylinder  and an e s t i m a t e  of heated  sheets  layers  the  a t l o w Re* a n d t h e  f o r a Karman V o r t e x  20,000 c p s ) o s c i l l a t i n g  fluid  the heated  i n the films  The t e a r i n g  velocity  predicted  fluid  the  to  dependence o f  slower  The main  a summary  i n the  request.  oscillating  directly quency  into  i n the supercritical  clearly  quency  on  the heat  films  c o u l d be d e t e r m i n e d  a t a known  Selected sections  combined  The  be  t o observe  films  speed  a s shown  The time  mechanisms  projecting a frame  by t h e h i g h  fluid  street.  mechanism  fre-  layers i s  at roughly  faster  of  can  the  fre-  At higher than  the camera  of rapidly  of vapor-like  Re*  fluid  (5000 i s  visible. Observations the  rate  slower at  of bubble  (0.01X)  than  supercritical Other  heat  transfer  from  the high  speed  movies  show  generation i n nucleate boiling t h e movement  of heated  clumps  that  i s much of  fluid  pressure.  o b s e r v a t i o n s from mechanism  the movies  a t the condition  suggest  that  o f maximum  the  heat  transfer ture the  coefficient  i s t h e same  differences.  Only  supercritical  fluid  one mechanism i n contrast  mechanisms  active  generation  and v a p o r - f i l m  The like  and like  supercritical  without  vapor-like fluid  from  tempera-  c o u l d be o b s e r v e d  fluid,  in  distinct  (nucleate  bubbl  formation.) heat  transfer  mechanism  in liquid-  c a n be d e s c r i b e d a s s t a b l e  a distinct fluid  higher  t o t h e two  i n the s u b c r i t i c a l  free-stream f l u i d  boiling  a s a t much  interface  between  the l i q u i d - l i k  b u t a i d e d by t h e t r a n s p o r t  the heated  cylinder  into  film  of  t h e wake.  vapor-  77  DISCUSSION  5.1  Free  c o n v e c t i o n heat  shown t h a t t h e h e a t  transfer  c o n v e c t i o n can reach temperature  just  fluid  temperature,  showed o n l y d e t e r i o r a t i o n temperature  exceeded  the experimental  ditions  and Aung  i n Figure  to  that observed  of  temperature  with  temperature  was  transfer  study  and t h e h e a t  coefficients  temperature.  o b t a i n e d by Knapp  The h e a t  [18] and  n e a r l y , t h e same b u l k transfer rate,  a smoothly  i n contrast  and d i d n o t show t h e s h a r p  No b u b b l e - l i k e f l o w was o b s e r v e d transfer  increase  by Knapp  i n the present  r a t e was o b s e r v e d  above t h a t o b t a i n e d by G o l d s t e i n and Aung.  con-  increasing function  the appearance of a b u b b l e - l i k e flow noted 4).  below t h e  a maximum v a l u e when t h e b u l k  [20] f o r v e r y  difference  coefficient  i n t h e p r e s e n t work a r e compared  by Knapp, was  (Fig.  for  temperature  the p s e u d o - c r i t i c a l  results  (41).  transfer  but the heat  from  Results obtained  Goldstein  i n free  temperature  f u n c t i o n of i n c r e a s i n g  Peak v a l u e s o f h e a t  pseudo-critical  obtained  The -heat t r a n s f e r r a t e however r e m a i n e d  o c c u r r e d whenever t h e b u l k  with  coefficients  l a r g e peak v a l u e s when t h e c y l i n d e r  increasing  difference.  t r a n s f e r measurements have  exceeds t h e " p s e u d o - c r i t i c a l  pressure.  a smoothly  fluid  RESULTS  Convection Free  the t e s t  OF  t o be c o n s t a n t l y  T h i s was  expected  78 because  of the smaller heated  study.  The  seemed  quite  flow  field  similar  cylinder  observed  to that  due  to small disturbances the flow  large  time.  temperature  oscillating attach  It  very was  that  after  resistivity  with  details.  noted  the v i b r a t i o n  during  around  the heated  wire.  was  much  to  initiate  in  heat  Knapp  can possibly  of  electrical  by  certain  resistance the  rate  fully  the temperature  temperature  annealed  It i s felt  e x p l a i n e d by with  alloys.  break. inter-  coefficient  and  the probe '  transfer  Figure  Note  to raise 400  that  the  shown that  the  observed  descrepancy  the  by  variation  temperature shows  observed  observed  the non-linear  (4 2)  were  deg F b u t  previously  difference  increasing  behaviour  condition.  intensity  a complicated  above  to  could  b u b b l e - l i k e f l o w was  vs temperature  resistivity  nichrome vs  be  effect  audible  not possible  the  observed  the non-linear  temperature  bubble-like flow.  transfer  with  d e g F)  was  increases i n heat  I t was  g r e a t e r than  1000  at very  of the nichrome,  b u t no  platinum-on-quartz-cylinder this  process,  Large  than  was  Aung  instability  current fluctuations,  temperature  construction  probe  cylinder  to buzz,  and  were r e p r o d u c i b l e  nichrome  vibration  transfer  f o r an  and an u n u s u a l  large  the wire  of the heat  fields  the heated  start  except  (greater  cylinder  might  quickly,  felt  action of  r e g i o n above  The w i r e  and  the i n i t i a l  differences  to the heated  occur. and  differences,  With  differences  d e s c r i b e d by G o l d s t e i n  low temperature  after  i n the present  a t a l l temperature  for  time  used  shown  actual  by Nichrome f o r a given  V in resistance  79 ratio  (or g i v e n  measuring  circuit)  temperatures. a wire  by  by  that  than  tion  include  flow  observed  flux  but  rate no  is a  the by  to  that  the  higher  more  imbalance  change  of  at  the  surface and  inferred  with  temperature.  b u b b l e - l i k e flow  a much  tend  to  higher  at  of  appears  temperature  F.  The  indicated  not  marked  least  original heat  that by  a  the  to  that  the The heat  by  transfer and  that  differen-  Sabersky  mechanism  appearance  heat  present  temperature  transfer  sugges-  same  difference  work done  sharp  this  the b u b b l e - l i k e  temperatures.  temperature at  of  roughly  confirm Goldstein's data function  support  occurrance  cylinder  bubble-like supercritical  f l o w was  or  bridge  constant, experimentally  occurred  the  like  a  which  Goldstein  deg  also  two  voltage  occurred  up  (12)  have  appearance  ces  Freon  a Wheatstone  resistivity  results  bubble-like flow 350  the  fact  smooth  to  of  of  reported.  a t much tend  can  assuming  actually  Further  results  wire  coefficient  Knapp  difference  imbalance  Knapp measured  i s suggested  noted  the  temperature  determined It  voltage  of  the  on  in bubble-  increase i n heat  transfer  rate. Knapp  concluded  that  a horizontal  b u b b l e - l i k e flow would  have  a  with  the  five  times  vertical  that  wall  also  from  i n under  supercritical  water,  dioxide  that  nearly  found the  either  same  as  the from  a horizontal  identical  and  Kato  heat a  heat  strip  conditions.  [26]  flux  flux  cylinder more  or  a  Holt  in supercritical  from  horizontal  a  flat  strip  cylinder.  