WADC TR 59-185 THE UN IV ER SIT Y OF MI CHI GAN COLLEGE OF ENGINEERING Department of Chemical Engineering Final Report THERMAL CONDUCTIVITY OF LUBRICATING OILS AND HYDRAULIC FLUIDS D. W. McCready UMRI Project 2774 under contract with: UNITED STATES AIR FORCE AIR RESEARCH AND DEVELOPMENT COMMAND WRIGHT AIR DEVELOPMENT CENTER CONTRACT NO. AF 33(616)-5745 WRIGHT-PATTERSON AIR FORCE BASE, OHIO administered by: THE UNIVERSITY OF MICHIGAN RESEARCH INSTITUTE ANN ARBOR May 1959

FOREWORD This report was prepared by The University of Michigan Research Institute under USAF Contract No. AF 33(616)-5745. This contract was initiated under Project No. 7360, "Materials Analysis and Evaluation Techniques," Task No. 73603, "Thermodynamics and Heat Transfer." It was administered under the direction of the Materials Laboratory, Directorate of Laboratories, Wright Air Development Center, with Mr. Hyman Marcus acting as project engineer. The principal investigator was Do W. McCready, Associate Professor of Chemical Engineering, who was assisted by Thomas E. Altenbern. This report covers work conducted, during the contract period from 1 July 1958 to 30 June 1959, and is in effect a continuation of research initiated under USAF Contract No. AF 33(616)-3543. This previous work was reported in December, 1958, in report WADC TR 58-405. WADC TR 59-185

ABSTRACT An all-metal concentric cylinder type of thermal conductivity cell was used to measure the thermal conductivity of twelve natural and synthetic base lubricating fluids. Thermal conductivity values in the temperature range of from 70 to 500~F are reported for fluids considered stable to the higher temperature. The maximum temperatures for other fluids were. limited by their instabilities under test conditions. Since each fluid has individual characteristics, no correlation of conductivity values appears possible. Values are considered precise and for possible correlation can be compared to those of a fluid chosen as a "standard reference." PUBLICATION REVIEW This report has been reviewed and is approved. FOR THE COMMANDER: L. F. Salzberg Chief, Materials Physics Branch Materials Laboratory WADC TR 59-185 iii

TABLE OF CONTENTS Page I. INTRODUCTION........................ 1 II. DESIGN OF THERMAL CONDUCTIVITY CELL............ 1 e III. PROOF OF THE THERMAL CONDUCTIVITY APPARATUS...5........ IV. VALUES OF THERMAL CONDUCTIVITY OF FLUIDS............. 8 V. CONCLUSIONS......................... 15 APPENDIXES Appendix I. Stability Test.................. 18 Appendix II. Operation of Cell.................. 19 Appendix III. Calculation of k from Data.. 22 Appendix IV. Identification of Thermal Conductivity Fluids.... 25 REFERENCES. 26 WADC TR 59-185 iv

LIST OF ILLUSTRATIONS Figure Page 1 Components of cell..... o..... o. 3 2 Assembly of cell,.............. o.... e 4 3 Front view of apparatus........ o.... 6 4 Top view of apparatus............... o o o 7 5 Thermal conductivity of calibration fluid.. 9 6 Thermal conductivity of 0-56-36, 0-56-57, 0-57-32......... 10 7 Thermal conductivity of 0-58-17, LRO-i, LRO-4....... 11 8 Thermal conductivity of MLO-58-586, MLO-58-587, MLO-58-588... 12 9 Thermal conductivity of MLO-58-589, MLO-58-590, ML0-58-591... 13 10 Temperature distribution in conductivity cell (Gulfpride 10 Base Oil)....................... 21 11 Aemf/'F vs. temperature for iron-constantan thermocouples.. 24 Table I Thermal Conductivity as a Function of Temperature....... 14 II Temperature Distribution of Thermocouples... o. 20 WADC TR 59-185 v

