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Flow regimes and pressure histories during blowdown from a vertical tube Steeves, Alan 1983

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FLOW REGIMES AND PRESSURE HISTORIES DURING BLOWDOWN FROM A VERTICAL TUBE  by  ALAN STEEVES B . A . S c , The U n i v e r s i t y of B r i t i s h Columbia, 1976  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE  in THE FACULTY OF GRADUATE STUDIES Department of M e c h a n i c a l E n g i n e e r i n g  We accept t h i s t h e s i s as conforming to the r e q u i r e d s t a n d a r d  THE UNIVERSITY OF BRITISH COLUMBIA April  1983  © A l a n S t e e v e s , 1983  In presenting an  this  thesis i n p a r t i a l  advanced degree a t the U n i v e r s i t y  the  library  further  shall  agree t h a t  make i t f r e e l y  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 of B r i t i s h  Columbia, I agree  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 .  permission f o r extensive  copying  of t h i s  that I  thesis for  s c h o l a r l y purposes may be g r a n t e d by the Head of my department or by h i s or h e r r e p r e s e n t a t i v e s . this  thesis  for financial  I t i s understood t h a t c o p y i n g o r p u b l i c a t i o n of gain  shall  permission.  ALAN STEEVES  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 of B r i t i s h Columbia  Vancouver, Canada  Date  not be a l l o w e d w i t h o u t my  written  ABSTRACT  A  series  discharging  of  blowdown  experiments  either vertically  have  been  performed  while  (upwards or downwards) or h o r i z o n t a l l y i n  o r d e r to compare the e f f e c t of body f o r c e on t r a n s i e n t f l o w p a t t e r n s pressure  histories.  polycarbonate Results,  Tests  done  using  p i p e 4 m l o n g w i t h a 32 mm presented  b a s i c nature  were  i n the  of the d e v e l o p i n g  form of  Freon-114  a  clear  I.D. flow  regime maps, show t h a t  flow i n a v e r t i c a l  the  p i p e when d i s c h a r g i n g  upward i s d i f f e r e n t than f o r the downward d i s c h a r g e c a s e . in  in  and  Both cases  are  t u r n markedly d i f f e r e n t than f o r h o r i z o n t a l d i s c h a r g e . Pressure  which  the  slowly  histories  pressure  to atmospheric;  n e a r l y the i n i t i a l drop. not  The be  rapidly a second  p r e s s u r e was  second c a t e g o r y  satisfactorily  g r a d i e n t , and case.  fell  were found  to  fall  to near  into the  two  c a t e g o r i e s : one  s a t u r a t i o n pressure,  in then  i n which t r a n s i e n t r e p r e s s u r i z a t i o n t o  observed  occurred  explained.  f o l l o w i n g the i n i t i a l  pressure  o n l y i n the v e r t i c a l p i p e and Rapid  changes  p o s s i b l e f l o w r e v e r s a l , were noted  in  axial  could  pressure  i n the r e p r e s s u r i z a t i o n  - iii  -  TABLE OF CONTENTS  Page ABSTRACT  i i  TABLE OF CONTENTS  i i i  LIST OF FIGURES  v  ACKNOWLEDGEMENTS  viii  1. INTRODUCTION  1  1.1 P r e l i m i n a r y Remarks  1  1.2  P r e v i o u s Work  2  1.2.1  Experimental  2  1.2.2  Theoretical  6  1.3  Scope of T h i s I n v e s t i g a t i o n  2. EXPERIMENTAL APPARATUS  8  10  2.1 G e n e r a l Concept of the E x p e r i m e n t a l Apparatus  10  2.2 D e t a i l s of the Apparatus  11  Components  2.2.1  Test S e c t i o n  11  2.2.2  P r e s s u r e Measurement  16  2.2.3  Temperature Measurement  18  2.2.4  P h o t o g r a p h i c Equipment  18  3. EXPERIMENTAL PROCEDURE  21  3.1 G e n e r a l  21  3.2  I n i t i a l P r e p a r a t i o n and C a l i b r a t i o n of the Apparatus  21  3.3  Procedure f o r Freon-114 Blowdown Measurements  23  - iv -  Page 3.4 Data A n a l y s i s  26  4. EXPERIMENTAL RESULTS  27  4.1 G e n e r a l  27  4.2 P r e s s u r e H i s t o r i e s f o r D i s c h a r g e H o r i z o n t a l l y  29  4.3 Flow H i s t o r i e s f o r D i s c h a r g e H o r i z o n t a l l y  29  4.4 P r e s s u r e H i s t o r i e s f o r D i s c h a r g e V e r t i c a l l y Down  32  4.5 Flow H i s t o r i e s f o r D i s c h a r g e V e r t i c a l l y Down  58  4.6 P r e s s u r e H i s t o r i e s f o r D i s c h a r g e V e r t i c a l l y Up  60  4.7 Flow H i s t o r i e s f o r D i s c h a r g e V e r t i c a l l y Up  77  5. DISCUSSION OF THE RESULTS  80  5.1 D i s c h a r g e H o r i z o n t a l l y  80  5.2 D i s c h a r g e V e r t i c a l l y  81  6. CONCLUSIONS  88  6.1 G e n e r a l  88  6.2 Normal d a t a  89  6.3 R e p r e s s u r i z a t i o n d a t a  90  6.4 S u g g e s t i o n s f o r F u r t h e r Study  91  REFERENCES  92  APPENDIX ONE  94  APPENDIX TWO  96  - v -  LIST OF FIGURES Page FIGURE  1. Schematic diagram of the e x p e r i m e n t a l apparatus  12  FIGURE  2. P r e s s u r e h i s t o r y showing the e f f e c t o f a p a r t i a l l y b l o c k e d d i s c h a r g e end on the i n i t i a l stages of decompression o f n i t r o g e n i n a h o r i z o n t a l p i p e  14  FIGURE  3. D e t a i l s of the end-diaphragm mechanism, i n c l u d i n g a t y p i c a l t r a n s d u c e r mounting arrangement  15  FIGURE  4. B l o c k diagram o f the data a c q u i s i t i o n system  20  FIGURE  5. P r e s s u r e h i s t o r i e s d u r i n g decompression o f n i t r o g e n from a h o r i z o n t a l tube 6. P r e s s u r e h i s t o r i e s d u r i n g the blowdown f o r a h o r i z o n t a l p i p e . Both p r e s e n t r e s u l t s as w e l l as those of Necmi and Hancox [4] a r e shown  30  7. P r e s s u r e h i s t o r i e s d u r i n g t h e i n i t i a l s t a g e s o f blowdown f o r a h o r i z o n t a l p i p e . Both p r e s e n t r e s u l t s as w e l l as those o f Necmi and Hancox [4] a r e shown  31  8. Flow regimes d u r i n g blowdown of Freon-114 from a h o r i z o n t a l p i p e , from Necmi and Hancox [4]  33  9. D e f i n i t i o n s k e t c h e s o f the t h i s s t u d y . Time advances h o r i z o n t a l d i s c h a r g e ; from d i s c h a r g i n g e i t h e r upwards  34  FIGURE  FIGURE  FIGURE FIGURE  f l o w regimes i d e n t i f i e d i n from l e f t t o r i g h t f o r top t o bottom f o r o r downwards  FIGURE 10. P r e s s u r e h i s t o r i e s a t two gauge s t a t i o n s  fora vertical  p i p e d i s c h a r g i n g down  36  FIGURE 11. Repeat of the d i s c h a r g e h i s t o r i e s o f F i g u r e 10 FIGURE 12. P r e s s u r e h i s t o r i e s a t two gauge s t a t i o n s  28  37  fora vertical  p i p e d i s c h a r g i n g down FIGURE 13. Repeat o f one of the d i s c h a r g e h i s t o r i e s o f F i g u r e 12 ... FIGURE 14. P r e s s u r e h i s t o r i e s a t two gauge s t a t i o n s f o r a v e r t i c a l p i p e d i s c h a r g i n g down FIGURE 15. Long term p r e s s u r e h i s t o r i e s f o r t h r e e gauge s t a t i o n s f o r a v e r t i c a l p i p e d i s c h a r g i n g down FIGURE 16. Long term p r e s s u r e h i s t o r i e s f o r t h r e e gauge s t a t i o n s f o r a v e r t i c a l p i p e d i s c h a r g i n g down  38 39  41 42 43  - vi-  Page FIGURE 17. Repeat of the d i s c h a r g e h i s t o r i e s of F i g u r e 15  44  FIGURE 18. P r e s s u r e h i s t o r i e s showing the r e p e a t a b l i t y of the d a t a o b t a i n e d f o r a v e r t i c a l p i p e d i s c h a r g i n g downward  46  FIGURE 19. P r e s s u r e h i s t o r y showing r e p r e s s u r i z a t i o n d u r i n g blowdown from a v e r t i c a l p i p e d i s c h a r g i n g downward  47  FIGURE 20. P r e s s u r e h i s t o r y showing r e p r e s s u r i z a t i o n d u r i n g blowdown from a v e r t i c a l p i p e d i s c h a r g i n g downward FIGURE 21. Repeat of the p r e s s u r e h i s t o r y shown i n F i g u r e 20  48 49  FIGURE 22. P r e s s u r e h i s t o r y showing r e p r e s s u r i z a t i o n d u r i n g blowdown from a v e r t i c a l p i p e d i s c h a r g i n g downward FIGURE 23. Repeat of the p r e s s u r e h i s t o r y shown i n F i g u r e 22 FIGURE 24. P r e s s u r e h i s t o r y showing r e p r e s s u r i z a t i o n d u r i n g blowdown from a v e r t i c a l p i p e d i s c h a r g i n g downward FIGURE 25. Long term p r e s s u r e h i s t o r i e s f o r t h r e e gauge s t a t i o n s f o r a v e r t i c a l p i p e d i s c h a r g i n g downward FIGURE 26. Long term p r e s s u r e h i s t o r i e s f o r t h r e e gauge s t a t i o n s f o r a v e r t i c a l p i p e d i s c h a r g i n g downward  51 52  53 55 56  FIGURE 27. P r e s s u r e h i s t o r i e s showing the r e p e a t a b l i t y of the r e p r e s s u r i z a t i o n b e h a v i o u r d u r i n g blowdown from a v e r t i c a l p i p e d i s c h a r g i n g downward  57  FIGURE 28. Flow regimes d u r i n g blowdown of Freon-114 from a v e r t i c a l p i p e d i s c h a r g i n g downward ( s e e F i g u r e 9)  61  FIGURE 29. P r e s s u r e h i s t o r y d u r i n g the i n i t i a l stages of blowdown from a v e r t i c a l p i p e d i s c h a r g i n g upward  62  FIGURE 30. P r e s s u r e h i s t o r y d u r i n g the i n i t i a l stages of blowdown from a v e r t i c a l p i p e d i s c h a r g i n g upward  63  FIGURE 31. P r e s s u r e h i s t o r y showing r e p r e s s u r i z a t i o n b e h a v i o u r d u r i n g blowdown from a v e r t i c a l p i p e d i s c h a r g i n g upwards  64  FIGURE 32. P r e s s u r e h i s t o r y showing r e p r e s s u r i z a t i o n b e h a v i o u r d u r i n g blowdown from a v e r t i c a l p i p e d i s c h a r g i n g upwards  66  - vii -  Page FIGURE 33. Repeat of the d i s c h a r g e  h i s t o r y shown i n F i g u r e 32  FIGURE 34. Pressure h i s t o r y d u r i n g the i n i t i a l stages from a v e r t i c a l pipe d i s c h a r g i n g upward  of blowdown  FIGURE 35. P r e s s u r e h i s t o r y d u r i n g the i n i t i a l stages from a v e r t i c a l pipe d i s c h a r g i n g upward  o f blowdown  FIGURE 36. Repeat of the d i s c h a r g e  67  68  h i s t o r y shown i n F i g u r e 35  69 70  FIGURE 37. P r e s s u r e h i s t o r i e s showing the r e p e a t a b l i t y of d a t a taken a t a gauge s t a t i o n t h a t d i d not show r e p r e s s u r i z a t i o n d u r i n g the blowdown from a v e r t i c a l pipe d i s c h a r g i n g upward  71  FIGURE 38. P r e s s u r e h i s t o r i e s showing the r e p e a t a b l i t y of data taken at a gauge s t a t i o n that d i d not show r e p r e s s u r i z a t i o n d u r i n g the blowdown from a v e r t i c a l pipe d i s c h a r g i n g upward  72  FIGURE 39. P r e s s u r e h i s t o r y showing the r e p e a t a b l i t y of the r e p r e s s u r i z a t i o n behaviour d u r i n g blowdown from a v e r t i c a l pipe d i s c h a r g i n g upward  73  FIGURE 40. Long term p r e s s u r e h i s t o r i e s f o r three gauge s t a t i o n s f o r a v e r t i c a l pipe d i s c h a r g i n g upward  74  FIGURE 41. Long term p r e s s u r e for  histories  f o r three gauge s t a t i o n s  a v e r t i c a l pipe d i s c h a r g i n g upward  FIGURE 42. Repeat of the p r e s s u r e  histories  shown i n F i g u r e 41  FIGURE 43. Flow regimes d u r i n g blowdown of Freon-114 from a v e r t i c a l pipe d i s c h a r g i n g downward ( s e e F i g u r e 9) FIGURE 44. P r e s s u r e p r o f i l e s along a pipe d i s c h a r g i n g downward when r e p r e s s u r i z a t i o n was noted ( I n i t i a l c o n d i t i o n s as i n F i g u r e 27) FIGURE 45. P r e s s u r e p r o f i l e s along a pipe d i s c h a r g i n g upward when r e p r e s s u r i z a t i o n was noted ( i n i t i a l c o n d i t i o n s as i n F i g u r e 29)  75 76  79  84  85  - viii -  ACKNOWLEDGEMENTS  I would l i k e t o express my s i n c e r e thanks t o my s u p e r v i s o r , D r . E. G. Hauptmann; w i t h o u t h i s h e l p and encouragement t h i s work may never been  finished.  Additional  thanks  a r e due t o Dr. P. G. H i l l  have  for his  i n v a l u a b l e comments and encouragement d u r i n g our noon hour d i s c u s s i o n s . T h i s work p r o b a b l y would never Dr.  W.  T. Hancox  have been s t a r t e d  p r o v i d i n g us a v e r y  e q u i p m e n t he used f o r h i s o r i g i n a l I would a l s o l i k e  generous  i f i t was n o t f o r  loan  o f much o f t h e  experiments.  t o thank P h i l Hurren, John R i c h a r d s , Fred Knowles,  Len Drake and Ed Able of the M e c h a n i c a l E n g i n e e r i n g Department staff  f o r their  assistance  i n the c o n s t r u c t i o n and r e p a i r  technical of the  apparatus. I would e s p e c i a l l y l i k e t o express my g r a t i t u d e to my Mom and Dad who have always supported any d e c i s i o n I have ever made.  - 1 -  CHAPTER  ONE  INTRODUCTION  1.1 P r e l i m i n a r y Remarks With  t h e widespread  use o f n u c l e a r  power  f o r the generation  e l e c t r i c i t y , many s t u d i e s have been done t o a s s u r e power p l a n t s . coolant  accident  blowdown system. a  An area  of great  (LOCA),  i s one o f r a p i d  the s a f e t y of nuclear  c o n c e r n i s the problem of a l o s s - o f -  o r blowdown.  E s s e n t i a l l y t h e problem o f  depressurization  of the r e a c t o r ' s  cooling  T h i s c o u l d occur as the r e s u l t of a pipe f a i l u r e , a s e a l break,  pump m a l f u n c t i o n ,  o r any c o n c e i v a b l e  system t o l o s e i t s p r e s s u r e - t i g h t  accident  that  r e a c t o r i s c o n s t a n t l y producing  could  cause t h e  seal.  A l o s s o f c o o l a n t can have s e r i o u s consequences. heat.  The f u e l i n a CANDU  Under normal o p e r a t i n g  conditions  the s u r f a c e temperature o f the f u e l i s over 300 degrees c e l s i u s . any  of  I f for  r e a s o n c o o l i n g of the f u e l i s I n t e r r u p t e d , t h e heat t h a t i s produced  i n t e r n a l l y may cause the f u e l t o m e l t . products  contaminating  the c o o l i n g  T h i s would r e s u l t i n the f i s s i o n water  and  producing  radioactive  steam. Before  a  reactor  can be  licensed  f o r operation  i n Canada, t h e  m a n u f a c t u r e r has t o prove t o the Atomic Energy C o n t r o l Board (AECB) t h a t the  reactor w i l l  scale  numerical  The v a l i d i t y  be s a f e d u r i n g  a blowdown i n c i d e n t .  c a l c u l a t i o n s a r e used  o f these  simulations  to simulate  i s checked  To do t h i s ,  accident  by u s i n g  what would happen d u r i n g blowdown from a s t r a i g h t tube.  large  conditions.  them t o p r e d i c t Data f o r these  - 2 -  "benchmark"  experiments  can  be  obtained  either  theoretically  or  experimentally. Theoretical  data  are obtained  by u s i n g v e r y  s o p h i s t i c a t e d computer  models. The t h e o r y i n v o l v e d i n these models i s such t h a t , w h i l e they can p r e d i c t what happens d u r i n g blowdown i n a applied  directly  s t r a i g h t tube, they can not be  to an a c t u a l r e a c t o r s i t u a t i o n .  This  i s because i n  t h e i r c u r r e n t s t a t e of development, these "benchmark" computer models can only  be e c o n o m i c a l l y  valves,  used  bends and o t h e r  for a straight  pieces  tube.  associated with  The c o s t of i n c l u d i n g a real  r e a c t o r becomes  p r o h i b i t i v e l y high. Experimental o b t a i n data Some  formation  use  flow  This data o r be  These blowdown  used  tests  test  setups.  1.2  PREVIOUS WORK  1.2.1  o f water  or some o t h e r  on p r e s s u r e , v o i d f r a c t i o n , and o t h e r i m p o r t a n t  studies  histories.  s t u d i e s use blowdown  visualization  to  determine  the  p r e d i c t i o n s of n u m e r i c a l  can be done e i t h e r  to  parameters. flow  can then be used to g i v e some i n s i g h t to v e r i f y  fluid  regime  i n t o model  simulations.  on s c a l e models o r f u l l  scale  Experimental  Blowdown  studies  demand  w i d e l y v a r y i n g parameters. of e x p e r i m e n t a l  an  understanding  This understanding  and a n a l y t i c a l work.  of  the e f f e c t s  i s gained by a  o f many  combination  S e v e r a l i n v e s t i g a t i o n s have been  done on the blowdown of h i g h e n t h a l p y water from h o r i z o n t a l p i p e s ; these i n c l u d e Edwards and O'Brien  [ 1 ] , Edwards and Mather [ 2 ] , and the r e c e n t  - 3 -  work of A l a m g i r , Kan and L i e n h a r d  [3].  