£5." ,-z$.& J!“ l I II” WI II "12 I‘V'JI] ‘10:? \I‘I) A 2.; g3“? ‘t‘ifi‘ 1 W‘ Z ‘ £3“ .1... .1. >5 , ‘ .kir ”5:: "IL V ' £3“: I}? I” 21%|, III ‘I I I“ +;¢§:‘i: 32' . ”477*, 3, .34 as”? *9 s ‘ M-- _ , A _ a. 1°11.- . - : I - I .1252. - . . v2; r ‘- I": 7x34; M kg: :34; ‘. - l u .‘ .__- —1& ~ 11‘? I 132:: . W. .J“ I I ”III 1:25 III “III?“ I m NII‘III , II»? ‘I I I 1:13», [ZIJ‘SI‘III'I "I’M”, I‘m] I“ I. I ‘ I I” I 'I .. 3'2. l.‘ m9?“ at: 1'} ‘ ”III? 'II‘ III XII IrI 'II‘II'I'I ‘ { “'qu ”1 I I ‘II’III'I‘I‘I‘ II :_...,_. .“I":I II III “I“ LIN!“ III I} ‘ I‘IIIIII’III I “I, III?" III 111:3}? " . II I» a 4’“ I II“! “It I;I IIIIJII .I' "is?“ ‘II II II I I I, (I i S: an‘efij... t1: .....z '57" -‘nr‘»=5;-§-r-€“ A . ' ”:9 ,II‘I‘I’ “II? II I i I 3, :3 _I W r. ,J I. ( ~— .3-{1 , J .... S1 a." A 2.3:. t .4 - . ‘4 ‘. L r“ .4: u ' r” _ fig. " A‘ 4... 1:27 «:- M. H ‘--I—- _ V' _ .I - “'2. ; .. , A :« ' _ AM, ' J ”.4, fawn..- I. - I . e M: .3“ ‘ _ . ' . ~ my? “_ 1? " r v . — .. ‘I . “i. V 2:. - I. ~I R—a 3 5:; wars) ’5‘» e e ...: ~71 ‘ .; $2322? ‘5:‘ t' .. . 5": .c:::“‘- “~— “:3? 47:555.:‘5-‘4 : . - ' "22‘1“": - ~ M 1 ~ , «~sz ,1" - ,r A , . . ‘1 E J - 4' . , 77:71:: 1 bee—m I; ~ ‘ .nt' 3* 4 1 s— . , , , J 3.; . -- ' ~1- 3 .. I ' ' ‘ A 4 «.— —. ‘ I ' «Ii 43!: a 12:4..._ < III 3r; I" 04‘“, I»? 3. “PI I‘M" I‘FP ' -— { I; ‘ vac-I “-r,‘ . K. “ v « .- < ‘~£E:.;:.=L=-;ff»a - 4r...— ‘ “27* - ~ ewfifib. $3.3" . " -e- .r' .. . _. 7 . fl 7 ~ 1‘3 ‘ .5 1‘ .1--. _‘ A ”E; - ; , '4 ‘I‘ 1 l,‘ L‘ '3 I‘ve, III“ I} II II "'"’:-1.‘5 g . If? ”\IG‘ “(3%!“ "Jl “N“ If“! I IV 9 [A III ”if: “I“ III -. III ““343? 91" 1”,. jL‘WI{' I z ' In I‘ k.“ Hum?) Min 12:39:“ “I Ji‘f‘caI: “IIII'I - ‘ “II‘I‘I'M III '{II I II “11:11in N ”11»); “:le IIUI ‘2', 2'” I“ IIIJ‘ III": ‘ L1“ ‘5', III‘. Wr- 3,; , :23: wI'ImLI In; I, W a,” II“ II III?“ :eé: I, . L; .9; 1-: I‘ I V ‘ . .. ‘ .> 'v . I - I ‘ ‘ I ' _ ,. Grooved wall for enhancement>of Vaporization. (a) details of geometry (b) heat transfer and pressure drop data for vaporization of R-22 . . . . . . . . . . . . . . . . . . 9 Annual publication in heat transfer enhancement . . . . . . . . . . . . . . . . . .10 Surface geometry of three commercially avail- able enhanced surfaces . . . . . . . . . . . .12 Boiling curve for three commercially available enhanced surfaces and their comparison with smooth surface . . . . . . . . . . . . . . . . .14 Surface factor comparison of three commercial surfaces. . . . . . . . . . . . . . .16 A comparison of High Flux surface heat transfer performance with a smooth surface . . . . . . .17 Long term performance of a High Flux tubing - . . . . . . . . . . . . . . . . . . . .19 Phase equilibrium diagram for an ideal binary mixture system . . . . . . . . . . . . .22 Phase equilibrium diagram for an azeotropic mixture system . . . . . . . . . . . . . . . . .24 Variation of AT with composition for ethanol- water system on a smooth surface (19). . . . . .25 Variation of AT with composition for ethanol- benzene system on a smooth surface (19). . . . .26 Phase-equilibrium diagram showing the decrease in local mole fractions of the morevolatilecomponent . .. . . . . . . .. . .28 Preliminary set—up for experiment . . . . . . .31 viii 4.10 4.11 Test—specimen sketch (not to scale) Nucleate boiling rig (not to scale) . . . . Power supply circuit . . . . . . . . Nucleate pool binding curve for ethanol- water system at 1.01 bar (High Flux tubing) Nucleate pool binding curve for ethanol- water system at 3.03 bar (High Flux tubing) High Flux tubing data for boiling in a pool of distilled water (2) at 1.0 bar . . Pure ethanol boiling at 1.0 bar (High Flux surface)(9) Wall superheat (AT) for different values of heat flux (ethanol-water at 1.01 bar) Wall superheat (AT) for different values of heat flux (ethanol-water at 3.03 bar) Pool boiling curve for ethanol-benzene 1.01 bar (High Flux surface) . . . . . Pool boiling curve for ethanol-benzene 3.03 bar (High Flux surface) . . . . . Wall superheat (.AT) at different heat (ethanol-benzene at 1.01 bar) . . . . Wall superheat (AT) at different heat (ethanol-benzene at 3.03 bar) . . . . Activation wall superheat for ethanol- benzene at 1.01 bar . . . . . . . . . at at Differing definition of a linear mixing law for an azeotropic mixture system . Local rise in boiling point (.AO ) for en- hanced surface at 1.01 bar (ethanol-water system) . . . . . . . . . . . . . . Local rise in boiling point (439 ) for smooth surface at 1.01 bar (ethanol-water system) (19, 23, 24) . . . . . . . . . . . . . ix 34 35 40 45 46 48 49 50 51 53 54 55 56 58 61 64 65 Local rise in boiling point (.AG ) for en— hanced surface at 1-01 bar (ethanol—benzene system) . . . . . . . . . . . . . . . . . . Local rise in boiling point (A9 ) for smooth surface at 1.01 bar (ethanol—benzene system) (19, 25, 26) . . . . . . . . . . . . . . . Enlarged view of portion of the tube show- ing one of the thermocouple locations (not to scale) . . . . . . . . . . . . . . Surface temperature computation analysis (not to scale) . . . . . .~. . . . . . . . WH'UQJS’ f—l NSCHHWFQ-Do'cz NI KI NOMENCLATURE area (m2) diameter of tube (mm) surface factor current (amperes) thermal‘ conductivity(kW/m—K) heated length (m) mass of mixture and components (grams) power supplied to Cartridge heater (kW) total heat flow (kW) heat flux (kW/m2) thermal resistance (mzK/kW) radiusr(mm) temperature (K) voltage (volts) mass fraction percentage of heat flux passing through additional area. liquid mole fraction vapor mole fraction Greek Symbols: 0 AT A0 heat transfer coefficient (kW/mZK) wall superheat (K) local rise in boiling point (K) xi AP/L 6x pressure drop (bar/m) thermal reSistance thickness (mm) Subscripts az azeOtrope b bulk bp boiling point c copper E enhanced e ethanol GT Gewa-T H heater (Cartridge) HF High Flux I ideal p plain st smooth tube 9 solder part sat saturated TE .Thermoexcel-E t tube side W water w wall mixture component one 2 mixture component two xii CHAPTER 1 INTRODUCTION Nucleate pool boiling from enhanced heat transfer surfaces is being studied for application to many areas of thermal engineering where it is desirable to obtain high heat fluxes while maintaining a low temperature difference between the heating fluid and the evaporating fluid. One area of application of these enhanced boiling surfaces is in the evaporation of multi-component liquid mixtures in natural con- vection driven flows in reboilers. While multi-component liquid mixtures are the rule rather than the exception in the chemical process industry, the understanding of binary mixture ‘boiling is a major step on the way to reliable prediCtion of heat transfer coefficients for multi-component convective boil- ing. ‘Successful application of enhanced boiling heat transfer surfaces to chemical process industry practice thus requires the dovetailing of research efforts on binary mixture boiling with enhanced boiling. An enhanced boiling surface has a special geometry which promotes high performance nucleate boiling with heat transfer coefficients about an order of magnitude greater than those of a conventional smooth surface. (The reference surface should be one with a surface finish similar to that of ordinary drawn tubing instead of a specially prepared mirror finish which many investigators use and hence obtain a much higher 2 degree of enhancement ). Quite a wide variety of surface geo- metries have been tested with single component fluids such as water, dielectrics, alcohOls, refrigerants and hydrocarbons (168). In the present study, High.Flux tubing (trademark Union Carbide) has been tested to determine its performance in evaporating ethanol—water and ethanol-benzene mixtures. These two mixtures were chosen because of their-well documented behavior for boiling on smooth surfaces. Enhanced boiling surfaces are thought to perform better than smooth surfaces for the following reasons. First, at low wall superheats, an enhanced surface is actively boiling while a smooth surface is still in the less efficient single-phase natural convection mode of heat transfer. Thus, the enhanced heat transfer coefficients at these low heat flux levels are typically of the order of 10 times the smooth surface ones. At higher heat fluxes where both types of surfaces are boiling vigorously, the enhanced surfaces are still outperforming the smooth surfaces but usually by a smaller margin. Smooth surface pool boiling heat transfer coefficients are much higher than those for single-phase natural convection due partially to the micro-layer evaporation underneath grow- l ing bubbles. The enhanced surface heat transfer coefficients A are higher yet because they provide much more surface area for this thin film evaporation process within the enhancement matrix. Nevertheless, Nakayama (8) showed experimentally that the percentage of the total heat flux from their test surface leaving in the form of latent heat drOps from about 90% at l kMVmZ to-ahout 30% at 20 kwymz. Therefore, the enhanced. surface must also greatly improve the single-phase convection mode of heat transfer in order to have the much higher heat transfer coefficients; Intuitively, this means either that the increased boiling site density on an enhanced surface augments the cyclic thermal boundary layer stripping mechanism on the outside surface, or a significant flow rate of liquid into and out of the enhanced matrix occurs which effectively superheats the liquid. Since the single-phase heat transfer coefficient is inversely proportional to the hydraulic dia- meter of the flow passage, the latter phenomenon seems more plausible due to the very small dimensions involved. It follows that while thin film evaporation within the enhancement matrix is important as a thermal mechanism as previously noted, it also appears to be significant in acting as a pump for passing liquid through the narrow passages. Therefore, a successful model and predictive equation for enhancement of boiling re- quires an inclusion of the vapor-liquid circulation phenomenon, which is not included in either the Gottzman model(9) or the more recent Nakayama model (8). It is a well established fact that the boiling heat transfer coefficients of mixtures on smooth surfaces can be significantly lower than those expected from evaluating an appropriate single component pool boiling correlation with the physical prOperties of the mixtures (see a recent review by Thome and Shock (10) for a complete discussion). Hence, the question arises as to whether boiling of mixtures on en- hanced surfaces also involves a serious deterioration of their performance similar to smooth surface boiling. The only published experimental results available for boiling of liquid mixtures from enhanced heat transfer surfaces are those of O'Neill and co-workers (11, 12) for various mixtures without single component data for comparison purposes. Arshad and Theme (13) proposed that the following method (14) found to be suitable for predicting mixture boiling from smooth surfaces may perhaps be similarly applicable to enhanced surfaces if it is assumed that all of the saturated bulk binary liquid enter- ing the porous matrix evaporates such that only saturated vapor exits. The heat transfer coefficient is then predicted as: GI AT AT + AT where I bp ATI = x1 ATl + X2 AT2 (1.2) a _ o and I f q/ AT: (1.3) - Apr. is the boiling range, the temperature difference between the dew point and the bubble point as shown in Figure 1.1. For ethanol-water boiling at 1.01 bar from a high flux tube, the above equations predicted only a marginal improve- ment in the heat transfer performance in going from the smooth to the enhanced surface because the boiling range Aflhp is larger than ATI for an enhanced surface. Thus, the objective P= cons'r Figure 1.1 Vapor-liquid phase equilibrium diagram snowing LT bc' of the present project is to study experimentally the be— havior of an enhanced surface with.two mixture systems having relatively small boiling ranges. CHAPTER 2 REVIEW OF BOILING A number of research papers have been published on the boiling of single component liquids on different types of en- hanced surfaces. An excellent article on the history, develop- ment and testing of these surfaces for a wide range of liquids has been written by Webb (15). The present study investigates the boiling of binary mixtures on an enhanced.surface. There- fore a brief discussion on enhanced surfaces and binary mixture boiling is presented. 2.1 Importance of enhanced surfaces Energy and material savings consideration, as well as economic incentives, have led to the recent expansion of efforts to produce more efficient heat exchanger equipment. The use of enhanced surface tubing in key boiling services makes possible first cost reduction, and also reduction in operating costs due to lower temperature differences. Heat exchanger size and weight reduction may be an important objective in aeronautical applications, electronic equipment cooling and in large re- frigeration and air-conditioning units. The use of enhanced surfaces and high performance fin geometries has successfully been employed to obtain size, weight and cost reductions. A variety of structured surfaces are applied to the out- side to enhanced shell-side boiling of refrigerants in industrial refrigeration and air-conditioning units. These include var- ious formed surfaces and also surfaces having a porous metallic 7 matrix. Some manufactures employ tube side enhancement for water flowing in the evaporator and condenser. Figure 2.1 (a) shews an enhanced tube designed for tube side boiling of Refrigerant 22 (16). The groove depth is bhly 0.5 mm.. Figure 2.1 (b) shews the average boiling coefficient is in— creased 40-75 percent with a pressure drop increase of approx- imately 10 percent. 