I. INTRODUCTION Under Contract Noo AF 33(616)-3543, determinations of the thermal conductivity of ten synthetic base and five mineral base lubricating fluids were initiated. Conductivities over the temperature range of 70-500F were required. Later twenty-five additional fluids were submitted for evaluation. This research under USAF Contract No. AF 33(616)-5745 is an extension of the above to measure the thermal conductivities of twelve additional fluids, to make a total of fifty-two fluids. The work was initiated because such data are required for engineering designs of heat-transfer equipment. Such data were not available in the literature or from other sources. Very few measurements of thermal conductivities of liquids have been made previously at temperatures above about 200~F. Those reported were made on apparatus of doubtful precision. Thus the only references to data in the literature are limited to those of value to this work and they are referred to when used. II. DESIGN OF THERMAL CONDUCTIVITY CELL Apparatus for the measurement of thermal conductivities of fluids may be classified into three general types on a basis of the directions of heat flow: (1) direct flow between flat plates; (2) radial flow through an annulus of fluid (between concentric cylinders); and (3) flow from a hot wire. All types were considered for this research. A concentric cylinder type of cell was chosen. Several such cells have been used by other investigators and have proven as precise means of measuring thermal conductivities. Factors considered in this selection were: (1) The high temperature (500~F) which limited materials to ceramics or metals except for gaskets where Teflon could be used. (2) The stability of the fluids to oxidation which required operation in the absence of air. Manuscript released by author May 22, 1959, for publication as a WADC Technical Report. WADC TR 59-185 1

(3) The stability of fluids in contact with metals, specifically copper, which accelerate thermal decomposition. (4) The high temperature which made it unfeasible to use a fluid as the final heat sink. The desire for flexibility so that heat fluxes and film dimensions could be readily changed. The metal chosen for the essential parts of the cell was copper because of its high thermal conductivity. Silver was considered too expensive for the initial cell. Corrosion-resistant metals were considered to have too low thermal conductivities, a conclusion drawn -after computations of expected temperature differentials. Copper is the least desirable metal to use from the standpoint of stability of the fluids, and so the copper surfaces were plated with chromium. Means of excluding air were devised, and a procedure, discussed later, was initiated to insure that the fluids were not operated under unstable conditions. The concentric cylinder type of cell consists of a central cylinder or core, which is the heat source, surrounded by another cylinder, which is heat Sink I. Heat flows from the core to Sink I through the sample contained in the annular space between the cylinders. A second sink (II) surrounds the whole to maintain controlled conditions; in most cases this is a fluid bath, but in this research a large cylinder of aluminum was used. Thermal conductivity of a fluid may be computed from the known heat input, temperature drop across the annulus, and dimensions of the annulus. The components and method of assembly of the thermal conductivity cell are shown in Figs. 1 and 2. Figure 1 shows the components, the filling and emptying tubes in the foreground, the central electric heater behind them, and in the rear, the bottom seal, seal gaskets, central core with top seal, and Sink I and Sink II. The central core and Sink I are of electrolytic copper and chromium-plated. Sink II is anodized aluminum. The seals are chromium-plated brass. The core and Sink I are 8 inches long. The thermocouple holes (8) in the central core are arranged 45~ apart. The bottoms of these holes are 1, 2, 3, 4, 4, 5, 6, and 7 inches from the top. The thermocouple holes in Sink I, at the same levels, are holes drilled to 1/16 of an inch of inner face and with channels leading from the holes to the top, through which the thermocouple wires pass. This sink is tapered to fit a similar taper in the central hole in Sink II. Figure 2 shows the means of assembling; the heater centered in the central core; the core is centered and bolted by the seals to Sink I, and Sink I is centered in Sink II. WADC TR 59-185 2

() i~i~liiii ~iii'~iiii~iiiii~iii1Qi~i~is~i0 I ~ ~ ~ ~ ~ ~ ~ ~ ~~~~~4 tl~:~,,0 0 t.~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~t A~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~1:~ WADO Th 59KL~~~~~~~~~~~~~~~~~~~~~~~~~~~35~~~E

C) A:~~~~~~ ~C3 r.. OZ~~~~~iS C)i 0; A 4 H A.sss~ase,3>XaS:iooosK;; H; aS, i i I f

