@prefix vivo: . @prefix edm: . @prefix ns0: . @prefix dcterms: . @prefix skos: . vivo:departmentOrSchool "Applied Science, Faculty of"@en, "Chemical and Biological Engineering, Department of"@en ; edm:dataProvider "DSpace"@en ; ns0:degreeCampus "UBCV"@en ; dcterms:creator "Kolke, Oscar Ernest"@en ; dcterms:issued "2012-03-14T20:23:29Z"@en, "1950"@en ; vivo:relatedDegree "Master of Applied Science - MASc"@en ; ns0:degreeGrantor "University of British Columbia"@en ; dcterms:description """The usual Bridgman cell for measurement of thermal conductivity has been modified to allow but a minimum of conduction. The film thickness for liquids used is approximately 0.045 cm., and hence a very small sample will suffice for measurement. Differential thermocouples were used for determining the temperature drop. Most of the heat losses in the metal contact have been prevented by a needle mounting. Measurements have been carried out on the four single-chain saturated aliphatic hydrocarbons C₂₂ H₄₆, C₂₆ H₅₄, C₃₀ H₆₂ and C₃₄ H₇₀ over a range of temperatures above their melting points. The thermal conductivities tend to increase with increasing molecular weight and with decreasing temperature."""@en ; edm:aggregatedCHO "https://circle.library.ubc.ca/rest/handle/2429/41391?expand=metadata"@en ; skos:note "THE THERMAL CONDUCTIVITY OF SOME HIGHER HYDROCARBONS by Osoar E. Koike, B.A.So. A Thesis submitted i n p a r t i a l f u l f i l l m e n t of the requirements for the degree of MASTER OF APPLIED SCIENCE i n CHEMICAL ENGINEERING THE UNIVERSITY OF BRITISH COLUMBIA THE THERMAL CONDUCTIVITY OF SOME HIGHER HYDROCARBONS Osoar E. Koike T H E U N I V E R S I T Y O F BRITISH C O L U M B I A VANCOUVER. CANADA D E P A R T M E N T O F C H E M I S T R Y October 18, 1950, To Whom I t May Concern: This i s to c e r t i f y that the th e s i s e n t i t l e d \"The Thermal Conductivity of Some Higher Hydrocarbons\" by Mr. Oscar E. Koike measures up t o the required standards of the Master's t h e s i s i n t h i s Department* Yours t r u l y , -ew ABSTRACT The usual Bridgman c e l l for measurement of thermal conductivity has been modified to allow but a minimum of oonduotion. The f i l m thickness for l i q u i d s used i s ap-proximately G.045 cm.v and hence a very small sample w i l l s u f f i c e f or measurement. D i f f e r e n t i a l thermo-couples were used for determining the temperature drop. Most of the heat losses i n the metal oontaot have been prevented by a needle mounting. Measurements have been c a r r i e d out on the four single-ohain saturated a l i p h a t i c hydrocarbons Ggg °£6 H 5 4 , G 3 0 H 6 2 a n < 1 c 3 4 H ? 0 over a range of temperatures above t h e i r melting points. The thermal conductivities tend to increase with increasing moleoular weight and with decreasing temperature. ACKNOWLEDGEMENTS The author wishes to acknowledge the ass i s -tance of Dr. D. S. Soott under whose supervision t h i s work was performed. He also wishes to thank Dr. L. W. Shemilt f o r information i n the prepar-ation of the hydrocarbons used. TABLE OF CONTENTS Page I, Introduction 1 I I . Theory 2 II I . Apparatus 6 IV. Procedure*. • 14 V. Materials. .15 VI. Results .. A. C e l l C a l i b r a t i o n ,....17 , B. Thermal Conductivity of the Hydrocar-bons 18 1. Docosane 18 2. Hexacosane.. 19 3. Triacontane 19 4. Tetratriaoontane 20 VII. Discussion of Results 20 VIII. Appendix A. Suggestions for Procedural Changes 85 B. Modifications i n C e l l Design 25 G. Experimental Data 28 IX. Bibliography 30 LIST OF ILLUSTRATIONS Page F i g . 1 Details of C e l l . . ... 7 F i g . 2 Assembly of Apparatus. . 10 F i g . 3 Photograph of C e l l 11 F i g . 4 E l e o t r i o a l Control Diagram...............13 F i g . 5 Photograph of Equipment ISA F i g . 6A Thermal Conductivities vs. Temperature. 21A F i g . 6B Thermal Conductivity vs. Moleoular Weight 213 F i g . 7 Suggested Modification 27 I... INTRODUCTION There i s l i t t l e available data on the conductivity of higher hydrocarbons• Palmer and Hazzard (8) using the law of corresponding states have predicted the ap-proximate value of hydrocarbons. Liquid hydrocarbons with chains up to twelve carbon atoms i n length have been measured. It i s therefore l o g i o a l to begin Inves-tigations into the thermal conductivity of higher hydro-carbons. Four hydrocarbons, s o l i d at room temperature and with melting points ranging from 44.4°0 to 78.9°C have been chosen. Measurements were carried out using a modified Bridgman o e l l . 2. I I . THEORY A mathematical d e f i n i t i o n of heat conductivity was presented by Fourier i n the equation: Q. ~-where Q = rate of heat flow = temperature gradient A - area perpendicular to heat flow K ~ the thermal conductivity whioh i s a property of the material through whioh heat i s flowing. This equation gives an o v e r a l l s i m p l i f i e d picture of heat conduction but does not explain the •-means whereby i t takes plaoe. Attempts to explain the mechanism of heat conduction i n l i q u i d s have to date met with l i t t l e success. However, several equations whioh r e l a t e physical properties to thermal conductivity have been advanced. About 1880, Weber (2) proposed the equation JUL ( 0 1 -Constant. Where £ i s the density of the l i q u i d C i s i t s speo i f i o heat M i s i t s molecular weight On invest i g a t i o n i t has been found that Weber1s constant varies f o r d i f f e r e n t l i q u i d s . Moreover, the constant varies for one l i q u i d at d i f f e r e n t temperatures. 