2.1.1 Historical development Attempts to increase the "normal" heat transfer co- efficient have been recorded since J. P. Joules cassical study of condenser water-side enhancement in 1861, and there is now a large store of information. As shown in Figure 2.2, the literature is growing at an exponential rate that is probably greater than that for scientific and engineering literature as a whole (17). The identity of nucleation sites for bubble formation was unsure and was the subject of much speculation until 1956. Soon thereafter, evidence appeared showing that small amounts of gas are trapped in microscopic pits and scratches. Several enhanced surfaces were produced for commercial appli- cations during the 60's utilizing this new information but failed to achieve commercial usage. Reference (8) lists six patents granted during 1968—77. The surfaces presently being used include tubes made by Trane Corporation for use in Trane refrigeration and air- conditioning equipment, heat exchanger tubes by the Linde (a) 111/1111/1/11mw1/2 Enlargement of A A 50 am 23?] L «102 Legend "' -0- — Smooth 20.. —0— Enhanced no 'E \ Nfl‘o- D ‘3 i v .0 a ‘4 5 " r5 P2 ‘ 2 3 4 E 8 5 573 a 23 30 W (kg/mzs) IPigure 2,1; Grooved wall for enhancement of vaporization. (a) Details of geometry (b) Heat transfer and pressure drOp data for vaporization of R—22. No. of publications appearing per year 10 2780 papers and reports total Hamid-1982) 200 " l- 100“ t. o 411i: “I H II all glnnlllllllllllllllll 1900 1920 1940 1960 1980 2000 Year of Publication Figure 2.2. Annual Publication in heat transfer enhancement. ‘ ll division of Union Carbide Corporation, by Hitachi in Japan, and by Wieland in West Germany. 2.1.2 Comparative study of commercially available surfaces The enhanced tubesavailable in the market differ in their surface configurations and by the manufacturing tech- niques used in preparing the surface. The method of manu- facturing consists of either deforming the original plain surface (e.g. Hitachi Thermoexcel-E*, Wieland Gewa-T* and Trane surfaces) or deposoting metal particles on the surface to create microscopic gas traps (e.g. Union Carbide High Flux*). Figure 2.3 shows armmlitatiVe comparison between the surface geometries of three commercially available tubes. Figure 2.3 (a) shows an enlarged view of T-shaped contour of a typical Gewa-T tube. A similar cross-section of a Thermo- excel tube is depicted in Figure 2.3 (b). This surface con- sists of circumferential tunnels which have irregular tri- angular pores connecting the liquid and the tunnels. The high-flux boiling surface is a porous matrix of metallic particles brazed to the tube wall. (This surface will be described in more detail in the next section as the high flux surface has been used in the present study). Yilmaz and Westwater (3) investigated the heat transfer performance of these tubes using one pure saturated hydro- carbon. All three enhanced surfaces were designed specifically for refrigerants (liquids of low surface tension and low * Trademarks 12 (a) Gewo-T \ ,\_ . ‘ \>‘ \ .‘C ' \‘\\:\\ \\\ {\\\§\ \‘X\\\ l\\‘\\\ \ ¢§&x\$ o§§§§§§§sbx ~ (b) Thermoexcel-E (Cltfimime Surface geometries of three commercially Figure 2.3. available enhanced surfaces. 13 thermal conductivity). For best comparison, all the tubes were.made of the same material (pure copper), equal overall lengths (457 mm) and equal heater length (127 mm). Figure 2.4 shows the boiling curves for these en- hanced surfaces and a similar smooth surface in a pool of p-xylene liquid. A portion of the curve for the.High Elux surface has been shown in the transition regime of boiling. It should be noted at this point that the wall superheat.AT, begins to drop down when the heat flux is increased beyond a critical value. It was not possible for the investigator to reach the peak heat flux value for the other surfaces due to a limited heat source supply temperature. In the region of nucleate pool boiling (to be in- -vestigated in this study), the high flux tube performed better than both the Thermoexcel-E and the Gewa-T tubes. The best least square fit for the given plain tube is given by the equation: 0p: 0.00209 (AT)3'16 (2.1) This is in good agreement with the plotted results. Similar expressions for the enhanced surfaces are: dHF 1.19 = 2.03 (.AT) for High Flux (2.2) qTE =13.05 (AT)l°03 for Thermoexcel—E (2.3) qGT = 5.81 (AT)1'32 for Gewa—T (2.4) A good method of comparing the performance of a plain tube with an enhanced tube, under identical experimental l4 . .Legend - O Plane 0 Wieland Gewa- T ‘00 ‘ A Hitachi Thermoexcel . e Union Carbide High Flux . 9 : 200< . A l N I. E . ./ E as A v a: d 4 80 '- 80 -I A 5.0 “ A A 40 - . \ 30 ‘ 20 ‘ 1o —] I Y 1 1' 1' U I' v 1 2 3 4 6 8 10 20 40 .AT(K) Figure 2.4. Boiling curve for three commercially available enhanced surfacesand their comparison with a smooth surface. r 15 conditions, is to find the surface factor of the enhanced surfaces. The surface factor, FS, is defined as the ratio of the wall to bulk liquid AT for the plain tube to the AT for the enhanced tube at a p.rticu1ar heat flux. In other words, Hp is.a factor of improvement in the nucleate pool boiling heat transfer coefficient for the enhanced surface over that for the plane surface or: F=flp_;-=_°'E . 5 (Eng? 0p (2.5) The surface factor is plotted versus heat flux in Figure 2.5. It is seen to decrease as the heat flux increases. It is not necessarily logical to compare the wall superheat of plain and enhanced surfaces at all heat fluxes because it is possible that when the plain surface is still in the single phase natural convection mode, the enhanced surface might be in the nucleate boiling regime. 2.1.3 High Flux Surface As the present study of boiling of binary mixtures has been done on a High Flux tubing (trade mark Union Carbide), it is essential to describe this surface in more detail. High Flux is a patented, engineered, heat transfer product to promote vigorous boiling at a very low temperature difference. A comparison of a High Flux surface with a smooth surface is shown in Figure 2.6 (18). The High Flux tube per- formance in boiling the three liquids, viz. ethanol, prophylene and Refrigerant-ll, is more than ten times better than for the 16 20 r I Y Y 1' |O_— — 8i -‘ L a 9 s» a U \- o ... LL 0 E ‘l u 2 (3 4A -1 “.00 o Wieland Geno-T :3 Hitachi ThermoexceI—E 0 Union Carbide Hugh Flux I . - ' 30 4O 60 80 ICC 200 ' 300 (o/A)st ' kW/mz Surface factor comparison of three commercial surfaces. Figure 2.5. 11 .momwhnm snooEm m sues oocmfinomuom mommamnu new: oommusm stm swam mo GOmHHmQEoo m .w.m.mflm on on 2 ad on ad ed 3: __.Q 9.. ed .6 v... . n6 - n b p E n p L p P n O- 1 . 3 1 Ian 13 a to. a to. 1 too— .7 . A K z A A r 8... ovatom £.ooEm Satan .3: :3: 73:39.33 fooEm ..> no: :9: no.“ a; (aw/Mn b 18 corresponding conventional bare tubing. The High.Flux boiling surface consists of a thin porous metallic matrix which is bonded to a metallic substrate. The surface layer is about 0.05 mm to 0.50 mm thick and contains a multiplicity of cavities or pores which function as sites for the generation of vapor bubbles. Porous boiling surfaces have been produced with almost every common metal such as copper alloys, aluminium alloys, steel and stainless steel alloys. Numerous tests have been made on the mechanical in- tegrity of the porous surface layers. The bond between the subtrate and the porous matrix has been found to be excellent. Deformation of the'subtrate up to 60% will produce cracks in the porous material but will not tear any particles from the surface. In fatigue tests the tube proper failed before any particles were broken loose from the porous matrix and the handling of the tubes and pulling of the tubes coated on the outside through the tube sheets tend to burnish the surface, but do not interfere with functional performance of the tube since the damage is superficial and does not alter the geo- metry of the boiling site. Figure 2.7 shows the long term performance for a prototype ethylene condenser utilizing porous surface tubes (18). The unit was installed on an ethylene column and con- denses ethylene at 17 bar against prOpylene boiling at 0.4 bar. The ethylene plant uses a reciprocating prOpylene refrigeration 50 4 . 1 1 l 40 d l' 30 -' I High Flux .Tubing Exchanger 20 - Legend " A Start-Up, December I967 0 After 182 days OAfter 600 days,August I969 10 d A / u / E / N / E Conventional Tubing / / ~— Exchanger / / ea / / / / 5 - / / / / / 4 1 / 3 . 2 1 l 1 1 I 5 6. 7 8 9 10 AT (K) Figure 2.7. Long term performance of High Flux tubing. 20 system. As a result the following-environment is probably as severe as can be encountered in such.applicatioh.. Inspite of these unfavorable conditions, performance was six times better than conventional technology. Finally, a few words about the application of the High Flux surface. It is particularly attractive in refriger- ation appliances where Operation at very lownAT is desired for high thermodynamic efficiency. Other applications are in 'Rankine cycle power generation using waste heat streams, ocean thermal energy conversion, refrigeration chillers, and in . liquid natural gas plants. 2.2 Binary Mixture Boiling The nucleate pool boiling of binary mixtures is of special interest to the petro-chemical, refrigeration, air separation and liquid natural gas (LNG) industries. A thermal design engineer wishes to predict the following three boiling parameters: (a) Peak nucleate heat flux: This is the maximum value of heat flux at an arbitrary composition in a binary mixture which keeps the boiling process in the nucleate boiling regime. An increase in the heat flux above this point will cause a de- crease in the heat transfer coefficient and the process will enter into transition boiling. (b) Minimum wall superheat: This is the lowest value of wall superheat, (TW - Tsat)’ which is required to initiate boiling on the surface to take advantage of the much higher heat transfer coefficient obtained for boiling compared to single- 21 phase natural convection. (c) Heat transfer coefficient: Prediction of the heat transfer coefficient as a function of either wall superheat or heat flux for the liquid composition of interest is the ul- timate goal of a design engineer; For boiling of a liquid mixture in a shell-and-tube heat exchanger, such as a kettle reboiler, the heat transfer coefficient for a particular tube is the sum of the nucleate pool boiling contribution to the induced convection caused by circulation. For enhanced surfaces, the single component boiling heat transfer coefficient is so high that the con- vection effect is not significant. Thus, in this case a single tube test in a pool boiling rig can be used directly for predicting the boiling side thermal performance. 2.2.1 Vapor-liquid phase equilibrium. In binary mixtures the vapor in equilibrium with the liquid phase does not usually have the same composition as the liquid phase. For equilibrium .to exist, the chemical po- tentials of the two phases must be equal. Thus the mole fraction of vapor, y, can be either less than, greater than or equal to the liquid mole fraction fi. Phase equilibrium diagrams are used to show the relationship between y and i at various saturation temperatures at constant pressure. Figure 2.8 shows a typical vapor-liquid phase equilibrium diagram for an ideal binary mixture. Mole fractions of the relatively more volatile component is on 22 l l P=constant o h :x *0 e. 0 a. S *- Tsat I l l l l l | l I I I | l J 0 it 37: 1 Vapor/Liquid Mole Fraction Figure 2.8 Phase equilibrium diagram for an ideal binary mixture system. 23 the x-axis and saturation temperature is plotted on Y-axis. The component having a lower boiling point at the pressure of interest is said to be 'more’leati'le; The dew point line depicts the variation in the equilibrium .vapor mole frac- tion with.saturation temperature. It is clear from the -diagram that y43?for the less voltile component. Figure 2.9 depicts the phase-equilibrium diagram of an azeotrOpic mixture. The azeotropic mixture is one which has an intermediate point where the composition of liquid and vapor phases are identical and 37 2 X to the left of azeotrope and 5; s 3? to the right of azeotrope. A mixture at the azeotrope behaves like a pure or single component liquid because compositions of the liquid and vapor phases are equal. 2.2.2. Previous studies on binary mixtures. The experimental investigationson nucleate pool boiling of binary mixtures have established that the boiling heat transfer coefficient of a mixture can be considerably lower than that of its equivalent pure fluid. An equiva- lent pure fluid is one with the same physical properties as the mixture but with no composition difference between the two phases, i.e. §'='§. Typical data for the variation in the wall ~superheat ( AT) with composition on a smooth surface at constant heat flux are shown in Figures 2.10 and 2.11, for ethanol—water and ethanol-benzene at 1.0 bar (19). These binary mixtures are under investigation .24 ~_ 7 .1‘ Temperature. 