In operation, the whole apparatus is insulated and heated by electrical tapes wound around Sink IIo The filling and emptying tubes connect to the top and bottom seals as shown with the top seal. All units are pictured in Figs. 3 and 4. Figure 3 shows almost all the parts; the K-2* potentiometer, galvanometer, standard cell on the left-hand tableand under the table the battery used with the potentiometer0 The left side of the instrument panel is the Wheelco Controller** with the temperatureindicating scale near the top and the temperature-controlling cam in the center. On the right-hand panel below the clock are the thermocouple switches. Further right are switches and ammeters for control of battery discharge and charge circuits. Power for the central core heater is supplied by the batteries on the floor and they are floating on the 110-volt d-c source in the building. In this way these batteries maintain a constant voltage. Just behind the panel is the volt box for measuring the voltage drop across the central heater. This voltage is measured by the K-2 potentiometer. Next behind is the ice chest which serves as ice storage and thermocouple cold junction. The white unit behind it is the thermal conductivity cell insulated with asbestos winding and blocks. Figure 4 shows the components behind the panel board: the large ice chest with the cold junction tubes apparent at the further end; the core reactor behind the ice chest; and the standard ohm resistance behind the insulated cell. The current to the central heater flows through. the standard ohm (0.1 Q) resistance and is evaluated as a potential drop across the standard ohm resistance by the K-2 potentiometer. III, PROOF OF THE THERMAL CONDUCTIVITY APPARATUS Thermal conductivity values are acceptable only if obtained with an apparatus of proven precision. Such precision is always difficult to confirm and generally is determined by comparison with accepted results of other investigations. Or the apparatus may be, after thorough study, considered a precision instrument, and the results obtained as absolute or at least comparable with expected results. The latter is the case with this apparatus. *Leeds and Northrup. Wheelco; Model 72000-5253 Chronotrol, 110 volt, 60 cycle, 0-600~F range for iron-constantan thermocouple, 1 rev in 3 days; and Saturable Core Reactoro WADC TR 59185 5

Fig. 3. Front view of apparatus. WADe TE 59185

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~c~-*:~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~..... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~:~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~.... i~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~L~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~3~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~ ~ ~~~~~~~~~...... z~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~..... ~~~~~~~~~~~~~~~~~~i-r~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~j ~~ ~ ~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~:::~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~..... ~~~~~~~~ ~~~~~~~~~~~~~~~:~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~:~~~~~~~~~~~~~~~:~~~~~~~~~~~~~~~:~~~~~~~~~~~~~~:~~~~~~~~~~~~~~~:~:~~~~~~~~~~~~~~~~~~~~~~~~~~~~:s::.:~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~...... ba~J On~~~~~i~. ~~~~~:~~~~~~~iti::~~~~~~~~~~~~~~~~~~~~:~~~~~~~~~~~~:~~~~~~~~:::i:~ ~ ~ ~ ~ ~ ~ ~ ~~~~.................... tur*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~............... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~3~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~......... %~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~........ I' a~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~..... hj::::~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~.......... 6~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~...... ~~~~~~~~~~~~~~~~~~~~~~~c~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ I~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~i ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~......::NE - )ii''''~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~......:i~~~~~~~~~~~~~~~~~~~i:I::~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~.... il~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~e ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~~~....... i~~~~~~~~i~~~~~~~ 9~~~~~~~l~~~~~~~i~~~~~~~i~~~~~~~i~~~~~~~i ~ ~ ~ ~ ~ ~ ~....... iii ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~.......:I:~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~..... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~.... -i-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~............................................ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~-~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~~~~~~~~~~............. g~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~........ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~....... — *J1 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~f ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~.... r3~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~......... I"C1~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~...... P~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~5 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~~~~~....... p, iii~~~~~~~~~~~~~~~~~~~~~~~~~~~iiii-i;:~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~-_ -- "~~~~~~~~~~~~~~~~~........ Yi~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~................. ~ ~iiiiiiiiiiiiiiiiiiiiiiiiiii:.i,: -:::::::::::::::::::::i::::::::............................................ ---: i:;:i~~~~~~~~~~~~iiii:~~~~~~~:;~~~~i~~iiiii';'iii;:ililii'iii~~~~~............... i iiiiil~~~liii ii~~iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii _ 1 --- -:::i-ii _ _ — iiiiiiii~~~~~~~~~~iii_:::iiiiiiiiiiiili iii —:_ i~~~~~~i i iii iii-i iiiiiiili......................................:: — - IW ~~~~~~i~~il:::-..................................................................................................iii......................................................................... I'l..........................................................................':'~ "...................:::::::::::.............................................................:::::::: - -i~ -i~...............................................................I........ L~~~~~il:~~~~~~~~ii' llil~~~~~~~~~~~~~~~l::,:l::::::: —:-: ~ ~ ~ ~ ~ ~ ~ ~ ~............................. lil i~~~~~~~~~~~~~~~~~~~~~~~~~~~~iiii~~~~~.................................::: ~3~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~:: 1:"~~~~~~~~~~~~~~~~~~~~~~~~~~~~....