than  short [17], i n carbon was  very  80  It  i s a l s o suggested  previously  o b s e r v e d may  transfer.  The  fluid  not  bubble-like  near the  be  reorganised  into a bubble-like  like  much l i k e  the  in stable  mechanism may  transfer  rate  has  The  not  be  could  the  the  previously  be  should  in a relatively convection  flow  be  observed  the  the  the  bubble-  i n heat  and  i s a very  [12]  and  h e a t t r a n s f e r r a t e and  by  circulating  large  increases  appeared very observation,  temperature  present  that  the  work  s i m i l a r to  F r e o n by  flow  fields  t o be  free  greatly temper-  t e s t loop.  The  occasionally  D o u g h t y and  disturbances  study,  minor  through the  by  apparatus.  shown t h e  c a u s e d by  those t r a c e d ,  to c i r c u l a t i n g  indicates  present  i n heat t r a n s f e r r a t e  in supercritical  temperature  experimental  disturbances bulk f l u i d  transfer  e l u s i v e phenomenon as i t  present  emphasized  constant  cylinder  The  heat  l a r g e volume t e s t chamber, has  v a r i a t i o n s i n the  unusual  and  even i f  Sabersky  mechanism o f  reported.  found w i t h the  It  ature  that  increase  data of  present  bulk conditions  bubble-like  not  affected  fluid,  the  insulating properties  idea  r e s u l t in a large  observed w i t h the  a t the  differences that  has  condition  vapor f i l m which covers  However a b u b b l e - l i k e  cylinder  vapor-like  This  heat  been n o t e d when  vapor-like  film boiling.  i s s u p p o r t e d by  mechanism  [20].  Goldstein  could  bubble-like  only  region,  subcritical  not  the  i m p r o v e d mechanism o f  c y l i n d e r i s i n the  is liquid-like.  cylinder  an  flow  free-stream  very  that  Drake  [13]  d i r e c t flow i n the  present  field study.  81 Small  differences  different  i n measured  investigators  conditions  are also  heat  working  probably  transfer  rate  at essentially  due t o c o n t a i n e r  between  t h e same  bulk  geometry  effects.  5.2  Forced  Convection  The the  purpose  variables  near-critical mechanism  carbon  a heated  have  been  heat  transfer  cylinder.  process  stream  velocities  carbon  dioxide.  mechanisms of  even  ordered heat  a slight free  Heat divided  into  established  i n the thermal  determine  transfer i n  t o understand strong  boundary  of the heated  described both  results  normal Contrary  speed  the  property  layer flow  fields  i n forced  with  very  low  observed.  was  The  t o break  and t o g r e a t l y  that  free-  in supercritical  e x p e c t a t i o n s no  been  however,  direct  c o n v e c t i o n show  cylinder  to i n i t i a l have  from  movies.  to a heated  transfer  velocity  as i t appears  are possible  convection flow  transfer  convection heat  Photographs  rates  o f heat  to  i n t h e r e g i o n where  and as i n t h e h i g h  transfer  was  f o r v a r i o u s o p e r a t i n g c o n d i t i o n s and the  Experimental heat  study  d i o x i d e and t o attempt  transfer  presented  observation  high  forced  c a n be e x p e c t e d  over  Transfer  of the present  affecting  of heat  variations  Heat  unusual effect  up t h e w e l l  increase the  rate. transfer  in near-critical  two d i s t i n c t regimes  classes;  d i o x i d e c a n be  subcritical  of nucleate, transient  film  with  roughly  the well  and n u c l e a t e ,  82 and  stable  basic at  film  heat  transfer  subcritical  isms;  boiling,  consists  extract  heat  ization  and c a r r y  of  a vapor  also the  from  fluid  mechanism  this  over  film  of distinct  the surface heat  from  a vapor  part  t h e second  increasing  tion  of a constant current  from  cylinder  surface  very clearly  coefficient  resulting  indicated  as t h e vapor from  the deterioration  film  began t o  a t a constant temperature  cylinder  over  contrast,  The v a r i a t i o n  t o be v e r y  voltage,  unstable.  difference  d i s a p p e a r s when  when t h e b u l k p r e s s u r e i s i n c r e a s e d  and becomes  except that  regime  Other  i s covered by a s t a b l e v a p o r - b l a n k e t .  the c r i t i c a l  drastically vection  time.  boiling  of the cylinder  transfer  may v a r y b y 1 0 % w i t h  i n destruc-  the free-stream fluid.  s u c h a s t h e rms component  rate  sharply  The p r e s e n t c o n s t a n t  The h e a t  just  but insulates  decreases  film  In  which  i s covered by  the transient  entire  consists  cylinder  indicate  the  which  mechanism  coefficient  heater.  the heated cylinder  observations,  mechan-  convection of  the surface  temperature d i f f e r e n c e ,  transfer  insulate  flow  transfer  or a l lof the heated  of the heated  with  heat  Forced  bubbles  the normal  blanket the heat transfer  temperature  vapor  one  the free-stream flow.  When o n l y  in  into  takes heat o f v a p o r i z a t i o n surface  heat  only  i n t h e form o f a heat of vapor-  the cylinder,  over part  i n which  has been observed.  p r e s s u r e s h a s two d i s t i n c t  the f i r s t  heated  and s u p e r c r i t i c a l  value the heat much l i k e  the f l u i d  transfer  mechanism  to changes  constant property forced  layers  which  roll  up i n t o  con-  Karmen  83 vortices  are regions o f heated  of  c a n be  fluid  maintaining  transported into  part  of their  film  boiling  like  and v a p o r - l i k e  fluid wake of  from  with  heat  transient  Heat also  free  fluid,  stream  ients just  large  values  fluid  very  ferred  when  transfer  near  the heated  density  surface into  difference  (therefore  convection temperature  with  process  cylinder. fluid  and t h i s  When t h e  transfer  coeffic-  temperature The  same  differences  occurring  The e x t r a  i n the  heat  trans-  transported directly wake  the l i q u i d - l i k e  increasing  free-  c a n be due t o t h e  properties  from  increases with the and  temperature).  i s more v e l o c i t y  difference  heat  temperature.  the cylinder  between  liquid-like  cylinder  coefficient  by t h e clumps o f heated  heated  peak  like  dioxide can  a t a l ltemperature  of the transport  super-  differences.  free-stream fluid.  the heated  to operate  carbon  classes;  the pseudo-critical  heat  the  component  i s n o t time-dependent  i s liquid-like,  appears  t h e peak  fluid  two b r o a d  into the  o f t h e rms  a t t h e same t e m p e r a t u r e  and v a p o r - l i k e  fluid  exceeds  mechanism  liquid-  hotter  heat  v o l t a g e show t h a t  s t i l l  resembles  the  by clumps o f  in supercritical  c a n be e x p e c t e d  mechanism  the  transfer into  between  Measurements  supply  boiling  be d i v i d e d  stream  and  power  transfer  film  The f l o w most  interface  but aided  and clumps  free-stream  surface which t r a n s f e r  the cylinder.  