03'" n: H r.._..__._._._._____ a. L.________.__._._ l I l 0 =4 3| a O : ol MI (I .L o - 1 xi i VAPOR/ LIQUID MOLE FRACTION Figure 2.9. Phase equilibrium diagram for an azeorropic mixture system. 25 24 22~ 20« 18- 16« 14‘ l2< Legend Wall superheat atza 10‘ heat flux of 200 kW/m for ethanol-water system (19). AT b————-————————-_————- r T 0 0.2 0.4 0T6 0T3 1.0 7 (Ethanol) Figure 2.10. Variation on T with composition for ethanol- water system on a smooth surface (19). 26 22 Legend: Wall superheat atza heatuflux of 170 kW/m for ethanol-benzene (l9) 201 18¢ 16« 14. l2‘ AT 10« b———_-——————_————— l I o 0.2 0:4 0.6 0.8 1.0 )((Ethanol) Figure 2.11. Variation of AAT with composition for ethanol- benzene system on a smooth surface (19). 27 in the present study on an enhanced surface. It is necessary to explain why the actual heat transfer coefficients are lower in the case of binary mix- tures compared with their respeCtive pure components and to predict the actual variation. Van Wijk et a1. ( 20 ) presented the first physical explanation for the decrease in the mixture boiling heat transfer coefficient. They noted that the equilibrium vapor mole fraction, 9', of the more volatile component in lthe bubbles growing near the heated surface is higher than that of the bulk liquid mole fraction 32. The more volatile component will evaporate faster to maintain equilibrium .be- tween phases and thus causes a reduction in the local liquid mole fraction of the more volatile component. This causes a rise in the local boiling point as shown in Figure 2.12, and hence a reduction in the heat transfer coefficient. Sternling and Tichacek (21) explained the lower heat transfer coefficient, in case of mixtures, due to the additional mass diffusion resistance of the volatile com- ponent to the vapor bubble. Stephan and Korner (22) showed analytically that the reversible work required for formation of a bubble in a binary mixture is greater than that for a single component.- Thus fewer bubbles are generated in mix- tures, which results in diminishing the heat transfer co- efficient. 28 L_ ,7 Dew Line Temperature Tsat llocall Tsatlbuikl BubMe/ Lane .(I .______ 0 xlocal xb local Figure 2. Phase equilibrium diagram showing the decrease in the local mole fractions of the more volatile component. 29 More recently Thome (14) showed that the bubble evaporation and thermal boundary layer stripping heat transfer mechanisms are partially responsible for the de- crease in the heat transfer coefficient in mixtures. These studies on binary mixturestherefore con- clude that heat transfer coefficients cannot be adequately predicted using only single component correlations. CHAPTER 3 EXPERIMENTAL APPARATUS AND METHODS All experimental work was carried out at the boiling heat transfer laboratory of Michigan State University. This section describes the test facility and the experimental procedures. 3.1 Preliminary set—up. The High Flux surface was tested in a pool of dis- tilled water in a heated pyrex beaker before it was fixed into the stainless steel test rig. (The details of the specimen are given in section 3.2 and those of rig in section 3.3). The idea was to make sure that the four thermo— couples attached to the High Flux tubing to measure the sur- face temperature recorded the same readings. Several dif- ferent designs of test specimen were tried before the final decision on the type was made. The preliminary set-up was used because it is time consuming to fix the specimen into the rig everytime and then take it out for modification. The preliminary set-up is shown in Figure 3.1. The specimen was dipped in a heated pool of distilled water at its boiling point. A hot plate was used to heat the water. A known voltage and current was given to the cart- ridge heater. The heat flux was calculated at different voltages and currents. The readings of four thermocouples were recorded on a temperature gauge with a resolution of 30 “—ll’ Figure 3.1. Preliminary set-up. 1. Test surface. 2. couple wires. 3. Power leads. 4. Bulk temperature thermocouple. 5. stand. 6. Distilled water. 7. Pyrex beaker. 8. Hot plate. (Not to scale). Thermo— 32 0.1OC. Another thermocouple was used to.measure the bulk temperature of the water (which remained constant at 1000C during the experiment). The difference between the average temperature of the four thermocouples and the bulk liquid temperature was calculated at each heat flux by considering the thermal resistance between the point at which the thermo- couples were located and the surface of the specimen (defined at the base of the porous surface). The test specimen heater power supply was increased slowly in steps and then decreased following the same steps. The readings recorded for increasing and decreasing heat flux matched fairly well. The pool boiling curve was plotted for the different designs. The criteria for selecting the best design was two-fold: 1. All four thermocouple should record nearly the same value of temperature. 2. The boiling curve should match closely with the previous investigators performing experiments on the High Flux surface in a pool of water at atmospheric pressure. 3.2 Test Specimen The High Flux test surface was made from a section of commercial stock provided by the Linde Division of Union Carbide Corporation. The tube wall material was a copper alloy containing 1% iron. The inside diameter of the tube was 17 mm 33 and the outside diameter was 18.7 mm with the porous enhance- ment and 18.55 mm without porous enhancement. _ The cartridge heater selected to supply the heat flux to the surface was of 3/8" (9.35 mm) diameter. A c0pper sleeve with.an internal diameter slightly less than the outer diameter of heater and an outer diameter slightly greater than the inner diameter of the High Flux tube was fabricated. Four holes of l/16" (1.59 mm) diameter were drilled axially along the wall of the tube. The drilled holes were 900 apart and were bored up to half the length of the Sleeve.A copper- constantan thermocouple (30 gauge) was slid into each wall and was soft soldered to the bottom of the well. The Cartridge heater was fit inside the sleeve by heating the sleeve to a higher temperature. The assembly of heater and sleeve were similarly fixed inside the High Flux tubing. The final design of the test specimen is shown in Figure 3.2. 3.3 Pool Boiling Rig Once the correct design of the test specimen was finalized, it was fixed into the stainless steel pool boiling rig. The Schematic diagram of the rig is shown in Figure 3.3. The stailness steel vessel is a 1/41 (6.35 mm) thick cylin- derical cross 4" (101.6 mm) in internal diameter) with four flange fittings. The top flange has four 1/4" (6.35 mm) tapped screw holes. Two of them were used for supplying coolant to the condenser coil fitted inside the rig. One .Amamom on nozv .Hmeaom umOm.omHsom .ma .monws mamsoooanosu How 0H0: Amman .mamHmmmmownwsm”flowmwmwowmwmwmsow .uoumon omonuuumo .m .m>0oam no 00 m . . .. .sxoam condom .m . . mm 6H0: on o>omam m IOEHmnu usom b may CH cmEfiom . .0 D xsam swam .H . . . Hmmmoo . .uomfioocmscm N A u . moan soamoa v m>mmam REM Ga mGOAmcmEflo Harv noumxm :mEHoomm 34 .N.m mosmflm «as an. v. «2 an. Tl NON ,_ - - i radardravawwrawfl rawvflwruarm - I. -II . NIH lnIulIIul ~~~~~~~~ HI-lll~lH~ n ~ ul A A x I . / . IIVlmNImmd—I I V o IWlll «and . l I l I Inc I l I l 5.2 t— _ - \WILI 1W1: l. . 1. y . _ - war/wars»;arr/awararrr/ra(:43. \NNII \. \ __ a .. 0 n O— 35 Figure 3.3: l. nucleate boiling rig. 2. Enhanced boiling surface. 2a Thermocouple wires. 2b solder. 2c. 1/16" drill hole, 2d. cartridge heater. 2e. heater leads, 2f. teflon plug, 29. poured epony. 3. sleeve to hold Specimen. 4. bulk liquid thermocouple. 5. temperature controller thermocouple. 6. immersion heater. 7- Sight glass windows. 8 liquid fill line. 9 condenser. 10. valve to vacuum pump/atmosphere. ll pressure gauge. 12. safety relief valve. (Not to scale). 36 of the openings was used to degas the system and to evacu- ate the rig as required. The fourth threaded hole was used to install the pressure gauge to measure the preSsure inside the rig during the experiment. The bottom flange has five openings, two for the temperature controller and bulk tem- perature thermocouples,respectively, and one for filling the rig with liquid. The other two were used for the ends of the coiled immersion heater. The front flange has a sight glass window for viewing boiling of the mixture during the exper- iment. The flange at the back was equipped with a 1" (25.4 mm) diameter hole in the center to accommodate the specimen. The four pairs of thermocouple wires and two heater leads coming out of the specimen were connected to a digital temperature measuring device and to an electrical circuit, respectively. The digital thermocouple readout device has a resulution of i 0.1 K. The device was zeroed and the upper range set using a voltage supply, a digital volt meter, and an ice point cell. The heat to the test section was supplied by a cartridge heater powered by a variac. The electrical power supplied was measured using a Keithley (4% digit) digital multimeter and a precision shunt. The heat flux (based on the uncoated tube diameter and heated length) was determined to within about i 2%. The closed system for mixture boiling was maintained at saturation conditions by a prOportioning temperature controller connected to the immersion heater and also by 37 manual control of the water coolant flow rate to the con— denser. The vapor pressure in the vessel was measured using a 300 psia (20 bar) Heise digital measurement system accurate to i 0.1% and zeroed against a mercury barmoter at atmospheric pressure. 3.4 Experimental Procedure and Measurements Table 3.1 shows the list of mixtures tested on the High Flux tubing. All of the experiments were done at two pressures, viz. 1.01 bar and 3.03 bar. The experimental procedure consistency was maintained with all mixtures. The experimental procedure started with preparation of the mixture. The mixtures were prepared on a weight basis by converting the corresponding mole fraction into mass fraction taking into consideration the molecular weights of the liquids being mixed. The accuracy of the weighing equipment was i 0.10 gm. Appendix A. shows the mass fraction calculations of ethanol-water mixtures and also depicts the respective ethanol-benzene mixture compu— tations. Double distilled water and reagent grades of ethanol and benzene were used to prepare the test liquids. The liquid mixtures thus prepared were accurate to about i 0.015 mole fraction. The mixture was then poured into a plastic vessel with a valve outlet and a hose. The hose is then inserted to the fill line in the bottom flange of the rig. The valve of the plastic vessel was then opened to fill the rig LIST OF MIXTURES TESTED Ethanol—water mole fraction (ethanol) m0 (Pure water) 0.05 0.15 0.30 0.45 0.60 0.75 0.894 (Azeotrope) * 1.0 (Pure ethanol) 38 TABLE 3.1 Ethanol—benzene mole fraction (ethanol) 0.0 0. 0. 0. 0. 0. 0. 0. 0 05 15 30 45 60 75 85 .92 (Pure benzene) (Azeotrope) * 1.0 (Pure ethanol) * Boiling of pure ethanol was tested once for both the systems. 39 with the mixture. The total capacity of the rig is 4.4 litres and care was taken to prepare the quantity of mixture according to the capacity of the rig. A cheek for leakage was performed everytime a new mixture was introduced into the rig. An applied pressure of up to 50 psi from a nitrogen gas bottle was used to test for leakage. Also, the stainless steel rig was evacuated everytime to boil out every drop of liquid remaining from the previous mixture composition tested. The mixture is heated to its saturation temperature by a separate immersion heater installed on the bottom flange of the rig and then a valve to atmOSphere was Opened to degas the system. The valve is closed after a few seconds of release of the gases. If the valve is left open for a long period, it is just possible that the mixture composition might change. The density before and after the experiment was measured to make sure that the mixture quality remained unchanged during the experiment. A highly sensitive balance with an accuracy of 0.01 mg was used to calculate the density of the mixtures for a standard volume. The heat flux to the specimen was given using the same 0-240 volts power variac mentioned previously. The current and the voltage were measured using a BM with measurable voltage of 0.01 millivolt. A schematic of the electrical circuit is shown in Figure 3.4. The following measurements were taken to calculate the heat flux input to the Specimen: no . -u—.—.-—- POWER SUPPLY HEATER 40 SHUNT DMM Figure 3 .4 Power Supply Circuit. 41 (a) Heater input voltage across cartridge heater = VH(volts) (b) VOltage drOp across the shunt = Vé (millivolts) Shunt resistance = R8 = 0.001 tL1%52 Then current through the specimen is calculated as: I =VS - —§—‘ . (3.1) s and power as P = V I (3.2) and then the heat flux ~q is determined from q: B kW/mz ' (3.3) A Appendix "B" gives the sample calculations. For the ethanol-benzene system a known heat flux was applied to the specimen before the start of the actual read- ings to record the activation wall superheat. This is the difference in surface and bulk temperature when boiling on the surface starts. The temperature drOps down suddenly to a lower value of AT as soon as the boiling surface becomes active. After the boiling activation superheat measurement, the heat flux is slowly increased to its maximum and allowed to boil for 15 minutes to activate all boiling sites on the enhanced surface and then is brought back to the initial heat flux value to start the experiment. 