Necmi and Hancox [4] d i d s i m i l a r  s t u d i e s but w i t h h i g h e n t h a l p y Freon-114. Edwards and O'Brien ran e x p e r i m e n t a l t e s t s which c o n s i s t e d of h e a t i n g a  water-filled  maintained  pipe  before  recorded  the  the  during  recorded KHZ. ft  required  temperature  c o n d i t i o n s , then  rupturing a glass disc  transient  on  The  the  above s a t u r a t i o n  pressure  pipe  to  the  a FM  pressure,  the  and  frequency  d e p r e s s u r i z a t i o n t e s t s were performed  l o n g and  2.88  The  initial  temperature  From t h i s work Edwards and  O'Brien  pressure  of  the  pipe.  They  d e n s i t y changes  along  measurements were  response  of DC  to  using a s t e e l pipe  inches i n i n t e r n a l diameter.  500 to 2500 p s i .  end  A l l transient  recorder with a  the  a d j u s t i n g to the r e q u i r e d  temperature  blowdown phase.  tape  at  with  The  80  13.44  range of p r e s s u r e  was  v a r i e d from 467°F to 636°F.  were a b l e to draw the  following  conclusions: 1.  the p r e s s u r e never  initially  reaches  that  falls  below, then r e c o v e r s s l i g h t l y ,  corresponding  to  the  initial  but  saturation  value; 2.  the  observed  wave  front  sound  in  propagation i s i n good  the  velocity  of  the  agreement w i t h  compressed  liquid  phase,  the  initial  decompression  isentropic  deduced  from  speed the  of  steam  tables; 3.  their  calculation  transfer  method,  based  to a c l o u d of b u b b l e s ,  on  conduction  i s capable  controlled  heat  of r e p r o d u c i n g  very  c l o s e l y the e a r l y stages of the d e p r e s s u r i z a t i o n of a s i n g l e p i p e system;  - 4 -  4.  both pressure  their  and v o i d f r a c t i o n time h i s t o r i e s i n d i c a t e t h a t  t h e o r e t i c a l c a l c u l a t i o n gave a h i g h e r  than a c t u a l  mass  discharge. Edwards and Mather [2] performed a s e r i e s of experiments i n the same manner.  They s t u d i e d  the blowdown of water from t h r e e d i f f e r e n t p i p e s .  The p i p e s were a l l 13 f e e t l o n g w i t h 1.25 i n c h , 3 i n c h and 8 i n c h nominal i n t e r n a l diameters. 500,  The t e s t s covered v a l u e s  1000 and 2000 p s i a , w i t h  cooled  most  of s a t u r a t i o n p r e s s u r e  of the t e s t s  of  s t a r t i n g from a sub-  c o n d i t i o n of 500 p s i o v e r - p r e s s u r e .  Their  experimental  equilibrium subcooled usually  work  i s not always  to saturated  indicated  appropriate.  pressure  be observed u n t i l  that  an  assumption  When t h e r e  of  thermal  i s a change  conditions, non-equilibrium  from  e f f e c t s can  the system has had time to n u c l e a t e  and grow  vapour b u b b l e s . S o z z i and F e d r i c k  [5] r a n t e s t s on the d i s c h a r g e  through a h o r i z o n t a l pipe. horizontal rupture  length  Their  a t the o t h e r  closed  a t one end by two  end to the bottom o u t l e t  of a one f o o t o u t s i d e diameter by 14 f o o t t a l l p r e s s u r e  vessel.  the v e s s e l was heated by means of s u b m e r s i b l e e l e c t r i c h e a t e r s 1000 p s i s a t u r a t e d the into  desired the  sparger.  water and steam.  amount of s u b c o o l i n g  lower  plenum  Pressure  drop  nozzle  Water i n to provide  B e f o r e the i n i t i a t i o n of blowdown,  was  the v e s s e l  achieved and  by i n j e c t i n g  horizontal  pipe  and temperatures were m o n i t o r e d a t s e v e r a l  i n the v e s s e l and a l o n g The p r e s s u r e  of  vessel  t e s t s e c t i o n c o n s i s t e d of a 110 i n c h  of 2 i n c h s c h e d u l e 80 p i p e ,  d i s k s and a t t a c h e d  of a p r e s s u r e  cold  water  through  a  locations  the h o r i z o n t a l p i p e .  h i s t o r i e s f o r the h o r i z o n t a l p i p e showed the u s u a l  t o below the s a t u r a t i o n  pressure  due  to a delay  rapid  i n nucleation.  - 5 -  However,  rather  than  the  pressure  s a t u r a t i o n p r e s s u r e i t was observed below the i n i t i a l  recovering  to  approximately  to recompress to a p p r o x i m a t e l y  50 p s i  pressure.  S o z z i and F e d r i c k b e l i e v e d t h a t the p r e s s u r e  r e c o v e r y was caused i n  p a r t by the growth of vapour bubbles I n the l o c a l l y decompressed and  also  by  speculated  the  choking  that  and  local  flow  friction  friction  i n c r e a s i n g the back p r e s s u r e  and  i n the  choking  test  limit  liquid  section.  the f l o w ,  They further  i n the t e s t s e c t i o n , r e s u l t i n g i n the f l u i d  p r e s s u r e r e c o v e r i n g to above the s a t u r a t i o n p r e s s u r e . No  attempt was made i n any of these  regime h i s t o r y .  s t u d i e s to determine the f l o w  Necmi and Hancox [4] were the f i r s t  regime h i s t o r y d u r i n g blowdown.  Their experimental  pressure  obtained  and v o i d  fraction  was  from a h o r i z o n t a l t r a n s p a r e n t  tube.  to i n v e s t i g a t e f l o w data on f l o w regime,  f o r the blowdown of Freon-114  The f l o w regime and v o i d  fraction  were determined from h i g h speed photography. Necmi and Hancox drew the f o l l o w i n g c o n c l u s i o n s : (1) b o i l i n g  occurs  expansion (2) a f t e r of  first  at  the  gauge  stations  wave passes, and i t i s suppressed  as  initial  between the s t a t i o n s .  100 m i l l i s e c o n d s , the f l o w a t the d i s c h a r g e plane c o n s i s t s  small  bubbly remains  liquid  flow  droplets  is still  propagates  uniformly  present  a t the d i s c h a r g e  gradually  i n vapour  i n the i n t e r i o r .  plane  inwards  dispersed  until about  the end one  show t h a t  dispersed  flow  follows a brief  while  Dispersed  flow  of blowdown  and  metre  v e l o c i t y reaches about 6 to 10 metres per second.  flow.  the  period  as  the  local  The c i n e f i l m s of  stratified  - 6 -  (3) a f t e r present above,  400 m i l l i s e c o n d s t h e bubbly  and the l i q u i d within  and vapour  one metre  f l o w regime i s no l o n g e r  phases  stratify.  o f the d i s c h a r g e  plane  As  noted  there  is a  t r a n s i t i o n between s t r a t i f i e d and d i s p e r s e d f l o w ; l i q u i d the  bottom  occupies  portion  o f the p i p e  the upper p o r t i o n .  while  occupies  vapour-droplet  mixture  F o r the remainder of the p i p e the  f l o w was s t r a t i f i e d u n t i l the end of the blowdown. 1.2.2  Theoretical  A two-phase m i x t u r e compressible  fluid.  disturbances  at limited  and  behaves, i n many r e s p e c t s , l i k e  It will  only  allow  velocities,  the p r o p a g a t i o n  similar  that  sonic  distribution  speed  i n two-phase  of the phases,  d i f f e r e n t f l o w regimes.  mixtures  therefore different  single-phase of  t o s o n i c speed  e x h i b i t s l i m i t e d d i s c h a r g e o r choked f l o w e f f e c t s .  shown  a  pressure  limitations,  Measurements have  i s dependent  on t h e  r e l a t i o n s h i p s apply to  Due t o t h i s , no s i n g l e t h e o r y w i l l d e s c r i b e a l l  a s p e c t s of t r a n s i e n t two-phase f l o w [ 2 ] . The results  complexity in  only  theoretically. documented additional  case  of  the r e l a t i o n s h i p s between  one-dimensional The g e n e r a l of  flow  treatment  single-phase  situations  being  i s an e x t e n s i o n  compressible  r e l a t i o n s h i p s to describe  the phases  fluid  the interchange  usually  considered  o f the w e l l dynamics  using  o f mass, momentum  and energy between the two phases [ 2 ] . The velocity  simplest  approach  i s based  on the assumption  e q u i l i b r i u m between t h e two phases.  V e l o c i t y Equal Temperature model (EVET). an  equation  pressure  of s t a t e  which  and temperature,  describes  This  o f thermal  i s called  and  the E q u a l  By use of these assumptions and the v a r i a t i o n  of d e n s i t y  with  i t i s p o s s i b l e t o o b t a i n a s e t of e q u a t i o n s  - 7  -  i d e n t i c a l i n form to those f o r s i n g l e - p h a s e f l o w .  These e q u a t i o n s may  e v a l u a t e d i n a s i m i l a r manner to the s i n g l e - p h a s e e q u a t i o n s .  be  U s u a l l y the  d i f f e r e n t i a l e q u a t i o n s are s o l v e d d i r e c t l y by n u m e r i c a l methods, w i t h the method of c h a r a c t e r i s t i c s b e i n g velocity  and  predictions  which  discrepancies mixtures,  equal  are  and  too  the most p o p u l a r .  temperature  do  not  f i t a l l the  too low low  assumption  The  leads  observed  f o r the  to  facts.  a p r e d i c t e d s o n i c speed  a value  use of the  theoretical The  two  i n low v o i d  choked d i s c h a r g e  equal  major  fraction  flow i n  steady  s t a t e s i t u a t i o n s [2]. Improved  agreement f o r s t e a d y - s t a t e choked  f l o w can  be  obtained  the i n t r o d u c t i o n of r e l a t i v e motion between the phases [ 2 ] . Unequal  Velocity  available is  done  Equal  Temperature  model  (UVET).  by  making  the  basic  assumption  that  an  e x i s t s , w i t h a f a s t moving c e n t r a l core of vapour. unable there  to p r e d i c t the is  insufficient  established. changing  f l o w from s h o r t p i p e s  Thus  time  the  c o n d i t i o n s of  for  an  correlations  are  are This  flow pattern  Such c o r r e l a t i o n s are  flow  of  piping.  annular  ( l/d less  annular  T h i s i s an  Correlations  to f i t a wide range of data from s m a l l diameter  by  than  pattern  little  use  20) to  in  where become  the  t r a n s i e n t decompression from a c o n s t a n t  fast-  diameter  pipe [2]. Necmi and Hancox [4] abandoned the assumption of t h e r m a l e q u i l i b r i u m , replacing  i t w i t h a statement  transferred  between  Temperature  model  existing  solution  characteristics  the  two  (EVUT)  phases.  gives  procedures  solution  of the r a t e at which heat and mass may  can  procedure  t h e i r experimental observations.  Their  equations be to  used. give  Equal  that  Velocity  are  They results  Unequal  hyberbolic,  used that  the  be  method  closely  and of  match  - 8 -  A t p r e s e n t t h e r e i s some work b e i n g done on Unequal V e l o c i t y Unequal Temperature  (UVUT) models.  elliptical,  l e a d i n g to some problems i n t h e i r s o l u t i o n .  was  able  results  to a p p l y he  These assumptions  the method of c h a r a c t e r i s t i c s  are  Lyczkowski  [6]  to an UVUT model.  The a  p i p e showed good agreement w i t h h i s e x p e r i m e n t a l o b s e r v a t i o n s .  Most of  the work to date  M o z a f f a r i [7] performed orientation  on  has  been performed  ratio  of  the blowdown of water.  of  the  differential) histories  gravity  for  for horizontal  pipes.  a t h e o r e t i c a l i n v e s t i g a t i o n of the e f f e c t of p i p e He used an EVET model to compare  the p r e s s u r e and v o i d f r a c t i o n h i s t o r i e s .  measure  that  o b t a i n e d when u s i n g h i s method f o r blowdown of steam from  horizontal  the  give equations  force  effect  of  there  was  the  upflow  to  pressure  gravity.  force  When  negligible and  T h i s i n v e s t i g a t i o n showed t h a t  GP  difference  downflow  (GP) was  was low  an  important  (high  pressure  the  pressure  between  cases.  However,  as  GP  was  i n c r e a s e d the d i f f e r e n c e between the u p f l o w and the downflow cases became more d i s t i n c t .  1.3  SCOPE OF THIS INVESTIGATION From the work of Necmi and Hancox [4] i t i s e v i d e n t t h a t f l o w  regimes  p l a y an i m p o r t a n t p a r t i n the blowdown of a l i q u i d from h o r i z o n t a l  pipes.  Their  o b s e r v a t i o n s of  disparity  the  flow h i s t o r y  between the observed  regimes  d u r i n g blowdown showed a l a r g e and  the s i m p l e  f l o w assumed f o r  most c a l c u l a t i o n models.  Body f o r c e s are a major f a c t o r  the  t h e r e f o r e i t was  flow  regime h i s t o r y ;  experiments  t h a t would examine the e f f e c t s  To  i t would be  and  do  this flow  regime  necessary  histories,  so  decided  i n determining  to d e s i g n a  of body f o r c e s on  to make measurements of both i t was  decided  that  set  of  blowdown. pressure  this  study  -  should  follow  equipment  the  used  lines  i n the  of  present  9  Necmi  -  and  Hancox.  experiments  was  In  the  fact  much  same as  of  t h a t used  the by  Necmi. A c c o r d i n g l y the present experimental of  using  angles body  here  blowdown  to show the forces  determine map  the  for  on  effects  the  p r e s s u r e and different  f o r the  of  Freon-114 of pipe  blowdown.  study was  from  a  straight  orientation  The  objective  flow regime h i s t o r i e s and  pipe  orientations.  designed w i t h the i d e a  and was  pipe  at  hence the e f f e c t s to  of  experimentally  to develop a flow regime  Experimental  data  are  blowdown of Freon-114 d i s c h a r g i n g h o r i z o n t a l l y ,  upwards and v e r t i c a l l y downwards.  different  presented vertically  - 10 -  CHAPTER TWO EXPERIMENTAL APPARATUS  2.1 G e n e r a l Concept o f t h e E x p e r i m e n t a l Apparatus The p r e s e n t study was concerned w i t h the blowdown o f Freon-114 from a s t r a i g h t tube.  I n p a r t i c u l a r i t was d e s i r e d t h a t measurements be made of  p r e s s u r e and f l o w regime h i s t o r y d u r i n g the blowdown.  As a g e n e r a l p l a n  it  with a  was  envisaged  liquid,  then  that  a  t r a n s p a r e n t tube  by some means  a l l o w i n g the f l u i d  a  rapid  to discharge.  be f i l l e d  break  would  be made  subcooled  a t one end  As t h i s was happening, measurements o f  the p r e s s u r e and f l o w regime h i s t o r i e s would be made a t v a r i o u s l o c a t i o n s a l o n g the tube. One c o n d i t i o n saturation plastic  f o r choosing a working  p r e s s u r e a t room  fluid  temperature.  was t h a t  T h i s would  tube making p o s s i b l e the f l o w v i s u a l i z a t i o n .  i t have a low  enable Until  use of a  the work of  Necmi and Hancox [ 4 ] , no e f f o r t had been made to v i s u a l i z e or o t h e r w i s e determine  the a c t u a l  were conducted  f l o w p a t t e r n s d u r i n g blowdown.  w i t h Freon-114,  i n a horizontal  tube.  Their  experiments  The same w o r k i n g  f l u i d was used here because i t was f e l t t h a t i t s c o n t i n u e d use would g i v e some base f o r comparing chosen 114  results.  The i n i t i a l  because a t t h i s p r e s s u r e the reduced  i s equal  t o t h e reduced  pressure  c o n d i t i o n s found i n a CANDU r e a c t o r . a r e a c t o r would  have the f l u i d  p r e s s u r e of 1500 kPa was  p r e s s u r e ( P r ) of the F r e o n -  o f water  under  the operating  I t s h o u l d be noted t h a t blowdown i n  b l o w i n g down t o a t m o s p h e r i c p r e s s u r e .  To  match t h i s i n a Freon-114 experiment the f l u i d would have t o blow down t o 15.0  k P a , r e q u i r i n g a l a r g e evacuated  s t o r a g e tank t o c o l l e c t the Freon  - 11 -  gas.  T h i s was not p r a c t i c a l f o r t h i s s e t o f experiments so a l l the t e s t s  were performed w i t h the f l u i d b l o w i n g down t o a t m o s p h e r i c p r e s s u r e . It  was planned  that  the system No  p r e s s u r e be c o n t r o l l e d  plans  were  made  by a s i m p l e  nitrogen-over-Freon  system.  f o r c o n t r o l l i n g the  system t e m p e r a t u r e .  A schematic diagram o f the e x p e r i m e n t a l apparatus i s  shown i n F i g u r e 1.  2.2 D e t a i l s o f t h e Apparatus Components 2.2.1  Test Section  The  blowdown  vessel  was  made  from  a  p o l y c a r b o n a t e tube ( i n s i d e d i a m e t e r = 32 mm). each  end o f the tube.  thermocouple  were h e l d  The vent  line,  4  m  long  transparent  F l a n g e s were welded  t h e Freon  supply l i n e  onto and a  by an aluminum b l o c k which was a t t a c h e d t o the  f l a n g e a t the c l o s e d end of the tube.  