the cylinder  critical  fluid  fluid,  t h e main  identity.  no d i s t i n c t  the heated  behind  vapor-like  vapor-like The  dependent with  forced increasing  i s i n agreement w i t h t h e  idea  that  the  extra  heat  of  vapor-like  to  the  idea  of  a  turbulent  by  Diessler  [4  ]  in  Jackson  et  speaking only  in  the  al.  the the  sublayer  similar  idea  clumps the  that  heated  clusters  a  plate  flat  cluster stream  time  and  base.  results  seem  of  clump  of  the  critical is  fluid  affected  than  the  was  in colder the  the  sublayer.  into  the  [32]  as  seemed of  In  [30]  such  to  temperatures  bulk  fluid  pseudo-critical  action  with  the  of  the  flow  over that  freethe  fluid been  the  pseudo-  to to the  being recently Present  intensity the the  proximity pseudo-  heated  cylinder  temperature.  the  appears  model.  related  case  a definite  has  cylinder  mixing  from  above  model.but  the  observed  vapor-like  be  in  present  of  have  to  valid  i n which  was  observed  The  the  by  Strictly  is  liquid-like  penetration a  recently  fluid  level  free-stream a  to  Hauptmann  with  similar  dioxide.  mechanism  temperature  packets  more  clumps  treated  transported  turbulence  re-inforce  and  be  the  clusters  and  apply  Hauptmann  the  fluid  to  is  diffusivity  by  that  Graham  not  strongest  of  the  first  carbon  eddy  and  plate  idea  water  surface.  seem  free-stream  temperature.  largest  hotter  of  m o v e m e n t was  bulk  heated  the  to  diffusivity  does  when  The  by  eddy  and  the  by  enhancement mechanism  turbulent  to  transported  postulated  a  through  fluid  directly  of  supplied  supercritical  described  genetation  critical  in  free-stream  into to  This  is  supercritical  [51]  adjacent  heated  sublayer  fluid.  transfer  much  clumps  85 Sharpest can  be e x p e c t e d  pressure  when  with  broadens  t h e peak  rate  does  critical  temperature  temperature transfer  will  rate  a  vapor-like  the than  half  colder  ation bulk  Re*  increasing  fluid,  pressures  cylinder. a very  bulk  Heat  small  becomes  from  the c r i t i c a l  like  fluid  i s very  decreases  only  and temperature  can be expected  heat  the pseudofluid  i n bulk  decrease  i n heat  vapor-like. transfer  as e f f e c t i v e  transfer  fluid  temperature  critical  exceeds the  Increase  rates  with  as  are  with less  5 t o 10 d e g F  difference.  t o show o n l y  difference  and t h e amount o f d e t e r i o r a t i o n  closest  the  and v a p o r - l i k e  i s not nearly  as w i t h  coefficients  with  exceeded  s u p e r c r i t i c a l heat  free-stream.  a s much  just  near  an i n c r e a s e u n t i l  i n only  convection  fluid  c o e f f i c i e n t and t h e  the free-stream  f o r t h e same  transfer  transfer  the heated  free-stream  liquid-like  bulk  coefficient  Increasing pressure  has been  until  Forced  heat  result  transfer  temperature  n o t show  i n contact with  i n heat  liquid-like  temperature.  transfer  is  i n heat  the cylinder  pseudo-critical and  peaks  in  Heat deterior-  vapor-like  i s sharpest  at  to the c r i t i c a l .  At pressures  the heat  transfer  c o e f f i c i e n t i n vapor-  nearly  independent  of  further  temperature  difference. The liquid-like ation  with  intensity  observed  flow  and v a p o r - l i k e temperature  of the mixing  fields fluid  difference  are very  similar  a n d show v e r y i n either  i n t h e wake  i n both  little  case.  The  and t h e amount o f  vari-  86 oscillation  noted  bulk  pressure,  flow  fields  and  the  determines  physical to  heat  transfer  results.  An  constants  However,  such  as  enhancement clumps model  of of  an  fluid  the  dimensionless  to  groups with  same  be  inside  heated  Re  Pr  and data.  and  the  form  of  as  very  present  field  also  at  present convection  that work  developed and  suit-  data.  limited  useful-  situations. suggest  r a t e due  included  were  temperature  resembles  The  predicted  experimental  be  the  transfer  dioxide  present  f i t the  transfer  must  fluid  carbon  i n the  flow  heat  heat  turbulent forced  i n the  only  to  i n any  that  the  the  diffusion  analytical  situation. development i n the  i t is felt of  the  qualitatively  heated on  similar.  experimental  variation  justified  fluid  two-phase  has  not  on  a  theoretical  near-critical  that  p r o p e r t i e s i n each problem  f i t the  for a  temperature,  [ 1 0 ] f o r flow  to  convection  two-phase  remarkedly  apply  flow  extension  be  would  further  as  a l l supercritical  expression  effect  the  attempted by  of  heated  No forced  an  but  supercritical  determined  i t would  Observations  to  coefficient be  dependent  f u n c t i o n of  pressures  could  bulk  Petukov  a  expression  transfer  Petukov  ness  as  the  are  to  coefficient  bulk  able  by  constants  evaluate  different  by  Nu  cylinder  for forced convective  properties of  used  heat  observed  developed  treats  the  velocity  expression  coefficient tubes  and  were  The  behind  the  problem  techniques  phase been  region  and  to  may to  date  completely  model has  best  even  the  solved.  been  be  include  of  handled  variable simplest  87  CONCLUSIONS  6.1  General Conclusions  the  heat  ism  i n near-critical  basis the  transfer  fields  photography. valid  only  carbon  fluids  carbon  Free  Convection In  exhibits ceeds  peak  free  temperature  that  mechan-  on t h e  and a study o f speed  cylinder  differences i n  the conclusions can  influence  behaviour  of velocity  on t h e mechanism  when  drawn  t o a heated  to the near-critical  Heat  transfer  t h e c o n c l u s i o n s drawn a r e  c o n v e c t i o n normal  the pseudo-critical i s a smoothly  presented  of heat  quali-  of other  and t h e pseudotransfer.  Transfer  convection the heat  values  been  coefficient,  o b s e r v a t i o n and h i g h  speaking,  It i s felt  temperature  and t h e heat  results  at various constant  be extended  transfer  d i o x i d e have  by d i r e c t  as t o t h e s t r o n g  critical  the heat  behaviour  Strictly  dioxide.  tatively  both  f o r forced  maintained  rate  rate  of the experimental  flow  6.2  about  the cylinder temperature  increasing  function  transfer  coefficient  temperature but the heat  just  ex-  transfer  of temperature  differ-  ence. Unusual ported  were  heat  not observed  transfer  mechanisms  but the heat  previously r e -  transfer  rate  and t h e  free  convection flow  disturbances  i n the  fields test  are  fluid  extremely  sensitive  properties  to  to  small  non-uniform  temperature. The a  free  convection heat  complicated function  ship  of  the  bulk  temperature, and  expected  and  A  is  the  when  transfer  Forced  bulk  rate  bulk  a  lesser  fluid,  relation-  pseudo-critical fluid  temperature  coefficients nearest  to  temperature  can  the  just  e x p l a n a t i o n f o r the  large  previously  by  of  nichrome  as  a  Heat  be  critical  exceeds  the  observed  the  variations  other  workers  c o e f f i c i e n t of  resistivity  wire.  