42 The following readings were taken at different input voltages: (a) Temperature at Thermocouple No. l = Tl (b) Temperature at Thermocouple No. 2 = T2 (c) Temperature at Thermocouple No. 3 = T3 (d) Temperature at Thermocouple No. 4 = T4 (e) Voltage drop across the test section heater = V (f) Voltage drop across the shunt = VS (9) Bulk liquid temperature = TSat The mean surface temperature was then calculated taking the average of four thermocouples, T through T but this 1 4’ is in fact not the actual surface wall temperature of the tube. The correct wall temperature was computed by considering the thermal resistance between the point at which the thermo- couple wires were soldered and the surface wall of the speci- men. For a detailed analysis of these calculations, see Appendix C. The experiment was performed at 10 values of heat flux by gradually increasing the heat flux in steps to its high- est value of 91.7 kWsz corresponding to a voltage input of 220 volts. The readings were then taken at the same heat fluxes by gradually decreasing the flux in steps. Very little hysterisis was observed and there was almost negli— gible difference between the two sets of readings. The average temperature calculated from the four thermocouples 43 readings are tabulated in Appendix D. Also listed are bulk temperatures, wall superheat recorded and actual wall superheat after applying thermal resistance corrections calculated in Appendix C. The experimental procedure for each mixture composition was always the same to insure the integrity of the results. The boiling curves for increasing heat flux were obtained followed by several other curves as discussed in Chapter 4. The curves for decreasing heat flux were not plotted be- cause the measured temperatures were almost the same as obtained for increasing heat flux values (steady-state con- ditions prevailed at each test condition). CHAPTER 4 EXPERIMENTAL RESULTS A total of 38 experimental runs were performed. Nineteen experiments were carried out at a pressure of 1.01 bar and another nineteen at a pressure of 3.03 bar. Out of these 19, nine experiments were performed in a pool of different ethanol—water mixture compositions and 9 in ethanol-benzene mixture compositions. One experiment with distilled water was repeated after all the other ethanol- water mixture runs were completed. Appendix D gives ex- perimental data in tabular form. All the results are presented in graphical form. They I'have been organised in a way to show the effect of applied heat flux on the wall superheat for the ethanol-water and ethanol-benzene mixtures. Presented also are the plots of wall superheat as a function of composition at five different values of heat flux. All these results are shown at pres- sures of 1.01 bar and 3.03 bar. Wall activation superheats for ethanol-benzene at 1.01 bar are also depicted. 4.1 Ethanol-Water Results The nucleate pool boiling curves for the ethanol-water system are shown in Figures 4.1 and 4.2 for pressures of 1.01 bar and 3.03 bar, respectively. Ethanol-water forms an azeotrOpe at an ethanol mole fraction of 0.894. The pool 44 tr... q (kW/m1) 45 Figure 4.1. ..............I... ...I ‘1...” [m/ / ”L/ /7//// / . /// //// / //.// /[7 // 77/ /l// / W Nucleate pool boiling curve for ethanol-water system at l. 01 bar (High Flux tubing). 46 100 no < Ethanol-Water (3.03bor) (“UH/m2) Lama; OWoter + 5%E'hanol-Woter x 15% ' A 30% 04596 V60°/. o 75% I 894% A1007. Ethanol 0.1 0 2 04 Figure 4.2. 0.6 AHK) Nucleate pool boiling curve for ethanol-water at a pressure of 3.03 bar (High Flux tubing). 47 boiling curve for pure water obtained after testing the ethanol-water mixtures was found to be similar to the one obtained at the beginning. However, another pure water boiling curve obtained after the completion of the ethanol- benzene runs showed a deviatiOn of 1°C to the right of the previous water curves. The present water results at 1.01 bar match the de- creasing heat flux values of Bergles and Chyu (2) quite well as shown in Figure 4.3. The pure ethanol data at 1.01 bar also compare quite well to those reported by Gottzman (9) as depicted in Figure 4.4. The comparison of these other results to the present ones do not necessarily match per- fectly because the characteristic dimensions of the porous matrices are not necessarily the same. The variation in wall superheat, defined as the mean wall temperature minus the bulk saturation temperature is plotted as a function of ethanol mole fraction for ethanol- water mixtures in Figures 4.5 and 4.6 at 1.01 bar and 3.03 bar, respectively, at five different heat fluxes. The minor swings in the data points are probably due to exper- imental error. The maximum wall superheat was observed at an ethanol- mole fraction of 0.05 whereas the minimum was for pure ethanol. The results at the pressure of 3.03 bar are similar to those at 1.01 bar. The wall superheats are noted to decrease with increasing pressure for a given heat flux and q. I 'lmz 48 105: F" C 'DENOTES RUN roa' C IENRCRAIURE JUHP L. ‘— .10 C L. ‘ o INCREASING 103~ 2‘ H B 55 c o DECREASING E - _ _ _ n INCREASING ~ 2‘ " 8 39 c . DECREASING ~ I _ - - - o INCREASING - 2‘ "‘ a ‘9 C . DECREASING - o INCREASING 2"" “'5“ o DECREASING 102 ‘4 1+ 1 141L141 1 1 1 L111) 10" 10° 10‘ 102 AT. °x Figure 4.3. High Flux tubing data for boiling in a pool of distilled water (2) at 1.0 bar. If 49 200 1 L 1 1 0 High flux data for ethanol-water [9] 100~ . 90" ' 00- - 70.. .- 60- - 50~ . :7 4o~ p E J 30- )- a: 20‘ - ‘0 V T 1 I 0.] 0.2 0.4 0.6 0.8 1.0 AJ(K) Figure 4.4. Pure ethanol boiling at 1.0 bar (High Flux surface) (9). Af(K) 50 l j l Ethanol- Watet (1.01bat) Legend: . 2.9 kW/m xIZJ '“ _ 0214 " 04&6 " -+7i9 " Figure 4.5. X (Ethanol) Wall superheat ( AT) for different values of heat flux (ethanol-water at 1.01 bar). 51 Eth anal - Water (3.03 bar) Legend: 0 2.9 lCW/m2 X IZJ ” (>214 " D<48AI “ + 75.9 " Figure 4.6. I T 0.6 0.8 1.0 (Ethanol) Wall superheat for five different values of heat flux (ethanoldwater at 3.03 bar). ‘ 52 composition. This behavior is the same as for boiling from a smooth surface. The dashed lines on Figure 4.5 are the ideal mixing lines for the ethanol-water system. In general, wall super- heats for the mixtures are above the ideal lines. There are two different concepts about the ideal mixing lines pre- sented by Thome (l4) and Stephan et al. (22). The details on the ideal mixing line and its comparison with our results are presented in the next chapter. 4.2 .Ethanol-Benzene Results The nucleate pool boiling curves for the ethanol- benzene system are plotted in Figures 4.7 and 4.8 at pressure of 1.01 bar and 3.03 bar, respectively. The ethanol-benzene mixture forms an azeotrope at an ethanol composition of 0.45. The effect of composition on wall superheat is por- trayed in Figures 4.9 and 4.10 at fixed values of heat flux. The wall superheats form maxima on both sides of the azeotrope. The boiling curves at 3.03 bar are again found to be shifted slightly to the left as compared to 1.01 bar curves. The maximum wall superheat was observed at an ethanol mole fraction of 0.05 and the minimum is for pure ethanol. The wall superheats are above the ideal lines. (Ideal mixing lines are not drawn on the ethanol-benzene results for clarity). In general deviation increases as the applied heat flux increases. (I‘IIW/mz) 53 “j s.....n-a......n.oubo.) ”277" / /" / ""7... 7//’/ / / / . /'/'// /"/"/ 33;; 7 //'//7/// / I 232;: I /./// //// / / ///// / / ////y/ 5 ////7/ / / Figure 4.7. AT(K) Pool boiling curve for ethanol-benzene at 1.01 bar (High Flux surface). A (“kW/m3) 54 100 00‘ 004 £04 20< [thanal- Santana (3.03 ha I) Lagand: a Ianxana + 5 % Ethanaljlanzana xg/ {/ x1536 “ " x 430% ~ /’ 04516 " " + voox ~ 075% ~ 3 a85% - 3 v92% ~ AI00% 0.1 0.2 04 0.5 an 1.0 2 3 G s G 7 a AHK) Figure 4.8. Pool boiling curve for ethanol-benzene at 3.03 bar (High Flux surface). 55 ‘0 Ethanol-Banzana‘lfll ha!) 9 ‘ Lagand: a 2.9 ICW/m2 8 _ x 12.1 " o 27.4 “ 7 ‘ o48b " +759 " 3 T 8' 3 2 ° 0. 2/ . o\ 2 x\\\\\\~ ?’/////’O_\\\\\‘o\\\\ 2 o . 0 , \M/X\x\o.£\ I i \% \X-x\ . \ o . . . 1 , , , o 02 04 0.6 08 IO iflthanol) Figure 4.9. Wall superheat ()AT) at five different values of heat flux (ethanol—benzene at 1.01 bar). 56 IO AHK) .__ f // Ethanol - Banzana (3.03 bar) lgand = o 2.9 kw/mz X I2.] u (>274 H (3485 " + 75.9 .. \\ §\;;\ .+/ 2 . I ° . °\O____o .:d;:\_ 1 V a .\X E—X———— \J‘D . .~——— .__—— o f T l I T O 02 Q4 06 Q8 LO X- (Ethanol) Figure 4.10. Wall superheat (.AT) at five different values of heat flux (ethanol—benzene at 3.03 bar). 57 4.3 Activation Superheat The activation superheat is the wall superheat required to initiate boiling. When a heat flux is applied to a sur— face, it takes a while for vigorous boiling to start. The wall temperature rises until boiling begins and then dr0ps due to the higher heat transfer coefficient for boiling. Several previous studies were on the onset of nucleate boiling in convective boiling and the others are on the activation of the first boiling site in nucleate pool boil- ing. Thome et. al. (19) have obtained activation and de- activation superheats for a smooth flat disk. The activation superheats for the ethanol-benzene systems at 1.01 bar were obtained experimentally. After degassing the system and vigorously boiling on the enhanced surface, the temperature was allowed to cool down to sat- uration conditions. Then a known value of heat flux,_12.2 kMsz, was given to the specimen and the wall temperature was noted when boiling initiated. The boiling activation data are plotted in Figure 4.11. A maximum and a positive deviation from ideality are evident to either side of the azeotrOpe line. The swing in the results are probably again due to experimental error in- volved in noting the correct activation superheat. The vigorous boiling on the High Flux surface starts so rapidly, it was very hard to note exactly the correct activation superheat. However, the general pattern is shown in Figure 4.11 A1'in‘cipiance (F) H IO 58 a lncipianca at 12.] ICW/m2 Azaatropa 2(Ethanol) Figure 4.11. Activation wall superheat for ethanol-benzene at 1.01 bar. 59 because each reading involved the same time lag between the actual activation point and the noted reading. The error involved may be of the order of :_0.5°C. CHAPTER 5 DISCUSSION OR EXPERIMENTAL RESULTS The ethanol-water and ethanol-benzene mixtures have been seleCted for the performance tests on the High Flux surface because of their well documented boiling behavior on smooth.surfaces. Before comparing the performance of the present surface with published smooth surface results, a brief discussion on the ideal mixing law is presented. 5.1 Ideal Mixing Law The ideal quantities are defined by an ideal mixing law; Figure 5.1 shows the values of ATexpected andIATideal for an azeotropic mixture. The point of concern at this stage is the definition of the ideal wall superheat. Some methods use a particular single component correlation while others use a linear mixing law. The problem associated with utilizing a single component correlation is that it may work well for one component e.g. water, but poorly for the second, e.g. alcohol. This is alleviated by use of a linear andeT-, utilizing perhaps 1 .. two different single component correlations to obtainATl molar mixing law to obtain AT andIATZ, but at the expense of loosing the effect onIAT ideal of non-linear variations in the physical properties with composition. Also, there is no uniformity in the application of the linear mixing law to mixtures forming an 60 .61 +0 ‘3 a: 4: L. a: a. 3 a) To 3 Korner 0 Liquid Mole Fraction 1.0 f Hg£$IDiffering definitions of a linear mixing law for an azeotropic mixture system. 62 azeotrope. \ As illustrated in Figure 5.1, Stephan and co-workers (22) do not necessarily match the wall superheat at the azeotrope‘toATI while Thome (14) does. For instance, to the left of azeotrope the ideal wall superheat is prorated by Theme (10} as: X Ti . (5.1) and to the right of azeotrope as: 13x1 "az AT2 X2 ATz (5.2) —_1 — x. +——"1 - x 3.2 3.2 Thome has studied four different predictive methods in his recent review (10) and his method Equation (1.1) of Chapter 1, has an accuracy of i 15% for ethanol-water mixtures at 1.0 bar. In summary the ThomeATbp method (Equation 1.1) appears to be one of the easiest methods to apply (only phase—equilibrium data is required) and also the most accurate. It was shown in another paper by Thome (14) that this method predicted wall superheats quite well at medium and high heat fluxes for other systems like etehanol-benzene,acetone—water, nitrogen-argon and nitro— gen—methane. 63 5.2 Deviation From Ideality The rise in the local boiling point,Afl , defined as the difference between the actual wall superheat and the ideal wall superheat obtained experimentally are plotted in Figures 5.2 and 5.4 for the ethanol-water and ethanolébenzene systems on the High Flux surface, res; pectively. The ideal wall superheat calculations for ethanoldwater and ethanol-benzene systems for the enhanced surface are presented in Appendix E. The value of A9 plotted against ethanol composition in Figure 5.2 shows a small increase as compared to Am - 59 (.AT- are obtained from the phase-equilibrium diagram of b the eihanoldwater system at 1.61 bar). This is in contrast to result expected by Arshad and Thome (13) as discussed in Chapter 1. Figure 5.3 depicts the smooth surface data taken from the studies by Shakir (19), Valent and Afgan (23) and Tolusbinsky and Ostrovskiy (24) for the ethanol-water system at 1.01 bar. These data are tabulated in Appendix F'. In contrast to Figure 5.2, Figure 5.3 shows typical smooth surface boiling behavior with.A9 being much larger . Note that at the P highest heat flux, 91.7 kw/m2 the value of 459 is about and being well approximated by.ATS 1K for the enhanced surface while A6 reaches about 12K for the smooth surface at a heat flux of 116 kw/m2 (24). no fun 64 I'J I/ ~ \\\ I \ Ethanol-Water (LOibar) 10“ I \ Enhanced Surface I \ Legend! 9‘ I \ o 2.9 kW/mz \ o 27.4 .. 3- I \ + 75.9 . I \ A 91.7 " 7. I \ m I \/ b9 6‘ I I \ I \ 5‘ I \ I \ 4— I \ I \ 3‘ I \ I \ _ 2- I \ \ I \ 1" \\ . \ \ . . 8/0§o \ ° 3v. . 1% \? 7"— "r .12 6.4 0:. at. m 5? (Ethanol) Figure 5.2. Local rise in boiling point (A6) for enhanced surface at 1.01 bar. IS i4 13 12 n 10 A600 0! 65 .5 Ethanol-Water (I.Oibar) Smooth Sofioce Legend: 0 zoow/m2 [i9] +190 " [23} e no .. [241' fi—CK j 1 i I (12 (14 (16 (18 ifiihanol) Figure 5.3. Local. rise in boiling point (A0) for Azeo'rope 1.0 ethanol-water at 1.01 bar (smooth surface). Mind 66 Ethanol - Benzene (1.0] bar) Legend: Enhanced Surface 2.9 kw m’ 2(Ethonol) Figure 5.4. Local rise in boiling point for ethanol- benzene at 1.01 bar (Enhanced surface). 67 The Apr- curve superimposed on the studies of other in- vestigators (19, 23, 24) for the ethanoldwater system on smooth.surfaces matches quite well. To compare our results for the ethanol-benzene system (Figure 5.4), the corresponding data for smooth surface boiling are plotted in Figure 5.5. They are taken from the studies of Shakir (19), Happel and Stephan (25) and Grigorev et. a1-(26). These data are tabulated in Appendix E. The ethanol—benzene results on the enhanced surface shown in Figure 5.4 surprisingly match with the' corresponding ATEP values (obtained from an ethanol-benzene phase-equilibrium diagram). The valLir'es of A0 become larger than those for ethanol-water system, even though this system's maximum boiling range is only about one-half that of ethano1; water. . Also A0 for this system is much higher to the left of the azeotrOpe point than to the right side. The local rise in boiling point,A0,fOr the smooth surface is again fairly well approximated byAT'bP as shown in Figure 5.5 rwherer and AT'bp match quite well on either side of the azeotrope point. In Figure 5.4, it is also noteworthy to point out that Afl increases as the heat flux increases. This is also generally true for mixture boiling on a smooth surface. The discussion of results obtained for 3.03 bar data could not be presented because the corresponding smooth surface data are not available in the literature. However, ”A9(K) 68 6 .EthanoI-Benzene (1.0] bar) Legend: . Smooth Surface OIOO'kW/mz [2,5 _ \ 0170 .. [393" +232 ~ 25‘; 5‘ J \ L. I \ I \ . \ . .\ 4.. \ I, . \ l \ / \ CHEF / \ / \ / + o / / Au! / I _ I / \ + + \\\+, . . p U 0 02 04 (£6 Figure 5.5. 5? (Ethanol) Local rise in boiling point for ethanol— benzene at 1.01 bar (smooth surface). 69 the enhanced surface.3.03 bar reSults show a slight shifting of the boiling curve to the left as eXpected, roughly of the order of 10.15%. 5.3‘ Heat Transfer Performance Comparing the enhanced heat transfer performance to the published smooth surface results shows that there is substantial improvement, even at the compositions near the maximum in Apr. For instance, at 91.7kW/m2 in ethanol-water at a mole fraction of 0.15 at 1.01 bar, the wall superheat is 3.1 K while the smooth surface values are in the neighborhood of 20 to 25 K. In similar circumstances, pure water has an enhanced surface value of 3.6 K and a smooth surface value in the range from 10 to 16 K and pure ethanol has a value of 1.8 K compared to 16 to 25 K. Thus, the mixture experiences about the same level of improvement as the pure components in this case. This is also true for the same conditions for an ethanol-benzene mixture with a mole fraction 0.15. This is an important conclusion since it means that enhanced surfaces can be successfully used in the chemical processing industry for evaporating liquid mixtures in hettle reboilers. Several important questions remain to be answered. First, why isAO so much smaller for the enhanced surface than a smooth surface for ethanol-water mixtures? Secondly, why is this not true for the ethanol-benzene case? One possible explanation to the first question is that the evaporation rate mabee so high for an enhanced 70 surface that phaseeequilibrium cannot be assumed to exist. Hence, the m61e fraction of the more volatile component in the vapor phase is less than the corresponding equilibrium value and approaches the liquid composition in value, as would be true for inertia controlled bubble growth. Another possible explanation is that the evaporating liquid film in an enhanced surface is constantly replenished with bulk liquid drawn into the porous matrix such that a significant composition gradiant cannot form. Instead, for microlayer evaporation under a bubble growing on a smooth surface, no replemishment of the liquid is possible and the local vapor-liquid interfacial temperature rises as the more volatileecomponent is exhausted (as noted by Thome and Davey ('27))until it reaches its asymtotic growth stage where A0 is assumed to be constant i.e. the Van Stralen bubble growth model for a mixture (28). ‘ Activation superheats are an important aspect of the industrial application of enhanced surfaces since the start up conditions of the heat exchanger may or may not be sufficient for boiling to begin. Figure 4.11 shows the activation of an enhanced surface for boiling of a mixture requires a higher wall superheat than expected from a simple linear interpolation between the pure components and azeo- trope point values. These results are coexistent with those of Thome, Shakir and Mercier (29) obtained for a smooth heated brass disk for ethanol-water mixtures at 1.01 bar, 71 although.the maxima here are much lower than the maximum of 44 K measured there. The positive deviation in the presented reSults from an ideal mixing law is attributed to mass diffu- sion effects on the trapped vapor pockets in the porous matrix of the High Flux surface. The effeCt of pressure on heat transfer performance of an enhanced boiling surface can be seen from comparing the 1.01 bar data to the 3.03 bar data. The heat transfer co- efficient tends to increase as the pressure increases which is true for a smooth surface also. In closing, it should be noted that all of these boiling results are for a particular enhanced boiling sur- face, High Flux, and may not be indicative of the mixture boiling performance of other commercially available enhanced surfaces due to the wide difference in surface geometries and thus, perhaps, the controlling heat transfer mechan- isms. Further work is recommended to test other enhanced -boiling surfaces and also other mixture systems with wider boiling ranges. Additional work is currently underway at the Michigan State University to test the High Flux sur- face with acetone-water and water-glycol mixtures systems which have much higher boiling ranges. CHAPTER 6 CONCLUSIONS The results of the study on the boiling of ethanol— water and ethanol—benzene mixtures on a High Flux surface are summarized as follows: 1. Nucleate pool boiling curves for an enhanced boiling surface were obtained for ethanoldwater and ethanol-benzene systems at 1.01 bar and 3.03 bar and it was observed that the increase in pressure increases the heat transfer co— efficients for the mixtures as also observed for single com- ponent liquids. 2. A9 for boiling on an enhanced surface can be much less than that for a smooth surface. It is thought to be due to preferential evaporation of the more volatile component. 3. The improvement in the heat transfer performance of an enhanced surface for mixture boiling is similar to that ob- tainable for single component boiling. 4. The activation superheats for an enhanced surface are higher for the mixtures. This is thought to be due to mass diffusion effects. 72 73 APPENDICES APPENDIX A PREPARATION OF A.MIXTURE OF KNOWN COMPOSITION All of the mixture compositions for the experiments were prepared on a mass basis. A sample calculation for com- puting a mass fraction, if a mole fraction is given, is preSented here. Let us first consider ethanol-water system and a mole fraction of 0.45 is chosen for sample calculation. For 100 moles of ethanol-water mixture there are: (a) number of ethanol moles = 45 (b) number of water moles = 55 (c) chemical formula for ethanol = C.H OH 2 5 2 x 12.01 + 6 x 1.008 + 16.00x 1 mass of one mole ethanol 46.068 gms. (d) ethanol molecular weight chemical formula for water = H20 mass of one mole water = 2 x 1.008 + 16 x 1 water molecular weight = 18.016 gms. now mass of 45 moles of ethanol = 2073.06 gms. mass of 55 moles of water = 990.88 gms. mass fraction, W, is defined as mass of ethanol divided by total mass of mixture or W = 2073.06 0.6766 2073.06 + 990.99 i.e. 45% mole fraction = 67.66% mass fraction for an ethanol- water mixture or: 74 75 W = f ' ' Me: Me + MM,' where’ Me = mass of ethanol Mw = mass of water From (A.l) (l - W) Me = W MW or .M W e Mw 1 -w (A.lY (A.2) Equation (A.2) can be used to find out the mass of ethanol if the fraction is known and an apprOpriate value of mass of water is chosen such that mixture total volume should not be more than the capacity of rig, which is 4400 ml. Note that volume will be obtained by dividing masses with corresponding densities of the c0ponent being mixed. The following table gives all values of mass fraction calculated against each mole fraction and the actual masses to prepare a certain mixture. 76 TABLE A—l. Masses of water and ethanol used in ethanol-- ‘water experiment. MolegFraction Mass Fraction Mass of water Mass of ethanol 'x‘ (ethanol) W ' (gramsmw (grams) Me 0 0 4000 0 0.05 0.1186 2600 ‘ 349.93 0.15 0.3109 2000 902.50 0.30 0.5229 1400 1534.34 0.45 9 0.6766 1000 2902.28 0.60 0.7932 600 2301.36 0.75 0.8847 300 2302.00 0.894 0.9558 130 2811.18 1.00 1.00 . 0 3000.00 The similar calculation for ethanol-benzene calcu- lations were carried out. The only change will be in num- bers because of the molecular formula of benzene (C6H6). The following values were used to prepare mixture for this system. 77 TABLE A—2. Masses of benzene and ethanol used in ethanol- benzene experiments Mole Fraction Mass Fraction Mass of benzene Mass of ethanol 3? (ethanol) W (grams) M3 (grams) Me 0 0 3500 0 0.05 0.0301 3400 105.50 0.15 0.0943 3000 312.22 0.30 0.2018 2700 682.44 0.45 0.3255 _ 2100 1013.33 0.60 0.4694 1600 1415.44 0.75 0.6389 1100 1946.23 0.85 0.7697 700 2339.40 0.92 0.8698 350 2374.00 1.00 1.00 0 3000 ill ‘ [1411‘ APPENDIX B HEAT FLUX CALCULATION The heat flux calculation has been based on the dia- meter of the High Flux tube withOut enhancement (18.55 mm). One sample calculation for an applied voltage of 100 volts is presented. From equation (3.2) power is defined as: P = VH I VH = current measured at above voltage in amperes Heat flux 0 = B A e where A = surface area of heated tube length = d = diameter of the tube without enhancement 1 = heated length: (0.1524 m) or q = V I _ H x 10 3' kwr/m2 ”'X 0.01855 X 0.1524 g = 0.1126 VHI at a voltage of 100 volts, the current noted down was 1.69 amperes, hence the heat flux is: 0 0.1126 x 100 x 1.69 kMsz 27.43 kW/m2 or q Similar calculations with other measured voltage and corresponding current gave the following table: 78 79 TABLE B—l. Heat Flux at different applied voltage V11 (volts) 4o 60 80 100 120 140 160 180 200 220 and current. (amp5) 1.00 1.34 1.69 2.03 q (kW/m2) 2.9 6.8 12.1 19.0 27.4 37.2 48.6 61.4 75.9 91.7 APPENDIX C CALCULATION OF ACTUAL SURFACE WALL TEMPERATURE It was shewn earlier in Figure 3.2 (Specimen Sketch) that the thermocouples wires were soldered inside the c0pper sleeVe by pouring soft solder through a drilled hole on the top of the sleeve at the midpoint. Therefore, the temperature readings recorded by the four thermocouples on the sleeve perifery will not record the surface wall temperature; instead they will give the temperatures of that particular point but we in fact are interested in finding out the surface wall temperature. This can be achieved by considering the thermal resistance involved between the point at which these thermocouple wires are soldered and the sur- face wall. The enlarged portion of the test specimen at which the thermocouples are soldered is shown in Figure Cl(a). The uniform heat flux, available at Section AA , will not distribute symmetrically. Instead, more heat flux will pass through the small area around the soldered grooved as the thermal resistance of surrounding area is less than that of the soldered part. (The thermal conductivity of c0pper is much higher than the thermal conductivity of the soldered part). Figure Cl(b) shows the temperature profiles. Point 1 is the actual surface wall temperature. Point 2 depicts 80 " I— O I—IIbO— m tube I Capper 850 -1b ——————— — — — — -— — I 4’ 928 I 2 3 Temp I l-A. A ‘ I HEAT FLUX 659 l (a) (0) /—-——-fi ------- TIC. a / ¥ T E sunounding )3 Tsurface (C) Figure C.l. Enlarged View of portion of the tube showing one of the thermocouple locations (not to scale). 82 the temperature to be recorded if there would have been no solder part in the heat flow path and Point.3 indicates the temperature being recorded in the present situation. Figure Cl(C) shews the horizontal temperature profile at the radius at which the thermocouple wires are soldered. The temperature value at the same radial section will be different inside the solder section and will be at a higher value than the corresponding c0pper section. The following analysis has been done to find out the temperature difference (.AT), at a particular value of applied heat flux between the surface and the point at which thermocouples are placed. ANALYSIS: ‘Thermocouples are soldered at a radius of 6.59 mm. Then the heat flux available at this surface will be (at a voltage of 220 volts and corresponding current value of 3.70 amperes). . _ P _ V I _ 220 x 3.70 _ 2 (Cl) qA — 3' _——§——— - 2 x x 6.59 x 0.152 - kWVm 2 firsl . where rS = radius at which solder starts (mm) 1 = length of the tube (m) then 4A: 129.3 kW/m2 Figure C2 shows five different situations for the analysis of the problem. Next we calculate the.AT equations in these five cases. (a) Figure C2(a) shows the section of the grooved solder part. Let us assume that X% of heat flux (qA) is passing through 83 A /Tub.e Thickness 0.775mm I Q -.....=J§ A" I . 1. 134mm 1. A0: Grooved 0 rec /'—Aa=Grooved area I TUE" Thi‘iknfls-"fi Ac: Surrounding area:A° Solder ' Copper (c) (L04) Tube Thickness A (IA +- (“1.x ) VI {/2 8.5mm: 0.590rnm 9.280 mm (d) (0) Figure C.2. Surface temperature computation analysis I (not to scale). 84 the solder and the rest of it through the surrounding area. Then ATa =qA . X . (R8 + Rt) where Rs = thermal resistance of solder part Rt = thermal resistance due to tube thickness or ATa = qAx ( 12%| + . J02: -) t ks where fixt = thickness of tube wall = 0.775 mm bxs = thickness of solder part = 1.913 mm kt = thermal conductivit ,of tube material = 0.242 kWVm-K (30) k = thermal conductivity of solder = 0.0465 kMV S - m-K (31) or . ATa = 0A X (0.0443) (C.2) NOW‘the problem is determining what percentage of the total heat flux is passing through the surrounding area and how much surrounding area will be affected due to this addié tional heat flux. We will compare equation C.2 with four other-relative situations and will evaluate the correct sur- faces wall temperature. (b) If we suppose that the additional heat flux is passing through a surrounding area equal to half of the solder area (Figure C2(b)), then the total heat flow equation can be written as: 85 Qc = qA Ac + QA (l-X) Aa where QC = total heat flow in section shown in Figure C2(b) AC = surrounding area Aa = grooved area If AS = 8 Aa then QC = qCAC -_- AC(qA + qA (1-x) 2:3) A c or qC = qA (1 + 2 (1-X)) ATb = qA (3-220 4. Re Re where Rc thermal resistance due to the c0pper sleeve = 6xc k c or ATb = qA (3-ZX) 6x9 02, _—k k, c bxc = thickness of c0pper material ; 1.913 mm k = thermal conductivity of copper material = 0.399HN c '15:: Mb =qA (3-2X) (0.0080) (c.3) 86 (c) The only difference between this case and (b) is that here we are considering that the surrounding area taking the additional heat flux is equal to the area of solder part. So the equation will be: ATC = qA (25X) (0.0080). _ (C.4) (d) In this situation we suppose that the additional heat flux is distributed to all the surrounding area along the length of the tube. This means that this heat will be dis- tributed radially and the composite cylinder form of thermal resistance will be applicable _ ° ._£_ 1 r. l r c r t r s c where Q = total heat available at radius rS kC = thermal conductivity of c0pper sleeve r c = outer radius of copper sleeve rt = radius of High Flux tubing now 0 = qA (2-X) 27rrsl (refer Figure 2c(d)). then .AT = q (2-X)' -£— 1n rc —l— 1n rt d A 1% k — + k (C.6) c r t -—— s r c AT = E11((2-X) 6.5875 1 ' 8.50 l 9.28. d '0".‘3‘9""9 "In _6.59 . +"“4‘0.2 2 1“ 8"‘—".50 (C.7) M6 = 9A (2-:X) (0.0066) (c.8) 87 (e) Next, we consider the extreme case for computing.AT 1w supposing that there is a_grooved of solder around the tube at the radius rs. This will give the smallest possible value of.AT and will help in estimating the most correct ,AT between the surface and soldered thermocouple. Again the radial heat flow equation of composite cylinderical section will be applicable or: _ "”1 ...r . . ATE - qux.rS(ES—- 1n rC + 1]; 1n rt) (C 8) s t r ° Or _ . .. 1 8.50 1 9.28 ' ATe ‘ ‘1A" 6'5875( 0.0465 .1“ 6.59“ + 0.242 1“ 8.50") ATe = qA:X'(0.03826) (c.9) The cases a, b, and c are closer to the actual heat' flow situations, where d and e have been computed to get an idea about the AT in extreme conditions. The table C-l gives a comparison of .AT calculated on the percentage of heat flux going through the soldered part (at different values of X). 88 Table Cul. Surface temperature correction comparative study. T at x=0.25 x=0.30 x=0.33 x=0.36 xe0.40 Fifial Sel'd. qu 129.3 kW/m2 §§39§1°f Ta 1.42 1.71 1.88 2.05 2.28 1.77 Tb 2.58 2.48 2.42 2.35 2.27 2.46 T5 1.81 1.75 1.72 1.69 1.65 1.74 Td 1.49 1.45 1.42 1.39 1.34 1.44 Te 1.24 1.48 1.63 1.78 1.98 1.53 The case(d)gives the smallest.AT. Additional heat flux is considered all over the c0pper sleeve and c0pper has high thermal conductivity. Case(e)gives a hypothetical case when there would have been a solder filled groove around the circumference of the tube; hence it is obvious that actual.AT will have a higher value than.ATe. Now case (b) and (c) are left to compare with (a) (actual situation). In situation (b) the additional area considered was half of the soldered area and the results are not comparable whereas in case(c)relatively nearer values ofATc are obi served with respect to (a). It is also noteworthy that there is an increase in value of AT by taking an increase in heat flux percentage through the soldered part and a corresponding 89 decrease just outside of it. The most correct value of Am I will be the one at which the.AT s (ATa & ATC) will be equal. But at the radius of 6.59 mm the value of AT; will be slightly higher than ATC so we will select the most correCt value of Am as the one at whichATa just became larger than Aflb and that value is found at a X value of 0.31. The corresponding.AT for the highest heat flux was found to be 1.77. Similar calculations for other heat fluxes yielded . the Table C.2. Table C.2. Corrected -.AT at Different Heat Flux. Vbltage VH Current I Heat Flux q" Heat Flux q. Correcthm (Volts) (amps) based on the§m- based on _ Appl'd.:. couples locat. outside dia. to AT (K.) (kMVhl) (kWVm ) 40 0.65 4.1 2.9 0.06 60 1.00 9.5 6.8 0.13 80 1.34 17.0 12.1 0.24 100 1.69 26.9 19.0 0.37 120 2.03 38.7 27.4 0.53 140 2.36 52.5 37.2 0.72 160 2.70 68.6 48.6 0.93 180 3.03 86.7 61.4 1.19 200 3.37“ 107.1 75.9 1.46 220 3.70 129.3 91.7 1.77 APPENDIX D EXPERIMENTAL DATA AND CORRECTED WALL SUPERHEAT Attached is the complete list of data redorded for the eXperimental work. The average temperature (Tw) is the average of the four thermocouple temperatures recorded. Tb is the bulk mixture temperature and the measuredfivalue onAT is the difference of Tw and Th. The corrected values of AT are found by applying the corrections calculated for the respective heat fluxes in Appendix C.‘ The tOp ten data points for each experiment are for increasing heat flux and the following nine for decreasing heat flux. The values for each mixture are listed for 1.01 bar as well as for 3.03 bar. 90 91 Table D.1.MIXTURE: Water Heat Flux 1.01 bar 1- 3.03 bar 9 (xv/m2) .1 . . frhcc) dez) :LAT (K) _ Tb(c) Tw(c) AT (K) Bulk Avg. Measid. Corr'd. Bulk Avg. Meas'd. Corr'd. 2.9 100 100.55 0.55 0.49 133.5 133.90 0.40 0.34 6.8 100 100.83 0.83 0.70 133.5 143.25 0.75 0.62 12.1 100 101.18 1.18 0.94 133.5 134.48 0.98 0.74 19.0 100 "101.53 1.53 1.16 133.5 134.83 1.33 0.96 27.4 100 101.98 1.98 1.45 133.5 135.35 1.85 1.32 37.2 100 102.50 2.50 1.78 133.5 135.78 2.28 1.56 48.6 100 103.13 3213 2.20 133.5 136.25 2.75 1.82 61.4 100 103.75 3.75 2.56 133.5 136.95 3.45 2.26 75.9 100 104.58 4.58 3.12 133.5 137.60 4.10 2.64 91.7 100 105.40 5.40 3.63 133.5 138.35 4.85 3.08 75.9 100 104.50 4.50 3.55 133.5 137.60 4.10 '2.64 61.4 100 103.73 3.73 3.10 133.5 136.95 3.45 2.26 48.6 100 103.13 3.13 2.56 133.5 136.25 2.75 1.82 37.2 100 102.50 2.50 2.20 133.5 135.78 2.28 1.56 27.4 100 101.95 1.95 1.75 133.5 135.35 1.85 1.32 19.0 100 101.43 1.43 1.35 133.5 134.83 1.33 0.96 12.1 100 101.13 1.13 1.11 133.5 134.48 0.98 0.74 6.8 100 100.80” 0.80 0.67 133.5 134.25 0.75 0.62 2.9 100 100.55 0.55 0.49 133.5 133.90 0.40 0.34 _ 92 Table D.2.MIXTURE: 5% ethanol-water Heat Flux 1.01 bar 3.03 bar c1 (KW/m2) Thm dez) AT (K) Tb(°c) Tw(°c) AT (K) Bulk Avg. Meas'd. Corr'd. Bulk Avg. Meas'd. Corr'd. 2.9 90:4 91.08 0.68 0.62 123.3 123.80 0.50 0.44 6.8 90.4 91.70 1.30 1.17 123.3 124.53 1.23 1.10 - 12.1 90.4 92.23 1.83 1.59 123.3 125.05 1.75 1.51 19.0 90.4 92.70 2.30 1.93 123.3 125.60 2.30 1.93 27.4 90.4 93.18 2.78 2.25 123.3 126.25 2.95 2.42 37.2 90.4 93.83 3.43 2:71? 123.3?126.75 3.45 2.73 48.6 90.4 94.38 3.98 3.05 123.3 127.38 4.08 3.15 61.4 90.4 95.15 4.75 3.56 123.3 127.95 4.65 3.46 75.9 90.4 95.80 5.40 3.94 123.3-128.63 5.33 3.87 91.7 90.4 96.68 6.28 4.51 123.3 129.43 6.13 4.36 75.9 90.4 95.80 5.40 3.94 123.3 128.63 5.33 3.87 61.4 90.4 95.13 4.73 3.54 123.3 127.95 4.65 3.46 48.6 90.4 94.38 3.98 3.05 123.3 127.35 4.05 3.12 37.2 90.4 93.85 3.45 2.73 123.3 126.58 3.28 2.56 27.4 90.4 93.25 2.85 2.32 123.3 126.13 2.83 2.30 19.0 90.4 92.75 2.35 1.98 123.3 125.43 2.13 1.76 12.1 90.4 92.20 1.80 1.56 123.3 124.88 1.58 1.34 6.8 90.4 91.70 1.30 1.17 .123.3 124.33 1.03 0.90 2.9 90.4 91.05 0.65 0.59 123.3 124.05 0.75 0.69 93 Table D.3.MIXTURE: 15% ethanol-water Heat Flux 1.01 bar 3.03 bar §:(kW/m2) o 6 6 Thc‘é) we) AT (K) Tbcc) Tw(c) AT (K) Bulk Avg. Meas'di Corr'd. Bulk Avg. Meas'd. Corr'd. 2,9 9454 '85.00 0.60 0.54., 116.4 116.83 0.43 0.37 6.8 84:4 ‘85.43 1.03 0.90 116.4 117.33 0.95 0.82 12.1 84.4 85.90 1.50 1.26 116.4 117.78 1.38 1.14 19.0 84.4 86.33 1.93 1.56 116.4 118.33 1.93 1.56 27.4 84.4 86.75 2.35 1.82 116.4 118.83 2.43 1.90 37.2 84.4 87.15 2.75 2.03 116.4 119.40 3.00 2.28 48.6 84.4 87.55 3.15 2.22 116.4 120.05 3.65 2.72 61.4 84.4 88.03 3.63 2.44 116.4 120.68 4.28 3.09 -75.9 84.4 88.53 4.13 2.67 116.4 121.28 4.88 3.42 91.7 84.4 89.23 4.84 3.06 116.4 122.05 5.65 3.88 75.9 84.4 88.53 4.13 2.67 '116.4 121.28 4.88 3.42 61.4 84.4 88.10 3.70 2.51. 166.4 120.65 4.25 3.06 43.5 84.4 87.43 3.03 2.10 166.4 119.83 3.43 2.50 37.2 84.4 87.05 2.65 1.93 166.4 119.12 2.72 2.00 27.4 84.4 86.48 2.08 1.55 166.4 118.57 2.17 1.64 19.0 84.4 86.00 1.60 1.23 166.4 188.07 1.67 1.30 12.1 84.4 85.73 1.33 1.09 166.4 117.58 1.18 0.99 5,3 84.4 85.45 1.05 0.88 166.4 117.15 0.75 0.62 2.9 84.4 84.98 0.58 0.52 166.4 116.78 0.38 0.32 94 Table D.4.MIXTURE: .30% ethanol—water Heat Flux 1.01 bar 3.03 bar q (mm/m2) The) TwC’c) M (K) T8 (2:) Twcé) AT (K) Bulk ' Avg. Meas'd. Corr‘d. Bulk Avg. Meas'd. Corr'd. 2.9 81.7 '82.30 0.60 0.54 113.4 113.63. 0.23 0.17 6.8 81.7 '82.65 0.95 0.82 113.4 113.93 0.53 0.40 12.1 81.7 83.10 1:40 1.16 113.4 114.48 1.08 0.84 19.0 81.7 83.43 1.73 1.36 113.4 114.83 1.43 1.06 27.4 81.7 83.78 2.08. 1.55 113.4 115.33 1.90 1.37 37.2 81.7 84.13 2.43 1.71 113.4 115.85 2.45 1.73 48.6 81.7 84.53 2.83 1.90 113.4 116.45 3.05 2.12 61.4 81.7 85.10 3.40 2.21 113.4 117.00 3.60 2.41 75.9 81.7 85.60 3.90 2.44 113.4 117.68 4.28 2.82 91.7 81.7 86.23 4.53 2.76 113.4 118.45 5.05 3.28 75.9 81.7 85.57 3.87 2.41 113.4 117.68 4.28 2.82 61.4 81.7 84.95 3.25 2.06 113.4 116.97 3.57 2.38 48.6 81.7 84.53 2.83 1.90 113.4 116.32 2.92 1.99 37.2 81.7 84.01 2.31 1.59 113.4 115.70 2.40 1.68 27.4 81.7 83.73 2.03 1.50 113.4 115128 1.95 1.32 19.0 81.7 83.23 1.53 1.16 113.4 114.78 1.38 1.01 12.1 81.7 82.90 1.20 0.96 113.4 114.48 1.08 0.84 6.8 81.7 82.53 0.87 0.74 113.4 113.93 0.53 0.40 2.9 81.7 82.22 0.52 0.46 113.4 113.68 0.28 0.22 95 Table D.5. MIXTURE: 45% ethanol-water Heat Flux 1.01 bar. 3.03 bar q (kW/m2) o o Thc‘c’n dez) AT (K) Tb(c) Tw(c) AT (K) Bulk Avg. Meas ’d. Corr'd. Bulk Avg. Meas'd. ,Corr'd. 2.9 80.3 '81.05 0.75 0.69 111.5 111.80 0.30 0.24 6.8 80.3 81.53 1.23 1.10 111.5 112.08 0.58 0.37 12.1 80.3 ‘81.80 1.50 1.26 111.5 112.30 0.80 0.56 19.0 80.3 82.13 1.83 1.46 111.5 112.68 1.18 0.81 27.4 80.3 82.35 2.05 1.52 111.5 113.23 1.73 1.20 37.2 80.3 82.83 2.53 1.81 111.5 113.90 2.40 1.68 48.6 80.3 83.23 2.93 2.00 111.5 114.53 3.03 2.10 61.4 80.3 83.80 3.50 2.31 111.5 115.03 3.53 2.34 75.9 80.3 84.38 4.08 2.62 111.5 115.88 4.38 2.92 91.7 80.3 85.00 4.70 2.93 111.5 116.70 5.20 3.43 75.9 80.3 84.90 4.20 2.79 111.5 115.91 4.41 2.95 61.4 80:3 83.80 3.50 2.31 111.5 115. 11 3.61 2.42 48.6 80.3 83.33 3.03 2.10 111.5 114.53 3.03 2.10 37.2 80.3 82.86 2.50 1.78 111.5 113.87 2:27 1.55. 27.4 80.3 82.38 2.08“ 1.55 111.5 113.05 1.11 1.01 19.0 80.3 81.98 1.68 1.31 111:5 112.65 1.11 0.78 12.1 80.3 81.63 1.33 1.09 111.5 112.22 0.72 0.48 6.8 80.3 81.35 1.05 0.92 111.5 112.00 0.50 0.37 2.9 80.3 81.03 0.73 0.67 111.5 111.75 0.25 0.19 '96 Table D.6. MIXTURE: 60%. ethanol—water Heat Flux 1.01 bar 3.03 bar» . 2 . q (mm )Th(°c) Twé) AT (K) TbCé) Tw(‘<’:) AT - » (9K)- Bulk Avg. Meas'd. Corr'd. Bulk Avg. Meas'd. Corr'd. 2.9 79.4 79.70 0:30 0.24 110-3 110.45 0.15 0.09 6.8 79.4 80.00 0:60 0.47. 110.3 110.58 0.28 0.15 12.1 79.4 ‘80.20 0.80 0.56 110.3 110.78 0.48 0.24 19.0 79.4 80.43 1.03 0.66 110.3 111.13 0.83 0.46 27-4 79.4 80.80 1.40 0.87 110.3 111.63 1.33 0.80 37.2 79.4 81.30 1.90 1.18 110.3 112208 1.78 1.06 48.6 79.4 81.70 2.30 1.37 110:3 112.48 2.18 1.25 61-4 79.4 82.15 2.75 1.56 110.3 113.33 3.03 1.84 75.9 79.4 82.58 3.18 1.72 110.3 114.08 3.78 2.32 91.7 79.4 83.08 3.68 1.91 110.3 114.83 4.53 2.76 7559 79.4 82.55 3.15 1.69 110.3 114.00 3.70 2.24 61.4 79.4 82.07 2.83 1.64 110.3 113.30 3.00 1.81 48.6 79.4 81.78 2.38 1.45 110.3 112.40 2.26 1.33 37.2 79.4 81.33 1.93 1.21 110.3 112.05 1.75 1.03 27.4 79.4 80.80 1.40 0.87 110.3 111.63 1.33 0.80 19.0 79.4 80.46 1.06 0.69 110.3 111.03 0.73 0.36 12.1 79.4 80.20 0.80 0.56 110.3 110.75 0.45 0.21 6.8 79.4 79.92 0.52 0.39 110.3 110.58 0.28 0.15 2.9 79.4 79.73 0.33 0.27 110.3 110.45 0.15 0.09 97 Table D-7oMIXTURE: 75% ethanol—water Heat Flux . 1.01 bar 3.03 bar a; (kw/r42) Thc‘é) Tw(%) AT- (K) T1366) Tw (2:) AT (K) Bulk Avg. Meas'd. Corr'd. Bulk Avg. Meas‘d. Corr'd. 2.9 78.7 78.95 0:25 0.19 ‘ 109.3 109.45 0.15 0.09 6.8 78.7 79.15 0.45 0.32 109.3 109.58 0.28 0.15 12.1 78.7 79.40 0.70 0.46 109.3 109.95 0.65 0.41 19.0 78.7 79.63 0.93 0.56 109.3 110.35 1.05 0.68 27.4 78.7 79.93 1.23 0.70 109.3 110.80 1.50 0.97 37.2 78.7 80.25 1.55 0.83 109.3 111.40 2.10 1.38 48.6 78.7 80.78 2.08 1.15 109.3 112.03 2.73 1.80 61.4 78.7 81.38 2.68 1.49 109.3 112.73 3.43 2.24 75.9 78.7 82.05 3.35 1.89 109.3 113.30 4.00 2.54 91.7 78.7 82.75 4.05 2.28 109.3 113.98 4.68 2.91 75.9 78.7 82.02 3.32 1.86 109.3 113.15 3.85 2.39 61.4 78.7 81.51 2.81 1.62 109.3 112.25 2.95 1.76 43.5 78.7 81.08 2.38 1.45 109.3 111.58 2.28 1.35 37.2 78.7 80.68 1.98 1.26 109.3 111.13 1.83 1.11 27.4 78.7 80.18 1.48 0.95 109.3 110.70 1.40 0.87 19,0 78.7 79.83 1.13 0.76 109.3 110.28 0.98 0.61 12.1 78.7 79.53 0.83 0.59 109.3 109.95 0.65 0.41 6.8 78.7 79.15 0.45 0.32 109.3 109.58 0.28 0.15 2.9 78.7 78.95 0.25 0.19 109.3 109.35 0.05 0.02 98 Table D . 8 . MIXTURE: 89 . 4% ethanol—water Heat Flux 1.01 bar 3.03 bar 6'; (Raw’mz) Th (°c) M (K) (K) Bulk Avg. Meas 'd. Corr'd. Bulk Avg. Mea's'd. Corr'd. dez) Tb(‘?:) Tw(°c) AT 78.5 2.9 78.73 0.23 0.17 109.1 109.23 0.13 0.07 6.8 78.5 78.98 0.48 0.35 109.1 109.50 0.40 0.27 12.1 78.5 79.25 0.75 0.51 109.1 109.88 0.78 0.54 19.0 78.5 79.58 1.08 0.71” 109.1 110.18 1.08” 0.71 27.4 78.5 79.93 1.43 0.90 109.1 110.50 1.40 0.87 37.2 78.5 80.33 1.83 1.11 109.1 110.88 1.78 1.06 48.6 78.5 80.80 2.30 1.37 109.1 111.33 2.23 1.30 61.4 78.5 81.33 2.83 1.64 109.1 111.75 2.65 1.46 75.9 78.5 81.90 3.40 1.94 109.1 112.23 3.13 1.67 91.7 78.5 82.55 4.05 2.28 109.1 112.73 3.63 1.86 75.9 78.5 81.87 3.37 1.91 109.1 112.08 2.98 1.52 61.4 78.5 81.25 2.75 1.56 109.1 111.51 2.42 1.33 48.6 78.5 80.62' 2.12 1.10 109.1 111.13 2.03 1.10 37.2 78.5 80.30 1.80 1.08 109.1 110.75 1.65 0.93 27.4 78.5 79.85 1.35 0.82 109.1 110.37 1.27 0.74 19.0 78.5 79.37 0.87 0.68 109.1 110.00 0.90 0.53 12.1 78.5 79.14 0.64 0.51 109.1 109.63 0.53 0.29 6.8 78.5 78.93 0.43 0.30 109.1 109.35 0.25 0.12 2.9 78.5 78.76 0.26 0.20 109.1 109.23 0.13 0.07 99 Table D. 9 . MIXTURE: 100% ethanol Heat Flux 1.01 bar 3.03 bar <1 (kW/"121 0 0 Tb(°c) Tw(2:) AT (K) Tb(c) Tw(c) AT (K) Bulk Avg. Meas’d. Corr'd. Bulk Avg. Meas'd. Corr'd. 2.9 78.4 78.65 0.25 0.19 109.2 109.35 0.15 0.09 6.8 78.4 78.83 0.43 0.30 109.2 109.45 0.25 0.12 12.1 78.4 79.05 0.65 0.41 109.2 109.68 0.48 0.24 19.0 78.4 79.30 0.90 0.53 109.2 109.95 0.75 0.38 27.4 78.4 79.60 1.20 0.67 109.2 110.23 1.03 0.50 37.2 78.4 79.98 1.58 0.86 109.2 110.53 1.33 0.61 48.6 78.4 80.40 2.00 1.07 109.2 110.95 1.75 0.82 61.4 78.4 80.93 2.53 1.34 109.2 111.40 2:20 1.01 75.9 78.4 81.40 3.00 1.54. 109.2 111.85 2.65 1.19 91.7 78.4 82.00 3.60 1.83 109.2 112.43 3.23 1.46 75.9 78.4 81.27 2.87 1.42 109.2 111.88 2.68 1.22 61.4 78.4 80.75 2.35 1.16 109.2 111.40 2:20‘ 1.01 48.6 78.4 80.32 1.92 0.99 109.2 110.92 1.72 0.79 37.2 78.4 80.13 1.73 1.01 109.2 110.43 1.23 0.51 27.4 78.4 79.75 1.35 0.82 109.2 110.13 0.93 0.40 19.0 78.4 79.40 1.00 0.63 109.2 109.85 0.65 0.28 12.1 78.4 79.13 0.73 0.49 109.2 109.53 0.33 0.09 6.8 78.4, 78.93 0.53 0.40 109.2 109.46 0.23 0.10 2.9 78.4 78.70 0.30 0.24 109.2 109.25 0.05 -0.01 100 Table D.10. MIXTURE: 92% ethanol-benzene Heat Flux ° 1.01 bar 3.03 bar- . 2 q Wm )Tbc‘e) Tth) AT (K) dez) Tw(?:) fiAT - ~ - -(-K)- - ~ Bulk Avg. Meas'd. Corr'd. Bulk Avg. Meas'd. Corr'd. 2.9 73.8' 74.33 0.53 0.47 108.9 106.43 0.53 0.47 6.8 73.8"74.70 0.90 0.77 105.9 106.65 0.75 0.62 12.1 73.8 75.05 1.25 1.01 105.9 107.45 1.15 0.91 19.0 73.8 75.38 1.58 1.12 105.9 107.45 1.55 1.18 27.4 73.8 75.95 2.15 1.62 105.9 107.98 2.08 1.55 37.2 73.8 76.50 2.70 1.98 105.9 108.53 2.63 1.91 48.6 73.8 77.08 3.28 2.35 105.9 109.05 3.15 2.22 '61.4 73.8 77.70 3.907 2.71 105.9 109.63 3.73 2.54 75.9 73.8 78.33 4.53 3.07 .105.9 110.23 4.33 2.87 91.7 73.8 78.93 5.13 3.36 105.9 110.88 4.98 3.21 75.9 73.8 78.25. 4.45 2.99 105.9 110.13 4.23 2.77 61.4 73.8 77.57 3.77 2.58 105.9 109.63 3.73 2.54 48.6 73.8 77.08 3.28 2.35 105.9 108.95 3.05 2.12 37.2 73.8 76.58 2.78 2.06 105.9 108.33 2.43 1.71 27.4 73.8 76.05 2.25 1.72 105.9 107.78 1.88 1.35 19.0 73.8 75.56 1.76 1.39 105.9 107.40 1.50 1.13 12.1 73.8 75.20 1.40 1.16 105 9 107.00 1.10 0.86 6.8 73.8 74.73 0.93 0.80 105.9 106.59 0.69 0.62 2.9 73.8 74.33 0.53 0.47 105.9 106.42 0.52 0.49 101 Table D.11 MIXTURE: 85% ethanol-benzene Heat Flux . 1.01 bar 3.03 bar c1 (kW/111,2) o o . Thcc) Twc‘b) M: (K) The) Tw(c) AT (K) Bulk' Avg. Meas'd. Corr'd. Bulk Avg. Meas'd. Corr'd. 2.9 71.8 72.50 0.70 0.64 104.1 104.38 0.28 0.22 6.8 71.8 72.80 1.00 0.87 104.1 104.63 0.53 0.40 12.1 71.8 73.08 1.28 1.04 104.1 104.95 0.85 0.61 19.0 71.8 73.40 1.60 1.23 104.1 105.33 1.23 0.86 27.4 71.8 73.80 2.00 1.47 104.1 105.70 1.60 1.07 37.2 71.8 74.23 2.43 1.71 104.1 106.25 2.15 1.43 48.6 71.8 74.73 2.93 2.00 104.1 106.80 2.70 1.77 61.4 71.8 75.40 3.60 2.41 104.1 107.30 3.20 2.01 75.9 71.8 76.10 4.30 2.84 104L1 107.85 3.75 2.29 91.7 71.8 76.85 5.05 3.28 104.1 108.55 4.45 2.68 75.9 71.8 76.07 4.27 2.81 104.1 107.80 3.70 2.24 61.4 71.8 75.43 3.63 2.43 104.1 107.25 3.15 1.96 48.6 71.8 74.81 3.01 2.08 104.1 106.83 2.73 1.80 37.2 71.8 74.31 2.51 1.79 104.1 106.30 2,20 1.48 27.4 71.8 74.02 2.22 1.69 104.1 105.85 1.75 1.22 19.0 71.8 73.65 1.85 1.48 104.1 105.50 1.40 1.03 12.1 71.8 73.28 1.48 1.24 104.1 105.05 0.95 0.71 6.8 71.8 72.90 1.10 0.97 104.1 104.73 0.63 0.50 2.9 71.8 72.58 0.78 0.72 104.1 104.43“ 0.33 0.27 102 Table D. 12.MIXTURE: 75% ethanol—benzene Heat Flux 1.01 bar 3.03 bar 6 (mu/m2) o 0 Th (9:) Tnm AT (K) Tb (c) Tw (c) AT (K) Bulk Avg. Meas'd. Corr‘d. Bulk Avg. Meas'd. Corr'd. 2.9 69.8 70.80 1:00 0.94 ’102.7 103.00 0.30 0.24» 6.8 69.8 71.23 1.43 1.30 102.7 103.25 0.55 0.42 12.1 69.8 71.60 1.80 1.56 102.7 103.60 0.90 0.66 19.0 69.8 71.98 2.18 1.81 102.7 103.98 1.28 0.91 27.4 69.8 72.43 2.63 2.10 102.7 104.43 1.73 1.20 37.2 69.8 72.90 3.10 2.38 102.7 104.90 2.20 1.48 48.6 69.8. 73.40 3.60 2.67 102.7 105.38 2.68 1.75 61.4 69.8 74.00 4.20 30.1 102.7 105.93 3.23 2.04 75.9 69.8 74.60 4.80 3.34 102.7 106.50 3.80 2.34 91.7 69.8 75.25 5.45 3.68 102.7 107.18 4.48 2.71 75.9 69.8 74.55 4.75 3.29 102.7 106.58 3.88 2.42 61.4 69.8 73.97 4.17 2.98 102.7 106.01 3.31 2.12 48.6 69.8 73.43 3.63 2.70 102.7 105.46 2.76 1.83 37.2 69.8 72.95 3.15 2.43 102.7 104.90 2.20 1.48 27.4 69.8 72.46 2.66 2.13 102.7 104.40 1.70 1.17 19.0 69.8 72.06 2.26 1.89 102.7 103.98 1.28 0.91 12.1 69.8 71.65 1.85 1.61 102.7 103.60 0.90 0.66 6.8 69.8 71.20 1.40 1.27 102.7 103.33 0.63 0.50 2.9 69.8 70.83 1.03 0.97 102.7 103.08 0.38 0.32 103 Tab.e D.l3. MIXTURE:' 60% ethanol—benzene Heat Flux 1.01 bar 3.03 bar , <1 (kW/I02) o 0 Th(?:) Tw(°c) AT (K) Th (c) '1‘w (c) AT (K) Bulk Avg. Meas'd. Corr‘d. Bulk Avg. Meas'd. Corr'd. 2.9 68.5 69.50 1.00 0.94 102.0 102-30 0.30 0.24 6.8 68.5 69.85 1:35 1..22 102.0 102.55 0.55 0.42 12.1 68.5 70.40 1.90 1.66 102.0 102.85 0.85 0.61 19.0 68.5 70.95 2.45 2.08 102.0 103.25 1.25 0.88 27.4 68.5 71.55 3.05 2.52 102.0 103.70 1.70 1.17 37.2 68.5 72.25 3.75 3.03 102.0 104.28 2.28 1.56 48.6 68.5 73.00 4.50 3.57 102.0 104.88 2.88 1.95 61.4 68.5 73.70 5.20 4.01 102.0 105.50 3.50 2.31 75.9 68.5' 74.45 5.95 4.59 102.0 106.23 4.23 2.77 91.7 68.5 75.18 6.68 4.91 102.0 106.95 4.95 3.18 75.9 68.5 74.35 5.85 4.49 102.0 106.15 4.15 2.69 61.4 68.5 73.60 5.10 3.91 102.0 105.42 3.42 2.23 48.6 68.5 72.85 4.35 3.42 102.0 104.80 2.80 1.87 37.2 68.5 72.15 3.65 2.93 102.0 104.28 2.28 1.56 27.4 68.5 71.35 2.85 2.32 102.0 103.73 1.73 1.20 19.0 68.5 70.80 2.30 1.93 102.0 103.25 1.25 0.88 12.1 68.5 70.35 1.85 1.61 102.0 102.85 0.85 0.61 6.8 68.5 69.85 1.35 1.22 102.0 102.50 0.50 0.37 2.9 68.5 69.50 1.00 0.94 102.0 102.50 0.25 0.19 104 45%.ethanol—benzene Table D. 14.MIXTURE: Heat Flux 1.01 bar 3.03 bar . . 2 q (kW/m )Thdfl Tw(2:) AT (K1 T1) (°c) Tw(‘c’:) AT (K) Bulk Avg. Meas'd. Corr'd. Bulk Avg. Meas'd. Corr'd. 2.9 68.2 68.80 0.60 0.54 102.0 102.30 0.30 0.24 6.8 68.2 69.15 0.95 0.82 102.0 102.55 0.55 0.42 12-1 68.2 69.50 1.30 1.06 102.0 102.90 0.90 0.66 19.0 68.2 69.95 1.75 1.38 102.0 103.35 1.35 0.98 27-4 68.2 70.40 2.20 1.67 102.0 103.78 1.78 1.25 37-2 68.2 70.95 2.75 2.03 102.0 104.35 2.35 1.63 48-6 68.2 71.55 3.35 2.42 102.0,104.90 2.90 1.97 61.4 68.2 72.30 4.10 2.91 102.0 105.58 3.58 2.39 75-9 68.2 73.10 4.90 3.44 102.0 106.30 4.30 2.84 91.7 68.2 74.05 5.85 4.08 102.0 107.08 5.08 3.31 75.9 68.2 73.02 4.82 3.36 102.0 106.30 4.30 2.84 61.4 68.2 72.30 4.10 2.91 102.0 105.65 3.65 2.46 48.6 68.2 71.60 3.40 2.37 102.0 104.95 2.95 2.02 37.2 68.2 70.85 2.65 1.93 102.0 104.45 2.45 1.73 27.4 68.2 70.35 2.15 1.62 102.0 103.73 1.73‘ 1.20 19.0 68.2 69.85 1.65 1.28 102.0 103.35 1.35 0.98 12.1 68.2 69.40 1.20 0.96 102.0 102.90 0.90 0.66 6.8 68.2 69.05 0.85 0.72 102.0 102.55 0.55 0.42 2.9 68.2 68.80 0.60 0.54 102.0 102.30 0.30 0.24 105 ' Table D. 15oMIXTURE: 30% ethanol—benzene Heat Flux _l.01 bar 3.03 bar 0 (kW/m2) . . ' That) I‘ve) AT (K) Tb(c) Tw(c) AT (K) Bulk Avg. Meas'd. Corr'd. Bulk Avg. Meas'd. Corr'd. 2.9 68.6 69.40 0.80 0.74 '103.0 103.90 0.90 0.84 6.8. 68.6 69.68 1.08 0.95 103.0 104.35 1.35 1.22 12.1 68.6 70.10 1.50 1.26 103.0 104.80 1.80 1.56 19.0 68.6 70.60 2,00 1.63 103.0 105.30 2.30 1.93 27.4 68.6 71.15 2.55 2.02 103.0 105.98 2.98 2.45 37.2 68.6 71.70 3.10 2.38 103.0 106.55 3.55 2.83 48.6 68.6 72.35 3.75 2.82 103.0 107.28 4.28 3.35 61.4 68.6 73.10 4.50 3.31 103.0 108.08 5.08 3.89 75.9 68.6 73.90 5.30 3.84 103.0 108.93 5.93 4.47 91.7 68.6 74.83 6.23 4.46 103.0 109.73 6.73 4.96 75.9 68.6 74.00 5.40 3.94 .103.0 108.88 5.88 4.42 61.4 68.6 73.20 4.60 3.41 .103.0 108.05 5.05 3.86 48.6 68.6 72.45 3.85 2.92 103.0 107.23 4.23 3.30 37.2 68.6 71.73 3.13 2.41 103.0 106.50 3.50 2.78 27.4 68.6 71.12 2.52 2.05 103.0 105.90 2.90 2.37 19.0 68.6 70.60 2.00 1.63 103.0 105.22 2.22 1.85 12.1 68:6 70.15 1.55 1.31 103.0 104.65 1.65 1.41 6.8 68.6 69.70 I 1.10 0.97 103.0 104.25 1.25 1.12 2.9 68.6 69.40 0.80 0.74 103.0 103.87 0.87 0.81 106 Table D. 16. MIXTURE: ‘ 15% ethanol—benzene Heat Flux 1.01 bar .3.03 bar <1 (KT/m2) . . . ThC’c) dez) AT (K) Tb(c) Tw(c) AT - (K) Bulk . Avg. Meas'd. Corr'd. Bulk Avg. Meas‘d. Corr'd. 2.9 69.7 70:90 1.20 1.14 106.0 107.25 1.25 1.19 6.8 69.7 71.43 1.73 1.60 106:0 107.95 1.95‘ 1.82 12.1 69.7 72.00 2.30 2.06 106.0 108.73 2.73 2.49 19.0 69.7 72.68 2.98 2.61 106.0 109.48 3.48 3.11 27.4 69.7 73.45 3.75 3.22 106.0 110.38 4.38 3.85 37.2 69.7 74.30 4.60 3.88 106.0 111.38 5.38 4.66 48.6 69.7 75.28 5.58 4.65 106.0 112.50 6.50 5.57 61.4 69.7 76.35 6.65 5.46 106.0 113.60 7.60 6.41 75.9 69.7‘ 77.53 7.83 6.37 106:0 114.88 8.88 7.42 91.7 .69.7 178.68 8.98 7.21 106.0 116.08 10.08 8.31 75.9 69.7 77.50 7.80 6.34 106.0 114.80 8.80 7.34 61.4 69.7 76.35 6.65 5.46 106.0 113.58 7.58 6.39 48.6 69.7 75.25 5.55 4.62 106.0 112.48 6.48 5.55 37.2 69.7 74.27 4.57 3.85 106.0 111.33 5.33 4.61 27.4 69.7 73.42 3.72 3.19 106.0 110.45 4.45 3.92 19.0 69.7 72.68 2.98 2.61 106.0 109.50 3.50 3.11 12.1 69.7 72.03 2.33 2.09 106.0 108.75 2.75 2.51 6.8 69.7 71.43 1.73 1.60 106.0 107.95 1.95 1.82 2.9 69.7 70.98 1.28 1.22 106.0 107.25 1.25 1.19 107 Table D.17..MIXTURE: 5% ethanol-benzene .Heat Flux .l.01 bar 3.03 bar . (.1 (kW/m2; o o . T5022) Twce) AT (K) Tb (c) Tw(c) AT. (K) Bulk Avg. Meas'd. Corr'd. Bulk Avg. Meas'd. Corr'd. 2.9 73.2 75.50 2.30 2.24 112.5 114.20 1.70 1.64 6.8 73.2 76.05 2.85 2.72 112.5 114.95 2.45 2.32 12.1 73.2 76.60 3.40 3.16 112.5 115.85 3.35 3.11 - 19.0 73.2 77.45 4.25 3.88 112.5 116.68 4.18 3.81 27.4 73.2 78.30 5.10 4.57 112.5 117.48 4.98 4.45 37.2 73.2 79.30 6.10 5.38 112.5 118.43 5.93 5.21 48.6 73.2 80.33 7.13 6.20 112.5 119.30 6.80 5.87 61.4 73.2 81.43 8.23 7.04 112.5 120.30 7.80 6.61 75.9 73.2 82.53 9.33 8.87 112.5 121.45 8.95 7.49 91.7 73.2 83.78 10.58 8.81 112.5 122.68‘10.l8 . 