The design and proof of the cell is detailed in WADC TR 58-405. Also in that report are the methods of making and calibrating thermocouples, and data on typical set of readings. The proving of the apparatus resulted in the realization that the apparatus was precise only at temperatures above. about 250~F with normal ambient temperatures. A "standard of reference" was therefore established to evaluate the apparatus and the test fluids, The "Standard" is a close-cut lubricating oil fraction from Pennsylvania crude without additives and having about the same viscosity as most of the test samples. It was obtained as a standard oil from the Gulf Research organization at Mellon Institute in 1951. At that time it was placed in glass bottles, deaerated, and sealed. Thermal conductivity vso temperature curves on this oil were obtained at the beginning and middle of the research, The results are plotted in Fig. 5 and the consistency of the results confirms the operation of the cell and the choice of the "standard of referenceo." IV. VALUES OF THERMAL CONDUCTIVITY OF FLUIDS The results of this research are most readily reported as the measured values of thermal conductivities of the fluids as a function of temperature. They are plotted as such in Figs. 6 to 9, and tabulated in Table I. Also apparent in the table are the maximum temperatures to which these oils could be heated for at least 20 hours in contact with copper without apparent decompositiono The details of the test are in Appendix I. Typical computations of thermal conductivities are in Appendix IIIo The high melting point of several fluids is also apparent in the table. Several attempts were made to see if the curves in Figs. 6-9 could be fitted to a typical curve, but all were unsuccessful. Each fluid has individual characteristics. Data on stability apply only to the test as made, namely, 20-hr duration. Stabilities under other than test conditions were not measured and are not inferredo No measurements of decomposition of the fluids were made after thermal conductivity determinations, although acid numbers were requested.Most of the fluids showed no visible change during a determination. As d 100% sample could not be obtained, and as apparent changes in the fluids were negative, acid numbers were not run. The method of determining acid numbers would depend on the chemical characteristics of the fluids, and it was considered that the expected small differences between fresh and used fluids would not be sufficient to warrant conclusions concerning stability. Stabilities were considered measured by tests reported in Appendix I. WADC TR 59-185 8

c) \J1 ko F-J CC) OD _ _ _.085 Gulf Pride 10 Base (2 September 1958) 0 LLo0~~~o o.080. o,..075 IGulf Pride 10 Base (28 November 1958).080 z 0 O ~~ ~ ~ ~ ~~~~~~~~~~~~~~~~~~~~~~~o o; o f3: ~ ~, ~ -I o Heat-ing curve 0 0 >~~~~~~~~~~~~~ o ar - - Cooling curve w.075 I100 150 200 250 300 350 400 450 500 TEMPERATURE (OF) Fig. 5. Thermal conductivity of calibration fluid.

.085.085 0 ~~~~~~~~0-56-36 (20 September 1958) 0 0 \-0.080 o CC) \31 I~~~~~~~~~ o o I I I I ~ ~ ~~~ ~~~~~~~~~~~~~~~~o o__n k j. ~ ~ ~ II ~ ~ ~~.075 LL 0 I — I-:z: cr ~~~~~~~~~~~~0-56-57 (30-October 1"958) >.085 a~~~~~~~~~~~~o H 0Hecrting curve 0 > Cooling curve o -- o.080 o ~~~~~~~~~~~~~~~~-r;.z 0 07 0-57-32 (17 October 1958).085 o.OT/'.080 - - _J -.0781 1 1 100 150 200 250 300 350 400 450 500 TEMPERATURE (OF) Fig. 6. Thermal conductivity of 0-56-36, 0-56-57, 0-57-32.