The s u p p l y l i n e was connected to a  Freon-114  isolation  storage  tank  through  an  valve  for filling  and  pressurizing. To b e g i n the experiment i t was n e c e s s a r y t o be a b l e t o cause a v e r y rapid  opening  available  at the discharge  fast  required.  end  Traditionally a fast  the shock  resulting  commercially  of breaking  the d i s c  The problem w i t h t h i s method i s i s transmitted  i n erroneous p r e s s u r e r e a d i n g s .  p l a n was t h a t  No  opening has been a c h i e v e d by u s i n g an  problem a t h i n m e t a l diaphragm was used  explode  the tube.  opening v a l v e was c a p a b l e o f opening as r a p i d l y as was  impact t o break a hardened g l a s s d i s c . that  of  a small  outward,  a balloon  the  fluid  I n an attempt t o s o l v e t h i s  t o s e a l the d i s c h a r g e end.  h o l e be punched i n t o  much l i k e  into  The  the diaphragm and t h a t i t  would when p r i c k e d  by a n e e d l e .  T h i s method d i d g i v e a v e r y r a p i d break but i n some p r e l i m i n a r y t e s t s i t  - 12 -  FREON-114 STORAGE TANKS  ^BOURDON PRESSURE GAUGE |VPRY N CYLINDER 2  THERMOCOUPLE SOLENOID VALVE  ALUMINUM CHANNEL THERMOCOUPLE SOLENOID VALVE DIAPHRAGM CAVITY ELECTRICALLY OPERATED PLUNGER CHANNEL SUPPORT  Figure  1. Schematic  diagram  of the e x p e r i m e n t a l  apparatus.  - 13 -  was  found t h a t the break was  not as c l e a n as was  necessary.  seen from the graph of p r e s s u r e vs time i n F i g u r e 2.  The  T h i s can  be  p l o t shows the  p r e s s u r e wave caused by the r e f l e c t i o n from the s e c t i o n of the diaphragm s t i l l b l o c k i n g the p i p e . The  final  s o l u t i o n , shown i n F i g u r e 3, i s a c o m b i n a t i o n  methods.  The  d i s c h a r g e end was  separated  from a  T h i s c a v i t y was Freon-114 isolated fired  by  Inconel  pipe.  solenoid  To  begin  valves  and  an  a 12 mm  long  thick  glass  cavity.  to match the p r e s s u r e of pipe  electrically  and  cavity  operated  the were  plunger  was  T h i s caused the c a v i t y to drop to  p r e s s u r e r e s u l t i n g i n a p r e s s u r e imbalance of 1500  mm  two  t h i c k g l a s s diaphragm  blowdown, the  to break the I n c o n e l diaphragm.  0.5  mm  diaphragm by  p r e s s u r i z e d by n i t r o g e n gas  i n the  atmospheric the  commercial  s e a l e d by a 0.5  of these  diaphragm,  causing  it  to  kPa  across  shatter.  This  arrangement p r o v i d e d a c l e a n break to the f u l l pipe c r o s s - s e c t i o n i n l e s s than 0.5 m i l l i s e c o n d s . In  using  diaphragm  this  method,  fluid  from  advantage was up  to  pressure  i n the  to break outwards; because of  t r a n s m i t t e d i n t o the Freon. the  the  1930  the  shock  this  pipe  there  caused i s no  Once  glass  impact  shock  I n e f f e c t the use of two diaphragms i s o l a t e s of  breaking  the  first  diaphragm.  t h a t the I n c o n e l diaphragm can o n l y w i t h s t a n d kPa.  the  this  diaphragm  breaks  the  whole  Another  pressures system  p r e s s u r e , s t o p p i n g the system p r e s s u r e from a c c i d e n t a l l y exceeding  of  loses a safe  limit. The to 1.6m  a  blowdown tube was  ten  i n c h aluminum c h a n n e l .  tubular  allowed  h e l d by f o u r p i p e s u p p o r t s , which were f a s t e n e d  steel  t r i p o d s as  f o r t e s t i n g at any  This shown  channel  i n Figure  was 1.  mounted between This  i n c l i n a t i o n of the p i p e , a l t h o u g h  two  arrangement t e s t s were  - 14 -  2 000  1  1  1  1  1  1  NITROGEN HORIZONTAL DISCHARGE Pi = 750  1000 o  Z  —  800  = 2.38 m  —  —  V W  Q_  VV V V  —  LU  kPa  V  600 -  rr  to 400  -  CO LU  or o.  V  V  200 h  V  V  V  100  0  V  v  V  1  6  V  V  V V  v  V  1  12  1  18  1  24  1  30  36  TIME ms  Figure  1  2. P r e s s u r e h i s t o r y showing the e f f e c t of a p a r t i a l l y blocked d i s c h a r g e end on the I n i t i a l stages of decompression of n i t r o g e n i n a h o r i z o n t a l p i p e .  42  - 15 -  THERMOCOUPLE HOLE \  NEOPRENE vGASKET  ^  ^ N GAS LINE 2  2  INCONEL  H/DIAPHRAGM GLASS DIAPHRAGM TRANSDUCER DIAPHRAGM CAVITY  PRESSURE 'TRANSDUCER  SCALE O  I  Figure  IN mm 20  I  I  40  I—i  3. D e t a i l s of the end-diaphragm mechanism, i n c l u d i n g a t y p i c a l t r a n s d u c e r mounting arrangement.  - 16 -  only  conducted  with  the  discharge  end  horzontal, v e r t i c a l l y  up  and  v e r t i c a l l y down. P r e s s u r e was F i g u r e 1.  c o n t r o l l e d by u s i n g r e g u l a t e d n i t r o g e n gas  The Freon-114 t h a t f i l l e d  tanks.  Nitrogen  was  supplied to  d i s c h a r g e assembly v i a a 2100 the  pressure  across  the tube was  the  the  top  of  kPa. r e g u l a t o r .  g l a s s diaphragm  n i t r o g e n s u p p l y l i n e c o u l d be vented  as shown i n  h e l d i n a s e r i e s of these  tanks  and  to  the  T h i s arrangement a l l o w e d  to  always  be  balanced.  to a l l o w the system  The  p r e s s u r e to be  lowered. The  two  ^ system  p r e s s u r e was  measured  by  a 0 t o 1500  p s i Heise-Bourdon  tube p r e s s u r e gauge, f a c t o r y c e r t i f i e d a g a i n s t a dead weight  t e s t e r to be  a c c u r a t e to .1% of the f u l l s c a l e r e a d i n g .  2.2.2  P r e s s u r e Measurement Seven p r e s s u r e gauge s t a t i o n s were l o c a t e d a t 40 mm,  1.62  m,  2.38  m,  Each of these strain  3.14  m and  gauge s t a t i o n s  gauge type p r e s s u r e  shown i n F i g u r e 3. circuit  to g i v e a  pressure  of  3.9  1500  m from  t r a n s d u c e r mounted  sensitivity and  d i s c h a r g e end  c o n s i s t e d of a P r e c i s e Sensor  These p r e s s u r e  kPa  the  of  with  3.0  mV/V  the  10  For  power  30 mV  model  211-3  supply  I.D.  machined  p r e s s u r e t i g h t s e a l was  to be  slightly  bridge  used  for  f o r the  the  tube  The  blocks A  formed by 0 - r i n g s on e i t h e r s i d e of the 0.5  inch  tube.  than  pressure  O.D.  p r e s s u r e tap i n the p o l y c a r b o n a t e  larger  as  output.  p l e x i g l a s s mounting b l o c k s served as a support  their  block  the maximum  t r a n s d u c e r s and as r e i n f o r c e m e n t f o r the p o l y c a r b o n a t e tube. had  mm,  tube.  a four-arm  nominal. volt  860  of the  in a plexiglass  t r a n s d u c e r s use  e x c i t a t i o n , the p r e s s u r e t r a n s d u c e r s produced The  180 mm,  - 17 -  The  pressure  pressure  over  transducers  the range  were c a l i b r a t e d  i n place against a  of 100 t o 1500 k P a .  The a c c u r a c y  static of the  c a l i b r a t i o n was one p a r t i n 1024 o r ± 1.4 k P a . Output from t h e p r e s s u r e differential staff.  amplifiers  t r a n s d u c e r s was i n c r e a s e d to f i v e v o l t s by  made by t h e M e c h a n i c a l  The t r a n s d u c e r response  amplification amplified  effects  pressure  to-digital  digital  was determined  including  Electrical  s i g n a l t r a n s m i s s i o n and  t o be 0.3 m i l l i s e c o n d s .  The  s i g n a l was f e d i n t o a D i g i t a l Equipment AR11 a n a l o g -  converter.  made by D i g i t a l  time  Engineering  The AR11 i s 1 0 - b i t a n a l o g - t o - d i g i t a l  Equipment  computers.  Limited  Each  for  pressure  use w i t h  their  transducer  converter  PDP 11  signal  was  series  scanned,  d i g i t i z e d and s t o r e d i n core memory every 0.5 m i l l i s e c o n d s by a PDP 11/10 digital  computer.  The d i g i t i z e d  pressure  s i g n a l s were then t r a n s f e r r e d  t o f l o p p y d i s c f o r permanent s t o r a g e . Due  to the l i m i t e d  amount  of core  storage  available  number of samples t h a t c o u l d be taken on any r u n was 9688. was  t h e maximum Therefore, i t  n e c e s s a r y t o be as e f f i c i e n t as p o s s i b l e i n t h e sampling method used.  To a v o i d w a s t i n g samples by s t a r t i n g t o o e a r l y a TTL e l e c t r i c s w i t c h was used.  This  switch placed  t h e ground s i d e on t h e I n c o n e l diaphragm and  the f i v e v o l t s i d e on the e l e c t r i c p l u n g e r . the  Inconel  The  PDP 11/10 was set-up  soon  diaphragm  as t h e v o l t a g e  the v o l t a g e  across  When t h e p l u n g e r  contacted  t h e s w i t c h dropped  to zero.  i n such a way t h a t i t would s t a r t  started  t o drop.  T h i s meant t h a t  s t a r t e d w i t h the b r e a k i n g of t h e I n c o n e l diaphragm.  sampling as t h e sampling  - 18 -  2.2.3  Temperature  Measurement  initial  of  The  state  the  Freon-114  measurement a t b o t h ends of the p i p e .  was  determined  i n c h O.D.  steel  s h e a t h s . The  which enabled them to be s e a l e d  by f i t t i n g s made by the M e c h a n i c a l E n g i n e e r i n g machine shop. the  temperature  These temperatures were measured  by c o p p e r - c o n s t a n t a n thermocouples, s e t i n s t a i n l e s s thermocouple sheaths were 1/16  by  Output  from  thermocouples were measured by a Newport L a b o r a t o r y I n c . model 267A-  TC1 d i g i t a l The  thermometer.  thermocouples  bath f i l l e d  were c a l i b r a t e d  with d i s t i l l e d  water.  i n a Calora  c o n s t a n t temperature  C a l i b r a t i o n was  two P r e c i s i o n 18 i n c h m e r c u r y - i n - g l a s s thermometers  by comparison  previously calibrated  a g a i n s t a Dymec model 2801 q u a r t z - c r y s t a l d i g i t a l thermometer 0.0001 degrees after  celsius.  After  two  with  calibrations,  one  a c c u r a t e to  b e f o r e and  the e x p e r i m e n t s , the r e a d i n g s d i d not v a r y by more than 1%.  thermocouples were o n l y used to f i n d They were not used  the i n i t i a l  t o make any dynamic  one The  s t a t e of the Freon-114.  measurements and a c c o r d i n g l y  no  measure of t h e i r dynamic response was made.  2.2.4  P h o t o g r a p h i c Equipment  Measurements of  flow  regime h i s t o r y  at various  locations  a l o n g the  p i p e were made by u s i n g a "Redlake Hycam" h i g h speed movie camera f r a m i n g at  2000 p i c t u r e s per second.  eight-sided  p r i s m and  high framing r a t e s .  The Hycam i s a 16 mm  an e i g h t - b l a d e d  segmented s h u t t e r  timing  timing  light  was  light  to a c h i e v e v e r y  The camera i s d r i v e n by an AC motor w i t h the camera  speed b e i n g a d i r e c t f u n c t i o n of the a p p l i e d v o l t a g e . built-in  camera t h a t uses an  which  triggered  marks a  p u l s e on  by an e x t e r n a l  The camera has a  the f i l m  signal  margin.  The  g e n e r a t o r and f o r the  - 19 -  present These  study  t i m i n g marks were  t i m i n g marks enabled  put on the f i l m  the c a l c u l a t i o n  every  0.001  o f the e x a c t  seconds.  framing  rate.  The p i c t u r e s were taken on Kodak type 7224 4-X n e g a t i v e f i l m , an ASA 400 f i l m i n t e n d e d f o r use w i t h h i g h speed cameras. The Hycam had an a c c e l e r a t i o n l a g between the time the camera s t a r t e d and  the time  duration  of  sychronizing proper  the f i l m was up to i t s o p e r a t i n g speed. the  blowdown  the b e g i n n i n g  speed.  To  do  i t was  necessary  of the experiment  this  a light  to  Due to the s h o r t  have  to the f i l m  e m i t t i n g diode  some  way  of  reaching i t s  and r e c e i v e r were  mounted a c r o s s the Hycam s h u t t e r , g i v i n g a p u l s e f o r each frame of f i l m . These p u l s e s were counted number  of  experiment.  frames  had  by an e l e c t r o n i c c i r c u i t and when the r e q u i r e d  elapsed  a  pulse  was  emitted  that  started  F i g u r e 4 shows a b l o c k diagram o f the p h o t o g r a p h i c  a c q u i s i t i o n systems.  the  and d a t a  - 20 -  C a m e r a reaches operating s p e e d  Plunger  I  Pressure transducers  triggered 3 0 m Volts  Plunger contacts metal d i a p h r a g m  I  Computer starts sampling  Amplifiers  5  Volts  Analog-to  digital  converter S a m p l e s written into core memory  I  Floppy  Figure  I  disc  I  Teletype  1  Oscilloscope  4. Block diagram of the data acquisition system.  - 21 -  CHAPTER THREE EXPERIMENTAL PROCEDURE  3.1  General E x p e r i m e n t s were r u n t o get blowdown d a t a f o r the tube o r i e n t e d w i t h  the  open  Pressure  end f a c i n g  horizontally,  vertically  down and v e r t i c a l l y  up.  measurements and h i g h  speed movies were taken  at several  l o c a t i o n s d u r i n g the blowdown.  The movies were a n a l y z e d  t o g i v e the f l o w  regimes.  The method  f o r t a k i n g and a n a l y z i n g  the d a t a  axial  i s described  below.  3.2  I n i t i a l P r e p a r a t i o n and C a l i b r a t i o n o f t h e A p p a r a t u s Due  to i t s high  c o s t , Freon-114 was r e p l a c e d  i n i t i a l p r e p a r a t i o n and c a l i b r a t i o n of the a p p a r a t u s . the I n c o n e l diaphragms, the i n i t i a l from 0.002 i n c h s t e e l shim s t o c k .  by n i t r o g e n  f o r the  A l s o , t o conserve  t e s t s were done w i t h diaphragms made Although  the s t e e l diaphragms d i d not  b r e a k as c l e a n l y as the I n c o n e l diaphragms they were s u i t a b l e f o r use i n s e t t i n g up the experiment. A f t e r the components of the system were assembled i t was p r e s s u r i z e d to  1500 k P a , and the blowdown v e s s e l and f i l l i n g  leaks.  S e v e r a l l e a k i n g f i t t i n g s were found and t i g h t e n e d .  gauge s t a t i o n sealed  l i n e s were checked f o r  blocks  was found  t o be l e a k i n g through the 0 - r i n g s  t h e gap between the b l o c k  remachining During  One o f the  and the tube.  This  was f i x e d  that by  t h e b l o c k and f i t t i n g i t w i t h l a r g e r 0 - r i n g s . s h i p p i n g the blowdown tube was c r a c k e d  a t gauge s t a t i o n two.  During  near the d i s c h a r g e end  the i n i t i a l t e s t s i t was n o t i c e d t h a t t h i s  - 22 -  c r a c k was was  getting  made  to  larger.  keep  this  In an attempt  section  p r e c a u t i o n a s i m i l a r clamp was  of  the  to f i x t h i s  tube  in  compression.  i n the g a i n of the a m p l i f i e r s was  one  of  in their  its  operating  circuits.  p r e s s u r e of 1500  approximately 5 v o l t s output. trim  p o t e n t i o m e t e r s to b r i n g  As  a  a t t a c h e d to the c l o s e d end of the tube.  Coarse adjustment the r e s i s t o r s  problem a clamp  kPa  The  and  system was  the r e s i s t a n c e s  F i n e adjustment was the output  made by changing brought  adjusted  up to  to g i v e  then made by means of  to 5 v o l t s ,  p l u s or minus 0.005  volts. The data a c q u i s i t i o n system was nitrogen that  gas  the  buffers traced  and  b r e a k i n g one  sampling  measuring  was only  to a v o l t a g e  from  AC  to  DC  too  the system  The  and  the s t e e l  starting  spike  broke the diaphragm.  of  checked by p r e s s u r i z i n g  soon,  initial  i n the s o l e n o i d problem was  adding  a  the tube w i t h  diaphragms. resulting  I t was in  found  a l l the  data  pressure.  This  used  the p l u n g e r that  to f i r e  problem  was  c o r r e c t e d by changing the s o l e n i o d  filter  to  stop  the  voltage  spike  that  remained. The the  system was  2000 samples Calculation  second  with  equivalent diffusing  the units  run a g a i n and  per second per channel t h a t was n e c e s s a r y . of  the  camera of  light  intensity  used  showed  light.  s c r e e n to g i v e  h i g h speed photography. clear  found to be more than capable of t a k i n g  A  this  1000  n e c e s s a r y f o r 2000 p i c t u r e s  that watt  intensity.  i t was  spotlight  was  To s e t the focus an i n k l i n e was  then a d j u s t e d u n t i l  both the l i n e  be photographed were i n f o c u s .  to used  have with  16 a  F o c u s i n g i s very important i n  f i l m and t h i s f i l m loaded i n the camera.  