Transfer  heated  showed but  transfer  complicated  cylinder  fluid  large the  pressure.  peak v a l u e s heat  transfer  coefficient  function  temperature,  to p s e u d o - c r i t i c a l  extent bulk  region  convection heat  s t r o n g and  temperature  coefficient critical  of  forced  velocity,  of  the  the  Convection-General  The measured  to  extent bulk  cylinder  Convection  Forced  temperature,  transfer  non-linear behaviour  6.3  stream  the  possible  temperature  was  lesser  coefficient is  temperature.  with  6.3.1  a  Largest heat  pseudo-critical  heat  to  cylinder  temperature  in liquid-like  pressure,  in  fluid  and  pressure.  of  transfer  the  of  proximity  temperature, The  heat  in parts rate  was  free-  and  to  transfer of  the  always  neara  89 smoothly ature  increasing  function  convection  very  large  heat  c a n be g r e a t l y  stream  velocity.  6.3.2  Effect  of  The  effect  of velocity  and heat  critical  bulk  pressures, bulk  transfer  rate  cylinder  i s largest  effect  than  when  the cylinder  critical  temperature.  and  bulk  by even  measured  a small  i s to increase  temper-  i n free  free-  at higher  b u t o n l y when  on heat  fluid  on  heat  differences  temperature.  transfer  just  The e f f e c t s  pressure  the pseudo-  doubling the free-  the cylinder  o r below  The  coefficient  exceeds  o f even  i n  the heated  nearest the c r i t i c a l  temperature  a r e above  temperature  of velocity  temperature  a r e s m a l l when b o t h  temperature  and  the pseudo-critical  bulk  the heat  c o e f f i c i e n t f o r a l l super-  The e f f e c t  of velocity  i n liquid-like  velocity  rates  temperatures,  free-stream fluid  i s hotter  strongest  transfer  investigated.  liquid-like  stream  and  Velocity  rate  differences  transfer  increased  transfer  and  velocity  difference. The  occurs  of increasing  the  temperature  pseudo-critical  temperature.  6.3.3  Effect  of Bulk  Temperature  When t h e b u l k critical maximum  temperature, at a cylinder  fluid  the heat  temperature transfer  temperature  i s below  the pseudo-  c o e f f i c i e n t show  slightly  above  a  the pseudo-  90 critical  temperature.  When t h e  pseudo-temperature  the  deterioration  with  increasing  peaks  transfer  ing  i n heat  velocity  critical heat  and  shift  decrease  rate,  slightly  pseudo-critical temperature  Effect  of  very  near  to  rate  i s larger  a  a  the  the  f o r the  shows  temperature. larger  above  only  The  with  the  the  increas-  pseudo-  supercritical pressure, temperature  temperature  the  difference,  approaches  and  decreased  sharply  the  pseudo-critical  as  the the  bulk  temperature.  Pressure  for a peak  at  given  bulk  beyond  Bulk  coefficient  further  constant  temperature  Except  pressures  at  increase  i s above  cylinder  slightly At  as  transfer  temperature  c o e f f i c i e n t become  temperature.  transfer  6.3.4  heat  bulk  narrow  range  nucleate heat  of  cylinder  flux,  the  heat  s u p e r c r i t i c a l pressures than same b u l k  temperature  and  temperatures transfer  at s u b c r i t i c a l  free-stream  velocity. At  s u p e r c r i t i c a l p r e s s u r e , whenever  cylinder  i s hot  the  heat  transfer  rate  The  heat  transfer  c o e f f i c i e n t decreases  ing  p r e s s u r e when  to  be  enough  the  i n contact with  6.3.5  Heat  Transfer The  dioxide  appears  heat  to  be  i n contact with  increases  cylinder  with  heated  vapor-like  increasing slightly  temperature  vapor-like  the  i s not  fluid,  pressure. with hot  increasenough  fluid.  Mechanisms transfer  t o be  normal  mechanism forced  is supercritical  convection with  no  carbon clear  distinction aided  by  between  clumps  of  the  liquid-like  vapor-like  and  fluid  vapor-like  which  fluid  diffuse  into  but the  free-stream. The the be  large  values  location  of  the  explained  in  terms  dictions  of  selected  mean  dependent  on  heat  the  of  heat the  transfer  property  pseudo-critical lytical  peak  of  proximity  of  temperature,  approach..  transfer  transfer large  rate  values  heat  c o e f f i c i e n t can  property  appear an  the  bulk  with  enhancement  be  and  probably  variations.  possible  but  should  coefficient  Pre-  suitably  factor,  temperature  to  included  any  in  the ana-  92  t  / /  60  70  80  90  100  /  110  TEMPERATURE [°F~  Figure  1  Summary  of Near-Critical  Region  Terminology  *  -  120  I  PRANDTL NUMBER [ p ] ( x 2 ) DENSITY (LB/FT ) r  3  H-  ro K> -3  ^< H-  O OJ l-l O 13 ro rt  <  OJ l-i H-  OJ rt H-  O cn H-  a ro OJ H I  o i-i H-  rt  H-  n  n  OJ ii  cr o t> D H-  O X  H-  ro  o  e6  DYNAMIC  CM  O  VISCOSITY  CM  130  94  Figure  3  P r o p e r t y V a r i a t i o n s which would occur i n Superc r i t i c a l C0 f o r the Free Convection Temperature D i s t r i b u t i o n Developed i n A i r 2  95  Bubble-Like  Figure  4  Bubble-Like Observed by  Flow  Heat T r a n s f e r Knapp  =  Mechanism  260  deg  F  Previously  WORKER  GEOMETRY  MATERIAL  Tb RANGE  Pb RANGE  TEMPERATURE DIFFERENCE RANGE 0-400°F  KNAPP & SABERSKY 1965.  HORIZONTAL CYLINDER SHORT VERTICAL WALL HORIZONTAL STRIP VERTICAL CYLINDER  0.010" NICHROME  49-137°F  1100-1500 psia  GOLDSTEIN & AUNG 1966 NISHIKAWA & MIYABE (Data=YAMAGATA) 1962-65  HORIZONTAL CYLINDER  0.015" PLATINUM  49-136°F  1075-1300 psia  HORIZONTAL CYLINDER  0.008" NICHROME  79-155°F  1050-1470 psia  DANIELS & BRAMALL 1965  HORIZONTAL CYLINDER  68-104°F  865-1265 psia  DUBROVINA & SKRIPOV 1964-65  HORIZONTAL CYLINDER VERTICAL CYLINDER  88-99°F  900-1275 psia  MONEL 0.001" PLATINUM  0-1500°F  (most to 400°F) 0-800°F  (most to 200°F) 0-200°F 0-0.5°F  (Measured along isotherms) 0-80°F  NISHIWAKI, KATO, KERATA 1967  HORIZONTAL CYLINDER  0.080"ST. STEEL  60-103°F  1176 psia  0-90°F  (most 0-35°F)  SHORT VERTICAL WALL  ALL ABOVE WORK WAS MAINLY WITH THE CIRCULAR CYLINDER GEOMETRY USING SHORT WALLS, OR VERTICAL CYLINDERS AS A CHECK AND WAS IN FREE CONVECTION. IN FORCED CONVECTION: NISHIWAKI, KATO, HIRATA 1967  HORIZONTAL CYLINDER IN FORCED CROSSFLOW (one flow rate was used but a Reynolds number variation due to property - variations was noted)  Figure 5  0.057" ST. STEEL  82-92°F  1176 psia  Summary of Previous Work With Heated Cy l i nders in S u p e r c r i t i c a l F l u i d s ~  0-30°F (most 0-20°F)  COMPRESSED AIR SUPPLY  COMPRESSED ? AIR EXHAUST  Figure  VACUUM PUMP  6  CANNED ROTOR PUMP  Schematic of N e a r - C r i t i c a l  Carbon  SYSTEM EXHAUST Dioxide  Forced  Flow  