Hs oHeating curvel L.080 j *Cooling curve H~1I l l | |0 LRO-I (21 November 1958) H o 0CC) Mr I I I r LR0-4 (14 November 1958) u- 00 TEMERATURE (November 1958) Fig. 7. Thermal conductivity of 0-58-17, LRO-1, LRO-4. I- o -— 502025 003040 5 -— ~~~~~~TMPRTR (oF)o: Fi.7 hra onutvy of -81,LO1,Lo4

MLO-58-586 (19 December 1958) 1 ~.080 0~~~~~~~~~~ OD \J1 -N bi I,I~~U '- - 2- 0 0 F- - -r~o —9 o o u_~~ o LL a~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~L a, 0751 La 0 MLO-58-587 (9 January 1959) 0 0 ~ ~ ~ ~ ~ ~ ~ 0 Ca.080 0~~~~~ 0 o o ~ --- l - ~~~z~~~~~~~~o 0 MLO-58-588 (6 February 1959) 2.085 w 01:: 'r' o Heating curve 0 0:i) ~~~~~~~~~~~~o I —o o o.080.078 100 150 200 250 300 350 400 450 500 TEMPERATURE (0F) Fig. 8. Thermal conductivity of MLO-58-386, mLo-58-587, mLo-58-588.

H (-O HP~~~~~~~~~ ~~~MLO-58-589 (5 March 1959) c3o 0.090 o o o o o o o U~ ~ LL I I I I ~ 'I I~~ ~ ~ I c.085.L ML0-58-590 (17 February 1959) -1.085 ~ >- o Heating curve > *0 Cooling curve - " 0 0 0 0 0 D 0.080 o z W.095 MLO-58-591 (23 February 1959) ~o o ~~~~~~~~~~~~~~~0 LU.095 100 150 200 250 300 350 400 450 500 TEMPERATURE (@F) Fig. 9. Thermal conductivity of 0LO-58-589, mLo-58-590, MLo-58-591.

\J1 TABLE I \07 THERMAL CONDUCTIVITY AS A FUNCTION OF TEMPERATURE(a) FluiA 1000F 1500F 2000F 2500F 3000F 3500F 4000F 4500F 5000F 0-56-56.o834.0823.0812.0802.0794.0789.0787.0786 0-56-57.o846.0835.0824.o815.o8o8.0802.0798.0796.0794 0-57-32.0832.0824.0817.o8io.0804.o800.0798.0797 0-58-17.o868.o858.0848.0840.o834.0829.0826.0824 LRO-1.0546.0545.0543.0541.0539 --- LRO-4.0551.0551.0550.0550.0551 --- NLO-58-586.0790.0785.0778.0775.0770.0768.0767.0766 MLo-58-587.0790.0785.0781.0778.0776.0774.0774.0774 MLOo-58-588 --- ---.0819.o8i8.0817.0815.0812.o808.o8o3 MLO-58-589 --- ---.o885.o884.o883.0882.0880.0878.0875 mLO-58-5go --- --- ---.0801.0814.0826.0837.o848.o86o mLO-58-591 --- --- ---.0915.0915.0915.0914.0912.0907 Gulfpride(b) 10 Base.0804.0800.0796.0795.0790.0787.0785.0780.0777 Gulfpriae(C) 10 Base.0800.0795.0786.0780.0775.0773.0771.0771 0 (a) Thermal conductivity is reported in [Btu/hr ft2 (OF/ft)1. (b) 2 September 1958. (c) 28 November 1958.

V. CONCLUSIONS The thermal conductivity apparatus, designed, built, and proven under Contract No. AF 33(616)-3543, was used for measurements on submitted samples of lubricating f luids. The values of thermal conductivities of the fluids are considered absolute or at least precise in references to a "standard oil." WADC TR 59-185 15