l e n s was  necessary  per  p l a c e d on some  The f o c u s i n g r i n g on the  on the f i l m and the o b j e c t to  - 23 -  As  a  properly  final a  check  r u n was  configuration with the  blowdown tube.  the  photographs  this  that made  the data under  acquisition  t h e same  system  conditions  as  working  the  final  t h e e x c e p t i o n t h a t n i t r o g e n , n o t F r e o n , was used i n A l s o , t o g i v e a b e t t e r i n d i c a t i o n o f the q u a l i t y o f  some c o n f e t t i was p l a c e d i n t h e tube.  r u n showed  was  that  the data  acquisition  system  The r e s u l t s o f was  working  as  expected. P r i o r t o b e g i n n i n g the a c t u a l experiments the tube had to be c l e a n e d . F i r s t i t was vacuumed t o remove most o f t h e c o n f e t t i . w i t h water and blown d r y w i t h n i t r o g e n gas.  I t was then washed  The tube was n o t de-greased  because the Freon t h a t was t o be used as t h e w o r k i n g f l u i d i s a v e r y good de-greasing  agent.  I t was f e l t  t h a t any c o n t a m i n a t i o n i n the form o f  grease would be removed by the f i r s t t e s t r u n . The system was p r e s s u r e t e s t e d and found t o be l e a k i n g through one o f the  solenoid  started. of  to i s o l a t e  the tube b e f o r e t h e blowdown was  T h i s v a l v e was d i s a s s e m b l e d and found t o c o n t a i n s e v e r a l p i e c e s  confetti  proper  v a l v e s used  t h a t were p r e v e n t i n g i t from  operation,  both  solenoid  closing  properly.  v a l v e s were d i s a s s e m b l e d  To ensure  and c l e a n e d .  The components were reassembled and found to be w o r k i n g p r o p e r l y .  3.3  P r o c e d u r e f o r Freon-114 Blowdown Measurements The  allow  initial direct  Freon-114 t e s t s were made i n the h o r i z o n t a l p o s i t i o n t o  comparison  p r o c e d u r e was used  with  to f i l l  Necmi  and Hancox  t h e tube.  inclined  escape.  The  Freon-114 was s u p p l i e d  s t o r a g e tanks and the tube a l l o w e d t o f i l l was  [4].  w i t h the vent open.  following from t h e The tube  s l i g h t l y w i t h t h e vent end up, a l l o w i n g any trapped a i r to  W h i l e the tube was f i l l i n g  p r e p a r a t i o n s were made t o enable t h e  - 24 -  computer  t o do the p r e s s u r e  complete  a  triggering  safety  switch  accidentally.  sampling. was  s e t that  The tube  Freon-114 was observed at the v e n t . valve that i s o l a t e s  Once these p r e p a r a t i o n s were  was  stopped  allowed  pressurize  the Freon s t o r a g e tank.  the system.  to f i l l  until  The  be  starting  used  N i t r o g e n gas was then used  As t h e p r e s s u r e was b e i n g r a i s e d  for calibrating  pressure  the i n i t i a l  the p r e s s u r e  o f 1500 kPa was  i s o l a t e the tube were c l o s e d .  reached  the solenoid  The thermocouples  temperature o f the F r e o n .  When t h e valves  The s a f e t y s w i t c h on the computer The r e a s o n f o r not  The camera was then s t a r t e d ;  addition  when i t reached i t s o p e r a t i n g  speed i t t r i g g e r e d the p l u n g e r which i n t u r n t r i g g e r e d the computer. computer  then  took  r e a d i n g s from  that  were then read t o g i v e  the l i g h t on e a r l i e r was t o a v o i d any unnecessary heat  t o the tube.  readings  These would  transducers.  was r e l e a s e d , then the camera l i g h t was t u r n e d on. turning  liquid  tube was then l e v e l e d  were taken a t 200 kPa i n t e r v a l s from 100 kPa t o 1500 k P a . later  from  The vent was then c l o s e d as was the  w i t h the use of a W i l d e s p l i t - b u b b l e l e v e l . to  the computer  each  The  o f the s i x p r e s s u r e t r a n s d u c e r s  e v e r y 0.5 m i l l i s e c o n d s . The 11/10.  d a t a from the experiment  was h e l d i n the core memory o f the PDP  B e f o r e the experiment c o u l d be r e p e a t e d i t was n e c e s s a r y t o save  the d a t a .  T h i s was done by c o p y i n g the c o n t e n t s of the c o r e memory t o a  128K  storage d i s c .  byte  storage d i s c  This o r g i n a l  t o p r o v i d e a backup.  d i s c was then c o p i e d t o another  Finally  a printout  o f the d a t a was  o b t a i n e d on the LA36 t e r m i n a l a t t a c h e d t o the PDP 11/10. On examining station  the t e s t  two had propagated  r i g i t was n o t i c e d c o m p l e t e l y around  t h a t the c r a c k near gauge the tube.  This probably  o c c u r r e d d u r i n g the blowdown as the r e s u l t o f the tube f l e x i n g .  To f i x  -  25  -  t h i s problem the d i s c h a r g e end  of the tube was  in  using  the  tube  together.  was The  r e p a i r e d by  support b l o c k was  the p i p e support was  the  gauge s t a t i o n . Once  horizontal  position.  The  The  the  tube  was  support was  the l e a k and  repaired  e x p e r i m e n t a l procedure  cement  to  vertical,  a  T h i s p l u m b - l i n e was tube to v e r t i c a l . the h o r i z o n t a l To  use  necessary  one  more  be  After  apparatus  attached  taken and  the  for tube  too  soon.  the  was  made  in  from the  To a i d i n s e t t i n g  to  the  top  pipe  the  support.  to s e t the  s t o r e d by the same method as i n  discharging from  This  vertically  i t s supports  and  upwards turn  It  was  i t so  the  T h i s r e q u i r e d t h a t some of the plumbing  piece  it  was  problem was  the computer be  found  that  f i x e d by  the  lengthened.  computer  r e p l a c i n g the  was  coaxial  b e i n g used by the a u t o t r i g g e r w i t h a s h i e l d e d t w i s t e d p a i r  Once t h i s problem was  the d a t a was  was  t h a t the c a b l e t h a t t r i g g e r s  c a b l e t h a t was cable.  The d a t a was  reassembling  triggering  run  the tube  then a l i g n e d w i t h the bottom p i p e support  c o u l d p o i n t up.  redone and  reassembled  f o r the v e r t i c a l tube d i s c h a r g i n g downward  plumb-line  remove  d i s c h a r g e end  pieces  case.  the to  two  crack  on e i t h e r s i d e of  prevented  i s b a s i c a l l y the same as f o r the h o r i z o n t a l tube. tube  the  d i s c h a r g e assembly was  moved so t h a t one  T h i s stopped  flexing.  to  The  remachined to p r o v i d e a b e t t e r f i t and  l a r g e r 0 - r i n g s were i n s t a l l e d . and  solvent  disassembled.  f i x e d the procedure  the same as f o r the o t h e r two  cases.  f o r t a k i n g and  storing  - 26 -  3.4  Data A n a l y s i s  The  bulk  PDP-11/10  minicomputer.  calibration pressure To  samples  during  obtain  the movies. capable second. had  of the work i n r e d u c i n g  been  A  for  program  each  the p r e s s u r e  data  was  was  that  takes  them  to  channel  written  and  uses  done by the  the  eight  compute  the  the blowdown (see A p p e n d i x ) . the flow  T h i s was  of framing  regime  data  i t was  o r i g i n a l l y done by u s i n g a 16 mm  forwards or backwards  However the f i l m was torn during  necessary  p r o j e c t o r and t e a r i n g .  e d i t o r to view the movies.  p r o j e c t o r that  and some of the sprocket  resulting  T h i s problem was  view was  at a r a t e as low as 1 frame per  very b r i t t l e  the f i l m i n g ,  to r e p e a t e d l y  i n the f i l m  slipping  holes i n the  c o r r e c t e d by u s i n g a manual  film  - 27 -  CHAPTER FOUR EXPERIMENTAL RESULTS  4.1  General The  as  a  initial  t e s t s on the apparatus were performed  substitute  f o r the more e x p e n s i v e  u s i n g n i t r o g e n gas  Freon-114.  These p r e l i m i n a r y  t e s t s were done to debug the d a t a a c q u i s i t i o n system and to d e c i d e on the final 2  c o n f i g u r a t i o n of the diaphragms i n the d i s c h a r g e assembly.  shows a graph  typical  of  the  oscillations  of p r e s s u r e v e r s u s results  are  obtained  present  because  time  f o r one  f o r the of  the  c l e a n l y and b l o c k i n g the end of the tube. p r e s s u r e wave was to  r e f l e c t e d and caused  Figure  gauge s t a t i o n  and  is  early  tests.  The  pressure  metal  diaphragm  not  breaking  Because of t h i s b l o c k a g e , the  the p r e s s u r e at the gauge s t a t i o n s  oscillate. Several  different  c o n f i g u r a t i o n s of diaphragm were t e s t e d , most of  which gave s i m i l a r r e s u l t s . same as  t h a t used  by  The  Necmi and  arrangement f i n a l l y d e c i d e d on was Hancox  [4].  F i g u r e 5 shows  r e s u l t s from two gauge s t a t i o n s f o r t h i s d i s c h a r g e assembly. seen  from  t h i s graph  wave appears  the o s c i l l a t i o n s have d i s a p p e a r e d and  to be t r a v e l l i n g at the speed  the  typical  As can be the p r e s s u r e  of sound i n n i t r o g e n f o r t h a t  temperature and p r e s s u r e . D u r i n g these experiments  the h i g h speed camera was  a l s o b e i n g used at  another  location.  T h i s r e q u i r e d the camera b e i n g p e r i o d i c a l l y moved to  another  building.  A p p a r e n t l y d u r i n g one  dropped,  knocking  the i n t e r n a l  t h i s was  pictures  of l e s s  prisms  out  of these moves the camera of a l i g n m e n t .  than i d e a l q u a l i t y .  The  The  result  movies s t i l l  was of  showed  - 28 -  2000  1  i  l  i  i  t  I O O O O O O O O O Q  o  1000  - •  o  800 o  CL UJ  rr CO CO UJ  —  600 NITROGEN HORIZONTAL 400  •  cr  Q_  Pj  = 1 5 0 0 kPa  o  Z  = 3.14  •  Z  =  180  DISCHARGE  m  mm  200 o  • D  100  Figure  D D  i  D°  d D  °  A  o ° e i 0 oeegaBBB8B88S o  12 I I  D  o  o88  18  i  24  TIME ms  i  30  u  i36  5. P r e s s u r e h i s t o r i e s d u r i n g decompression of n i t r o g e n from a h o r i z o n t a l tube.  42  29  -  how  the  flow  individual  p a t t e r n s developed,  frames.  It  i n d i v i d u a l frames was t h i s work. the  Instead  various  flow  was  -  but  felt  i t was  that  the  difficult quality  so poor that there was  to see  of  that  were  on  enlargements  of  no reason to i n c l u d e them i n  flow regime maps have been developed patterns  detail  observed  have  and  been  sketches of included  to  e x p l a i n these maps.  4.2  Pressure H i s t o r i e s f o r Discharge Two  tests  t e s t s had from  18.4  an  were made w i t h initial  to  18.9  the  Horizontally  tube  p r e s s u r e of 1500  degrees  discharging horizontally.  kPa,  Celsius.  while  The  g r a p h i c a l l y summarized i n F i g u r e s 6 and  the apparatus  and  Hancox  f o r one  [4].  gauge s t a t i o n  During  this  which probably e x p l a i n s why  run  the  the temperatures  results  for  these  ranged  tests  are  Freon-114  run  7.  F i g u r e 6 compares the p r e s s u r e h i s t o r y of  Both  f o r the i n i t i a l  and  data from work done by Necmi  tube  broke at gauge s t a t i o n  two,  there i s not b e t t e r agreement between the  two  s e t s of d a t a . After  the  horizontal results from  tube  was  position.  obtained  these  by  graphs  The  the  this  case  2000 frames per gross  flow  as  set-up was  and  patterns.  from [4] very  run  i n Figure w e l l and  repeated  are  compared  7.  As  can  therefore i t  for  the  to  the  be  seen  appears  Horizontally t h a t f o l l o w the  as a r e s u l t No  this  was  working p r o p e r l y .  i n the ones  second  experiment  Hancox  compares  Flow H i s t o r y f o r D i s c h a r g e In  the  data  the  results  Necmi and  t h a t the e x p e r i m e n t a l  4.3  repaired  attempt  p i c t u r e s were taken  the f l o w v i s u a l i z a t i o n s was  made to  look  at  show o n l y  f o r very  short  250  o  CL  200  h  150  L 8  LU  rr  ZD  CO CO LU  rr CL  CO  o  100  50  HORIZONTAL DISCHARGE Pii * I 5 0 0 kPa PRESENT WORK o NECMI DISTANCE FROM CLOSED END Z = 40 mm L_  0.4  0.8  1.2  1.6  TIME s Figure  6.  Pressure h i s t o r i e s d u r i n g the blowdown f o r a h o r i z o n t a l p i p e . Both present r e s u l t s as w e l l as those of Necmi and Hancox [4] are shown. The dashed l i n e i n d i c a t e s the s a t u r a t i o n pressure a t the i n i t i a l temperature.  2.0  - 31 -  2000 HORIZONTAL DISCHARGE Pj = I 500 kPa v,x NECMI  1000  PRESENT  800  DISTANCE FROM DISCHARGE v , • Z = 40 mm Z = 3.14 m  o  ^  WORK  600  END  LU  cr 400 CO CO LU  rr  CL  200 v  100  xx x x xxx  I  I  1  1  12  18  24  30  36  TIME ms  7. P r e s s u r e h i s t o r i e s d u r i n g the i n i t i a l stages of blowdown f o r a h o r i z o n t a l p i p e . Both present r e s u l t s as w e l l as those of Necmi and Hancox [4] a r e shown. The dashed l i n e i n d i c a t e s the s a t u r a t i o n p r e s s u r e a t the i n i t i a l temperature.  42  - 32  time p e r i o d f l o w p a t t e r n s .  -  T h i s would have r e q u i r e d f i l m i n g i n the  of 10,000 frames per seconds which was At 2.92  i m p r a c t i c a l f o r these  m (91.25 tube d i a m e t e r s ) from the d i s c h a r g e  s t a r t e d 13 m i l l i s e c o n d s a f t e r the diaphragm was  experiments.  end,  broken.  order  nucleation  I t was  believed  t h a t the p r e s s u r e t r a n s d u c e r s , which were mounted on the top of the might a c t as p r e f e r e n t i a l n u c l e a t i o n s i t e s . was  expected,  time o r g a n i z e d  The At  However, c o n t r a r y to what  the bubbles were formed on the bottom of the tube.  bubbly flow continued this  u n t i l 230 slugs  of  approximately  410  liquid  milliseconds  on the bottom and  c o l l a p s e onto the l i q u i d and stratified remained  with  vapour on  stratified  the  by 550  f o r the  top  flow  was  definitely The  regime  stratified,  bubbles seemed to  m i l l i s e c o n d s the f l o w was and  r e s t of  liquid the  on  the  tube.  less distinct.  completely  bottom.  experiment.  This  c o u l d be observed by w a t c h i n g the p i p e as the blowdown was Necmi and  Near  were n o t i c e d moving down the  bubbles on the top.  the  This  m i l l i s e c o n d s I n t o the e x p e r i m e n t .  waves i n t h i s s l u g f l o w g r a d u a l l y become s m a l l e r and  with l i q u i d  tube,  The  flow  flow regime  occurring.  Hancox [4] have done a d e t a i l e d i n v e s t i g a t i o n of the  history for  the  blowdown of  T h e i r r e s u l t s are shown i n F i g u r e 8. regimes observed d u r i n g  the p r e s e n t  Freon-114  from  As can be  horizontal pipe.  F i g u r e 9 shows s k e t c h e s investigation.  The  i n v e s t i g a t i o n are superimposed on the f l o w regime map [4] i n F i g u r e 8.  a  flow  of the  flow  r e s u l t s of  this  of Necmi and  Hancox  seen from t h i s f i g u r e , once a g a i n , the  two  s e t s of r e s u l t s are i n good agreement.  4.4  Pressure H i s t o r i e s f o r Discharge The  into  V e r t i c a l l y Down  p r e s s u r e d a t a f o r d i s c h a r g e v e r t i c a l l y down were observed to two  distinct  classes  which  have  been  called  regular  fall and  - 33 -  5000  lOOOh  tn  E  uj  100  0  1 DISTANCE  Figure  2 FROM  3 OPEN  END  Z  m  8. Flow regimes d u r i n g blowdown of Freon-114 from a h o r i z o n t a l p i p e , from Necmi and Hancox [4].  - 34 -  horizontol dischorg"e|  logo'  stratified  stratified bubbly  slug  bubbly  discharging up  discharging down  m annular (liquid core)  Si; ojoo'  bubbly (large and well defined)  &2  t  slug  bubbly slug  bubbly  slug  annular (vapor core)  annular  'O'O;O;O'D. A Wo  Figure  9 . D e f i n i t i o n sketches of the f l o w regimes i d e n t i f i e d i n t h i s study. Time advances from l e f t to r i g h t f o r h o r i z o n t a l d i s c h a r g e ; from top t o bottom f o r d i s c h a r g i n g e i t h e r upwards or downwards.  - 35 -  r e p r e s s u r i z a t i o n data. Figures  10 t o 17.  The  The  r e g u l a r d a t a a r e summarized  p r e s s u r e h i s t o r i e s d u r i n g the i n i t i a l stages of  blowdown a r e shown i n F i g u r e s 10 to 14. h i s t o r i e s measured of  the p i p e .  rapidly of  graphically i n  F i g u r e 10 shows the  pressure  a t the two gauge s t a t i o n s c l o s e s t t o the d i s c h a r g e end  As can be seen from t h i s graph the p r e s s u r e dropped  to the s a t u r a t i o n p r e s s u r e of Freon-114.  