Pool boiling—binary liquid mixtures

Chemical

Engineering

Science, 1972, Vol. 27, pp. 1687-1697.

Pergamon

Printed in Great Britain

Press.

Pool boiling - binary liquid mixtures W. F. CALUS

and P. RICE

Department of Chemical Engineering, Loughborough University of Technology, Loughborough, Leicestershire, England. (Received6September

1971; inrevisedform

21 December

1971)

Abstract-Pool

boiling data were obtained for 7 concentrations of isopropanol in water and 9 concentrations of acetone in water, as well as for 3 pure components. The heating element was a nickelaluminium alloy wire of 0.03 15 cm in dia. These experimental results were correlated with the equation

[g][er =‘[

l+

I,,”

-Px;(a,D)0.5r”

This equation also correlated the experimental data of Stemling of water with glycerol and water with glycol. Our experimental results and those of Ref. [ 121 indicate factor” is determined mainly by the nature and structure of the of the liquid to this factor is very small, within the accountable constant E in the correlating equation is mainly a function of the INTRODUCTION

A RELATIVELY small number of research workers have been concerned with pool boiling of binary liquid mixtures. Most of the publications in this field are listed by Stephan and Korner [ 191 and Filatkin [20]. Striven [ 161 investigated theoretically bubble growth rate in the bulk of a binary mixture. Starting with the fundamental relationships of continuity, momentum, energy and mass diffusion he produced an equation from which the bubble radius in an infinite fluid can be calculated as a function of time. To make the mathematics of the problem manageable the following simplifying assumptions were made: viscous forces are negligible, heat is transferred to the bubble by conduction only, the thermal properties of the liquid and gas phases are taken as constant, mass is transferred by molecular diffusion only, heat of mixing is negligible, heat capacities of the two components are equal, surface tension effects are negligible, and finally the vapourliquid equilibrium relationship is linear. Striven [ 161 described his final result R=2/3X&

(1)

and Tichacek [ 121for several mixtures that the “liquid-surface combination heat transfer surface. The contribution experimental error. The value of the surface.

as providing “adequate description of bubble growth during all but the earliest stages”. Equation (1) is applicable to situations with large superheats, more common in industrial practice. The value of j3 is defined by Eq. (70) and the full expression for the radius R is given by Eq. (72) of Ref. [ 161. Van Stralen [ 17, 181 continued this work and summarised it in Ref. [ 171. He introduced a modification into the Striven’s equation for the bubble growth rate. The modification consists of using an alternative method in accounting for the difference between the apparent and actual superheats. It may be shown that Striven’s Eq. (72) in Ref. [16] and Van Stralen’s Eq. (27) in Ref. [ 171 are the same and can be transformed into a more convenient form

Stephan and Kiirner [ 191 considered the thermodynamics of bubble formation in an infinite binary mixture and concluded that the rate

1687

W. F. CALUS

of heat transfer to a bubble decreases with an increase in the value of (y* -x). They also developed an empirical equation making it possible to calculate the temperature difference driving force needed for a given heat flux in pool boiling of binary mixtures. The equation contains an empirical constant which has a different value for each binary mixture. Also the boiling curves for pure components of a binary mixture must be known if their equation is to be applied. Stephan and Kiirner[ 191 emphasize that the maximum value of (y* -x) coincides with the minimum value of the heat transfer coefficient for a constant heat flux. The same observation was made by Sternling and Tichacek [ 121. The object of this work is to investigate whether the results of Striven and Van Stralen can help to devise a macroscopic correlation which would account for the main mechanisms of heat transfer at work in pool boiling of binary mixtures. EXPERIMENTAL EQUIPMENT TECHNIQUES

AND

The apparatus and the experimental techniques were described in detail in Ref. [22]. Also the wire used for the pool boiling of singlecomponent liquids reported in Ref. [22] was used again in the pool boiling of isopropanol-water mixtures. The wire was of nickel-aluminium alloy, 0.0315 cm in dia. and the length used in the heat transfer tests was 8.9 cm. It must be emphasized that the stabilising procedure of the wire consisted of keeping it in boiling water for approximately 36 hr prior to the experiments with single component liquids reported in Ref. [22]. After the completion of those experiments the working age of the wire was about 200 hr. About two months elapsed before the experiments with isopropanol-water mixtures were commenced. In that interval the wire was exposed mainly to the laboratory atmosphere. This wire will be referred to as “wire 200”. The wire used for the pool boiling of acetonewater mixtures will be referred to as “wire 24”. It comes from the same spool as the “wire 200”, its diameter was also O-0315 cm and the test

and P. RICE

section 7.26 cm long. The “wire 24” was kept in boiling liquid for 20 hr, then exposed to the laboratory atmosphere for about 6 months due to an interruption in the experimental work. On resumption of the experiments the test section was again kept 4 hr in boiling liquid prior to the experiments with acetone-water mixtures. PHYSICAL