3. This proved the equation of l i t t l e use i n pre d i c t i n g values of thermal conductivity. In 1923 an equation was put f o r t h by Bridgman (1) i n the form K 2 <*• V/g*. where «C i s the gas constant V i s the v e l o c i t y of sound i n l i q u i d 6 i s the mean distance between oentres of mole-cules. This i s arrived at by use of the formula assuming cubical arrangement of the molecules. M i s the absolute weight of one molecule i n the v l i q u i d . On checking t h i s equation against measured values i t was found to show a maximum deviation of 39$ and a mean deviation of 16$. In 1936 Smith (5) proposed an empirical equation that has been the most consistent i n i t s application to d a t e . It was i n the form 3 a A IS - O oooo// y \\±£.—^—— y i — i l l y, J i where Gp i s the s p e c i f i c heat £ i s the density M i s the molecular weight and Y i s the kinematic v i s c o s i t y i n oentistokes. This equation checked with an average error of 6.7$. However, i n some cases i t was subjeot to a large error and i t has been pointed out, that i n the f i e l d of thermal 4 oonduotivity, i t i s impossible to predict when large dev-iat i o n s from the equations might oeour. In 1948, Palmer (8) pointed out that there was a tendency for l i q u i d s to divide themselves into classes, those that can be f i t t e d with empirical equations and those that deviate considerably. In the l a t t e r class oculd be found the associated l i q u i d s such as water and the alcohols. Palmer states that molecular weight i s one of the most important factors i n thermal conductivity, conduc-t i v i t y generally decreasing with molecular weight, i'his statement i s made for corresponding temperatures, i n this case at .56 of the c r i t i c a l temperature. Symmetry may be a factor, since carbon tetrachloride with a higher mole-cular weight also has a higher conductivity than chlor-oform. However, associated l i q u i d s have a higher conduct-i v i t y than expected. This l e d him to consider the hydrogen bond. Obviously the equations put forth to date needed a factor which was sen s i t i v e to hydrogen bonding. The entropy of vaporization (Trouton's Constant) was chosen as the most promising. The equation of Weber (2) was chosen to be modified since i t was the simplest form proposed. By assuming 21 as an a r b i t r a r y value f o r Trouton's oonstant Palmer (8) arrived at the \\ equation Q.94 7p fyf/y 5 where p i s the density of the l i q u i d Gp i s the s p e c i f i c heat M i s the molecular weight L v i s the molecular latent heat of vaporization. On checking t h i s equation with 48 l i q u i d s the average error was found to be 8.8$. One i n t e r e s t i n g feature of t h i s equation i s the f a c t that i t f i t s the associated l i q u i d s better than the others. The average error being 5.5$ as compared to 8*8$ o v e r - a l l average. The error i n the equation as given by Weber (2) may be due to the equation or due to the error i n values of thermal conductivities as experimentally measured and given i n the l i t e r a t u r e . The difference i n values as determined by d i f f e r e n t methods of thermal conductivity measurements i s as great and greater than the above mentioned discrepancies. The thiok disk method as used by Bates (11) (12) gives r e s u l t s higher than those determined by the Bridgman th i n s h e l l method. A comparison shows the thermal con-d u c t i v i t y of water at 3o°Cto be /+&ox /s*by Bates (11) -6 thick disk method and */o by the Briagman (1) thin s h e l l method. Thus i t seems impractical to attempt to obtain an expression for more accurate p r e d i c t i o n of thermal conductivities u n t i l a standard and exact method of experimental measurement i s developed. 6. I l l APPARATUS To make the thermal conductivity measurements i n t h i s i n v e s t i g a t i o n a Bridgman o e l l (1) with Sehoening's (6) suggested modifications was used. Two brass cylinders, (see figure 1), were assembled con c e n t r i c a l l y . The out*, side diameter of the inner oore was 0.84 om and the inside diameter of the outer cylinder was 0.93 om. This l e f t an annular space 0.045 cm wide between the two cyli n d e r s . The bottom of the centre core, which was 6.2 om i n length, was supported by a pointed pin made of steel and set i n the base of the outer cylinder. The space about the cen-tre oore contained the l i q u i d to be measured. The upper end of the oore was supported by a dome shaped cap with three pointed legs made of short pieces of piano wire. The whole of the core and dome were held firmly i n place by a p i n which screwed down through the top support. To ensure