F i g u r e 11 i s a r e p e a t  F i g u r e 10 but i t i s f o r a d i f f e r e n t r u n o f the experiment.  for  these two runs compare v e r y w e l l .  milliseconds  for Z  =  40  mm  very  The  data  However on run 2 ( F i g u r e 11) at 5  there  i s some e v i d e n c e  of  the  pressure  undershoot caused by d e l a y e d n u c l e a t i o n not seen f o r run 1 ( F i g u r e 10). The p r e s s u r e h i s t o r i e s measured shown i n F i g u r e 12. to  a t the middle  As b e f o r e t h e r e i s a v e r y r a p i d drop i n the p r e s s u r e  near the s a t u r a t i o n p r e s s u r e of Freon-114.  metres  shows a p r e s s u r e  caused by d e l a y e d  two gauge s t a t i o n s a r e  spike beginning  nucleation.  the speed of sound  The p r e s s u r e f o r Z =  a t 6.5  milliseconds,  From t h i s graph we  i n Freon-114.  The d a t a was  give  range  to the c a l c u l a t e d  some b a s i s  f o r comparision.  p r e s s u r e t r a n s d u c e r (Z = 860 mm) g i v e s a speed of sound between for  the p r e s s u r e  speed  r e c o r d e d a t 2000 samples  860  different similar the  The  first  at between 2 and 2.5 m i l l i s e c o n d s .  This  340 and 430 metres per second.  the d i s c h a r g e  run i n Figure  13.  of  sound  from  this  still  the  transducer at Z =  from  a c o u s t i c wave passes  1.62  The  metres  end  of  pressure  graph  the speed  Similarly  of sound i s  The p r e s s u r e h i s t o r y a t the gauge the p i p e history  to the one shown f o r run 1 ( F i g u r e 12).  speed  second.  mm  This w i l l give a  of speed of sound but should  between 360 and 405 metres per second. station  probably  can get some i d e a of  per second g i v i n g a time i n t e r v a l of 0.5 m i l l i s e c o n d s . large  1.62  i s between  i s repeated shown here  for a  i s very  As f o r the p r e v i o u s r u n 340  t o 430  metres  per  - 36 -  2000  VERTICAL .DISCHARGE DOWN RUN 1 Pi = 1500 kPa Tj = 18.9 °C  'fJ00|E 800 o  CL  DISTANCE FROM OPEN END o Z = 40 mm • Z = 180 mm  600  *c  LU  rr  400  Z> CO CO LU  rr CL  • ICO  200  100  °_Rrrxxrq  12  18  24  30  36  TIME ms  Figure  10. P r e s s u r e h i s t o r i e s at two gauge s t a t i o n s f o r a v e r t i c a l p i p e d i s c h a r g i n g down. The dashed l i n e i n d i c a t e s the s a t u r a t i o n p r e s s u r e at the i n i t i a l temperature.  42  - 37 -  2000  Co VERTICAL, DISCHARGE DOWN RUN 2 P: = I 500 kPa  1000  o CL  LU  rr  CO CO LU  800  i  = 189  °C  DISTANCE FROM OPEN END o Z = 4 0 mm • Z = 180 mm  600  400  rr  co •  CL  200  100  12  18  24  30  36  42  TIME ms  F i g u r e 11.  Repeat of the d i s c h a r g e h i s t o r i e s of F i g u r e 10. The dashed l i n e i n d i c a t e s the s a t u r a t i o n p r e s s u r e at the i n i t i a l temperature.  - 38 -  2 000  1  1  1  "V  o  CL LU  rr co CO LU  —  800  —  1  I  VERTICAL, DISCHARGE DOWN RUN 1  V  1000  1  Pj * 1500 kPa T  A  —  = 18.9 ° C  DISTANCE FROM OPEN END •  —  600  A  A  400  Z = 1.62 m Z = 860 mm  —  — V  rr  —  A  .  .JUAA.  ^TTT O^AAAAAAAAAAAAAAAA  100  ...  1  AAAAA  1  1  1  1  12  18  24  30  1  36  TIME ms  Figure  12. P r e s s u r e h i s t o r i e s at two gauge s t a t i o n s f o r a v e r t i c a l pipe d i s c h a r g i n g down. The dashed l i n e i n d i c a t e s the s a t u r a t i o n p r e s s u r e a t the i n i t i a l temperature.  42  - 39 -  2 000 ' i  AA  A  VERTICAL , DISCHARGE DOWN RUN 2 — -  LU  i  A  1000  800  1  1  i  Pj  = 1 500  Tj  = 18.9  kPa °C  —  DISTANCE FROM OPEN END  A  600  -  Z =860 mm  rr  ZD  CO CO LU  -  400 A  rr  200  100  ^  A  1  A  A.  _  L  1  1  1  12  18  24  30  l  36  42  TIME ms  F i g u r e 13. Repeat of one of the d i s c h a r g e h i s t o r i e s of F i g u r e 12. dashed l i n e i n d i c a t e s the s a t u r a t i o n p r e s s u r e at the i n i t i a l temperature.  The  - 40  Figure nearest rapid  14  the  shows  c l o s e d end  drop t o near  metres  there  milliseconds calculated  the  of  a  long  lasting  from  the  histories  pipe.  The  at  the  two  gauge  p r e s s u r e here  the  dip  in  until  data  are  19  the  pressure  i n the  range  of  For Z =  beginning  milliseconds.  The 340  390  of  a  3.14  at  speed  to  stations  a l s o showed  the s a t u r a t i o n p r e s s u r e of Freon-114.  was and  pressure  -  11.5 sound  metres  per  second. Long-term  pressure  F i g u r e s 15 to 17.  histories  for  the  regular  data  are  shown  in  F i g u r e s 15 and 16 shows the l o n g - t e r m p r e s s u r e h i s t o r y  measured d u r i n g run 1.  These two graphs show t h a t i t took  100  the  milliseconds for  pressure  p r e s s u r e , then at a p p r o x i m a t e l y below s a t u r a t i o n .  The  reason  0.6  to  stabilize  at  approximately  the  saturation  seconds the p r e s s u r e s t a r t s  the graphs do not extend  to drop  past 0.8  seconds  i s , because of l i m i t a t i o n s i n computer memory, o n l y 9688 samples c o u l d be taken.  I f p r e s s u r e r e a d i n g s were taken f o r a l l s i x gauge s t a t i o n s  s a m p l i n g c o u l d o n l y l a s t f o r 0.8  seconds.  F i g u r e 17 i s a r e p e a t of F i g u r e 15 except for  just  three  seconds. (Figure  The 15).  gauge  This data  summarize  drops  rapidly to  travelling  resulting  i n data  being  recorded  stored for  1.6  to  shows the p r e s s u r e g o i n g  to atmospheric  at  1.3  test. the  behaved as would be very  stations  t h a t the d a t a was  d a t a f o r t h i s run compares v e r y w e l l w i t h t h a t f o r run 1  seconds i n t o the To  the  regular  expected.  the  The  saturation  atmospheric between  data  the  i t can  be  said  that  the  pressure  p r e s s u r e a t each gauge s t a t i o n  pressure  of  pressure.  The  pressure  transducers  Freon-114,  pressure at  wave  the  drops  then g r a d u a l l y appears  speed  of  to  be  sound  in  - 41 -  2000  VERTICAL .DISCHARGE DOWN RUN I P I = I 500 kPa  1000 o  CL  Tj = 189  800  DISTANCE FROM OPEN END o Z * 3.14 m O Z = 2.38 m  600  rr CO CO LU  °C  400  cr CL  200  100  12  18  TIME  24  30  36  ms  F i g u r e 14. P r e s s u r e h i s t o r i e s at two gauge s t a t i o n s f o r a v e r t i c a l pipe d i s c h a r g i n g down. The dashed l i n e i n d i c a t e s the s a t u r a t i o n p r e s s u r e at the i n i t i a l temperature.  42  300  200 Q  100  o  VERTICAL , DISCHARGE DOWN RUN 1 Pj = 1500 kPa Tj = 18.9 °C DISTANCE FROM OPEN END • Z = 180 mm A Z = 860 mm o Z = 40 mm  0.25  0.50  0.75  1.0  TIME sec F i g u r e 15. Long term pressure h i s t o r i e s f o r three gauge s t a t i o n s f o r a v e r t i c a l pipe d i s c h a r g i n g down. The dashed l i n e i n d i c a t e s the s a t u r a t i o n p r e s s u r e at the i n i t i a l temperature.  275  i  VERTICAL.DISCHARGE DOWN RUN I Pj = 1500 kPa Tj = 18.9 °C DISTANCE FROM OPEN END * Z = 1.62 m o Z * 3.14 m O Z = 2.38 m  o  CL 2 2 5  g9  LU  9  _ oo Iooo o0 ooo ,  rr  0 0  ooI  ZD  V  ^ooooooo^T oooo y 7ooo v  v  * v v * „ oo0oo0 0 v  0<>0  CO CO LU  rr  v  V  oo  OJ  'OoooAo  175  125  0.25  0.50  0.75  1.0  TIME sec F i g u r e 16. Long term pressure h i s t o r i e s f o r t h r e e gauge s t a t i o n s f o r a v e r t i c a l pipe d i s c h a r g i n g down. The dashed l i n e i n d i c a t e s the s a t u r a t i o n pressure at the i n i t i a l temperature.  300  VERTICAL,DISCHARGE DOWN RUN 2 * 1500 kPa Tj * 18.9 °C  1  DISTANCE FROM OPEN END o Z 8 40 mm A Z ' 860 mm • Z = 180 mm  a CL 2 0 0  LU  o o  rr  _  ^o_°-°-o o o .. ° g a  ZD  CO CO LU  rr  o  n  a  4>  § 4 a a a a.  100  CL  0.5  1.0  1.5  2.0  TIME sec F i g u r e 17. Repeat of the d i s c h a r g e h i s t o r i e s of F i g u r e 15. The dashed l i n e i n d i c a t e s the s a t u r a t i o n p r e s s u r e a t the i n i t i a l temperature.  - 45 -  Freon-114.  F i g u r e 18 shows an example of the agreement  that  can be  o b t a i n e d w i t h i n t h i s s e t of d a t a . The r e p r e s s u r i z a t i o n s e t of d a t a The in  a r e summarized i n F i g u r e s 19 t o 26.  p r e s s u r e h i s t o r i e s f o r the i n i t i a l Figures  19 t o 24.  Figure  stages o f the blowdown a r e shown  19 i s a graph  of the pressure  history  measured a t t h e gauge s t a t i o n 860 mm from the d i s c h a r g e end of the p i p e . D u r i n g the i n i t i a l d a t a f o r runs pressure  stage of the t e s t the d a t a compares v e r y w e l l w i t h the  1 (Figure  dropped  milliseconds  to  near  the f l u i d  approximately  12) and 2 ( F i g u r e the  13).  saturation  pressure  increased  1000 kPa a t 24 m i l l i s e c o n d s  A t 2.5 m i l l i s e c o n d s the  pressure,  however  r a p i d l y , reached  and then f e l l  at  21  a peak o f  r a p i d l y back t o  200 kPa a t 28 m i l l i s e c o n d s . F i g u r e 20 shows the p r e s s u r e h i s t o r y a t the gauge s t a t i o n 1.62m from the d i s c h a r g e end o f the p i p e . initial  Again  t h e r e i s good agreement w i t h the  stage of the d a t a f o r r u n 1 ( F i g u r e  pressure  drops  milliseconds  r a p i d l y t o the s a t u r a t i o n  1 2 ) . A t 4 m i l l i s e c o n d s the  pressure  o f Freon-114.  At 7  t h e r e i s some p r e s s u r e r e c o v e r y , a l s o seen f o r r u n 1 ( F i g u r e  12 ) . From 12 m i l l i s e c o n d s on the p r e s s u r e h i s t o r y f o r t h i s r u n d e v i a t e s from  t h a t o f r u n 1.  As can be seen from the graph  h e r e was i n the form of two peaks; reached 400  200  the f i r s t began a t 17.5 m i l l i s e c o n d s ,  a maximum p r e s s u r e o f 1120 kPa a t 20 m i l l i s e c o n d s , then f e l l t o  kPa by 23.5 m i l l i s e c o n d s ;  reached  the r e p r e s s u r i z a t i o n  the second  began a t 23.5 m i l l i s e c o n d s ,  a maximum p r e s s u r e o f 800 kPa a t 24.5 m i l l i s e c o n d s , then f e l l t o  kPa by 28 m i l l i s e c o n d s .  different  run of  similarity  i n these  F i g u r e 21 i s a r e p e a t o f F i g u r e 20 f o r a  t h e experiment. two graphs.  the p r e s s u r e peaks a r e d i s p l a c e d  I t i s interesting  t o note  the  The times f o r the b e g i n n i n g and end of by a p p r o x i m a t e l y  1 m i l l i s e c o n d , but t h e  - 46 -  2 000  VERTICAL , DISCHARGE DOWN Pj * 1500 kPa Tj * 18.9 °C • RUN 1 • RUN 2 DISTANCE FROM OPEN END Z = 180 mm  1000  s.  800 600  _•  LU  rr  400  3 CO CO LU  —  -  •  rr Q_  2 0 0 U agio  100  12  18  24  30  36  TIME ms  F i g u r e 18. P r e s s u r e obtained  h i s t o r i e s showing the r e p e a t a b l i t y of the f o r a v e r t i c a l p i p e d i s c h a r g i n g downward.  42  - 47 -  VERTICAL, DISCHARGE DOWN RUN 4  2 000  Pj  = 1500  kPa  Tj  = 20.7  °C  DISTANCE FROM OPEN END Z s 860 mm  o  CL 1 0 0 0  LU  800  rr  600  rr  400  CO CO LU  200  100  12  18  24  30  36  42  TIME ms F i g u r e 19. P r e s s u r e h i s t o r y showing r e p r e s s u r i z a t i o n d u r i n g blowdown from a v e r t i c a l pipe d i s c h a r g i n g downward. The dashed l i n e i n d i c a t e s the s a t u r a t i o n p r e s s u r e at the i n i t i a l temperature.  - 48 -  -1  1  1  I  1  .  VERTICAL,DISCHARGE DOWN RUN 3 Pj = 1 500 kPa Tj  = 20.8 °C  DISTANCE 2000  FROM OPEN END  Z = 1.62 m v  w  V  £  1000 -  -  800 —  —  LU  rr  co co LU  rr  V  v  V  600  -  V V  400 V  v 200  -  100 0  v  V  V  V v  W  V  v v ^  -  1  1  1  1  1  1  6  12  18  24  30  36  TIME ms F i g u r e 20. P r e s s u r e h i s t o r y showing r e p r e s s u r i z a t i o n d u r i n g blowdown from a v e r t i c a l pipe d i s c h a r g i n g downward. The dashed l i n e i n d i c a t e s the s a t u r a t i o n p r e s s u r e a t the i n i t i a l temperature.  4  - 49 -  1  1  1  1  1  1  VERTICAL t DISCHARGE DOWN RUN 4  2 000  Pj = 1500  kPa  Tj = 20.7  °C  —  DISTANCE FROM OPEN END Z = 1.62 m  «*  V  o  ^  LU  1000  800  V  or S  — 600  CO LU CL  V  V —  V  400  v  ^  v  v  v  *  200  —  v  100  V  12 1  1  18  24  TIME ms 1 1  —  36  30 I  I  F i g u r e 2 1 . Repeat of the p r e s s u r e h i s t o r y shown i n F i g u r e 2 0 . The dashed l i n e i n d i c a t e s the s a t u r a t i o n p r e s s u r e at the i n i t i a l temperature.  42  - 50 -  shape  and d u r a t i o n  p r e s s u r e reached  o f the peaks  a r e almost  identical.  The maximum  i n the peaks o f F i g u r e 21 a r e a p p r o x i m a t e l y 150 t o 200  kPa lower then those of F i g u r e 20. F i g u r e 22 shows the p r e s s u r e h i s t o r y a t the gauge s t a t i o n 2.38m from the d i s c h a r g e end o f the p i p e . with  A g a i n the p r e s s u r e h i s t o r y compares  the normal r u n shown i n F i g u r e 14.  four  occurrences  milliseconds, then f e l l  of  reached  pressure  The d a t a d i s p l a y e d  recovery.  a peak p r e s s u r e  The  milliseconds,  then  fell  reached  reached  t o 180 kPa by  a t 34 m i l l i s e c o n d s  35.5 m i l l i s e c o n d s . a t 37.5 m i l l i s e c o n d s Figure Again  The f i n a l  a t 15.5  milliseconds,  repressurization  30 m i l l i s e c o n d s .  The  third  t h e peak p r e s s u r e of 500 kPa  and then the p r e s s u r e f e l l  t o 200 kPa by  r e p r e s s u r i z a t i o n shown on t h i s graph  began  and reached a peak of 500 kPa a t 39.5 m i l l i s e c o n d s .  23 i s a r e p e a t  there  The second  shows  a peak p r e s s u r e o f 800 kPa a t 26.5  r e p r e s s u r i z a t i o n began a t 33 m i l l i s e c o n d s , was  began  o f 1120 kPa a t 18  to 300 kPa by 25.5 m i l l i s e c o n d s .  began a t 25.5 m i l l i s e c o n d s ,  first  here  will  i s very  good  p r e s s u r e peaks a r e d i s p l a c e d  of the p r e s s u r e h i s t o r y agreement  between  shown i n F i g u r e 22.  these  two graphs.  The  s l i g h t l y on the time a x i s , but the shape and  d u r a t i o n o f the peaks a r e v e r y s i m i l a r i n both c a s e s . F i g u r e 24 shows 3.14 m from  the p r e s s u r e h i s t o r y f o r r u n 3 a t the gauge s t a t i o n  t h e d i s c h a r g e end of the p i p e .  v e r y w e l l w i t h the i n i t i a l The  pressure  recovery. kPa  history  The f i r s t  The second  s e t of data  compares  s t a g e o f the normal r u n shown i n F i g u r e 14.  f o r run 3  shows  three  began a t 13 m i l l i s e c o n d s ,  a t 15 m i l l i s e c o n d s ,  This  then decreased  occurrences reached  of  pressure  i t s peak o f 1260  t o 300 kPa by 28.5 m i l l i s e c o n d s .  p r e s s u r e r e c o v e r y s t a r t e d a t 28.5 m i l l i s e c o n d s , reached a peak  - 51 -  VERTICAL, DISCHARGE DOWN RUN 3 Pj  * 1 500 kPa  Tj = 20.8  DISTANCE FROM OPEN END  2 0001-  Z = 2.38 m  o o  CL IOOO LU  rr  CO CO LU  rr CL  °C  800 600  o oo  400  o o  o  o o  o o 200  o  100  12  18  24  30  36  42  TIME ms F i g u r e 22. P r e s s u r e h i s t o r y showing r e p r e s s u r i z a t i o n d u r i n g blowdown from a v e r t i c a l pipe d i s c h a r g i n g downward. The dashed l i n e i n d i c a t e s the s a t u r a t i o n p r e s s u r e a t the i n i t i a l temperature.  - 52 -  1  1  1  1  1  1  VERTICAL, DISCHARGE DOWN RUN 4 Pj * 1500 kPa Tj  £  CO CO LU  rr  —  Z = 2.38 m  o  1000  o <>o  °  800  LU  °C  DISTANCE FROM OPEN END  — 2000 k  o  = 207  6 0 0 —'  V  \  o 400  o  o  CL  —  oof  &  —  o  o o  o  o  °  o  1  A  <*>°  A  200  o 100  1  1  1  1  1  12  18  24  30  1  36  TIME ms F i g u r e 23. Repeat of the p r e s s u r e h i s t o r y shown i n F i g u r e 22. The dashed l i n e i n d i c a t e s the s a t u r a t i o n p r e s s u r e at the i n i t i a l temperature.  42  - 53 -  1  1  1  1  1  1  VERTICAL, DISCHARGE DOWN RUN 3 Pj  * 1500  kPa  Tj  = 20.8  °C  DISTANCE FROM OPEN END Z = 3.14 m 2 000 h  —  r i f r n p >"y> w >  o  ^  LU  rr  to to  O  1000  800  ^  O  —  «»v$>0  °  600  LU  rr  °  —  400  h  % o"  o  O  \J  o  o  o  -O  °o  ° o  200 h  100  o  1  ( 12  t  i 18  l 24  -  l 30  36  42  TIME ms F i g u r e 24. P r e s s u r e h i s t o r y showing r e p r e s s u r i z a t i o n d u r i n g blowdown from a v e r t i c a l pipe d i s c h a r g i n g downward. The dashed l i n e i n d i c a t e s the s a t u r a t i o n p r e s s u r e a t the i n i t i a l temperature.  - 54 -  of  800 kPa a t 32 m i l l i s e c o n d s , then f e l l to 200 kPa by 33.5  The  last  r e p r e s s u r i z a t i o n shown on t h i s graph  and reached  25  and  stations  behavior.  began a t 36  milliseconds,  i t s peak of 700 kPa a t 37 m i l l i s e c o n d s .  Figures gauge  milliseconds.  26  show the  during  two  of  long-term  pressure  the  that  runs  histories  showed  for  three  repressurization  The l o n g - t e r m p r e s s u r e h i s t o r i e s f o r the r e p r e s s u r i z a t i o n  show a much g r e a t e r time was  necessary  runs  f o r the p r e s s u r e to s t a b a l i z e a t  the s t a t u r a t i o n p r e s s u r e , 500 m i l l i s e c o n d s f o r the r e p r e s s u r i z a t i o n d a t a as compared to 100 m i l l i s e c o n d s f o r the normal d a t a . d a t a the time to reach atmospheric In  summary  the  For both groups of  p r e s s u r e are a p p r o x i m a t e l y the same.  repressurization  data  appears  to be  r e g u l a r d a t a f o r the i n i t i a l stage of decompression.  much l i k e  As w i t h the r e g u l a r  d a t a the r e p r e s s u r i z a t i o n d a t a shows a r a p i d drop to near  the s a t u r a t i o n  p r e s s u r e of Freon-114, however, 10 to 15 m i l l i s e c o n d s l a t e r (depending the gauge s t a t i o n ) pressure. discharge  It end  the p r e s s u r e  i s interesting increased  the  jumps to w i t h i n 500 to  note  pressure  that  as  recovery  the  kPa  the  of the  initial  d i s t a n c e from  occurred  on  the  sooner  and  the  this  group  of  w i d t h of the f i r s t peak i n c r e a s e d . Figure data. runs  27  shows an  example  of  the  agreement w i t h i n  R e p r e s s u r i z a t i o n o c c u r r e d d u r i n g runs t h r e e and f o u r of the made  histories  with  t h e r e was  the d a t a was definitive  the  not  discharge  end  down.  As  shown  by  the  five  pressure  good agreement among the d a t a i n t h i s group, however  r e p r o d u c i b l e on demand.  cause f o r what was  triggering  At p r e s e n t we  do  not have a  the r e p r e s s u r i z a t i o n .  A more  d e t a i l e d e x p l a n a t i o n and p o s s i b l e causes f o r these unusual r e s u l t s can be found i n the next c h a p t e r on the d i s c u s s i o n of the r e s u l t s .  300  VERTICAL , DISCHARGE DOWN RUN 3 I 500 kPa  o  208 °C  o  2  200  DISTANCE FROM OPEN END V z s 162 m O z = 2.38 m o Z = 3.14 m  O^S* 8  LU  rr  co co LU  rr  tt« O° nOO 0o  n  100  0.5  1.0  1.5  2.0  TIME F i g u r e 25. Long term pressure h i s t o r i e s f o r three gauge s t a t i o n s f o r a v e r t i c a l pipe d i s c h a r g i n g downward. The dashed l i n e i n d i c a t e s the s a t u r a t i o n p r e s s u r e at the i n i t i a l temperature.  I VERTICAL, DISCHARGE DOWN RUN 4  300  i  DISTANCE A Z v Z O Z  0.5  kPa °C  FROM OPEN =860 mm = 1.62 m = 2.38 m  1.5  1.0  TIME  I 500 20.7  END  2.0  sec  F i g u r e 26. Long term pressure h i s t o r i e s f o r t h r e e gauge s t a t i o n s f o r a v e r t i c a l pipe d i s c h a r g i n g downward. The dashed l i n e i n d i c a t e s the s a t u r a t i o n pressure at the i n i t i a l temperature.  - 57  1  i  -  r  i  DISTANCE FROM OPEN  ***** IOOO LU  Z  •  -  END  = 1.62 m  -  — •  800  rr z>  600  rr  400 —  CO CO LU  1  VERTICAL, DISCHARGE DOWN Pi = 1500 kPo v Tj = 20.7 °C (RUN 3) • Tj = 20.8 °C (RUN 4)  2 000  o  i  V  V  -  -  •  Q_  200  •  100  1  1 12  1 18  1 24  1  1'  30  36  TIME ms  F i g u r e 27. P r e s s u r e h i s t o r i e s showing the r e p e a t a b l i t y of the r e p r e s s u r i z a t i o n behaviour d u r i n g blowdown from a v e r t i c a l pipe d i s c h a r g i n g downward.  42  - 58 -  4.5  Flow H i s t o r y f o r D i s c h a r g e V e r t i c a l l y Down Flow v i s u a l i z a t i o n  repressurization. the  d i d not shed  any l i g h t  on the reasons  The r e p r e s s u r i z a t i o n o n l y covered  f i l m and t h i s was i n s u f f i c i e n t  f o r the  2 t o 15 frames o f  to make any s i g n i f i c a n t  observations  as to what was c a u s i n g the r e p r e s s u r i z a t i o n . However, i t was p o s s i b l e to observe how the g r o s s f l o w p a t t e r n s changed w i t h  time.  Sketches of the v a r i o u s f l o w regimes observed  f o r the present  work  are show i n F i g u r e 9. The f i r s t discharge  camera p o s i t i o n was 460 mm  end  of  the  tube.  Nucleation  m i l l i s e c o n d a f t e r the diaphram b r o k e . b u b b l e s had grown u n t i l of  the tube.  f l o w was  The  from t h i s  but o c c u r r e d  started  around  location  was  a vapour-core  the w a l l s  annular  flow p a t t e r n to  460 m i l l i s e c o n d s .  bubbly  Around  of organized  The l a s t f l o w regime observed  annular  one  core remained a t the c e n t e r  m i l l i s e c o n d s i n t o the blowdown t h e r e was some evidence of bubbles moving down the p i p e .  at  from the  By 40 m i l l i s e c o n d s the amount of  only a small l i q u i d  transition  indistinct  (1.44 tube d i a m e t e r s )  flow p a t t e r n , beginning  640  slugs  at t h i s  around  970  m i l l i s e c o n d s i n t o the blowdown. The next  movies were taken  d i s c h a r g e end. small but  amount  1.22  m  (38.13 tube d i a m e t e r s )  Three m i l l i s e c o n d s a f t e r the blowdown s t a r t e d t h e r e was a  of n u c l e a t i o n on the p r e s s u r e  the f l o w regime r e t u r n e d  transducer  to a l l - l i q u i d .  regime  By t h i s Organized  time  remained  until  the l i q u i d  slugs  of f l u i d  f l o w regime was v e r y  around  core  indistinct.  This l i q u i d - c o r e  200 m i l l i s e c o n d s i n t o  had d i s a p p e a r e d  where  s i d e of the tube  At 25 m i l l i s e c o n d s t h e r e  were bubbles a l l around the w a l l s of the tube. flow  from the  seen around  annular  the blowdown.  and the f l o w was  bubbly.  560 m i l l i s e c o n d s , but  this  - 59 -  The  third  discharge  camera l o c a t i o n was 2.03 m (63.44 tube diameters) from the  end.  milliseconds liquid.  There  into  was  some  the flow,  nucleation  however  At 89 m i l l i s e c o n d s  at  the f l o w  the  regime  225  on the o p p o s i t e s i d e .  milliseconds  by which  This  milliseconds  returned  to  time  the tube was f u l l  t h e r e was j u s t  a thin  film  a l l -  on the  amount of bubbles  annular flow remained  until  of b u b b l e s .  some vapour-core annular flow b e g i n n i n g a t around 930  center s i x  a g r e a t d e a l of bubbles were formed  p r e s s u r e t r a n s d u c e r s i d e of the tube w i t h only a s l i g h t formed  tube  around  There was  590 m i l l i s e c o n d s .  of l i q u i d  By  d r a i n i n g down the  w a l l s of the tube. The  next  discharge side  of  pattern by  were  taken  end of the tube. at eight  was r a p i d l y  formed  time  the l i q u i d  of s l u g s  2.92 m  Nucleation  the tube  which  pattern  movies  being  s l u g s of l i q u i d  and  s i z e of the bubbles at the c e n t e r l i n e  350  milliseconds  The  last  centerline  10  annular  the  to  broken  flow  135 m i l l i s e c o n d s ,  by the bubbles  and a  By 190 m i l l i s e c o n d s The amount  seemed to grow u n t i l by around  vapour-core  of  pictures  discharge  until  were  end.  into  annular.  into  around  a  taken  at  This  flow  m  (111.25  tube  at  tube  3.56  Nucleation  the f l o w .  By 210 m i l l i s e c o n d s  coalesce  around  annular  regime  ended at 960 m i l l i s e c o n d s .  milliseconds  flow pattern  was observed. seemed  the flow was  series  from  liquid-core  had d i s a p p e a r e d and the flow was bubbly.  the f i l m  diameters)  d i a m e t e r s ) from the  and bubbles was formed.  the  continued u n t i l  A  and c o n t i n u e d u n t i l was  tube  began a t the p r e s s u r e t r a n s d u c e r  milliseconds.  core  of l i q u i d  (91.25  began  There  72 m i l l i s e c o n d s ,  was when  the tube was f u l l  vapour-core  annular  a  the  liquid-core  some s l u g  of bubbles,  flow  regime  by  flow which 320  - 60 -  milliseconds.  The amount of f l u i d  a t the w a l l s decreased  u n t i l a t 670  m i l l i s e c o n d s t h e r e was j u s t a f i l m of l i q u i d d r a i n i n g down the tube. The r e s u l t s of these f l o w v i s u a l i z a t i o n s have been used t o make the f l o w regime map shown i n F i g u r e 28.  4.6  P r e s s u r e H i s t o r i e s f o r D i s c h a r g e V e r t i c a l l y Up Pressure  discharging pressure  data  vertically  data  apparatus. made b e f o r e  i s available  was  up.  lost  T h i s problem our s u p p l y  f o r only  During  because  two  the f i r s t  of a  test  problem  with  the  tube  d i s c h a r g i n g up t h e  with  the  experimental  was c o r r e c t e d but o n l y two a d d i t i o n a l runs were o f Freon  was exhausted.  summarized g r a p h i c a l l y i n F i g u r e s 29 t o 42. of  tests  the blowdown a r e shown i n F i g u r e s  This pressure data i s  The f i r s t  29 t o 39.  few m i l l i s e c o n d s  Figure  29 shows t h e  p r e s s u r e h i s t o r y f o r the gauge s t a t i o n n e a r e s t the d i s c h a r g e end (Z = 40 mm).  The p r e s s u r e h i s t o r y f o r t h i s d i s c h a r g e up r u n i s v e r y s i m i l a r t o  those f o r the "normal" d i s c h a r g e down runs ( F i g u r e s 10 and 1 1 ) . Figure end.  Again  30 shows the p r e s s u r e this  history  pressure h i s t o r y  a t 180 mm  i s similar  from  the d i s c h a r g e  t o those f o r the "normal"  runs d i s c h a r g i n g down ( F i g u r e s 10 and 1 1 ) . F i g u r e 31 shows the p r e s s u r e h i s t o r y 860 mm from  t h e d i s c h a r g e end.  The i n i t i a l stage o f t h i s p r e s s u r e h i s t o r y was v e r y s i m i l a r t o those f o r the d i s c h a r g e down runs  ( F i g u r e s 12, 13 and 1 9 ) . However on t h i s  there  peaks,  a r e two p r e s s u r e  reaches and time  one i s c e n t e r e d  graph  a t 17 m i l l i s e c o n d s and  a peak o f 500 kPa and t h e o t h e r i s c e n t e r e d a t 28 m i l l i s e c o n d s  reaches  a maximum o f 280 k P a .  shown on t h i s  graph  p r e s s u r e of Freon-114.  I t should  the p r e s s u r e  be noted  i s always  t h a t d u r i n g the  above the s a t u r a t i o n  - 61 -  5 000  DISTANCE  FROM  OPEN  END  Z m  F i g u r e 28. Flow regimes d u r i n g blowdown of Freon-114 from a v e r t i c a l pipe d i s c h a r g i n g downward (see F i g u r e 9).  - 62 -  2 000  VERTICAL, DISCHARGE UP RUN 7 Pj  1000  Tj = 20.8 °C  800  —  DISTANCE FROM OPEN END Z = 40 mm  o  CL  • —  = 1500 kPa  600  LU §5 4 0 0 CO CO LU  rr CL  200  100  b&  12  18  TIME  24  30  36  42  ms  F i g u r e 29. P r e s s u r e h i s t o r y d u r i n g the i n i t i a l stages of blowdown a v e r t i c a l p i p e d i s c h a r g i n g upward. The dashed l i n e i n d i c a t e s the s a t u r a t i o n p r e s s u r e at the i n i t i a l temperature.  from  - 63 -  2 000  t  VERTICAL, DISCHARGE UP RUN 7  1000 o  CL  800  i  = 1500  kPa  Tj  = 20.8  °C  DISTANCE 600  Z  FROM OPEN END s  180 mm  LU  rr co  400  CO LU  rr CL  200  100  12  18  24  TIME ms  F i g u r e 30. P r e s s u r e h i s t o r y d u r i n g the i n i t i a l stages of blowdown f a v e r t i c a l pipe d i s c h a r g i n g upward. The dashed l i n e i n d i c a t e s the s a t u r a t i o n p r e s s u r e at the i n i t i a l temperature.  42  - 64 -  2 000  1  1—  1  i  1  i  VERTICAL, DISCHARGE UP RUN 7 A  1000  CL  rr  600  ZD  co co  400  A  1  —  A  A A  100  °C  A  rr  200  Tj = 20.8  A  LU  a.  kPa  DISTANCE FROM OPEN END Z = 860 mm  800  LU  Pj = 1500  A  . A M  \  *  A r f ^  1  1  1  1  1  1  12  18  24  30  36  42  TIME ms  F i g u r e 31. P r e s s u r e h i s t o r y showing r e p r e s s u r i z a t i o n behaviour d u r i n g blowdown from a v e r t i c a l pipe d i s c h a r g i n g upwards. The dashed l i n e i n d i c a t e s the s a t u r a t i o n p r e s s u r e at the i n i t i a l temperature.  - 65 -  F i g u r e 32 shows t h e p r e s s u r e measured a t 1.62 m from end  of the p i p e .  compares  very  beginning  well  Again with  not  that  f o r the d i s c h a r g e  a t 7 m i l l i s e c o n d s t h e r e were a s e r i e s  d i m i n i s h i n g amplitude. is  the time f o r the i n t i a l  for a different  the d i s c h a r g e  decompression down  to s t a r t  runs.  However  of recompressions  of  F i g u r e 33 i s a r e p e a t of F i g u r e 32 except t h a t i t  run.  As can be seen,  show any s i g n s of r e c o v e r y .  the pressure f o r t h i s run d i d  I n s t e a d t h e r e was a r a p i d drop to 900  k P a , then the s l o p e of the p r e s s u r e d e c l i n e became much more g e n t l e . F i g u r e 34 shows the p r e s s u r e h i s t o r y meters.  The d a t a here showed a r a p i d drop to 600 kPa a t 6 m i l l i s e c o n d s .  The s l o p e of the p r e s s u r e decrease  then became much more g e n t l e .  F i g u r e 35 shows the p r e s s u r e h i s t o r y meters,  d u r i n g r u n 7.  f o r the gauge s t a t i o n a t 3.14  The d a t a showed a r a p i d drop i n p r e s s u r e t o 700  kPa b e g i n n i n g a t 9 m i l l i s e c o n d s . r a t e l e v e l i n g o f f a t 400 k P a . run 8.  f o r the gauge s t a t i o n a t 2.38  The p r e s s u r e then d e c l i n e d a t a slower  F i g u r e 36 i s a r e p e a t of F i g u r e 35 but f o r  The p r e s s u r e drop seen here b e g i n s  a t the same time as t h a t o f  run 7 but the p r e s s u r e d e c l i n e i s a t a much slower Figures  37 to 39 show the r e p r o d u c i b i l i t y  rate.  among these s e t s of d a t a  f o r the i n i t i a l stages of the t e s t s . Figures All  40 and 41 show the l o n g - t e r m  pressure h i s t o r i e s  f o r r u n 7.  the p r e s s u r e h i s t o r i e s show a d i p a t a p p r o x i m a t e l y 0.1 seconds and a  p r e s s u r e peak a t between 0.25 and 0.35 seconds i n t o the f l o w . F i g u r e 42 shows the l o n g - t e r m p r e s s u r e h i s t o r i e s f o r r u n 8. is  very d i f f e r e n t  from  the d a t a  f o r run 7 (Figure 42).  The d a t a  Run 8 d i d not  show the p r e s s u r e d i p seen i n r u n 7, but i n s t e a d showed a g r a d u a l d e c l i n e i n p r e s s u r e , l e v e l i n g o f f a t a p p r o x i m a t e l y 0.25 seconds, f a l l a g a i n a t 0.5 seconds,  r e a c h i n g atmospheric  then s t a r t i n g to  p r e s s u r e a t 1.0  seconds.  - 66 -  2  o CL LU  rr z> CO CO LU  000h  VERTICAL, DISCHARGE UP RUN 7  1000  Pj  = 1500  kPa  Tj  = 20.8  °C  DISTANCE FROM OPEN END  800  Z = 1.62 m  600 V  V V  400  V  rr CL  V V  w  V  200  100  -I 12  18  TIME  I 24  30  36  ms  F i g u r e 32. P r e s s u r e h i s t o r y showing r e p r e s s u r i z a t i o n behaviour d u r i n g blowdown from a v e r t i c a l pipe d i s c h a r g i n g upwards. The dashed l i n e i n d i c a t e s the s a t u r a t i o n p r e s s u r e at the i n i t i a l temperature.  42  - 67 -  2 000  1  I  I  1  I  1  V  1000 -  o CL LU  V  800 ^  ^  ^  ^  ^  600  rr  co co  V  400  —  LU  rr CL  DISTANCE FROM OPEN END Z = 1.62 m  200  100  -  VERTICAL , DISCHARGE UP RUN 6 Pj = 1500 kPa Tj = 22.6 °C  1  1  1  i  i  i  12  18  24  30  36  TIME ms  F i g u r e 33. Repeat of the d i s c h a r g e h i s t o r y shown i n F i g u r e 32. The dashed l i n e i n d i c a t e s the s a t u r a t i o n p r e s s u r e a t the I n i t i a l temperature.  42  - 68 -  T  1000  -  CL  800  -  LU  600 h  rr co co LU  T  VERTICAL , DISCHARGE UP RUN 7 Pj = 1500 kPa T| = 20.8 °C  2 000 h  O  T  DISTANCE FROM OPEN END Z = 2.38 m  400  rr  200  100  12  18  24  30  36  42  TIME ms  F i g u r e 34. P r e s s u r e h i s t o r y d u r i n g the i n i t i a l stages of blowdown a v e r t i c a l pipe d i s c h a r g i n g upward. The dashed l i n e i n d i c a t e s the s a t u r a t i o n p r e s s u r e at the i n i t i a l temperature.  from  -  69 -  VERTICAL , DISCHARGE UP RUN 7  2 OCX)  o  O CL LU  rr co co  LU  1000  800  Pj  * 1500 kPa  Tj  = 20.8  °C  DISTANCE FROM OPEN END Z =3.14 m  o o  600  400  rr  CL  200  100  12  18  24  30  36  TIME ms  F i g u r e 35.  P r e s s u r e h i s t o r y d u r i n g the i n i t i a l stages of blowdown from a v e r t i c a l pipe d i s c h a r g i n g upward. The dashed l i n e i n d i c a t e s the s a t u r a t i o n p r e s s u r e at the i n i t i a l temperature.  42  - 70 -  2 000  lOOOh  o LU  rr co co  LU  rr  Q_  18  24  TIME ms  F i g u r e 36. Repeat of the d i s c h a r g e h i s t o r y shown i n F i g u r e 33. dashed l i n e i n d i c a t e s the s a t u r a t i o n p r e s s u r e a t the initial temperature.  The  - 71 -  2 000  1  1  1  1  1  1  >  VERTICAL , DISCHARGE Pj = 1500  kPa  o  Tj  = 20.8  °C (RUN 7)  •  Tj  = 22.6  °C (RUN 8)  —  o CL LU  rr ZD  CO CO LU  DISTANCE  600  FROM OPEN END  Z  o 400  UP  = 40 mm  h  rr CL  200  100  %.«8SSSSH8o-8S88*  1  8 8 8 M 8 8 8 8 8 8 8 S S 8 S 8 8  1  1  1  12  18  24  I  30  "  I  36  TIME ms  F i g u r e 37. P r e s s u r e h i s t o r i e s showing the r e p e a t a b l i t y of d a t a taken a t a gauge s t a t i o n t h a t d i d not show r e p r e s s u r i z a t i o n d u r i n g the blowdown from a v e r t i c a l pipe d i s c h a r g i n g upward.  42  - 72 -  2 000  1 p  1  1  VERTICAL , DISCHARGE  •  i ooo F UJ  rr co co  800  kPa  •  Tj  = 20.8  °C (RUN 7)  •  Tj  = 22.6  °C (RUN 8)  Z  1  UP  = 1 500  DISTANCE  600  1  Pj  •  o CL  1  FROM OPEN END  = 180  —  mm  400  UJ  •  rr CL  200  100  •  -o  i  i  i  i  i  12  18  24  30  1 36  TIME ms  F i g u r e 38. P r e s s u r e h i s t o r i e s showing the r e p e a t a b l i t y of d a t a taken at a gauge s t a t i o n t h a t d i d not show r e p r e s s u r i z a t i o n d u r i n g the blowdown from a v e r t i c a l pipe d i s c h a r g i n g upward.  42  - 73 -  2000  VERTICAL , DISCHARGE  h  A  UP  Pj  = 1 500  kPa  A  Tj  = 20.8  ° C (RUN 7)  A  Tj  s  22.6  °C (RUN 8)  A  DISTANCE FROM OPEN END Z = 860 mm  I000 800  —  —  600 A  A A AA A  400  *** AA A A  200  *  A  A  A  A  A* A  A A  A A  A A  A  AA A A  ^  A  A A  A A  100 12  18  24  30  TIME ms  F i g u r e 39. P r e s s u r e h i s t o r y showing the r e p e a t a b l i t y of the r e p r e s s u r i z a t i o n behaviour d u r i n g blowdown from a v e r t i c a l pipe d i s c h a r g i n g upward-  36  42  700  VERTICAL , DISCHARGE UP RUN 7  o Q_  Pj T:  500  1  DISTANCE FROM OPEN END o •  LU  cn  A  co co  A A  LU  or  « 1500 kPa = 20.8 ° C Z 8 40 mm Z = 180 mm Z = 860 mm  AA.  300  CL  8 2a •° o o 9  D  0  0  n O  D  D  A  D ° ° 0  •  100  0.25  0.50  0.75  1.0  TIME s F i g u r e 40. Long term pressure h i s t o r i e s f o r three gauge s t a t i o n s f o r a v e r t i c a l pipe d i s c h a r g i n g upward. The dashed l i n e i n d i c a t e s the s a t u r a t i o n p r e s s u r e a t the i n i t i a l temperature.  700  o  T  500  oo  LU  o  oo oo o<>Ooo oo  o  o  I  VERTICAL .DISCHARGE UP RUN 7 Pj = I 500 kPa Tj = 20.8 °C DISTANCE FROM OPEN END v Z = 1.62 m O Z * 2.38 m o Z =3.14 m  0  rr  ZD  CO CO LU 3 0 0  —o—  rr  0  % * 0 S  Q.  100  0.25  0.50  0.75  TIME S F i g u r e 41. Long term pressure h i s t o r i e s f o r three gauge s t a t i o n s f o r a v e r t i c a l pipe d i s c h a r g i n g upward. The dashed l i n e i n d i c a t e s the s a t u r a t i o n p r e s s u r e a t the i n i t i a l temperature.  1.00  700  VERTICAL , DISCHARGE UP RUN 8 o  2  oo 500  V  -0.  13j  = 1500  kPa  T|  = 22.6  °C  DISTANCE v Z 0 Z o Z  o LU  rr  ZD CO CO LU 3 0 0  FROM = 1.62 = 2.38 = 3.14  OPEN END m m m ON  rr CL  100  F i g u r e 42. Repeat of the pressure  h i s t o r i e s shown i n F i g u r e 41.  dashed l i n e i n d i c a t e s the s a t u r a t i o n p r e s s u r e initial  temperature.  at the  - 77  To  -  summarize the d i s c h a r g e up d a t a , r e p r e s s u r i z a t i o n was  runs.  However the r e p r e s s u r i z a t i o n was  stations  ( F i g u r e s 31,  32 and  open end  showed a r a p i d  Freon-114 ( F i g u r e s 29, the c l o s e d end became  much  39).  The  37 and  two  38).  the p r e s s u r e dropped  more  o n l y seen at the middle  shallow  at  a  two  gauge s t a t i o n s c l o s e s t  drop to approximately 30,  seen on  gauge to the  the s a t u r a t i o n p r e s s u r e of  At the two  rapidly, pressure  both  but  gauge s t a t i o n s n e a r e s t the slope of the graphs  well  above  the  saturation  pressure.  4.7  Flow H i s t o r i e s f o r D i s c h a r g e V e r t i c a l l y The  open  first  end  after  of  the  flow.  camera p o s i t i o n was the  increasing.  this  of  This  bubbly-slug  bubbles. vapour flow  slug  at  and  was  regime  the  size  flow  of l a r g e bubbles flow  which  continued  time  c o u l d be  regime  tube diameters)  approximately  f o l l o w e d by of  the  the  second end.  f o l l o w e d by until  flow  from  around  53  appeared  until  the  very  ran  to  be  i n the bubbles.  tightly  the  packed  at the edges and w i t h  milliseconds into  camera  smaller  bubbly  milliseconds after  became a mass of  256  of  the  1 millisecond  a p e r i o d of  bubbles  a slug  flow, having l i q u i d  seen around  continued  milliseconds after  discharge  (1.44  started  broken,  A p e r i o d of annular  core,  The  mm  Around 20 m i l l i s e c o n d s i n t o the blowdown the flow was  form  blowdown,  Nucleation  diaphragm was  During  a  tube.  460  Up  out  of  the  flow.  film  a  This  at  1106  the blowdown.  camera The  p o s i t o n was flow  regimes  those d e s c r i b e d p r e v i o u s l y .  2.56 at  m  this  (80  tube  location  diameters) are  very  from  similar  Nucleation started 6 milliseconds after  the to the  - 78 -  blowdown. 37  I t was f o l l o w e d by a p e r i o d of bubbly  milliseconds.  until  The b u b b l y - s l u g  72 m i l l i s e c o n d s , when  This lasted u n t i l  flow  the flow  described  regime  flow  529 m i l l i s e c o n d s at which time  pattern  milliseconds  into  changed  to  the flow  an  which  However, a t 1132 m i l l i s e c o n d s the flow and  start The  last  those  milliseconds bubble  at  after  very  fluid  began moving very this  two  the flow h i s t o r y a t t h i s  flow  regime  f o r the r e s t  can be seen  locations.  the blowdown.  around  flow.  around  630  of the t e s t .  to r e v e r s e  little  This  movement  was  Nucleation followed  i n the f l u i d .  590 m i l l i s e c o n d s when the tube was f u l l  time.  and there  visible  flow.  direction  rapidly.  an annular  f o r the remainder  flow  of the t e s t  pattern. with  started  by a  continued  of bubbles  flow  and the  of s l u g  had migrated  This  10  period of  This  There was some evidence  By 837 m i l l i s e c o n d s the bubbles was  from the  The flow p a t t e r n s were c o n s i d e r a b l y d i f f e r e n t  the p r e v i o u s  until  walls  to bubbly  camera p o s i t i o n was 3.56 m (111.25 tube diameters)  growth w i t h  around  i s evident  to flow back down the tube.  d i s c h a r g e end of the tube. from  until  by showing some s l u g  annular  continued  earlier  returned  l o c a t i o n d e v i a t e d from t h a t d e s c r i b e d e a r l i e r This  flow which l a s t e d  flow  to the  regime  was  the flow r e v e r s i n g d i r e c t i o n  around 1273 m i l l i s e c o n d s . The  data  from the movies taken  summarized i n F i g u r e 43.  f o r d i s c h a r g e v e r t i c a l l y up have been  - 79 -  5 000  Flow  Annular  1000  Bubbly  in  E  UJ  Reversal  Flow  100  K  Bubbly-Slug  Flow  oBubbly  Flow  •o  10  Liquid  0  1 DISTANCE  2 FROM  3 OPEN  END  4 Z m  F i g u r e 43. Flow regimes d u r i n g blowdown of Freon-114 from a v e r t i c a l pipe d i s c h a r g i n g upward (see F i g u r e 9 ) .  - 80 -  CHAPTER FIVE DISCUSSION OF THE RESULTS  5.1  Discharge H o r i z o n t a l l y The  primary  reason  f o r conducting  experiments  with  d i s c h a r g i n g h o r i z o n t a l l y was t o o b t a i n d a t a f o r comparison Necmi and Hancox [ 4 ] . to  those o f Necmi.  the  tube  w i t h that of  F i g u r e 7 compares the p r e s e n t p r e s s u r e h i s t o r i e s F o r both cases the d a t a showed a r a p i d decrease i n  p r e s s u r e to a p r e s s u r e near the s a t u r a t i o n p r e s s u r e o f the Freon-114 f o r the  initial  temperature.  The p r e s s u r e wave appears  a l o n g the tube a t 360 metres per second which of  sound i n l i q u i d  one l o c a t i o n  Necmi.  travelling  i s a p p r o x i m a t e l y the speed  Freon-114.  F i g u r e 8 compares the f l o w regimes at  t o be  along  the pipe w i t h  observed  d u r i n g the p r e s e n t work  the f l o w regime  map  compiled  Once a g a i n t h e r e i s good agreement between the two r e s u l t s .  should  be noted  Another  that  interesting  liquid  some s l u g  point  f l o w not seen  i s that  by Necmi was  the complete  by It  observed.  stratification  o f the  and vapour phases o f the f l o w t h a t Necmi r e p o r t e d was a l s o  seen  d u r i n g these t e s t s . The  results  encouraging. noted  obtained  from  the h o r i z o n t a l  The d a t a was much as i t was expected  t h a t a l t h o u g h the blowdown apparatus  investigations,  the  different.  the c l o s e agreement  obtained  experiments  From  by Necmi  working p r o p e r l y .  we  method  of  inferred  between  the  data  our d a t a  the data  was  very  I t should be  was the same f o r both  acquiring  that  t o be.  were  these  completely  and the r e s u l t s  acquisition  system  was  - 81 -  5.2  Discharge The  Vertically  p r e s s u r e d a t a f o r d i s c h a r g i n g v e r t i c a l l y up and f o r d i s c h a r g i n g  vertically "normal"  down can be d i v i d e d  group which  expectations. saturation  two d i s t i n c t  groups.  There i s a  c o n s i s t s of p r e s s u r e r e a d i n g s t h a t conformed t o our  This  pressure  into  group  shows  a t the i n i t i a l  a rapid  pressure  temperature.  drop  t o near the  The p r e s s u r e  wave  appears t o be t r a v e l l i n g between the p r e s s u r e t r a n s d u c e r s a t the speed of sound  i n Freon-114.  group  i s i n fact  F o r a s h o r t time much  like  interval after  the pressure  data  the blowdown t h i s  f o r the  horizontal  discharge. The  second  resemble blowdown.  or "unusual" group o f d a t a shows p r e s s u r e h i s t o r i e s  t h e "normal"  data  However, a f t e r  f o r the f i r s t  the i n i t i a l  p r e s s u r e had o c c u r r e d , a r e c o m p r e s s i o n  that  few m i l l i s e c o n d s o f the  decompression  t o the s a t u r a t i o n  t o a p r e s s u r e s l i g h t l y under the  i n i t i a l p r e s s u r e o f the f l u i d was o b s e r v e d . Both  groups  of data  were  reproduced  ( a l t h o u g h n o t on demand) and  agreement w i t h i n the groups i s v e r y good. The p r i m a r y o b j e c t i v e o f t h i s i n v e s t i g a t i o n was t o examine the e f f e c t of  body f o r c e s on the blowdown of a tube.  Body f o r c e s were not expected  to  have much i n f l u e n c e on the time f o r the i n i t i a l  decompression  p a s s , because the f i r s t passage i s s t r i c t l y a c o u s t i c . pressure  t o drop  data confirm t h i s .  to saturation  i n both  the "normal"  for  The times f o r the and the " u n u s u a l "  F o r example, a t the gauge s t a t i o n 3.14 metres (98.13  tube d i a m e t e r s ) from the d i s c h a r g e end, the i n i t i a l at  wave t o  10.0 m i l l i s e c o n d s f o r the h o r i z o n t a l  decompression  starts  d i s c h a r g e , a t 9.0 m i l l i s e c o n d s  the v e r t i c a l down d i s c h a r g e and a t 9.5 m i l l i s e c o n d s f o r the v e r t i c a l  up d i s c h a r g e .  - 82 -  The e f f e c t s of g r a v i t y a r e more e v i d e n t i n the f l o w regime h i s t o r i e s . The  time  s c a l e s here are much l o n g e r and w i t h i n c r e a s i n g time the r a t i o  of p r e s s u r e see  to body f o r c e s becomes s m a l l e r , meaning we  the body f o r c e s h a v i n g more i n f l u e n c e .  should expect to  The most obvious  e f f e c t of  body f o r c e s i s t h a t f o r d i s c h a r g e up the tube never empties. about 90% of the Freon  i s d i s c h a r g e d d u r i n g the blowdown.  In fact  The o t h e r 10%  remains b o i l i n g i n the tube. From the f l o w regime map  f o r d i s c h a r g e up ( F i g u r e 43) i t can be seen  t h a t the f l o w r e v e r s e s d i r e c t i o n and s t a r t s to run down the tube a t about one second I n t o the blowdown. a p p r o x i m a t e l y atmospheric  At t h i s time the p r e s s u r e i n the tube i s  ( F i g u r e s 40, 41 and 4 2 ) .  Another and h o p e f u l l y more obvious d i s c h a r g e down the tube does empty A  great  d e a l o f time  occurrence  of  discharge  data.  the  e f f e c t of body f o r c e i s t h a t f o r  completely!  has been spent  i n attempting  recompression  phenomenon  As  definitive  of y e t no  In  some  answer  t o e x p l a i n the of  the  vertical  has been  obtained,  thought  t o be the  a l t h o u g h a number of p o s s i b i l i t i e s have been proposed. When the recompression  was  first  observed  r e s u l t of a p r e s s u r e undershoot as observed i n c l u d i n g Alamgir  and L i e n h a r d  recovery  [ 3 ] , Necmi  [ 1 ] . T y p i c a l l y what was  With  the f l u i d  observed  the onset  p r e s s u r e had dropped below the s a t u r a t i o n  of n u c l e a t i o n the p r e s s u r e would r e c o v e r to  s l i g h t l y above the s a t u r a t i o n p r e s s u r e and then the f l u i d gradually  experimenters  s t u d i e s was a r a p i d drop i n the f l u i d p r e s s u r e and a d e l a y  in nucleation until pressure.  by a number of  [ 8 ] , A l a m g i r , Kan and L i e n h a r d  and Hancox [4] and Edwards and O'Brien d u r i n g these  i t was  drop as the l i q u i d  continued  to b o i l .  p r e s s u r e would  U s u a l l y the p r e s s u r e  i s to a p o i n t near the s a t u r a t i o n p r e s s u r e of the f l u i d  a t the  - 83 -  initial number  temperature o f times  discharge).  [8],  The r e s u l t s of d e l a y e d n u c l e a t i o n can be seen a  i n t h i s work ( s e e F i g u r e 7 f o r the case  of h o r i z o n t a l  P r e s s u r e r e c o v e r y was seen f o r both groups o f d a t a w i t h the  tube d i s c h a r g i n g v e r t i c a l l y down.  F i g u r e 12 shows some p r e s s u r e r e c o v e r y  10 m i l l i s e c o n d s i n t o the d i s c h a r g e d u r i n g one of the "normal"  runs a t the  gauge s t a t i o n 1.62 metres (50.63 tube d i a m e t e r s ) from the d i s c h a r g e end. Figure  20 shows t h e same p r e s s u r e  recovery  during  one o f t h e " r e p r e s s u r i z a t i o n "  f o r t h e same gauge  runs.  Pressure  station  undershoot  and  r e c o v e r y can a l s o be seen f o r the d i s c h a r g e v e r t i c a l l y up d a t a ( F i g u r e s 29,  30  and  31).  Delayed  nucleation  was  rejected  as  a  possible  e x p l a n a t i o n f o r the l a r g e p r e s s u r e r e c o v e r y seen i n the " u n u s u a l " d a t a i n the  present  work, s i n c e i t was f e l t  that delayed  n u c l e a t i o n c o u l d not  e x p l a i n a p r e s s u r e r e c o v e r y of such a l a r g e magnitude. The next was caused reversal  possibility  t h a t was c o n s i d e r e d was t h a t t h e r e c o m p r e s s i o n  by a f l o w r e v e r s a l . was  seen  repressurization.  on  As noted  the movies  at  earlier times  no evidence  of flow  corresponding  to the  F i g u r e 44 shows the p r e s s u r e p r o f i l e s a l o n g the p i p e  a t v a r i o u s times f o r a r e p r e s s u r i z a t i o n r u n w i t h the d i s c h a r g e v e r t i c a l l y down  and  Figure  vertically gradient  up.  along  45  shows  similar  As can be seen the pipe  reversed  pressure  from  this  rapidly  profiles  figure  during  f o r discharge  the a x i a l  pressure  the r e p r e s s u r i z a t i o n .  T h i s would i n d i c a t e a r a p i d d e c e l e r a t i o n o f the f l o w , i f not a  complete  r e v e r s a l , must have o c c u r r e d a l o n g the p i p e . The  last  explanation considered  c o u l d be the r e s u l t  f o r the r e c o m p r e s s i o n  of some type o f e x p e r i m e n t a l f a i l u r e .  number o f p o s s i b l e e x p e r i m e n t a l shortcomings t o r e s u l t s of the k i n d o b s e r v e d .  was t h a t i t There a r e a  that could p o t e n t i a l l y lead  The f i r s t one c o n s i d e r e d was the e f f e c t  - 84 -  2 000  TIME 3 ms o • 9 ms 15 ms o 21 ms 27 ms X 33 ms 100  _L  I  2  3  DISTANCE FROM OPEN END m  Figure 44. Pressure p r o f i l e s along a pipe discharging downward when repressurization was noted ( i n i t i a l conditions as i n Figure 27).  - 85 -  2 000  1000  eoo 600 LU  rr  CO CO  400  LU  rr  CL  TIME o 3 ms • 9 ms 15 ms o 21 ms X 27 ms * 33 ms  200  100  1  2  3  DISTANCE FROM OPEN END m F i g u r e 45. P r e s s u r e p r o f i l e s along a p i p e d i s c h a r g i n g downward when r e p r e s s u r i z a t i o n was noted ( i n i t i a l c o n d i t i o n s as i n F i g u r e 2 9 ) .  - 86 -  of  gas i n s o l u t i o n .  S o z z i and F e d r i c k  water that gas i n s o l u t i o n had l i t t l e during as  blowdown.  the t e s t  work  of  significant that  In f a c t  that  effect  shield  f o r Freon,  study  inert  the  gases  pressure  by some  measurements.  and  that  no  transducers  evidence  was  can have  I t should  to b o i l  i s used  unpublished  i n solution  the Freon was allowed  the gas i n s o l u t i o n  around  work with  e f f e c t on the p r e s s u r e measurements  i t has been suggested  on e x p e r i m e n t a l  i n the present  eliminate  i n their  However, t h i s may not be the case when Freon  fluid.  Sozzi  [5] showed  be  a  noted  i n an attempt to  o f gas forming  observed  i n any  a  of the  photographs. Another  potential  problem  area  i s a flow  diaphragms not b r e a k i n g c l e a n l y . was  observed  mentioned  during  earlier  The e f f e c t  the i n i t i a l  the r e s u l t i n g  restriction  caused  of such a f l o w  nitrogen tests  by the  restriction  of the a p p a r a t u s .  As  p r e s s u r e o s c i l l a t i o n s were the r e s u l t of  the diaphragms not b r e a k i n g  cleanly.  I t i s p o s s i b l e the recompression  observed  tests  caused  during  the Freon  However, a t the end of each t e s t  was  by  a  similar  mechanism.  there was no evidence of the diaphragms  b l o c k i n g the end of the tube. S o z z i and F e d r i c k [5] saw a s i m i l a r the  discharge of a r e s e r v i o r  through  a pipe.  p r e s s u r e r e c o v e r y was t h a t i t was caused bubbles  i n the l o c a l l y  friction choking  i n the t e s t limit  section, pressure.  decompressed section.  the flow,  resulting  further  recompression  and a l s o  believe  increasing  i n the p r e s s u r e  T h e i r e x p l a n a t i o n of the  i n p a r t by growth of the vapour  liquid  They  i n t h e i r work w i t h  that  back  recovering  by choking local  friction  pressure  to above  and f l o w and  i n the t e s t  the s a t u r a t i o n  - 87 -  Lienhard, observed "to  be  Kan and Alamgir  [3] i n r e f e r r i n g  to the r e p r e s s u r i z a t i o n  by S o z z i and F e d r i c k [ 5 ] , s t a t e that they the combined  reflected  result  rarefaction  This gives r i s e experiment  to  wave  interacting  One  the c o n d i t i o n s  p o s s i b l e answer  the behaviour  of the r e s e r v o i r  with  to the q u e s t i o n how would recreate  experiment.  of the presence  suspect  the r e c o v e r i n g  and the  pressure."  i t be p o s s i b l e f o r the present of  the S o z z i  and  Fedrick  i s , i f f o r some reason  [5]  the s o l e n o i d  v a l v e a t the c l o s e d end of the tube remained open i t would have b a s i c a l l y duplicated  the e x p e r i m e n t a l  a tube as was the case adequately  i n the S o z z i and F e d r i c k experiment.  of h i g h  T h i s would  profiles  pressure  profiles  of F i g u r e  occurred  a t the middle  end  of high  45  pressure  moving  down the tube.  However t h i s  i t can be seen  that  the p r e s s u r e  two gauge s t a t i o n s .  theory  passing  A  pressure  experimental  readings release  contributing large  From the  recovery  the two gauge s t a t i o n s n e a r e s t  the c l o s e d  i f the r e c o v e r y was the  was of  factor  effect  considered  the e l a s t i c  load.  While  i t is felt  that  as a source  vibration this  tests  the tube  was  of the s p u r i o u s  of the tube w a l l  possibly  could  subjected  due to a  have  i t was not the primary  r e p r e s s u r i z a t i o n seen i n some of the present  horizontal  been  reason  elastic  a  cause of the  results.  to the same sudden  During the r e l e a s e of  p r e s s u r e , but d u r i n g these experiments no r e p r e s s u r i z a t i o n was seen. this  only  of a r e s e r v o i r d i s c h a r g i n g . final  sudden  would  There was no i n d i c a t i o n of a  of the tube, which would had to have o c c u r r e d  result  case.  o f F i g u r e 44 i t appears as though t h e r e was a  not e x p l a i n the r e p r e s s u r i z a t i o n seen i n the d i s c h a r g e up case.  slug  through  e x p l a i n the r e p r e s s u r i z a t i o n seen i n the d i s c h a r g e down  From the p r e s s u r e slug  c o n d i t i o n s of a r e s e r v o i r d i s c h a r g i n g  For  v i b r a t i o n of the tube w a l l has been r u l e d out as the  p r i n c i p l e cause of the r e p r e s s u r i z a t i o n .  - 88 -  CHAPTER SIX CONCLUSIONS  6.1  General The  o b j e c t i v e of the present  study was to e x p e r i m e n t a l l y i n v e s t i g a t e  the e f f e c t o f pipe o r i e n t a t i o n on the flow regimes and p r e s s u r e d u r i n g blowdown from a p i p e . is  to  gain  some  insight  The reason into  histories  f o r a i n v e s t i g a t i o n of t h i s  the mechanism  o f blowdown  that  type could  u l t i m a t e l y be used i n the f o r m a t i o n of an a n a l y t i c model. As has  explained  p r e v i o u s l y the p r e s s u r e  been d i v i d e d i n t o  that  showed  horizontal  pressure discharge  repressurization Despite  these  conclusions in  the  two d i s t i n c t  decompression  and an  effect  that  groups.  that  were  "unusual" could  do time  be drawn from  not  appear  to  or the long-term  the s h o r t - and long-term  f o r discharging v e r t i c a l l y There was a "normal"  very  group  not be  anomalies i n the p r e s s u r e  can s t i l l  data  histories  data  that  showed  to  histories,  explained.  i t i s felt  results.  affected  either  flow h i s t o r i e s .  those f o r  an anomolous  satisfactorily  the present have  similar  group  that v a l i d  The anomalies the  initial  Conclusions  about  e f f e c t s of body f o r c e s on the blowdown of a tube  d i s c h a r g i n g v e r t i c a l l y up and d i s c h a r g i n g v e r t i c a l l y down have been drawn on  the b a s i s  study  of the e x p e r i m e n t a l l y  of the flow regime h i s t o r i e s  photographs.  Strictly  speaking,  measured resulting  pressure  histories  from viewing  the c o n c l u s i o n s  and the  the h i g h speed  drawn are v a l i d  only  - 89 -  for  d i s c h a r g e v e r t i c a l l y up or v e r t i c a l l y down, however, i t i s f e l t  the  conclusions  different  6.2  can  qualitatively  extended  to  include  pipes  at  orientations.  Normal d a t a The p r e s e n t  on  be  that  flow  regimes,  blowdown  from  discharging whereas  a  a  pipe. (or  For l a t e r  the v e r t i c a l  the  and  early  horizontally) annular  times  either  stratified.  gradients In  liquid-core  discharging  becomes  show t h a t body f o r c e s have a s i g n i f i c a n t  pressure  upward  downward. when  results  flow  (after  upward  stages a  bubbly  ms)  the flow  first  during  while  sudden  transient develops  while  a bubbly-slug  downward,  F o r times approaching  rates  of  develops  400  or  discharge  effect  a  while first,  discharging  flow  develops  horizontal  one second a f t e r  pipe  the t r a n s i e n t  pipe d i s c h a r g i n g downward i s n e a r l y empty, w h i l e  the upward  d i s c h a r g e case r e v e r s e s flow d i r e c t i o n and l e a v e s some f r a c t i o n of l i q u i d in  the pipe (around Despite  the  early  different to the  be  10% i n the present  the g r e a t l y v a r y i n g  flow  p o r t i o n of the t r a n s i e n t  tests). regimes,  initial  higher  during  decompression  horizontally,  upward  decompression  is  and  strictly  upward is  histories  d i d not change s i g n i f i c a n t l y  d i r e c t i o n s of d i s c h a r g e , a l t h o u g h  slightly  pressure  discharge  acoustic  This and  f o r the  a tendency f o r the p r e s s u r e s was  approximately  downward.  during  noted. equal  i s because pipe  The time f o r for  the  orientation  discharge  the  initial  should  not  -  effect  -  90  the p r e s s u r e h i s t o r y d u r i n g the i n i t i a l  has been shown to be c o r r e c t by the p r e s e n t  6.3  stages.  This  hypothesis  study.  Repressurization Results It  is  difficult  repressurization definitive causes leaks  to  observed  draw in  any  some of  conclusions the  data  because  e x p l a n a t i o n f o r the r e p r e s s u r i z a t i o n has  such and  as  fluid  impurities,  end-diaphragm  partial  outgassing, wall restrictions  regarding at  the  present  been found.  no  Likely  nucleation effects,  have been  systematically  examined and r e j e c t e d as p o s s i b l e causes i n t h i s c a s e . This  gives  rise  to  the  obvious  r e p r e s s u r i z a t i o n d a t a be b e l i e v e d ? the  results  that  were  r e p e a t a b l e , a l t h o u g h not data  was  observed  very was  the r e s u l t s  good.  not  and Hancox [ 4 ] . were w o r k i n g in  the  would  should facts  repressurization  agreement w i t h i n  indicate  of some unusual  f o r the h o r i z o n t a l  repressurization,  The  on demand, and  the r e s u l t  why  A number of d i f f e r e n t  observed.  This  question,  that  the  support  data  this  was  group of  repressurization  s e t of c i r c u m s t a n c e s .  c a s e , none of which  the  Also  showed any  s i g n s of  compared v e r y w e l l w i t h the r e s u l t s observed  by Necmi  T h i s shows t h a t the d a t a a c q u i s t i o n and h a n d l i n g systems  correctly.  vertical,  apparatus-generated.  but  Indeed not  In f a c t  the f a c t t h a t r e p r e s s u r i z a t i o n was  the  horizontal  i t is difficult  case  suggests  it  is  noted not  to come to any c o n c l u s i o n  - 91 -  other  than  that  the r e p r e s s u r i z a t i o n i s somehow  linked  t o the  pipe  orientation.  6.4  Suggestions Further  f o r F u r t h e r Study  experiments  repressurization  are necessary  seen d u r i n g  some  t o determine  of the t e s t s .  the cause  of t h e  Of a l l the p o s s i b l e  e x p l a n a t i o n s put f o r t h i n Chapter F i v e i t i s f e l t t h a t the f i r s t one t h a t should  be i n v e s t i g a t e d i s the d i s c h a r g e  of a r e s e r v o i r through a p i p e .  T h i s c o u l d be accomplished by a l t e r n a t e l y r u n n i n g  the experiment w i t h the  v a l v e on the i n l e t s i d e open and c l o s e d . Another area t h a t should of  inert  pressure  gases  such  be i n v e s t i g a t e d more t h o u g h l y  as a i r or carbon  dioxide  on b o t h  i s the e f f e c t the f l o w  and  histories.  Other conditions subcooling.  possibilities on  the  for further  results,  study  especially  a r e the e f f e c t  pressure  I t would a l s o be i n t e r e s t i n g t o repeat  d i f f e r e n t p i p e s i z e s and d i f f e r e n t pipe o r i e n t a t i o n s .  and  the  of  initial  amount  of  the experiments w i t h  - 92 -  REFERENCES  1. Edwards, A.R. 135,  and O ' B r i e n , T.P.,  J o u r n a l of BNES, V o l . 9, pages  125-  1970.  2. Edwards, A.R.  and Mather, D.J.  "Some UK S t u d i e s R e l a t e d to the Loss of  C o o l a n t A c c i d e n t " , S a f e t y and R e l i a b l i t y D i r e c t o r a t e , UKAEA C u l c h e t h , W a r r i n g t o n , Lanes (1973).  3. A l a m g i r , Md.,  Kan, C.Y.  and L i e n h a r d , J.H.  " E a r l y Response of  P r e s s u r i z e d Hot Water i n a P i p e to a Sudden Break", E l e c t r i c Power Research  I n s t i t u t e Report NP-1867, June  4. Necmi, S. and Hancox, W.T.,  1981.  "An E x p e r i m e n t a l and T h e o r e t i c a l  I n v e s t i g a t i o n of Blowdown From a H o r i z o n t a l P i p e " , S i x t h Heat T r a n s f e r Conference  T o r o n t o , Canada, August 7-11,  International  1978, Volume 5  pages 83-88.  5. S o z z i , G.L.  and F e d r i c k , N.A.,  "Decompression Waves i n a P i p e  and  V e s s e l C o n t a i n i n g Subcooled Water a t 1000 P S I . " NEDE-13333, G e n e r a l E l e c t r i c Company, March  6. L y c z k o w s k i  ,Robert W.,  1973.  " T r a n s i e n t P r o p a g a t i o n B e h a v i o r of Two-Phase  F l o w E q u a t i o n s " , A paper s u b m i t t e d to the s e s s i o n "Two the 15th N a t i o n a l Heat T r a n s f e r Conference, 13,  1975.  Phase Flow" at  San F r a n c i s c o , August  10-  - 93 -  7. M o z a f f a r i H., " P r e d i c t i n g the E f f e c t s of V e r t i c a l P i p e O r i e n t a t i o n  by  the Method of C h a r a c t e r i s t i c s D u r i n g Sudden D i s c h a r g e of a Two-Phase F l u i d " , M.A.Sc. T h e s i s ,  U n i v e r s i t y of B r i t i s h C o l u m b i a , 1979.  8. A l a m g i r Md. and L i e n h a r d J.H., " C o r r e l a t i o n of P r e s s u r e Undershoot D u r i n g Hot-Water D e p r e s s u r i z a t i o n . " , 102, November,  Journal  of Heat T r a n s f e r ,  Volume  1980.  9. Massey B.S., "Mechanics of F l u i d s " , Van Nostrand R e i n h o l d Company, 1970, pages 414 t o 417.  - 94  -  APPENDIX CALCULATIONS AND  ONE ERROR ANALYSIS  A. P r e s s u r e Measurements As  the  pipe was  11/10  being  pressurized calibration  the  PDP  f o r each of the  s i x pressure  one  of these t a b l e s i s g i v e below  P r e s s u r e (kPa)  The  transducers.  Digital  100  0  300  144  500  291  700  435  900  582  1100  728  1300  871  1500  1017  the f l u i d  reading  410  pressure would  be  from  the d i g i t a l  converted  to  a  An  by  example of  Reading  computer program that d i d the data r e d u c t i o n used  calculate digital  samples were taken  readings. pressure  these t a b l e s to For example the  i n the f o l l o w i n g  manner: 1.  The  program would  find  the d i g i t a l  is  291  to 435 which corresponds  range,  which  to a p r e s s u r e of 500  in this to 700  case kPa.  - 95 -  2. The r a t i o o f the d i g i t a l  r e a d i n g s t o the p r e s s u r e range would  then g i v e the p r e s s u r e i n c r e a s e above the base p r e s s u r e , i n t h i s case 500 k P a .  The d i g i t a l r e a d i n g o f 410 would be c o n v e r t e d as f o l l o w s :  =  410 435  (±1) - 291 (±1) (±1) - 291 (±1)  119 144  (±2) (±2)  X  119 (±1.7%) 114 (±1.4%)  X  700 kPa (±0.7 kPa) - 500 kPa (±0.5 k P a )  200 kPa (±1.2 k P a )  X  200 kPa (±0.6%)  165 kPa (±3.7%) 165 kPa (± 6.1 kPa) above the base p r e s s u r e o f 500 kPa (±0.5 k P a ) P r e s s u r e = 165 kPa (±6.1 kPa) + 500 kPa (±0.5 k P a )  = 665 kPa (±6.6 kPa)  B. B u l k Temperature Bulk 267A-TC1 direct the  Temperature digital  immersion  experiments  was measured  thermometer. i n a heated i t was  The bath.  estimated  measurements I s l e s s than 1%.  by a Newport  Laboratory  thermocouples  were  From c a l i b r a t i o n s that  the e r r o r  I n c . model  calibrated  by  b e f o r e and a f t e r  i n the  temperature  - 96 -  APPENDIX  TWO  PROPERTIES OF FREON-114  A. Speed o f Sound  From Massey [9] the speed of sound i n a p i p e i s g i v e n by t h e formula:  C = /(K'/p)  Where: C = the speed of sound 1/K' = 1/K + D / ( t ) ( E ) K = the b u l k modulus of Freon-114 = 225,000 l b / ( i n )  2  D = the d i a m e t e r of the p i p e = 1.35 i n t = the t h i c k n e s s of the p i p e = .1875 i n E = the e l a s t i c  modulus of the p i p e = 320,000 i b / ( i n )  p = the d e n s i t y of Freon-114 = 92  Using t h i s  formula g i v e s :  C - 1367 f t / s = 416  m/s  lb/(ft)  3  2  -  97  -  B. S a t u r a t i o n P r e s s u r e a t V a r i o u s Temperatures  Temperature(°C)  Pressure(kPa)  4  104  10  128  16  156  21  188  27  225  32  268  

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