8.41 75.9 73.2 82.48 9.28 7.82 112.5 121.45 8.95 7.49 61.4 73.2 81.40 8.20 7.01 112.5 120.25 7.75 6.56 48.6 73.2 80.30 7.10 6.17 112.5 119.30 6.80 5.87 37.2 73.2 79.28 6.08 5.36 112.5 118.43 5.90 5.18 27.4 73.2 78.28 5.08 4.55 112.5 117.48 4.98 4.45 19.0 73.2 77.38 4.18 3.81 112.5 116.65 4.15 3.78 12.1 73.2 76.60 3.40 3.16 112.5 115.90 3.40 3.16 6.8 73.2 76.05 2.85 2.72 112.5 114.95 2.45 2.32 2.9 73.2 75.55 2.35 2.29 112.5 114.25 1.75 1.69 1.08 Table. D.18.MIXTURE: 100% benzene Heat Flux 1.01 bar 3.03 bar 9IIKV/m2) o - o 6 ThCC) Tw(%) AT (K) Tb(c) Tw(c) .AT (K) Bulk Avg. Meas'd. Corr'd. Bulk Avg. Meas'd. Corr'd. 2.9 80.0 80.70 0.70 0.64 120.0 120.25 0.25 0.19 6.8 80.0 80.98 0.98 0.85 120.0 120.45 0.45 0.32 12.1 80.0 81.38 1.38 1.14 120.0 120.75 0.75 0.51 19.0 80.0 81.83 1.83 1.46 120.0 121.13 1.13 0.76 27.4 80.0 82.33 2.33 1.80 120.0 121.65 1.65 1.12 37.2 80.0 82.85 2.85 2.07 120.0 122.25 2.25 1.53 48.6 80.0 83.48 3.48 2.55 120.0 122.80 2.80 1.87 61.4 80.0 84.05 4.05 2.86 120.0 123.43 3.43 2.24 75.9 80.0 84.83 4.83 3.36 120.0 124.08 4.08 2.62 91-7 80.0 85.58 5.58 3.81 120.0 124.75 4.75 2.98 75.9 80.0 84.85 4.85 3.38 120.0 124.10 4.10 2.64 61.4 80.0 84.10 4.10 2.91 120.0 123.35 3.35 2.16 48.6 80.0 83.50 3.50 2.57 120.0 122.78 2.78 1.85 37.2 80.0 82.95 2.95 2.17 120.0 122.28 2.28 1.56 27.4 80.0 82.40 2.40 1.87 120.0 121.68 1.68 1.15 19.0 80.0 81.93 1.93 1.56 120.0 121.20 1.20 0.83 12.1 80.0 81.43 1.43 1.10 120.0 120.88 0.88 0.64 5.3 80.0 81.03 1.03 0.90 120.0 120.55 0.55 0.42 2.9 80.0 80.70 0.70 0.64 120.0 120.30 0.30 0.24 eI APPENDIX E CALCULATIONS FOR LOCAL RISE IN BOILING POINT FOR ENHANCED SURFACE The local rise in boiling point,Afl, is plotted in Figures 5.2 through 5.5 for the ethanol—water and ethanol— benzene systems on enhanced and smooth surfaces. The calculation forAO requires ATI (ideal wall superheat) . TheATI calculation and corresponding values are computed in this Appendix. The ideal mixing law is defined as: AT *5?- 1 "Si '- 34' AT left of azeotrope (E.l) I ':" 'x] ATAZ + ( :2 I l az az and ATI £1 - Kaz 3‘62 = TIT—it— wait—1:2- )flaz right of azeotrope (E.2) - az az The required values ofATI at different compositions of a binary mixture at any constant heat flux can be easily computed if we have experimental values of.ATaz, AT, and .AT (pure component wall superheats) for that binary mix- 2 ture at the respective composition and heat flux. A sample calculation forATI for an ethanol-water system is presented for a heat flux value of 2.9 kWsz. From our data for the enhanced surface the following values are obtained: 109 110 .ATaz = wall superheat of ethanoldwater system at the azeotrope (0.894 mole fraction) at a heat flux of 2.9 kwym2 = 0.17 K AT1 = water wall superheat at 2.9 k‘W/m2 = 0.49 K xaz = 0.894 then equation (E1) for q = 2.9 kw/m2 becomes: AT = 0.17 '56: + 0.49 (52 -‘§.;) I _0.894 0.894 az 1 or ATI = 0.1902 x. _+ 0.5481 bcaz - 2.1) (E.3) Now, this equation will be used to find outATI at different values of ethanol mole fraction 651). The results are tabulated as follows where A9 is equal to (AT - ATI) : 111 TABLE 13.1. ATI andAOfor Ethanol—water system at 2.9 kMsz. 9 “375 _(ethanol)ATI (K) AT (K) A0: AT— ATI (K) 0 0 49 0.49 0 0.05 0.47 0.62 0.15 0.15 0.44 0.54 0.10 0.30 0.38 0.54 0.16 0.45 0.33 0.69 0.36 0.60 0.28 0.24 ' -0.04 0.75 0.22 0.19 -0.03 0.894 0.17 0.17 0 1.00 0.19 0.19 0 Note thatAlT is taken from Appendix D and is the actual AT obtained at the respective mole fraction at a heat flux value of 2.9 Kmymz. The equations similar to E.3 for other heat fluxes are similarly obtained. Note that equation E.2 is not used in the ethanol-water case as there are no data points obtained between azeotrope and pure ethanol. Tables E.2 through E.4 show values calculated at some of the other heat fluxes. 112 TABLE E.2. ATI and A0for ethanol—water system at 27.4 kW/mz. i (ethanol)ATI (K) AT (K) ‘ A0(K) 0 1.45 1.45 0 0.05 1.42 2.25 0.83 0.15 1.36 1.82 0.46 0.30 1.27 1.55 0.28 0.45 1.17 1.52 0.35 0.60 1.08 0.87 -0.21 0.75 0.99 0.70 -0.29 0.894 0.90 0.90 0 1.00 0.67 0.67 0 113 TABLE E.3. ATI and A0 for ethanol—water system at 75.9 Id(i/mz. 3? (ethanol) ATI (K) * AT (K) A0(K) 0 3.12 3.12 0 0.05 3.05 3.94 0.89 0.15 2.92 2.67 -0.25 0.30 2.72 2.44 -0.28 0.45 2.53 2.62 0.09 0.60 2.33 1.72 -0.61 0.75 2.13 1.89 -0.24 0.894 1.94 1.94 O 1.00 1.54 1.54 0 114 TABLE E.4. ATI and A6 for ethanol-water system at 91.7 kW/mz. 32' (ethanol) ATI (K) AT (K) . A0(K) 0 3.63 3.63 0 0.05 3.55 4.51 0.96 0.15 3.40 3.14 -0.34 0.30 3.18 2.76 -0.42‘ 0.45 2.95 2.93 -0.02 0.60 2.72 1.72 -l.00 0.75 2.50 2.28 -0.22 0.894 2.28 2.28 0 1.00 1.83 1.83 0 All these tabulated data are plotted in Figure 5.2. Ethanol-benzene System. The ethanol-benzene system has an azeotrope at X1 = 0.45. The data in this system lie to each side of the azeotrope. The twoATI expressions were computed using equations E1 and E2. The corresponding Values are tabulated in tables E5 through E8. TABLE E.5. 115 ATI and.06for ethanol-benzene system at 2.9 kW/mz. A600 1.61 0.53 0.17 0.50 0.59 0.35 0.23 116 TABLE E.6. AT and A0 for ethanol-benzene system at 1 27.4 kW/mz. zr(ethanol) ATI (K) AT (K) A0(K) 0 1.80 1.80 0 0.05 1;79 4.57 2.78 0.15 1.76 3.22 1.46 0.30 1.71 2.02 0.31 0.45 1.67 1.67 0 0.60 1.40 2.52 1.12 0.75 1.12 2.10 0.98 0.85 0.94 1.47 0.53 0.92 0.82 1.62 0.80 1.00 1.67 1.67 0 117 TABLE E.7. ATI andHAOfor ethanol-benzene system at 75.9, kW/mz. 35(et'hanol) ATI (K) AT (K) 00(K) 0 3.36 3.36 0 0.05 3.37 7.87 4.50 0.15 3.39 6.37 2.98 0.30 3.41 3.84 0.43 0.45 3.44 3.44 0 0.60 2.92 4.59 1.67 0.75 2.40 3.34 0.94 0.85 2.06 2.84 0.78 0.92 1.82 3.07 1.25 1.00 1.54 1.54 o TABLE E.8. ATI and A0 for ethanol-benzene system at 91.7 3? (ethanol) 0 0.05 0.15 0.30 0.45 1.83 AT (K) 1.83 A9(K) These tabulated values are plotted in Figure 5.4. APPENDIX F LOCAL RISE IN BOILING POINT FOR SMOOTH SURFACE The data for Figure 5.3 has been taken from the results of other inveStigators, who have teeted smooth surfaces for the ethanol-water system. Their reSults are presented here for ready reference. TABLE F.l Shakir (19) data at q: 200 kW/m2 for ethanol- water system. 119 iiethanol) ATI (K) AT (K) A0(K) 0 12.71 12.71 0 0.06 12.91 20.20 7.29 0.11 13.08 22.48 9.40 0.20 13.39 21.46 8.07. 0.31 13.76 20.37 6.61 0.51 14.44 20.37 5.93 0.68 15.01 18.65 3.64 0.78 15.35 16.95 1.60 0.91 15.79 15.79 0 1.00 -- -- 0 120 TABLE F.2. Valent and Afghan (23) data at q = 190 kW/m2 for ethanol—water systsm. 32 (ethanol) ATI (K) AT (K) 0 21.8 21.8‘ 0.053 22.2 28.1 0.094 22.6 '32.6 0.12 22.8 37.4 0.17 23.2 35.7 0.24 23.75 33.9 0.55 26.2 31.8 1.0 29.9 TABLE F.3. 33' (ethanol) All these tabulated values are plotted in Figure 5.3. ATI (K) 11.5 11.9 12.0 12.4 13.2 14.2 15.3 18.1 23.4 AT (K). 11.5 18.2 19.7 22.0 24.9 25.5 26.0 26.0 23.4 Tolubinskiy and Ostrovskiy (24) data at 116 ldN/m2 for ethanolewater system. A0(K) 11.7 11.3 10.7 7.9 122 Ethanol-benzene System The data values for the local rise in the boiling point for the ethanol—benzene system on smooth surfaces are also taken from other investigator's results: I TABLE F.4. Happel and Stephan (25) data at q = 100 kW/m2 for ethanol-benzene system. K(ethano1) ATI(K) AT (K) A0(K) 0 18.3 18.3 0 0.146 17.1 20.5 3.4 0.277 16.0 19.0 3.0 0.434 14.7 14.7 0 0.861 12.4 16.4 4.0 0.991 11.9 16.3 4.4 1.00 11.6 11.6 123 TABLE 5.5. Grigorev et. a1 (26) data at q =_232 kW/m2 for ethanol-benzene system. 19.8 19.8 36 (ethanol) ATI (K) AT (K) A0(K) ’0 29.1 29.1 0 — 0.037 28.7 31.65 2.95 0.065 28.4 32.70 4.30 0.089 28.1 32.10 4.0 0.129 27.6 29.8 2.2 0.178 27.0 28.1 1.1 0.233 26.4 27.04 0.64 0.345 25.1 25.5 0.40 0.40 24.5 _24.5 0 I 0.447 24.1 25.36 1.26 0.541 23.4 23.40 0 0.645 22.7 23.75 1.05 0.74 22.1 25.5 3.4 0.83 21.1 25.1 4.0 0.93 20.4 22.7 2.3 124 TABLE F.6.. Shakir (19;) data at q =.l70 law/m2 for ethanol-benzene system. 5?. (ethanol) AT I (K) - AT (K) A0(K) 0 16.22 16.22_ 0 0.10 15.61 20.83 5.22 0.22 14.89 17.31 2.42 0.31 14.34 15.34 2.0 0.45 13.49 13.49 0 0.62 13.19 13.64 0.45 0.70 13.05 14.26 1.21 ‘0.90 12.70 14.21 1.51 1.00 12.52 0 Figure 5.5. 12.52 These tabulated values are plotted in LIST OF REFERENCES Fujii, M., Nishiyama, E., and Yamanaka, G., Nucleate Pool Boiling Heat Transfer from Micro-Porous Heating Surface, in'AdvanceS'in Enhanced Heat Transfer, eds. J. M. Chenoweth et al., pp. 45—51, ASME, New York, 1979. Bergles, A. E. and Chyu, M. C., Characteristics of Nucleate Pool Boiling from Porous Metallic Coatings, in Advances in Enhanced Heat Transfer--198l, eds. R. L. Webb et al., pp. 61-71, ASME, New York, 1981. Yilmaz, S. and Westwater, J. W., Effect of Commercial Enhanced Surfaces on the Boiling Heat Transfer Curve, in Advances in Enhanced Heathransfer--l981, eds. R. L. Webb et al., pp. 73-91, ASME, New York, 1981. Marto, P. J. and Kepere, J., Pool Boiling Heat Transfer from Enhanced Surfaces to Dielectric Fluids, in Advances in Enhanced Heat Transfer--198l, eds. R. L. wean et al., pp. 93-102, ASME, New York, 1981. ' Carnavos, T. C., An Experimental Study: Pool Boiling R-ll with Augmented Tubes, in Advances in Enhanced Heat Transfer-~1981, eds. R. L. Webb et al., pp. 103-108, ASME, New York, 1981. Stephan, K. and Mitrovic, J., Heat Transfer in Natural Convective Boiling of Refrigerants and Refrigerant—Oil- Mixtures in Bundles of T-Shaped Finned Tubes, in Advances in Enhanced Heat Transfer--l981, eds. R. L. Webb et aIi, pp. 13I¥I46, ASME, New Yofk, I981. Marto, P. J. and Hernandez, B., Nucleate Pool Boiling Characteristics of Gewa-T Surface in Freon-113, A. I. Ch. E. Symposium Series, V01. 79, No. 225, pp. 1-10, 1983. Nakayama, W., Daikoku, T., Kuwahara, H., and Nakajimi, T., Dynamic Model of Enhanced Boiling Heat Transfer on POrous Surfaces in Advances in Enhanced HeaE_Transfer, eds. J. M. Chenoweth et al., pp. 31443, ASME, New York, 1979. Gottzman, C. F., Wulf, J. B. and O'Neill, P. 8., Theory and Application of High Pefformance Boiling Surfaces to Components of Absorption Cycle Air Conditioner, Proc. Nat‘l. Gas. Res. Tech., Session V, Paper 3, Chicago, 1971. ‘ 125 126 10. Thome, J. R. and Shock, R. A. W., Boiling of Multi- component Liquid Mixtures, in Advances in Heat Transfer eds. T. J. Irvine, Jr. and J. P. Hartnett, Vol. 16, Academic Press, New York, 1984. - 11. Antonelli, R. and O'Neill, P. 5., Design and Appli- cation Considerations for Heat Exchangers with En- hanced Boiling Surfaces, International Conference on Advances in Heat Exchangers, Dubrovnik, Yugoslavia, 1981. 12. Czikk, A. M., O'Neill, P. S., and Gottzman, C. F., Nucleate Boiling from Porous Metal Films: Effect of Primary Variables, in Advances inggnhanced Heat Transfer 1981, eds. R. L. Webb et al., pp. 109-122, ASME, New York, 1981. 13. Arshad, J. and Thome, J. R., Enhanced Boiling Surfaces: Heat Transfer Mechanism and Mixture Boiling, Proc. ASME/JSME Thermal Engineering Joint Conference, Honolulu, Vol. 1, pp. 191-197, 1983. 14. Thome, J. R., Prediction of Binary Mixture Boiling Heat Transfer Coefficients Using Only Phase Equilibrium Data, Int. J. Heat Mass Transfer, Vol. 26, pp. 965-974, 1983. 15. Webb, R. L., The Evolution of Enhanced Surface Geometries for Nucleate Boiling, Heat Transfer Engineering, Vol. 2, No. 3-4, pp. 46-69, 1981. 16. Ito, M., Kimura, H., and Senshu, T., Vol. 2, Development of High Efficienty Air-cooled Heat Exchangers, "Hitachi" Review, Vol. 26, 1977., pp. 323-26. 17. Bergles, A. E., Nelson, R. M., and Webb, R. L., "Assessment Development and Co-ordination of Technology Base Studies in Enhanced Heat Transfer", Quarterly Pro- gress Report 5 on DOE Grant No. DE-FGO781ID—12222, Iowa State University, December, 1982. 18. O'Neill, P. S., Gottzman, C. F. and Terbot, J. W., Novel Heat Exchanger Increase Cascade Cycle Efficiency for NGL, 68th National AI Ch.E. meeting, Houston, Texas, 1971. 19. Shakir, S., Ph.D. Thesis, Michigan State University, 1984 (anticipated). 20. Van Wijk, W. R., Vos, A. S., Van Stralen, Heat Transfer to Boiling Binary Mixtures, Chem. Engg. Sci. 5. 68—80, 1956. . 4- v.llwu.U‘.oP ‘ 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 127 Sternling, C. V., and Tichacek, L. J., Heat Transfer Coefficient for Boiling Mixtures, Chem. Engg. Sci. 16, pp. 297-337, f1961.. Stephen, K., and K Orner, M., Calculation of Heat Transfer in Evaporating Binary Mixtures, Chemic. Ingr. Tech. 41 (7), 409-417, ’1969. Valent, V., and Afgan, N. H., Bubble Growth Rate and Boiling Heat Transfer in Pool Boiling of Ethyl Alcohol- Water Mixture, Warmeydund Stoffubertragung, Vol. 6, pp. 235-24-, 1973. Tolubinskiy, V. I. and Ostrovskiy, Y. N., Mechanism of Heat Transfer in Boiling of Binary Mixtures, Heat Transfer Soviet Res., Vol. 1, No. 6, pp. 6-11, 1969. Happel, O. and Stephen, K., Heat Transfer from Nucleate to the Beginning of Film Boiling in Binary Mixtures, Proc. 5th Int. Heat Transfer Conf., Versailles, Vol. 6, paper B7-6, 1970. ‘Grigor'ev, L. N., Khairullin, I. Kh., and Usmanov, A. G., An Experimental Study of Critical Heat Flux in Boiling of Binary Mixtures, Int. Chem. Engng.,Vol. 8, No. 1, pp. 39-42, 1968. Thome, J. R. and Davey, G., Bubble Growth Rates in Liquid Nitrogen, Argon and Their Mixtures, Int. J. Heat Mass Transfer, Vol. 24, pp. 89-97, 1981. Van Stralen, S. J. D., Bubble Growth Rates in Boiling Binary Mixtures, Br. Chem. Engng., Vol. 12, No. 3, pp. 390—394, 1967. Thome, J. R., Shakir, S., and Mercier, C., Effect of “ Composition on Boiling Incipient Superheats in Binary Liquid Mixtures, Proc. 7th Int. Heat Transfer Conf., Munich, Vol. 4, paper PB14, 1982. Thermal Conductivity Value Supplied by Linde Division of Union Carbide.Corp0ration. Thermal Conductivity Value for 50-50 Pb-Sn Solder taken from Properties and Selection of Metals, Metals Handbook, Vol. 1, 8th Edition. MWIMHOfijHlLTIM»flifljfijflfitififlujfllflfilr