APPENDI5XES WADC TR 59-185

APPENDIX I STABILITY TEST The protection of the thermal conductivity cell against corrosive attack of the fluids or vice versa had to be determined. It was proposed that a test be made on all sarrmples by subjecting them to elevated temperatures in contact with copper, the metal of which the cell is constructed. The following test was devised. A 5/8-in.-ID x 6-in. heavy-walled Pyrex test tube is used. Into it is placed a polished and bent piece of copper sheet about 1 inch square. The test tube is then drawn down to a narrow neck to form an open ampoule about 3 inches long. The fluid sample is carefully pipetted into the ampoule to prevent any oil contacting the glass surface that will be heated in sealing the ampoule. The fluid completely covers the copper; the fluid sample is then deaerated under high vacuum with care being taken to avoid vaporization of the fluid. While under vacuum the ampoule is sealed by fusing the glass at the drawndown portion. The ampoules are then placed in a controlled temperature oven and observed at intervals. Conditions of this test are considered comparable to the conditions within the calorimeter. Maximum Temperature to Which the Fluids Are Stable for 20 Hours 0-56-56 450oF ML0-58-586 500~F 0-56-57 500 MLo-58-587 500 0-57-32 45o MLO-5 8-588 500 0-58-17 450 IMLo-58-589 500 LO -1 300 nML-58-590 500 LRO-4 300 MLo-58-591 500 Gulfpride 10 Base Oil 500 The five fluids which- are stable only below 5000F had such doubtful stability that it was felt that they might decompose and do harm to the apparatus if run up to and down from the maximum temperature of 500~F. Permission was granted to limit the determination on the fluids in this group to the maximum temperature determined by the test. WADC TR 59-185 18

APPENDIX II OPERATION OF CELL The thermal conductivity cell is filled by applying a vacuum to the top fill tube, forcing the fluid into the annulus by the pressure of its own vapor from a reservoir at the bottom fill tube. It is felt that this procecure effectively eliminates entrained air. The cell is regulated by the controller to induce a heating, or cooling, rate of 20OF/hr. (The controller regulates the heating tapes on Sink II.) There are 16 thermocouples in the cell which are paired across the annulus to measure the temperature differential at 8 locations in the cell. The locations are circularly about the annulus at levels of 1, 2, 3, 4, 5, 6, 7, and 4 inches depth. Only the temperature differentials at levels of 2, 3, 4, 5, 6, and 4 inches are used to calculate the average "k" value for a given set of readings. This is done to prevent errors due to heat losses at the ends of the cell at positions 1 and 7. An example of the temperature distribution of the thermocouples on a cooling and heating cycle is shown in Table II and Fig. 10. Outside couples are odd-numbered and are located in Sink I; inside couples are even-numbered and are in the central core. Readings are taken at exact one-minute intervals and are repeated approximately every 45 minutes throughout the complete heating and cooling run. WADC TR 59-185 19

TABLE II TEMPERATURE DISTRIBUTION OF THERMOCOUPLES (Gulfpride 10 Base Oil -28 November 1958) Depth Heating Cycle Cooling Cycle Thermocouple (inches) emf emf (millivolts) (millivolts) 1* 1 10.5622 9.3653 2* 1 10.8761 9.7095 3 2 10.5738 9.3431 4 2 10.9341 9.7345 5 3 10o. 5884 9o 3288 6 3 10.9544 9.7187 7 4 10. 6021 9.3113 8 4 10.9716 9.7043 9 5 10o.6221 9.3018 10 5 l0.9816 9.6820 11 6 10o.6301 9.2815 12 6 11.0040 9.6750 13* 7 10.6260 9.2470 14* 7 11.0010 9.6290 15 4 10. 6673 9.2611 16 4 11.0405 9.6611 Not used in calculations. WADC TR 59-185 20

OUTSIDE COUPLES INSIDE COUPLES 9.36 - - _ - 9.74 v, 9.34 1 1 1 I I r 1 r r r 9.72 \.J1 0 9.32 - - __ - 9.70 H~~~ co.j9.30 - 9.68 9.28 9.66 Line 34 Line 34 9.26 28 November 19589.64 28 November 1958 9.24 9.62 10.74 11.06 10.72 11.04 10.70 11.02 ~ 10.68 - 11.00 o 10.66 10.98 - 10.64 10.96 10.62.- 10.94. 10.60 10.92 tw JLine 18 Line 18 28 November 1958 28 November 1958 10.58 - 10.90 10.5 { 1 - 10.88 10.54 10.86 I3 5 7 9 1I 13 15 17 19 2 4 6 8 10 12 14 1618 THERMOCOUPLE THERMOCOUPLE Fig. 10. Temperature distribution in conductivity cell (Gulfpride 10 Base Oil).

APPENDIX III CALCULATION OF k FROM DATA NOMENCLATURE q = heat/time, Btu/hr k = heat/time length temp, Btu/hr-ft (~F/ft) A = length2 normal to flow, ft2/in. T = temperature, ~F X = distance along direction of flow, ft ro = outside radius of central core, in. rl = inside radius of Sink I, in. do = outside diameter of central core, ino di = inside diameter of Sink I, in. V = voltage, volts I = current, amperes emf = emf of thermocouples, millivolts H.L, = heater length, in. (a) q = kA dT dX Since the annular spacing is only.036 in., AX may be used in place of dX. Solving for k, then, 1 AX (b) k = qA AT AX = (ri-ro/12) A = [(r +ro o)/144] AT = [Aemf/.0290 mv/0F] for temperature range- 700-122 ~F [Aemf/ 0295 mv/~F] for temperature range 123 0-142 0F [Aemf/. 0300 mv/OF] for temperature range 143 ~0-239OF [Aemf/.0305 mv/OF] for temperature range 2400-299~F [Aemf/.0309 mv/OF] for temperature range 3000-5000F *Values approximated from Fig. 11, Aemf/~F vs. temperature for iron-constantan thermocoupleso This figure is based on data taken from Ref. 11. WADC TR 59-185 22

= (VI)o42 B tu/hr. 2 (_ Btu/hr watt x(H.Li 19 1 in. 3.42 144 1 (rl-ro) 1 = L9-31 (rl+ro) 12 AT noting that: r_-ro di-do.0362 rl+ro dl+do 1. 8072 (c) k - VI 3.42 12 ~.0362 VI551 - AT 19.31 - 1.8072 AT The values used for VI are the average values of the beginning and end of a line. SAMPLE CALCULATION Data from MLO-58-589 run of 5 March 1959 El line 13 start = 66.4890l EI = 66.3982 watts EI line 13 end = 66.30735 avg Average temperature line 13 = 3930F Position: 4A line 13 Aemf couples 7 and 8 = 0.3139 k 12 66.38 k 1=.~3551 ~ 10- 0.5139. 0309 = 0.0884 Btu/hr-ft2 (~F/ft) WADC TR 59-185 23

.0320 \1 H.0300.0280 0260 Ill L..0240.0220 02,00 -200 -100 0 100 200 300 400 500 600 700 800 TEMPERATURE (OF) Fig. 11. Aemf/~F vs. temperature for iron-constantan thermocouples.

APPENDIX IV IDENTIFICATION OF THERMAL CONDUCTIVITY FLUIDS Sample No. Identification 0-56-36 Conoco 9372 0-56-57 CRC 156 0-57-32 Richfield L7-52 0-58-17 Shell WRGL 31 LRO-1 Halocarbon 4-11V LRO-4 Halocarbon A0213 MLO-58-586 Phenyl ether MLo-58-587 Phenyl ether* MLo-58-588 1, 4 Diphenoxybenzene MLO-58-589 1, 4 Diphenoxybenzene* MLO-58-590 Bis (p-phenoxyphenyl) ether MLO-58-591 Bis (p-phenoxyphenyl) ether* *Irradiated 1011 ergs/gm Co WADC TR 5 9-185 25

REFERENCES 1. Dick, M,, Synthetic Lubricants, Univ. of Micho Eng. Res. Inst. Final Report M-779, Ann Arbor, Appendix III. 2. Sakaides, B C., and Coates, J., Louisiana State Univ. Eng. Exp, Station Bull. Nos. 34 (1952), 48 (1954), 35 (1953), and 45 (1954). 3. Mason, H. L., Trans. ASME_, 761, 817 (1954). 4. Bates, K. O., Hazzard, G.., and Palmer, G., Ind. En. Chem., Anal. Ed., 10, 314 (1938). 5. Briggs, DK. H., En nd Eg Chem., 492 418 (1957). 6. Reidel, L., Chem. Ing. Tech., 23, 321 (1951). 7. Reidel, L., Chem, In. Tech., 23, 465 (1951). 8. Smith, J.F.Do Ind, Eng. Chem., 22, 1246 (1930). 9. Smith, J.F.Do, Trans. ASME, 58, 719 (1936). 10. Sakaides, B. C., and Coates, J., Jour. AIChE, 1, 275 (1955). 11. U. S. Bureau of Standards, Circular 561, Reference Tables for Thermocouples, April 27, 1955. 12. McCready, D. W., Thermal Conductivity of Lubricating Oils and Hydraulic Fluids, WADC TR 58-405, December, 1958. WADC TR 59-185 26