PROPERTIES USED

OF THE

FLUIDS

Distilled water, redistilled isopropyl alcohol and redistilled acetone were used to prepare mixtures of them of various concentrations. The physical properties of the pure components and their mixtures were obtained in various ways: Some of these properties at boiling points were found in literature, others by extrapolation of the properties at lower temperatures. In many cases it was necessary to determine them experimentally in this laboratory. The densities of binary vapour mixtures were calculated from the ideal gas law as all the experiments were carried out at atmospheric pressure. Physical properties of water-glycerol and water-glycol mixtures were obtained by the same methods. Table 1 shows the origin of the properties used and indicates which of them were obtained by extrapolation and which were determined experimentally. To extrapolate mass diffusivity the WilkeChang [2 11 equation was used. According to Olander[21] this equation gives good results for mixtures of water with organic solvents provided that water is the solvent. But when water is the solute the values of diffusivity extrapolated to higher temperatures could be wrong by a factor of 1.5-2.5. This method is still less satisfactory if the viscosities of the two components differ widely. This situation exists in the case of water-glycerol mixtures and water-glycol mixtures. THEORETICAL CORRELATION

BASIS FOR THE OF BINARY DATA

A macroscopic correlation for pool boiling of single-component liquids was developed by these authors[22] by modifying the existing

1688

Pool boiling - Binary liquid mixtures Table 1. Physical properties

IPA/H,O mixtures IPA

PC

PI.

k,.

CL

9 3-191

6

9 3-204

talc.

3 3

talc.

9 3-191 Glycerol/H,0 mixtures Glycol

8

Acetone/H,0 mixtures

talc.

9 3-123

10 p. 38

p. 27

1 E-3

2 p. 98

3

4

11 S-228

p. 94

6

8 p. 266

p. 24

6 P. 6

talc.

(+

6 P. 6

Cd.

Glycol/H,O mixtures

PI.

2

6

8

I

7

p.2

p.51

8 p.246

7 p.2

7 p.51

147

Equil. data

3t

2 p.94

6

3

2

*

p. 93

6

6

6t

p. 25

p. 15

p. 21

talc.

6 p. 15

6 p. 27

11 5-137

5t

6

*

5t

8 p. 245

8t

15t

7 p. 57

7

talc.

p. 57 8t

8 p. 47

p.41

D

-

p. 266

p. 24

p.246

8t

he,

p.43

13

p.44

*Obtained experimentally in this laboratory. tobtained by extrapolation from values at lower temperatures.

equation of Borishanskii and Minchenko. modified correlation has the form [$$][$T

= E[PeP7.

The

(3)

There is no basic difference in the mechanism of heat transfer to single-component boiling liquids and to binary liquid mixtures. The mechanism of heat transfer to binary mixtures is of the same type, but more complex due to the simultaneous mass transfer which, it appears from the published information, constitutes an additional impedance to heat transfer. If a suitable correction factor accounting for this additional resistance is included in Eq. (3) the equation so corrected should be applicable to binary mixtures. Equation (2) is relevant to this problem. The contents of the square brackets in the denominator of Eq. (2) form a correction due to simultaneous heat and mass transfer. It has been

arrived at by the theoretical analysis of the problem for the rate of bubble growth in an infinite fluid, therefore it is strictly applicable to that situation and not to the whole process of boiling on a solid surface. On the other hand this correction, or part of it, must be relevant to the whole process of boiling. It is generally assumed that heat is transferred from the solid surface through a thin boundary layer of liquid by conduction, and then converted partly into vapour bubbles and partly transferred by convection into the bulk of the liquid. Evaporation into the bubble involves the diffusion of heat and of the lighter component through the boundary layer surrounding the bubble. The mass diffusion is a considerably slower process than the heat diffusion and hence the dimensionless ratio (cK/D)~‘~in Eq. (2) is a measure of the additional resistance to heat transfer and will play the same part in the macroscopic process of boiling. The mass driving force (y * -x) determines the mass diffusion rate, and hence for higher flow rates of