Loop  f  X  <*0  Figure  7  Cutaway View  of Test  Section  Arrangement  Figure  8  Section  of  Test  Section  Block  100  Figure  9  General  Layout  of  Experimental  Equipment  TEST SECTION  T/C (1) COLD  COPPER  PYE  N  SELECTOR  GALVANOMETER  ICE BATH  SWITCH  6  L&N VENTURI  K-5 POTENTIOMETER  CONSTANTAN  METER T/C(2)  Figure  6  10  Thermocouple  Measuring  Circuit  o  I— 1  Tb=80°F ?h- m o o PS-IA 300  • • • • n O • • •43°  •  40  80  120  TEMPE F i g u r e 11  200  DIFFERENCE R e p r o d u c i b i l i t y o f Data  2  Figure  13  Flow F i e l d Convection  Around  Probe  and  Supports  i n Free  ADJUSTABLE CUTOFF . _\  MIRROR  1  SCHLIEREN LENS TEST SECTION BLOCK  HEATED  MIRROR SOURCE CONDENSER  Figure  14  ^SCHLIEREN LENS  Arrangement of S c h l i e r e n  System  SCREEN OR CAMERA CYLINDER  1  I  1  CN  1  1  1  1  1  +  1  CN  Re*  Tb : 8 0 ° F o  Pb :  CN  O  1100 P S I A o  I  i  o  o  o  O  o  -  o  r\  o  o°  A  •  A A  A  o o  600  A  o  o O  °  o  o o  x  °^-°1050-  o  00 I  o  o  A  •  A  •  a  a  D  D  D  n  —300  •  A  • •  n  •  D  A A A  A  o *± „ •• Oo A OA o ° ° ° • A  •  • nD  A  _  A  D  A  oo  D  CD  0 •  .  • •  •  •  • • •  •  °  1  1  160  200  •  40  80  120  TEMPERATURE Figure  15  Effect of Velocity 1100 p s i a  on  DIFFERENCE  Heat T r a n s f e r  Rate  240  280  [°F]  i n CO., a t 80 2  deg  F  and  320  I  A-  1  1  CN  U. CM  or  c5b  h- o  o ° O  I—  Pb = 1100 PSIA  o o A  «o  Re  O A  °0  •  1050 — 600 •••300  O  ....  A  A  LU O  o  A  LU  a •  A  • •  o  9  40  —  80 120  E f f e c t of V e l o c i t y and 1100 p s i a  O  n  O  8 0  o  °  >  n  o  F i g u r e 16  I  Tb = 80°F  A*A  CN  2  I  TPC  • fV  O A"  A  A  •  •  9  •  o  O o  A  A  •  A  O  o  200  240  TEMPERATURE DIFFERENCE  on Heat T r a n s f e r C o e f f i c i e n t  o  •  I 160  o  280  [°F]  i n CO, a t 80 deg F z  320  Tb = 87  Re  F  Pb =1100  PSIA  625  . • • • ' + •  •  •  • V  v  . • • v  „ v  9 © 0  40  v  •  • v  •  •  V  +  *  . ' v  T  17  310  v  V  v  T  v  -  O  ®—0  9  o © " 80  120  160  200  240  TEMPERATURE DIFFERENCE re  —  Effect of Velocity 1100 p s i a  on  Heat  Transfer  Rate  i n CO, 2  at  280  [°F] 87  deg  F  and  320  CN  O  CN  V |~y  ^  Tb ~-87  •  V  °F  Pb= 1 100  •  PSIA  •  V  _ v  • * • ^  v  v  '  ^  • ••^^ ^  „  Re v  v  ®**»o  •  @ a  j—310 —-155 v  ° 40  • •  #  80 T  18  T  I  v  „  "  Figure  I  v  •  120 E  M  P  E  Effect of Velocity a n d 1100 p s i a  R  A  ®  160 T  U  on Heat  R  E  D  9  9  200 I  Transfer  F  F  E  R  E  9-0  240 N  C  Coefficient  E  [  280 °  i n C0 2  F  o  ]  a t 87 d e g F  320  io CN  1  CN  O CN  Z>  Tb = 9  h-  DQ  Pb  i  1  °F  = 1 1 00  Re  PSIA  — ^ lO  "o  600  A  x  *—^ o X "  • — 300 — 1 50  <  A  LU 3Z  A "  D  40  •  0  • O  A  a  D  120  80  160  TEMPERATURE Figure  19  E f f e c t of Velocity 110Q psia  on  Heat  Transfer  200  240  DIFFERENCE Rate  in  CO  at  280  [°F] 91  deg  F  and  320  1  I  CN  Tb = 91 "F  O CN CO I  Pb = 1100  Tb = Tpc V  I  PSIA  ' -  Re*  to  A  A A A  rtn  A  A  B  A  •  •  9  9  9  D  A  ®  40  80  120  160  TEMPERATURE 20  A  9  9  Figure  -  !  ° — 3 00 • • • • •l 5 0 9 • • • • 0  A  I  6 00  —  Effect of Velocity a n d 1100 p s i a  on  Heat  200  240  280  320  DIFFERENCE [ °F  Transfer  Coefficient  i n C0  0 z  at  91  deg  F  CN  O CN  Tb =80 °F A-  Pb =1300 PSIA  A A A  *  A  A  ° •  "  D  A "  *  n  A A A  • •  n  •  D  A  *°  ° . ••  A  AO  0  •  n  •  •  • '  *  •  40  80  120  160  TEMPERATURE Figure  21  Effect.of 1300 p s i a  Velocity  on  Heat  Transfer  2 00  240  DIFFERENCE Rate  i n C0  o 2  at  [°F] 80  •i  1  o  CN  CN  h-  Ll_  cr X.  Tb = 8 0  T pc  O  CN  °F  Pb = 1 3 0 0 P S I A  hG Q  i i  o  CN  A A ^ A  " to  .AA  ,__  X  •  •  n D  °n  •  A •  h-  •  Re*  LU  u  A—600  LU  N  O O —I  @  o  •  0  40  22  O  80 T  Figure  @  o  120 E  M  P  E  E f f e c t of V e l o c i t y a n d 1300 p s i a  R  A  on  T  160 U  Heat  R  E  D  200 I  Transfer  F  F  E  R  E  N  C  E  Coefficient  —300  ©  o o*>—0  240  280  [  °  F  i n CO  ]  at 2  320  80  deq  F  I  CN  I  I  T  ^  I  |  Re* Tb=86'°F  O CN  0-——-950  Pb = 1 3 0 0 PSIA  o  °  o  o  '  o  IT)  o  o  o-  o O A  £n  o  A A  o A  A  "  .  A  A  •  • *  a  40  23  • •  A  i  i  80  i  120  160  TEMPERATURE Figure  •  o  A  i •  . 0  O  ^ 6 0 0  A  o o  A  A  E f f e c t o f V e l o c i t y on .1300 P s i a  Heat  2  00  DIFFERENCE  Transfer  Rate  2 80  240  i n C0„ 2  at  [°F] 86  deg  F  and  FILM COEFFICIENT ( x i c f )  [BTU/HRFT F  2  0  15 9  H CD  K>  2o  ">r  o e o  o>>  9  o  20  o  25  o  TJ" O  o  3 Hi P i ttv fD H O oo r t o o  o  o  oo o  Hi  TJ  cn < H- CD (U I— 0  1  o  Hft ^<  O ffi CD CU rt Hi H 0) cn Hi  CD H  o  H  m -o m  o o  > H  TO  Q  o o  m  HO HCD  m O m  Hi Hi  rt H-  n o  t\J>  Ui rt  oo cn  Pi CD  o o  cr ll  —  co  o o  o  o o  "0  CO  o  > to o  o o  > o  to  9  o  9  CJ  t o  >  o  00  ro o  "0  o  o  O CD  o  o  70  m  9  o o o o  o  o  70  CD O  o  Oi  o  cr II  00 Os -n  ' = 80  Tb  '  '  Re* —------  °F  600  A A  Pb = 1500 PSIA  A A A  A  A  O  "  A  •  D  • A  • O  A  •  A  • • •  D a  A  •  A n  A a  m  ^  3  a  °  * o •  I  I  40  80  I  25  '  120 E  Effect of Velocity 1500 p s i a  M  P  on  E  R  A  Heat  l_  200  160 T  •  •  0  O  9  T  are  © •  A  D  .  D  U  R  E  Transfer  D  I  F  F  Rate  E  R  E  N  C  I  I  240  280  E  i n C0„ a t 2  [ ° F ]  80  deg'F' a n d  32  Tpc  Tb = 80  ° F  Pb =.1.500 PSIA A  A  A A  A  A  •••••  Dn  Re  •  s  A  A—600  —300  n  9  9  S  0  40  26  9  80 T  Figure  o  9  9 O 9  E  •  9  9  120 M  P  E  Effect of Velocity and 1500 p s i a  R  A  T  •  9  160 U  on Heat  R  E  D  9  •  200 I  Transfer  F  F  E  R  E  N  9  9  240 C  E  Ceofficient  [  °  280 F  i n CO, 2  9"^9"0  ]  a t 80 d e g F  320  to r  CN  1  CN  cr  CN  i  CD  [?]  Tb  O  Pb=1100  _i  ••• 80 ••86  PSIA  ...  ID i  •• 1 05  Re:300  o X  a o  *—^ o x  9 0  B O  -  •  • o  h<  a o  0  *  A  V  40  • V •  -  V  V  *  A  V  V  •o  ^  H O  LU  0  o  •  v  V  v  80  120  160  2 00  240  280  320  TEMPERATURE DIFFERENCE [ ° F ] Figure  27  Effect  o f B u l k T e m p e r a t u r e on H e a t T r a n s f e r R a t e a t 1 1 0 0 p s i a  (Re*=300)  00  F  I  L  M  C  O  E  F  0  F  I  C  I  E  5  N  (xio" ) 2  T  10  [  B  15  T  U  /  H  R  20  H-  <  iQ  fD  <  <  o  Hi Hi  < <  <  (D O — rt  X- H i  — ?r  m  oo o  3  fD H PJ rt  70  o  K0  70  a  m  o o  m  ro o o  fD 0) rt  o o  o  <  B  <  m  CO  B  < <  •  i-3  Ui  cn Hi  fD H  n o fD Hi Hi H-  O  H-  CD  70  m  o o o  B  O ro o  ro oo o  co ro o 6TT  o o  rt 0» rt  <•  •  —  NO  00  o  o  a  C/t O  o o  "0  o •  ~0  CO  B  >  fD  70  Si  o  fD TJ  o  t  fD O  O H  CB  < .  co  II u> rjd o C  B  00  o  i—i o i i  F  T  2  O  F  25  ]  Figure  29  Effect of (Re*=600)  Bulk  Temperature  on  Heat  Transfer  Coefficient  at  1100  psia  I  1  CN  CN  Io CN  Pb - 1 100 PSIA  Tb  i—  CO I  I  80 86  Re =6 00  40  [-F]  o  105  X  X Z)  o  I—  B-*  < LU  X  IO  v  V  •7  J.  40  120  80  160  200  240  280  320 to  T  Figure  30-  E  M  P  E  R  A  E f f e c t : o f .Bulk-Temperature psia (Re*=600)  T  U  on  R  E  Heat  D  I  F  F  E  R  Transfer  E  N  C  E  [ ° F ]  Coefficient  at  1100  CN  8  Pb -- 1 3 0 0  PSIA  o  Re"=600  A A  -  —  80  —  o  A  • .  D  86  A •  A A  A A  •  A  ^  *h A  •Oh A  a  O  40  O  •  •  o o  105  o  °  O  o  o  °  80  120 T  Figure 31  O  O  . o  O  O  O  n  O  O  n  •  O  O  A  *  ...  n  E  M  P  E  R  A  160 T  U  R  E  D  200 I  F  F  E  R  E  N  240 C  E  280  320  [ ° F ]  Effect of. Bulk Temperature on Heat Transfer Rate at 1300 psia  (Re*=600)  £  CN  Pb = 1 3 0 0 PSIA  it  O CN  Re - 6 0 0  A  Po oo  •• „  o00  O  ° ° ° 0 ° ° °  °  o  O  A  A  °  °.  n  * ° •  o o  o  * n  °  Q 0  40  T  Figure  32  120  80  Effect of (Re*=600)  E  M  Bulk  P  E  R  A  T  160 U  Temperature  R  *  0  D  I  on  Heat  F  F  E  R  E  Transfer  -  °  0  o _  240 N  C  E  8  0  - - 8 6  D  200  E  A  [  T  0  5  280 °  F  Coefficient  32  ]  at  1300  psia  1  I CN  CN  Pb [PSIA]  cr  x  Tb : 8 0 . 5 °F TV Re = 6 0 0  o CN  CD i  i  A _  x X Z>  •  O • o  •  1500  o  1300 11 0 0 o  o-  O  a  © ~ 1 0 00  o •  e  < LU X  0  40  80  120  160  200  240  280  TEMPERATURE DIFFERENCE Figure  33  Effect  of Bulk  Pressure  on  Heat  Transfer  Rate  a t 80 d e g F  320 4^  (Re*=600)  o  Tb^ B0.5 o  R^600  Pb  o  [PSIA]  • ..... 1500 o . . . . 1300  co  1100 — " 1000  A  o CN 0°g A  on °  a  O  On  °  a  O  •  • O  •  40  T  Figure  34  120  80 E  M  P  E  R  A  T  •  •  160 U  R  E  n  o o S S •  =d o  n  •J  D  0  •  m  -  200 I  F  F  E  R  E  o  -  240 N  C  E  [  E f f e c t o f B u l k P r e s s u r e on H e a t T r a n s f e r C o e f f i c i e n t (Re*=600)  280 °  F  320  ]  a t 80 d e g  F  to  126  127  Re*  36-A Figure  36  1300  =  600  Re*  psia  Flow F i e l d V a r i a t i o n and 1300, 1500 psia  =  36-B with  Velocity  at  80  600  1500 deg  psia F  Free  Convection  Free  After Figure  37  - Pump O f f  Convection  Circulating  - Pump On  Disturbance  Flow F i e l d V a r i a t i o n w i t h C i r c u l a t i o n V i b r a t i o n - Free Convection  a n d Pump  1 29  Figure  38  Flow F i e l d V a r i a t i o n w i t h C y l i n d e r Temperature I n c r e a s e i n S u b c r i t i c a l and S u p e r c r i t i c a l Free Convection  130  131  Figure  40  Flow F i e l d V a r i a t i o n w i t h P r e s s u r e and C y l i n d e r Temperature V a r i a t i o n i n Forced Convection  IT)  I CN  1 CN  Q Knapp 77 ° G ree n 80 • G o l d s t e i n 73  CN  !  I  a o~  i o  FREE  CONVECTION  P =1100  X 3  b  PSIA  Q  9  a  <  ®  UJ  a  a  •  •  n  in  a  0  & 9  o  40  80  120  160  200  240  280  320  TEMPERATURE DIFFERENCE [ ° F ] F i g u r e 41-A  Comparison o f E x p e r i m e n t a l F r e e C o n v e c t i o n D a t a w i t h O t h e r Workers NJ  K"> 1  CM  1  CN  Tb = 30 °F X  o  a  Pb = 1 5 0 0 PS  CM i  i  O X  *—"  x  o  —  a  _J  —Knapp  9  LU  r<-  Free  a °a  80  a  A  »  9  •  9  9  LU A  A  °  3 _ 9 9  9  •  * '  9  J.  80  120  160  200  240  2 80  320  TEMPERATURE DIFFERENCE [ ° F ] F i g u r e 41-B  Comparison o f E x p e r i m e n t a l F r e e C o n v e c t i o n D a t a w i t h O t h e r Workers  M U)  CO  o  Oh-  o  Assumed  Linear  o  8  Actua  CN  o o o 200  600  1 ooo  TEMPERATURE Figure  42  1400  1800  °F  E l e c t r i c a l R e s i s t e n c e Change o f Nichrome V w i t h Temperature (Minimum C u r v e f o r A n n e a l e d N i c h r o m e Wire From [40])  u>  135  REFERENCES 1.  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Nishikawa, K . , and Miyabe, K . , "On the B o i l i n g - l i k e Phenomena at S u p e r c r i t i c a l Pressures," Memoirs of the Faculty of Engineering at Kyusa University, V o l . 25, No. 1, December 1965, pp. 1-25.  Technology,  137  23.  Nishikawa, N . , Shimomura, R . , Hatano, M . , Nagatomo, H . , "Investigation of Surface Boiling under Free Convection", B u l l , JSME, V o l . 10, No. 37, 123-131 (1967).  24.  Skripov, V.P.aand Dubrovina, E . N . , "Convective Heat Transfer i n The S u p e r c r i t i c a l Region of Carbon Dioxide," Proceedings of Second A l l - S o v i e t Union Conference on Heat and Mass Transfer, V o l . 1, C. Gazley, J r . , J . P . Hartnett and E . R . G . Eckert, eds. C a l i f o r n i a University Press, 1966, pp. 36-45.  25.  Daniels, T . C . and Bramall, J . W . , "An Experimental Investigation of the Heating Mechanism of Carbon Dioxide Above the C r i t i c a l Point," Proc. I n s t i t u t e of Mechanical Engineers, 1965-66.  26.  Kato, H . , Nishiwaki, N. and H i r a t a , M . , "Studies on the Heat Transfer of Fluids at a S u p e r c r i t i c a l Pressure," B u l l e t i n of JSME, V o l . 11, No. 46, 1968, pp. 654-663.  27.  G r i g u l l , U. and Abadzic, E . , "Heat Transfer from a Wire in the C r i t i c a l Region," Symposium on Heat Transfer and F l u i d Dynamics of Near C r i t i c a l F l u i d s , B r i s t o l , March 1968, Paper 8.  28.  Baumeister, K . J . , and Simoneau, R . J . , "Saturated Film P o i l i n g of Nitrogen from Atmospheric to the C r i t i c a l Pressure," NASA Technical Memorandum, NASA TM X-52615, (1969). : ~~ !  29.  Hasegawa, S. and Yoshioka, K . , "An Analysis for Free Convective Heat Transfer to S u p e r c r i t i c a l F l u i d s , " Proceedings of the Third International Heat Transfer Conference, AIChE, V o l . 2, 214-222 (1966).  30.  Hauptmann, E . H . and Sabersky, R . H . , "An Experimental Investigation of Forced Convective Heat Transfer to a F l u i d i n the Region of i t s C r i t i c a l Point," International Journal of Heat and Mass Transfer, V o l . 10, 1967, pp. 1499-1508. :  31.  Simoneau, R . J . , and Williams, J . C . , "Laminar Couette Flow with Heat Transfer Near the Thermodynamic C r i t i c a l Point," Int. J . Heat Mass Transfer, V o l . 12, 120-124 (1968).  32.  Graham, R.W., "Penetration Model Explanation for Turbulent Forced-Convection Heat Transfer Observed i n NearC r i t i c a l F l u i d s , " NASA TND-5522, 1969.  33.  Dryden, H . L . , and Schubauer, G . B . , "The Use of Damping Screens for the Reduction of Wind Tunnel Turbulence," J . Aero, S c i . , V o l . 14, 221-228 (1947).  138 34.  Lumlet, J . L . , and C a r v e r , J . F . , "Reducing Water Tunnel Turbulence by Means of a Honeycomb," ASME Paper 67-FE-5, (1967).  35.  "Fluid Meters - Their Theory and Application", Report fo ASME Research Committee on F l u i d Meters, F i f t h Edition 1959, ASME, New York 18, N.Y.  36.  Sprenkle, R . E . , "Piping Arrangements for Acceptable Flowmeter Accuracy," Trans. ASME, V o l . 67, 345-350 (1945).  37.  Robbins, R . J . , M.A.Sc. Thesis, University of B r i t i s h Columbia, Vancouver, B r i t i s h Columbia (April 1969).  38.  Instruction Manual, Heat Flux System Model 1010 (Modified to 2.5 Amps) Thermo-Systerns I n c . , Minneapolis, Minnesota.  39.  Advances in Heat Transfer - Volume 1, T . F . Irvine and J . P . Hartnett, eds. Academic Press, New York, N.Y. (1964).  40.  Nichrome And Other High Nickel A l l o y s , Driver-Harris Company, Harrison, New Jersey, Catalog R-59.  41.  Michels, A. and C. Michels, "Isotherms of CO., between 0° and 150° and Pressures from 16 to 250 atm," Proc. Roy. Soc. London/ A 153 (1935), pp. 201-214.  42.  Michels, A . , B. B l a i s s e , and C. Michels, "The Isotherms of CO2 in the Neighborhood of the C r i t i c a l Point and Round the Coexistence Line," Proc. Roy. Soc. London, A 160 (1937), pp. 358-375.  43.  Michels, A . , A. Botzen, and W. Schuurman, "The Viscosity of Carbon Dioxide between 0°C and 75°C and at Pressures up to 2000 Atmospheres," Physica, V o l . 23 (1957), pp. 95-102.  44.  Michels, A . , J . V . Sengers, and P.S. Van Der Gulik, "The Thermal Conductivity of Carbon Dioxide in the C r i t i c a l Region," Physica, V o l . 2 8 (1962), pp. 1216-1237.  45.  Ackerman, J . W . , "Pseudo b o i l i n g Heat Transfer to Superc r i t i c a l Water in Smooth and Ribbed Tubes," ASME- Paper 6 9-WA/HT-2, November 1969,.  46.  Baumeister, K . J . and Hamill T . D . , "Laminar Flow Analysis of Film Boiling From A Horizontal Wire," NASA Technical Note, NASA TN D-4035, July 1967.  139  47.  Brodowicz, K. and Bialokoz, J . , "Free Convection Heat Transfer from a V e r t i c a l Plate to Freon 12 Near the C r i t i c a l State," The Archive of Mechanical Engineering, V o l . X, No. 4, Warsaw (1963).  48.  Bourke, P . J . and Denton, W.H., "An Unusual Phenomenon of Heat Transfer Near the C r i t i c a l Point," Memorandum, AERE 1946, United Kingdom Atomic Energy Authority, Harwell, B i r k s h i r e , 1967.  49.  Cornelius, A . J . and Parker, J . D . , "Heat Transfer Ins t a b i l i t i e s Near the Thermodynamic C r i t i c a l Point", Proc. Heat Trans, and F l . Mech. I n s t . , 317-329 (1965).  50.  H a l l , W.B., Jackson, J . D . and Warson, A . , "A Review of Forced Convection Heat Transfer to Fluids at S u p e r c r i t i c a l Pressures," Symposium on Heat Transfer and F l u i d Dynamics of Near C r i t i c a l F l u i d s , B r i s t o l , March 1968, Paper 3.  51.  H a l l , W.B., Jackson, J . D . , Khan, S . A . , "An Investigation of Forced Convection Heat Transfer to S u p e r c r i t i c a l Pressure Carbon Dioxide," Proceedings of the Third International Heat Transfer Conference, AIChE, V o l . 1, 257-266 (1966).  52.  Hasegawa, S. and Yoshioka, K . , "A Complete Study for Laminar Free Convective Heat Transfer to S u p e r c r i t i c a l Fluids Near the Transposed C r i t i c a l Point".  53.  Hess, H . L . , and Kunz, H . R . , "A Study of Forced Convection Heat Transfer to S u p e r c r i t i c a l Hydrogen," J . of Heat Transf., V o l . 87, 41-48 (1965).  54.  P i t t s , D . R . , Yen, H.H. and Jackson, T.W., "Transient Film Boiling on a Horizontal Wire," ASME Paper No. 68-HT-3.  55.  P i t t s , C C . anf Leppert, G.,"The C r i t i c a l Heat Flux for E l e c t r i c a l l y Heated Wires i n Saturated Pool B o i l i n g , " Int. J . Heat Mass Transfer, V o l . 9, 365-377 (1966).  56.  Sengers, J . V . and Sengers, A . L . , "The C r i t i c a l Region," Chemical and Engineering News, June 10, 1968.  57.  Schnurr, N . M . , "Heat Transfer to Carbon Dioxide i n the Immediate V i c i n i t y of the C r i t i c a l Point,"-ASME Paper . No. 68-HT-32  58.  Shiralkar, B . S . , and G r i f f i t h , P . , "Deterioration i n Heat Transfer to fluids at S u p e r c r i t i c a l Pressure and High Heat Fluxes," J . of Heat Transfer, February 1969, pp. 27-36.  APPENDIX I  PROPERTIES OF NEAR-CRITICAL CARBON DIOXIDE  DYNAMIC VISCOSITY O F C A R B O N DIOXIDE ( D a t a t a k e n f r o m [19])  *  1  1  50  100  150  1  200  1  250  I  300  I  350  TEMPERATURE - °F  DYNAMIC VISCOSITY O F C A R B O N DIOXIDE (Data taken from [19])  L _  400  50  100  150  200  250  300  350  400  4 50  TEMPERATURE - °F DENSITY O F C A R B O N DIOXIDE ( D a t a t a k e n f r o m [19]) ro  E N T H A L P Y O F C A R B O N DIOXIDE (Data taken from [19])  T H E R M A L CONDUCTIVITY O F CARBON ( D a t a t a k e n f r o m [19])  DIOXIDE  145  APPENDIX I I SUMMARY AND  A taken  over  below. been  list  of a l l high  the course  Segments  combined  observations.  LISTING  speed  16 mm  which  were  summarizes  taken  view,  the center  two-thirds  films  were  a t 5000 p p s , w i t h  taken  a t 3000 p p s a n d w i t h  taken  work  and white  with  o f the heated  a larger  have  the experimental  t h e same  field  cylinder,  the exception field  films  i s contained  2, 3, 4, 6, 7, 8, 1 2 , a n d 13  a movie  A l l films  PHOTOGRAPHS  black  of the experimental  of films  into  OF F I L M S AND  of  and a l l  of film  1  o f view.  /  146  APPENDIX II SUMMARY AND LISTING OF FILMS AND PHOTOGRAPHS  Film No. »T  P, b  T, b  T cy  SUMMARY  1100  80  400  Free convection showing vapor columns r i s i n g from the cylinder and the breakof the laminar flow into the turbulent plume (3000 pps and a large f i e l d of view was taken).  1100  80  400  Forced convection (Re*=165) showing the tearing of f l u i d from the c y l i n d e r .  1100  80  400  Forced convection (Re*=50) showing the breakdown of the free convection flow f i e l d with very small free-stream velocity.  1100  80  400  Forced convection (Re*=650) showing the effect of a larger free stream v e l o c i t y on the heat transfer mechanism. The o s c i l l a t i n g region behind the cylinder is v i s i b l e .  1070  80  100  Free convection just under the c r i t i c a l pressure to show the stable film b o i l ing in which the f l u i d flows a x i a l l y along the cylinder and r i s e s in a vapor column.  1100  80  400  Free convection at 5000 pps to base a time rate on the speed of the r i s i n g vapor-like disturbances which r i s e from the heated c y l i n d e r .  1050  75  400  Free Convection stable film b o i l i n g at the cylinder temperature used for Film 6 to show the difference between subc r i t i c a l and s u p e r c r i t i c a l free convection.  1050  75  86  Free convection nucleate b o i l i n g c l e a r l y showing the very rapid bubble generation and the d i s t i n c t bubble motion below the c y l i n d e r .  147  Film No.  P,  9  1100  80  98  10  1100  90  400  Forced convection (Re*=165) to show the effect of operating with bulk f l u i d very near the p s e u d o - c r i t i c a l temperature. The large property variations show up in the free stream and the average heat transfer rate i s less than 80% of that with bulk f l u i d 10 deg F colder,  11  1500  75  425  Free convection to show the effect of small disturbances generated by the motion i t s e l f on the flow s t a b i l i t y . The probe had been in s t i l l f l u i d at room temperature for two hours and was suddenly started at 425 deg F . The film was started after one minute of operation and shows the unstable nature of the free convection as the plume breaks down. Heat transfer rate increased by 15% during the breakdown.  12  1100  77  450  This film shows the developing flow f i e l d when the probe was suddenly turned on in s t i l l f l u i d . The camera had reached more than 3000 pps before the probe was started and a record of the e l e c t r i c a l response was also obtained during the transient. The transient time scale obtained from frame by frame examination shows the following; 0 to 3 msec . . . . thermal capacitance of the probe and f l u i d in contact with the probe surface—a large voltage spike while the probe reaches temperature. 3 to 10 msec . . . . thickening of the heated layer about the cylinder and the layer starts to r i s e around the cylinder. 10 to 16 msec . . . . the f i r s t section of heated f l u i d breaks free of the cylinder and r i s e s to 3 diameters above the cylinder  cy  SUMMARY  F o r c e d convection (Re*=50) to show the v e l o c i t y effect at the conditions corresponding to maximum film c o e f f i c i e n t . The flow i s e s s e n t i a l l y as observed in Film 3 but shows some unsteady behaviour.  148 Film No.  P. b  T, b  T  SUMMARY  cy 16  t o 2 0 0 msec . . . . t h e h e a t e d fluid r i s e s i n a plume and f i r s t becomes t u r b u l e n t a t 2 0 0 msec 200 t o 2 5 0 msec . . . . t h e f l o w f i e l d becomes f u l l y d e v e l o p e d w i t h t h e t u r b u l e n t plume o s c i l l a t i n g about a stable location. 13  1000  80  85  Forced convection b o i l i n g a t the locat i o n o f maximum f i l m c o e f f i c i e n t (peak nucleate heat f l u x c o n d i t i o n i n forced flow) (Re*=300).  14  1000  80  85  F o r c e d c o n v e c t i o n b o i l i n g a t the peak n u c l e a t e h e a t f l u x b u t a t a much slower velocity (Re*=70).  15  1000  80  425  F o r c e d c o n v e c t i o n b o i l i n g a t a much higher temperature d i f f e r e n c e t o produce film boiling (Re*=75) f o r c o m p a r i s o n with the s u p e r c r i t i c a l case i n F i l m 3 and 16.  16  1500  80  425  F o r c e d c o n v e c t i o n (Re*=75) t o i l l u s t r a t e the e f f e c t o f v e l o c i t y i n f l u i d above b u t away f r o m t h e c r i t i c a l p r e s s u r e . The f i l m i l l u s t r a t e s t h e s i m i l a r i t y o f a l l s u p e r c r i t i c a l flows by comparison w i t h F i l m s 3, 9 , 1 0 .  149  APPENDIX III CALCULATIONS AND ERROR ANALYSIS Values of heat transfer rate, temperature difference, and heat transfer coefficient  were calculated for each data  point following the example shown below:  A.  Power Dissipated  2  P = I Rop  (watts)  % error error xn i n e, P•  p  ^  = = ^ R  = 0.1% + 2 x 0.5%  =  (.608x.608x4.06)  + o  p  +^2I $1  =  = 4.06 °-  Q Q 4  1.50  + .608 Q  0 0 3  watts  X  x 2  1.1%  The error in current i s taken as t y p i c a l of a l l operating points and is a combination of the rms fluctuation and the meter inaccuracy.  B.  Heat Transfer Rate  Q  = AREA  « error  =  . i  n  3.1416 x d x L 3  4  3  (BTU/hr-ft ) = 72290 B T U / h r - f t  _ 6 Q 6 P fid ^ 6 L Q; — = — + + — =  = 1.1% + 1.0% + 0.8% = 2.9%  2  . ^ 0.00005 ^ 0.0005 0.6% + +- ^ y c o  -  0  Q  5  4  2  150 C.  Temperature  = 1 + a  Rc  A  T  A  T  in  Heat  h  =  %  error  '  •  „  h;  = 2.9% + 2.2%  Values ential  readings.  V  +.K t  h  =  C,  /—~4 1-6  d  ^  e  '  F  ±  r  Coefficient  d e g F) =  2  6h  6Q  j -= ^  =  7  2  2 }  9  °  =  760  BTU/hr-ft  2  deg F  , SAT +  —  5.1%  of velocity  typical  Free-Stream  2  1.0)  2.2%  were  across  of the venturi A  '  5  -  Rc  6a ^ 6Rop 6Rc + • + — a Rop Rc  pressure developed  coefficient  E.  =  (BTU/hr-ft  m  9  -—-=• = —  A m  Transfer  =  0  6AT AT  AT;  = 2% + .1% + 1%  D.  a  " i - *  (  error  AT = i  A  .000994 I77!  =  %  Difference  meter  calcualtion  calculated  from  the venturi was  taken  0  1  P  n  L  =  meter.  a s 0.96  i s reprqduced  Velocity  /2g(P -P  _ _ _ _ _  1.01/2gl44Ap  '  P  the  differDischarge  for a l l  below.  151 if  in a typical  Ap  = 10.0  case  psig,  a t 80  p =  deg F,  =1.01  psia  48 l b ft  V_, th  1100  3  /2x32.2x144x10  =1.01  /1850  =  43.0  ft/sec '  48  2.0% +  %  C  calculate  A  TT  in V  Values  F.  on  Re  P  3.5%  the  probe;  AV 6V., 6A.. 6A P th , th , p —*- = + + — — V V.. A., A p th th p  ;  £  =  6%  of free-stream  assuming  cylinder  Reynolds  2  sec  = 3.5% + 2% + 5%  based  P  2  =  1 6p_  the v e l o c i t y past  P  calculated  B  1 6p  P  •  error  b'  .5% + 1.0%  ^  o  B)  v  t h  V  h  To  6(C, ^d  th  % error in V ; th  constant  Reynolds  number  free-stream  (Re*) w e r e  properties  and  were  diameter.  Number  Vd  Vdp  v  v  = -— - - ~  .  where  ,  0. 0054  d = —=-=  it  _  f t ,  _  48 l b  p = -Fr3~/  it  y =  1 / l n  -  1  4  lb  0  f  t  h  r  152 Re*  %  error  in  =  6.%  1.0%  Note  -  so  +  At  varied 4  1.9.5X.0054x48x3600 12x.l40  =  by  a  that within  G.  Bulk  main  %  H.  bulk  test  1 psia at  in full  any  The  6d  6p  d  p  2%  =  11%  condition, free differential  bulk  stream  velocities  pressure  by  % error  i n Re*  condition  a  of  change  <SRe* Re*  pressure  was  block  scale.  measured  using  Gauge  6P —  in Pressure;  and  temperature Northrup  thermocouples  a  i n stagnant  Heise  pressure  bourdon could  be  =  0.1%  +  0.1%  =  from  the  immersion  were in a  was  K-5  determined  potentimeter  gauge read  calibrated heated  bath  using and  the  in  accurate to  1  the  measured 0.5?-,.  same c i r c u i t  standard  t a b l e s agreed  50  E r r o r s would  proportionately smaller  be  emf  accurate, to  emf-temperature  F.  fluid  0.2%  constantan deg  factor  were  Temperature  Leeds  direct  6V V  reading.  error  Bulk  a  a  section  Bulk on  the  1075  Pressure  The  psia  +  bulk  changing  approximately  to  2.%  given  is  the  cSRe* Re*  Re*;  +  =  within  0.1  by  copperdeg at  F  in  higher  153 temperature  %  The  error  fluid  between shown  I.  d i f f e r e n c e s b u t maximum  i n temperature:  was  assumed  the thermocouple  on  the s c h l i e r e n  Property  tally have which  drawn  an  readings  0.2  and  by  +0.2%  deg  F  =  by  as;  0.7%  a  comparison  the density  gradients  image.  [18]  by M i c h e l s t o be  a r e reporoluced tvpical  evaluation  bulk  conditions  from  other  variations  0.5%  within  p r o p e r t i e s were  Knapp  assumed  The  as  by  measured been  =  estimated  Evaluation  Transport curves  uniform  6T —  e r r o r c a n be  43,  accurately portrayed  i n Append].x  44]. by  smooth experimenProperties  these  curves  I.  —- error described p  show g o o d  from  the p r o p e r t i e s  e t a l . [ 4 1 , 42,  uncertainty  tables [22].  through  evaluated  only.  agreement  of n e a r - c r i t i c a l  above  was  Spot  checks  with  property  carbon  considered  at selected  dioxide  evaluations property  

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