UNCLASSIFIED UNCLASSIFIED AD AD The University of Michigan, The University of Michigan Re-The University of Michigan, The Univer-ity of Michigan Research Institute, Annrbor, Michigan. THERMAL CONDUCTIV- earch Institute, Arbor, Michigan. THERMAL CONDUCTIVITY OF LUBRICATING OILS AND HYDRAULIC FLUIDS, by D. W. ITY OF LUBRICATING OILS AND HYDRAULIC FLUIDS, by D. W. McCready. May 1959. 26p. c. illus. tables (UMI Final McCready. May 1959. 26p. c. illus. tables (UMRI Final Report 2774-1-F; WADC TR 59-185) [Contract AF 33(616)-5745] Report 2774-1-F; WADC TR 59-185) [Contract AF 33(616)-5745] Unclassified report Unclassified report An all-metal concentric cylinder type of thermal conductiv-An all-metal concentric cylinder type of thermal conductivity cell was used to measure the thermal conductivity of ity cell was used to measure the thermal conductivity of twelve natural and synthetic base lubricating fluids. twelve natural and synthetic base lubricating fluids. Thermal conductivity values in the temperature range of from Thermal conductivity values in the temperature range of from 70 to 500~F are reported for fluids considered stable to the 70 to 500OF are reported for fluids considered stable to the higher temperature. The maximum temperatures or other flu- higher temperature. The maximum temperatures for other fluids were limited by their instabilities under test condi-ids were limited by their instabilities under test conditions. Since each fluid has individual characteristics, no tions. Since each fluid has individual characteristics, no correlation of conductivity values appears possible. Values correlation of conductivity values appears possible. Values are considered precise and for possible correlation can be are considered precise and for possible correlation can be compared to those f a fluid chosen as a "standard reference.compared to those of a fluid chosen as a "standard reference." UNCLASSIFIED UNCLASSIFIED UNCLASSIFIED UNCLASSIFIED AD AD The University of Michigan, The University of Michigan Re- The University of Michigan, The University of Michigan Research Institute, Ann Arbor, Michigan. THERMAL CONDUCTIV- search Institute, Ann Arbor, Michigan. THERMAL CONDUCTIVITY OF LUBRICATING OILS AND HYDRAULIC FLUIDS, by D. W. ITY OF LUBRICATING OILS AND HYDRAULIC FLUIDS, by D. W. McCready. May 1959. 26p. incl. illus. tables (UMRI Final McCready. May 1959. 26p. incl. illus. tables (UMRI Final Report 2774-1-F; WADC TR 59-185) [Contract AF 33(616)-5745]1 Report 2774-1-F; WADC TR 59-185) [Contract AF 33(616)-5745] Unclassified report Unclassified report An all-metal concentric cylinder type of thermal conductiv- An all-metal concentric cylinder type of thermal conductivity cell was used to measure the thermal conductivity of ity cell was used to measure the thermal conductivity of twelve natural and synthetic base lubricating fluids. twelve natural and synthetic base lubricating fluids. Thermal conductivity values in the temperature range of from Thermal conductivity values in the temperature range of from 70 to 500~F are reported for fluids considered stable to the 70 to 500~F are reported for fluids considered stable to the higher temperature. The maximum temperatures for other flu- higher temperature. The maximum temperatures for other fluids were limited by their instabilities under test condi- ids were limited by their instabilities under test conditions. Since each fluid has individual characteristics, no tions. Since each fluid has individual characteristics, no correlation of conductivity values appears possible. Values correlation of conductivity values appears possible. Values are considered precise and for possible correlation can be are considered precise and for possible correlation can be compared to those of a fluid chosen as a "standard reference." compared to those of a fluid chosen as a "standard reference." UNCLASSIFIED UNCLASSIFIED

UNIVERSITY OF MICHIGAN 1 111 111111 J1I1II1111111111111111 3 9015 03483 1977