1689

W. F. CALUS

the more volatile component there will be a higher resistance to heat diffusion. The square brackets of Eq. (2) contain also the quantities (C,/h,) and (dT/dx). The quantity (C,,/h,,) is already present in the Peclet number of Eq. (3). The superheat of the liquid layer at the base of the bubble is very different from that on the top of it, unlike around a bubble in an infinite liquid. It is difficult to assign any physical significance to the quantity (dT/dx) in this location. Mathematically, there is no justification for omitting (CJh,) and (dT/dx) but it was decided to investigate experimentally the effect of changing the correction factor in this way: First the variation of the contents of the square brackets of Eq. (2), i.e. 1 -(Y* -x)(;)@5(~)(~)]

(4)

with concentration was examined. Then procedure was repeated with the factor

this

[

[l+ iy* -xl(a/D)@“l.

(5)

It was found that the variation of the correction factor (5) corresponds very closely with the variation in the Nusselt number at the same concentrations of the mixtures. This will be shown in the next section of this report. On these grounds the quantities (C,lh,) and (dT ldx) were dropped and the factor (5) adopted for correlating the experimental results. The absolute value of (y * -x) is taken so that the expression (5) is always larger than unity. In Eq. (2) this device was not necessary because (y * - x) and (dT/dx) are mutually of opposite sign. Equation (5) describes quantitatively the additional resistance to heat transfer, in a purely evaporative process, on a heating surface. However the macroscopic process of boiling includes convective mechanisms and hence the effect of the correction factor (5) will be weaker than in the equation for bubble growth. At present it is not possible to establish analytically the relative contribution of the evaporative and convective mechanisms and it is proposed to arrive at them by obtaining an empirical exponent for the correction factor (5).

and P. RICE

Thus Eq. (3) applied to binary mixtures will have the form

The value of II is to be obtained from experimental data. CORRELATION

OF THE DATA

EXPERIMENTAL

Boiling curves were obtained for the mixtures of isopropanol with water and for the mixtures of acetones with water. The concentrations used and the range of the operating variables employed are shown in Table 2. The experimental results are reported in Figs. 1 and 2 as plots of (Nul K,,“‘7)(TS/T,,)4 against the Peclet number. In Fig. 1, representing the data points for nine mixtures of isopropanol with water it was possible to draw only five correlating lines. The data points for the concentrations: 0 wt.%, 87.7 wt.% (azeotrope) and 100 wt.% isopropanol are correlated by a single line. Each of the concentrations: 74 wt.%. 65 wt.%, and 54 wt.% isopropanol requires a separate line. The data points for the concentrations: 10 wt.%, 20 wt.% and 42.5 wt.% isopropanol are correlated by a single line. Inspection of Figs. 3 and 5 shows that there is a correspondence between the position of these five lines and the values of the factor [l + Iy* --xl(c~/D>~.~] associated with the data points on them. The data points on or around a correlating line have, practically, the same value of the heat and mass transfer factor. It is quite evident from Figs. 1 and 5 that if the Peclet number of every data point is divided by its heat and mass transfer factor ail the five lines are brought on to one line. This situation is shown in Fig. 7. It may be concluded that the exponent on the factor [ 1 + (y * -x l(a/D)“.5] in Eq. (6) is 0.7, the same as on the Peclet number. Therefore the final correlating equation for binary mixtures of this work is

[3[3’= 4

1690

1 +

Iy*

-;(a,D)o.5]o’7* t7)

Table 2

Author This work

Heat transfer surface

Heating medium

NickelElectric aluminium alloy power, D.C. ‘wire 200”

Gectric This work Nickelaluminium alloy power, D.C. “wire 24”

Pressure atm. 1.0

Binary system Isopropanolwater

Range of Concentration of boiling the lighter Rangeof points “C component, wt. % AT, “C

Range of heat flux

80-4-100

0, 10,20,42.5, 54,65,74,87.7, 100

6.8 to 51.7

21,000 to 0.945 to 1,909,OOo 1Mo

5.5, 11.5,22.0, 39.6,55.0,66.0, 80.0,90.5,95.8, 100

10.3 to 57.2

9,400 to 0.882 to 1,451,OOo 0.972

1.0

acetonewater

56.5-89.6

Stemling and Tichacek iI21

Electric Stainless steel hypodermic tube power 0.18 in. O.D.

1.0

waterglycerol

102-280

0.33, 1.69, 1.73, 4.05,4.28,9.09, 9.64, 18*6,25.5, 28*9,40.8,49.8, 67.4.74.7

Stemling and Tichacek

Stainless steel Electric hypodermic tube power 0.18 in. O.D.

1.0

waterglycol

103-194

0.28,264,10.1, 19.3,47.65, 73.3

[121

W/m=

Range of T, [

1 TSW

8.8 to 74.8

25,000 to 495.008

1.004 to 1.48

12.4 to 51.8

28,000 to

1.005 to 1.25

451,000

W. F. CALUS

and P. RICE

Fig. 1. Isopropanol-water mixtures, application of the single component correlation. Wt. % isopropanol: A 100 + 87.7, 074,‘J65,x54,042.5,~20,* 10,40. X, itopropaml, wt. fraction

Inspection of Fig. 7 shows that more than 86 per cent of the data points lie within 220 per cent accuracy lines. It is estimated that the cumulative experimental error is about 5 per cent. It is impossible to estimate the cumulative error due to the inaccuracy and inconsistency of the physical properties of the liquids, and it is felt that it would be considerably larger. The experimental data points for the acetonewater mixtures were analysed in the same manner in Figs. 2, 4 and 6, and are finally correlated in Fig. 8. Here about 92 per cent of the data points are within the *20 per cent accuracy lines.

Fig. 3. Isopropanol-water mixtures, variation of (a/D)0’5 and 1y* -xl with concentration.

EXPERIMENTAL

DATA OF STERNLING TICHACEK

The experimental data of Stemling and Tichacek [ 121 for the aqueous solutions of ethylene glycol and glycerol were chosen to test Eq. (6). The binary mixtures water-glycerol and water-glycol are, with respect to surface tension, classed as surface tension negative. This constitutes a contrast with the two mixtures used

X, acetone,

Fig. 2. Acetone-water mixtures application of single component correlation. Wt. % acetone: 0 100, A 95.8, 0 90.5, 0 80, V 66, x 55, + 39.6, * 22,. 11.5, n 5.5.

AND

wt. fraction

Fig. 4. Acetone-water mixtures, variation of ((u/D)@~and Iy* --xl with concentration.

1692

Pool boiling - Binary liquid mixtures

0

I

0.1

1

0.2

I

0.3

04

X,isoproponol,

1

I

I

0.5

0.6

0.7

I

I

0.6

0.9

I.0

wt. fro&ion

W[l+ly*-x

Fig. 5. Isopropanol-water mixtures, variation of the group [ 1+ 1y* -xl (cz/D)@~]with concentration.

by these authors as they are surface tension strongly positive. Stemling and Tichacek [ 121 used stainless steel hypodermic tubing as their heat transfer surface with the dimensions: 0.18 in. o.d., 0.015 in. wall thickness and 3.5 in. long. Electric power was the heating medium. They tried a variety of methods to stabilize the surface. Finally they found that polishing the surface with No. 200 silicon carbide grit and thorough washing gave a surface providing reproducible

1(o/D )““I

Fig. 7. Isopropanol-water mixtures, correlation of the experimental dam. Wt. % isopropanol: A 100+87.7,0 74, V 65, x 54,0425.0 20, * 10,9 0.

boiling curves. Their results cover a wide range of concentrations and heat fluxes which are shown in Table 2. The sets of data for 95.5 wt.% and 90.5 wt.% water in glycol are not reported here as they contain obvious inconsistencies. The plot of the experimental data for water-glycerol mixtures, in accordance with Eq. (7), is shown in Fig. 9. It may be seen that 85 per cent of the experimental data points lie

6-

5-

4-

3-

2--

II 0

01

I 0.2

I 03

/ 04

I 05

I

I

I

06

07

08

I 09

IO

x )acetone.wt.froctiin

6. Acetone-water mixtures, variation of the group [ 1 + Iy* -xl (LX/D)@~]with concentration.

Fig. 8. Acetone-water mixtures, correlation of the experimental data. Wt. % acetone: 0 100, A 95.8, 0 90.5, 0 80, V 66,x55,+39.6, * 22,e 11.5,m5.5.

1693 C.E.S.Vol.27No.P--F

W. F. CALUS

and P. RICE

IO+

I

IO2

IO' Pe/Cl + 1 y*-

Fig. 9. Water-glycerol mixtures, correlation of the experimental data of Stemling and Tichacek[ 121. Wt. % water: n 0.33+ 1.69 and 1.73, V 4.05 and 4.28, x 9.09 and 964, 0 18.6,O 25.5,. 28.9, 0 40.8, * 49.8, j, 67.4, 9 74.7.

within the *20 per cent accuracy limits. More than half of the points outside these limits are those for the 67.4 and 74.7 wt.% water in glycerol solutions. A possible reason for this discrepancy is a larger error in the extrapolated values of mass difisivity for the less concentrated solutions than for the more concentrated solutions of water in glycerol [2 11. A plot of the water-glycol data is shown in Fig. 10. Again 15 per cent of the data points are outside the &20 per cent accuracy limits for the same reason as in the case of the water-glycerol mixtures. However the error in the data points outside the accuracy limits for water-glycerol is considerably larger than that for water-glycol system. This again is in agreement with the explanation given in Ref. [ 2 11. DISCUSSION

OF RESULTS

The lines of Figs. 7, 8, 9 and 10 represent the binary data of this work for isopropanolwater and acetone-water, and those of Sternling et al.[121 for water-glycerol and water-glycol. Inspection of each plot shows that the data points for each concentration tend to form separ-

4

14

xl WDPJ]

Fig. 10. Water-ethylene glycol mixtures, correlation of the experimental data of Stemling and Tichacek[ 121. Wt. % water: * 0.28,0 264, q lO.l,+ 19.3, V 47.6,O 73.3.

ate groupings. Fitting to the heat and mass transfer factor [ 1 + 1y * - x ~(cY/D)~~“I an experimental exponent slightly different from unity would improve the situation but it is thought that more experimental evidence is required to justify this refinement. Each of the lines in Figs. 7-10 has a slope 0.7, thus in the equation (7) the heat and mass transfer factor has an exponent 0.7 also. Comparison with Eq. (2) for the growth rate of a bubble in the bulk of the liquid mixture, where this exponent is unity, indicates that the heat and mass transfer factor plays a considerably smaller part in the macroscopic heat transfer from a solid surface This is to be expected because the macroscopic process is promoted by at least one more mechanism which is microconvection in the liquid boundary adjacent to the surface and macroconvection further away from the solid surface. It should be noted that the four liquid mixtures used in this work are extremely irregular as far as the variation of (y* -x) and (cJD)~.” with concentration is concerned as shown in Figs. 3-6. With binary liquid mixtures having these relationships of an approximately linear

1694

Pool boiling- Binary liquid mixtures

type, the value of the heat and mass transfer factor is very close to unity for the whole range of concentrations. Therefore the variation of heat transfer coefficient with concentration for a given heat flux should approximate to a linear relationship as suggested in Ref. [ 191. A mixture of e.g. n-heptane with methylcyclohexane approaches this ideal situation. The lack of knowledge of the relevant physical properties made it impossible to verify this. The four sets of data considered here provided a good confirmation of the correlating value of mixtures the ratio T, IT,,. Isopropanol-water exhibit the smallest range of this parameter and those of water-glycerol the largest. The lines of Figs. 7- 10 are superimposed in Fig. 11. Each of the lines represents Eq. (7) with the value of the constant E given in Table 3. Inspection of this table and of Fig. 11 shows the dominating part played by the nature and structure of the heat transfer surface in the “liquid-surface combination factor”. Line 5 in Fig. 11 is the correlating line for

T

43 :2

single component liquids reported in an earlier paper by these authors[22], (Water, toluene, carbon tetrachloride, methanol, isopropanol, n-propanol and isopropanol/water azeotrope). In the case of single component liquids the heat and mass transfer factor is unity. If the “wire 200” were not subjected to the prolonged action of the laboratory atmosphere prior to the experiments with isopropanol-water mixtures, curve 1 would be expected to have the same value of the constant E as curve 5. The data represented by curve 2 was obtained on a specimen of wire from the same spool but subjected to a slightly different preparation technique before commencement of the experimental work. Thus the displacement of lines 1, 2 and 5, in Fig. 11, is mainly due to the different treatment of each surface, and less due to the nature of the liquids. The fact that curves 1 and 5 also include water data points confirms this view. The displacement of curve 4 relative to curve 3 is 6.6 per cent. It is difficult to account for this because of the uncertainty with respect to the accuracy of physical properties, particularly mass diffusivity. According to Olander[il] the error in the extrapolated value of mass diffisivity will be larger for the water-glycerol system than for the water-glycol one and could be even larger than 6.6 per cent. It is thought therefore that the displacement of lines 3 and 4 is due to the inaccuracy in the value of mass diffisivity and does not represent the liquid component of the “liquid-surface combination factor”. This conclusion is made on the assumption that the surface of the stainless steel hypodermic tube did not suffer any changes between the two series of experiments of Stemling and Tichacek [ 121. CONCLUSIONS

Pe/[I+ly*-xj(a/Df-]

Fig. 11. Summary of the correlated data for four binary systems. Curve 1, Isopropanol-water mixtures on the nickelaluminium alloy “wire 200”. Curve 2, Acetone-water mixtures on the nickel-aluminium alloy “wire 24”. Curve 3, Water-glycerol mixtures on a stainless steel hypodermic tubing. Curve 4, Water-glycol mixtures on a stainless steel hypodermic tubing. Curve 5, Seven single component liquids, the same wire as in 1 before it was subjected to the prolonged action of the laboratory atmosphere.

(1) The heat and mass transfer factor [l + IY* -X ](cx/D)@~]was used successfully together with the modified Borishanskii-Minchenko equation to correlate pool boiling data for the binary liquid mixtures of this work and those of other workers. (2) These results indicate that the dominating component of the “liquid-surface combination

1695

W. F. CALUS

and P. RICE

Table 3. Heat transfer surface

Curve number Binary in Fig. 11 system

Constant E in Eq. (6)

1

Isopropanol and water

Nickel-aluminium alloy, “wire 200”

5.8 x 10-d

2

Acetone and water

Nickel-aluminium alloy, “wire 24”

4.7 x 10-d

3

Water and glycerol

12.2 x 10-4 Stainless steel hypodermic tubing

4

Water and glycol

asin

5

Seven single component liquids

The same wire as in 1 before it was subjected to the prolonged action of the laboratory atmosphere

factor” is the nature and structure of the heat transfer surface. The nature of the liquid contributes negligibly to this factor. (3) The correlation developed in this work for the pool boiling of binary liquid mixtures accounts well for the properties of the liquid phase while the effect of the heating surface remains unknown. (4) This work confirms the value of the ratio (TJT,,) as a correlating factor and extends its validity to binary liquid mixtures.

11.4 x 10-d 6.3 x lo-*

TS saturation T SW X

Y*

P

temperature of pure liquid or liquid mixture, “K saturation temperature of water, “K at system pressure mass fraction of the lighter component mass fraction of the lighter component in equilibrium with the liquid phase heat flow rate thermal diffisivity bubble growth constant =

p”

a ‘+AT 0

NOTATION

A C d

D E g hfg P R t AT

surface area specific heat

=J-g(p,

P u

-PC)

Laplace constant used as bubble diameter at departure

mass dithrsivity constant in Eqs. (5) and (6) acceleration of gravity latent heat of evaporation pressure bubble radius time superheat

density surface tension

NU

y

Pe

6%.k?&. c, .

I

Nusselt number

hfc/ PC

KP Subscripts L liquid G vapour 1696

k.

d

peclet

number

Pool boiling-

Binary liquid mixtures

REFERENCES [II Handbook of Chemistry and Physics. Chemical Rubber Co. 46th Edn. 1965. HATCH L. F., IsopropylAlcohol, McGraw Hill, New York, 1961. ::; DEED D. W., SCHUTZ P. W. and DREW T. B., Ind. Engng Chem. 1947,39, No. 6,766-744. [41 McEWEN R., M.Sc. Research Report, Loughborough University of Technology, 1968. [51 GARNER F. H. and MARCHANT P. J. M., Trans. Instn Chem. Engng 196139 397-408. 161 NEWMAN A. A., Glycerol, Morgan-Grampian, London, 1968. [71 CURME G. 0. and JOHNSTON F., Glycols. Reinhold, New York, 1952. J., The Physico-Chemical Constants of Binary Systems in Concentrated Solutions, Vol. 4. Inter[a TIMMERMANS science, New York, 1960. Handbook, 4th Edn. McGraw-Hill, New York, 1963. 191 PERRY J. H., (Ed.), ChemicalEngineers’ 1101 KAYE W. C. and LABY T. H., Tables ofphysical and Chemical Constants. Longman, 1966. Critical Tables of Numerical Data, Physics, Chemistry and Technology. McGraw-Hill, New York, illI International 1928-1930. L. J., Chem. Engng Sci. 1961 10 297-337. t121 STERNLING C. V. andTICHACEK [I31 CHIN CHU JU, Distillation Equilibrium Data. Reinhold, New York, 1950, p. 23. [I41 RIEDEL L., Chem. Inger. Techn. 195 123 465-469. (Ed. D. McGraw-Hill, New York, 2nd Edn., 1963 1151, American Inst. of Physics Handbook 2-212, ___ ~._. .,_E. GRAY) __ [16] SCRIVEN L. E., Chem. Engng Sci. 1959 10 No. l/2, 1-13. [171 VAN STRALEN S. J. D.,Brit. Chem. Engng 1967 12 No. 3,390-394. [18] VAN STRALEN S. J. D., The mechanism of nucleate boiling in pure liquids and in binary mixtures, Int. J. Heat Mass Transfer, Part I, 1966 9 995-1020: Part II, 1966 9 1021-1046; Part III, 1967 10 1469-1484: Part IV, 1967 10 14851498. [ 191 STEPHAN K. and KORNER M., Chemie fnger Techn. 1969 41 No. 7,409-417. [20] FILATKIN V. N., Boiling heat transfer to water-ammonia mixtures. Symposium on Problems of Heat Transfer and Hydraulics of Two-Phase Media, (Ed. S. S. KUTATELADZE), pp. 13 l-136. Pergamon Press, London, 1969. [21] OLANDERD.R.,A.I.Ch.E.J. 19617(No. 1), 175-176. [22] RICE P. and CALUS W. F., Chem. Engng Sci. 1972 27 1687. R&urn4 -

Les auteurs obtiennent des donnees de I’ebullition de 7 concentrations d’isopropanol dans de l’eau et de 9 concentrations d’acetone dans de l’eau, ainsi que de 3 composes purs. L’element de chauffage est un fil de 0,03 15 cm de diamttre forme d’un alliage de nickel et d’aluminium. Ces donnees experimentales sont corrdlees avec l’tquation:

Cette equation a aussi correle les donnees experimentales de Stemling et Tichacek [ 121 de plusieurs melanges d’eau et de glycerol, et d’eau et de glycol. Nos resultats experimentaux ainsi que ceux de[ 121 indiquent que le “facteur de combinaison liquide-surface” est determine principalement par la nature et la structure de la surface du transfert de chaleur. La contribution du liquide ace facteur est minime. La valeur de la constante E dans l’equation de correlation est en grande partie fonction de la surface. Zusammenfassunz-

Es wurden Poolsiedetemperaturdaten erhalten fur 7 Konzentrationen von Isopropanol in Wasler und 9 Konzentrationen van Aceton in Wasser, sowie fur 3 reine Komponenten. Das Heizelement war ein Draht aus Nickel-Aluminiumlegierung von 0,03 15 cm Durchmesser. Diese Versuchsergebnisse wurden mittels der Gleichung -

[~][~l’=E[,+,y*-~(o,D)‘..]o”’ in Korrelation gebracht. Diese Gleichung ermiiglichte ebenfalls eine Korrelation der Versuchsergebnisse von Stemling und Tichacek[ 121 fur verschiedene Mischungen von Wasser mit Glyzerin und Wasser mit Glykol. Unsere Versuchsergebnisse, sowie die nach Schrifttumsstelle[l2], deuten darauf hin, dass der “Fliissigkeit-Oberfkache Kombinationsfaktor in erster Linie durch die Art und das Gefiige der WarmeiibertragungsoberlI%che bestimmt wird. Der Beitrag der Fliissigkeit zu diesem Faktor ist sehr gering innerhalb des Versuchsfehlers. Der Wert der Konstanten E in der Korrelationsgleichung ist in der Hauptsache eine Funktion der Oberflkhe.

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