concentric placing a probe was used to test the distance between the cylinders. Heat was supplied to the inner cylinder by passing a current of e l e c t r i c i t y through a high-resistance wire i n the heater channel. This wire was soldered to the base of the inner core by forcing solder into the lower end of the heater channel. The heat flowed r a d i a l l y through the inner cylinder and l i q u i d to the outer cy-lin d e r from which i t flowed d i r e c t l y i n t o the constant temperature o i l bath. The o e l l was i n d i r e c t contact with the bath due to the revised construction whioh 7. Thermocouple fVe//s Overflow We// Top Support Heater Channel in CELL AS USED F/G. / 8. allowed a thin brass pipe 8 inches long to be screwed d i r e c t l y onto a threaded seotion on the upper part of the outer cylinder. Heat leakage through me t a l l i c contact due to s i l v e r soldering the ends of the o r i g i n a l Bridgman type of o e l l was reduced to a minimum by using sharply pointed m e t a l l i c supports. Also heat losses from the ends of the o e l l were reduoed as only one end of the o e l l was exposed, the lower end being covered by the l i q u i d under i n v e s t i g a t i o n . Thus the lower end contributed to the area of l i q u i d aoross which heat flows. The temperature difference of the cylinders, was measured by three d i f f e r e n t i a l thermocouples plaoed i n se r i e s . Thus the reading obtained was three times the temperature drop and increased the accuracy. In taking these readings i t i s assumed that the temperature at the thermocouple junction i s the same as at the surface of the l i q u i d , inner and outer, respectively. This approx-imation i s very olose due to the high thermal conduc-t i v i t y of the metal as compared to that o f \"the l i q u i d s . The thermocouples were constructed of Leeds and Northrup 30-guage, glass-covered, duplex, copper-constantan wire and were soldered together. The thermocouples were so situated that t h e i r junctions came h a l f way down the inner cylinder to avoid end ef f e c t s as far as possible. The couples were wrapped with s i l k thread and insulated 9. with several coats of g l y p t a l . A small piece of cotton wool was placed at the bottom of the well into whioh they were inserted. Then several drops of o i l were plaoed i n the well to afford better heat conduction to the thermo-couple while the cotton wool supplied i n s u l a t i o n from the bottom. The wells were situated at 120-degree i n t e r v a l s around the c e l l . The f i l l i n g of the modified c e l l was simple as a few drops of l i q u i d could be placed i n the bottom of the o e l l and the centre core inserted whioh forced the l i q u i d up the sides into the annular r i n g . The o e l l as constructed required only the brass pipe to be screwed onto the top to prevent the bath o i l from seeping into the o e l l . However, i n s e r t i o n of the thermo-couples into the wells oaused some d i f f i c u l t y and foroing often oaused a s h i f t i n the p o s i t i o n of the core whioh then had to be reoentred. A s l i g h t modification des-cribed i n d e t a i l l a t e r would eliminate t h i s d i f f i c u l t y i n a new o e l l . The o i l bath temperature was controlled by a mer-cury type thermoregulator whioh actuated a mercury r e l a y that controlled the 25G watt knife heater. The input of the knife heater was further controlled by a variac whioh aided a great deal i n cutting down input la g . At higher temperatures a supplementary 125 watt k n i f e heater was used to a s s i s t i n r a i s i n g the temperature more rap-i d l y , thus cutting down time between readings. With t h i s arrangement i t was possible to hold the bath temper-ature constant to t o o t degrees at 45 degrees 10. ft u. Her 2 0,/H^ COO + Ez - • 2 C^H^COO + H^O — 2 CH^OOH + 0 2 C^HJBOO — ^ 2 GO* The other aoids react i n a l i k e fashion. On eleotro-l y s i s the hydrocarbon separated as an o i l whioh formed a layer at the surface of the solution i n the o e l l . To pu r i f y the hydrocarbons the following treatment was used. The hydrocarbons were freed of acid by b o i l i n g 15 grams of product with 5 grams K 2 C O 3 I N 7 5-ml water. The product was then repeatedly boiled i n d i s t i l l e d water. After t h i s they were freed of esters by b o i l i n g i n 75 ml water containing 5 grams KOH. The product was again 17 repeatedly boiled i n d i s t i l l e d water. The f i n a l p u r i f i c -ation was done by r e c r y s t a l i i z i n g from absolute alcohol u n t i l a constant melting point was obtained on consecutive r e e r y s t a l l i z a t i o n s . 71 RESULTS A. CELL CALIBRATION For c a l i b r a t i o n of the o e l l a high grade of conduc-t i v i t y water was used. The f i r s t c a l i b r a t i o n was done be-fore any hydrocarbons were measured. The second c a l i b -r a t i o n was done after doeosane and hexaoosane were measured. Sinoe an experimental constant had to be obtained to allow f o r the shape of the oell-the Fourier equation was modified as: