Heat Transfer to Boiling Styrene and Butadiene and Their Mixtures

Heat Transfer to Boiling Styrene and Butadiene and Their Mixtures with Water CHARLES

F.B O N I L L A A N D A R T H U R A . E I S E N B E R G '

T H E J O H N S H O P K I N S U N I V E R S I T Y , B A L T I M O R E 18. M D .

Because of t h e i m p o r t a n c e of heat transfer t o a n d f r o m water-styrene a n d water-1,3butadiene m i x t u r e s in GR-S synthetic rubber plants, tests o n t h e b o i l i n g of these m i x t u r e s were carried out. It was f o u n d t h a t in t h e b o i l i n g of m i x t u r e s of components t h a t are n o t m u t u a l l y soluble t h e necessary At, based o n t h e e q u i l i b r i u m temperature, w i l l be appreciably larger t h a n f o r either component alone a t t h e same q / A . I n t h e b o i l i n g of relatively shallow depths of m i x t u r e s of insoluble liquids, considerable superheating of t h e m i x t u r e m a y be expected, in contrast t o t h e b o i l i n g of two-phase m i x t u r e s of p a r t i a l l y soluble liquids. If t h e l i q u i d phase of lower density has a lower b o i l i n g p o i n t , b o i l i n g of t h e denser phase m a y n o t occur until h i g h heat transfer ratesare reached,asthe h e a t t r a n s fer takes place a t lower rates b y n a t u r a l convection. A t a low rate of b o i l i n g t h e l i g h t e r layer w i l l n o t m i x sufficiently w i t h t h e denser layer t o be carried down t o t h e heating surface, a n d a t t h e b o i l i n g rate a t w h i c h t h i s starts a d i s c o n t i n u i t y in t h e A t value w i l l be observed.

2

boiling. For the iuns 171th p u ~ butadlerle e :t section 01 steel pipe of the same dimensions mas used instead, for safety. Sheet lead gaskets were employed at the edges of the cylinders The pipe through n.hich the vapor and the conderlsate had llo cooling jacket over its bottom 16 inches; the returning liquid iTas therefore very near if not a t the saturation temDerature. Pressures befow atmospheric mere produced by a water jet aspirator, andabove Y atmospheric by a nitrogen cylinder. An empty cylinder floated on the line to maintain uniform pressure. The liquid temperature thermocouple was in t'he bottom of a copper well which ended about 1 inch above the plate. The liquid temperature indicated was thus the average from about 1 to 2 inches above the plate. The plate temperature was obtained by tlvo thermocouples in O.05-inch diameter holes drilled radially towards the center of the disk parinch allel t o and about below the surface. The couples employed No. 30 1938 calibration Leeds &: Northruq constantan and copper m e . Correction for temperature drop through the t'hicknes's of copper to the surface TTas applied. The largest correction encountered was 2 2 7 of the gross observed At; for most runs it was well under 57,. Heat losses were roughly proportional t o the difference betwecn the temperatures of the top of the plate and of the room, and rvere so estimated; data for the proportionality constant n-ere obtained by runs with n o liquid. With the glass cJ-linder 18.9 B.t.u. per hour X square feet of plate surface were lost per 1O F. difference between the plate and the room, and with the iron cglinder 33.9 were lost. Figure 1. Diagram of B o i l i n g Apparatus

sirllu~~axleous boiling of tKo liquid phases, formed from T E i i s c i b l e or miscible volatile has industrial applications in steam distillation and other fields. However, no studies on this subject have been found in the literature, Kith the exception of atmospheric pressure runs on the trvo-phase n-butyl alcohol-water constant boiling mixture (1). On account of the importance of heat transfer to and from ivater-styrene and water-1,3butadiene mixtures in GR-S sJ-nthetic rubber plants, a program of tests n-as carried out on the boiling of these mixtures. ..\ feature of these pairs is that ill the first case the hgdrocarbon is less volatile, and in thc other case more volatile than the water. A total of 300 runs was carried out, some on the pure compancnts, some on the binarj- mixtures with water, and several on h e p tane, for comparison of the apparatus with similar ones previously employed ( 2 , S). APPARATUS

The equipment used in this 7rork is shoivn in Figure 1. It includes the 3-inch diameter horizontal electrically heated heavy chromiuinplated copper boiling surface employed h v Bonilla and Perry in their'first tests (1). glass qlinder 4 inches high formed the walls of the chamber and permitted observation of the !

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Present

address,

Southern

Lacquer Co., Baltimore, Md.

~~

1113

Vol. 40, NG 6

INDUSTRIAL A N D ENGINEERING CHEMISTRY

1114

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Boiling of Commercial n-Heptane

Figure 7,

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On a s l i g h t l y scratched 3 - i n c h d i a m e t e r horizontal plate N u m b e r represents pressure In atrnospheres O t h e r results o n s m o o t h 4-inch plates: D u n n a n d Schaffner. - - - - - Cichelli a n d Bonilla. - - B o n i l l a a n d Perry

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WrPv Jakob a n d L i n k e Correlation for B o i l i n g of Pure L i q u i d s Average l i n e of B o n i l l a a n d Perry (slope 0.73) L i n k e (slope 0.80)

- .-L i n e of Jakob a n d

t 2

p Heptane, d i r t y surface

Butadiene 0Water (slope 0.73) @ Styrene Heptane

I

. . Boilina of Water a t Constan< Level

,orrected temperature difference. Whenever a straight line has heen dotted its location was deterniined by the method of aveiages Kith .he heptane data iFigure 2 an atmospheric pressure curve ohtained ~y Dunn and bchaffner subaequently ( 3 ) on Boiiilla and Perry's &inch diameter horizontal plate (11 !R also shown. The 3-inch plats 3hows in general a 2 5 5 l o w r At than +he 4-inch plate, which is believed h e to the presence of more light matches and dents on the 3-inch plate. Cichelli and Bonilla's data on mother similar 4-inch apparatus ( 2 ) we not for exactly the same condisions; they also in general show aomewhat higher AL raluea (,except, when diity) than the clean 3-inch plate, probably for the same reason. The water rune also are seen (Figure 3) T*, qive about 25% loner Af values

Table I .

Boiling of n-Heptane, Water, Styrene, and Butadiene

K Ulr Yo.

lleptane Heptant Heptane iieptanr IIentmt Heijtane Heptant Heptan,

700 i01 702 703 704 io3 706 707 708 710 i18 719 720

33 33 33 33 33 33 33 33 33 33 33 33 33

13,730 22.600 3z.300 46.300 63,000 87,200 100.300 117,100 133.500 101,400 109,500 82,800

23 0

ii.XOI1

31 1

9,830 24 800 31,800 38,330 46.700 60.000 68,300 72,300 !00,000 68,500 42,200 28,400 35.830 1 4 430

24 32.l 34.0 35.9 40.5 44.2 46.8 48.6 G1.3 34.3 45.5 40.1 36.2 18.9 18.6 72,s 6; 65.6 44.9 42.1 39.8 36.7 28.0

1495 Film boiling 1485 1410 1190 1020 663 338

15,600 3G. 1 40,; 22,700 43.9 39.200 42.9 16,760 56.2 25,500 58.3 37,600 63.4 46,400 69.5 62,000 64,800 61:1 52,900 40.900 55.6 27,300 52.4 32,900 55.4 20,500 49.4 12,800 38.0 9,500 30.2 4,900 30.9 ~ , 8 ~ 32.4 0 23.6 a.950 3,300 16,3

400 560 895 39 1 455 645 733 892 Film boiling 865 735 32 1 593 416 337 314 320 305 259 202

25.8 2i.2 28.2 31.i 36.2 39.9 16.6 68 .53 3

$$ 4

.j ti

597 '877 1296 1543 lYR0 2410 2510 2510 Film boiline 1990 2460 2210 183;

!A3 966 1427 182Y 1433 3310 3790 4410 5010 1843 1110 3162

147 152 154 137 161 1Rb

170 186 194 183 !70 A62 1.70

153,; 286., 288.2 289.4 292.8. 297 3 301 0 307.7 31Q 0 312.2 303. L .'!17.0

291 4

4tni. tie~laIlt.

fIeptanr Heptani FIebtane Heptane Heptane Heptane Heptane Heptanr Heptane Heptane Heptane Heotane Heptane Her~tane Heptane Heptane Heptane Heptane Heptane Hentane IIeijtane Heptane

66 I 662 663 664 665 666 667 668 669 671 672 673 674 675 676 677 ill 712 713 714 715 71G 717

1 1 1

1

1 1

? 1 1 1 1 1

ii

! I 1 1 I

iS:SSO

109,000 99,500 82,800 63,300 50,000 40,700 24,300 9,450

102 758 935 1069 1153 1385 1462 1484 1630 1261 926 io9 991 763

90,s

452 1lj000

1132 1490 1797 2275 2585 2730 3740 2600 1641 1140 1404

fils

007 3980 3725 3112 23'25 1975 1575 982 437

9;

10.4 103 106.8 111.5 114.0 116.5 112 134.3 129.5 119.5 114 109.5 34.5 92.5 114.5 128 122 112 109 106 104

229 278

!I

279,:i 241.0 2 4 3 , ,j 249.2 232 1 254 1 266. 5. 260 251 2 246 1 241.9 224.9 224.3 278 .j 266 0

46

260.: 249. I 246 . b 244.5 241.2 232 $7

910 1505 667 994 1435 1755 2240

92 91 95 62 0 72 5 76.5 77.5 84 n

220,i 221.5 225,2 182 8 196.6 200 6 203.9 212.6

1987 1552 1058 1264 812 524 403 418 417 0 269 ;I 169 .i

79 76 73 74 70 62 fi0 61 60 54 5 ;10 5

Z(i4'. 3

SIm. Heutaut. Heptane Heptane Heptane Hentane Heptane Heptane Heptane Heptane Heptane Heptane Heptane Heptane Heptane Hentane Hrbtane Heptanr H-ptanr HeptdnP H?pranr

Water K a ter Water Water \i-a t e t

Warer

Water Water Water Water K a t er Water Water Kater Kater Water Water \\ ater Kater Water Kate. Xater Water Water Water Katrr \l-a t cr Water Water Water Kater Wa t r r Water Water \Tat er W'nter

69; 698 699 679 680 681 682 683 684 686 687 688 689 690 69 1 692 693 691 fig5 696

j00 500 500 235 235 235 235 235 235 235 235 235 235 235 235 235 235 233 233 235

ii5i

33 33 33 33 33 33 33 33 ;3 3 33 33 33 33 33 33 :? 7 33 73 33 itm. 1 1 1 1 1

958 959 960 961 963 966 972 973 974 973 976 977 978 975 980 981 982 ')83 i8b i89

790 791 792

922 923 924 925 930 931 932 934 967 968 969 1017 1018 1019

!

1 1 1

1 1 1 1 1

1 1 1 1

2 8, 1011 44,000 44.100 65,300 89,500 185,500 242,000 110.000 166,200 207,000 1.51,000 179,500 204,700 78,700 51,400 33,400 79.000 154,000 185,500 188,600 258,000 I18,000 71,500 39,100 72,000 164.000 268.000 209,000 119,300 75,100 23,900 17,400 39,800 16,700 18,320 17,400 43,700 27,500

9.0 7.0 8.0 10.0 12.0 19.4

20.0 13.3 17.0 21.7 16.0 19.1 24. d 10 3 10.8 9.0 11.8 16 3 19.0

24.3 2i,CI 14.9 15.6 12.0 15.4 23.4 31.6 30.2 18.4 16 4 12.9 8.7 11.6

;:;

8130 6280 5500 6.530 74.50 9530 12100 8310 9080 9530 9430 9100 8400 7480 5000 5950 6700 94.50 9750

7750 9850 7900 4380 3230 $670 8 010 8480 6920 6490

4,580 18%

2000 3130 1880

2781) 2200 7.9 4120 9.9 3130 8.8 (Continued o n nert p a g e )

735

112.5 1707 I700 9471 3350 6823 8870 +120.0 6020 7620 j580 6fi20

7.520 2960 1975 1390 2970 ,5680 6820 6Y20 9350 4350 267i

1306 2690 6020 980il iR30 4400 2800 Y4i 7051 1821

c;uo

# 10 7011

16.57 1074

110 117 110 111 118 123 125 12.5 130

133 128 130 137 120 120 115 120

125 12,: 105 I08

97 97 34 89

96 106 102 93 YO 86

61 u0

88 48 81 82

x2

198.8 194.9 196.8 191.9 181 .fi 175.5 175.4 l(4.5 1G6.2 159 P

258.4 266.4 262.5 263,2 268, 2i7.4 273 2in.U

278.5 277,s 272.2 274 5 278.7 267.2 26i.0 2iii 0 2RR 0 2i2.6 174.2 1313 3 240 0 227.2 ?Si 7 223.9 227.2 2 X i '2 243 4 241 I 2 : x .5 223.i 22i.1

220. l i 224 0 220.5 21R.4 21Lj 222 1 221.3

Vol. 40, No. 6 than water did on t h e t w o 4-inch plates. The plate fouled rapidlv with polymer when styrene was boiled at atmospheric p r e s sure, so that only two points were accepted (Figure 4). However, no difficulties w e r e encountered a t lonver t e m p e r a tures, nor Kith b u t a d i e n e (Figure 5 ) . The iron cylinder was employed for t h e b u t a d i e n e runs and the depth of liquid could not be checked by observation, but was m a i n t a i n e d approximatell a t 2.5 inches by weighing the butadiene additions. The new data o n s i n g l e components were employed to check several previously published correlations, The At at the representative value of q / A of 50,000 was found to decrease Kith pressure (Figure 6), or the h to increase, in good a g i e e m c n t with the 0.25 pon-er of pressure, p r e v i ously reported (1). The variation of h with boiling rate was found to follow the 0.73 or 0.8 power of the Jakob and Linke c o r r e l a t i o n (1) closely (Figure 7). Hon-ever, t h e water and butadiene coefficients, in p a r t i c u l a r , reach twice the absolute magnitude expected and the others average somewhat h i g h This variation must again be due to greater rough~

t

4

INDUSTRIAL AND ENGINEERING CHEMISTRY

June 1948

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At("F) Figure 10. B o i l i n g of Styrene-Water M i x tures a t 1.OO Atmosphere Absolute Figure 8.

Correlation of M a x i m u m B o i l i n g Rates

A l l two-layer m i x t u r e s are p l o t t e d t w l c e o n o n e dashed line. T h e lower p o i n t is based o n t h e Pc of t h e denser ( w a t e r ) phase, t h e u p p e r o n t h e Pc o f t h e o t h e r phase

0 Kater

One Liquid Layer: Pressure,

Heptane

Two Liquid Layers Vol. % of

0.184 10a 59h

r

0.184

z

Styrene Styrene n-Butyl alcohol

50 (2)

1

140

1

-

20 0,000

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A

120 -

1000

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l0,OOO 1 -

--

0. *E

.-

50 25

__----

s,OOOA~ 20' 'do' "io0

--

-

-

'200

At("F1

Figure 11. B o i l i n g of Styrene-Water M i x t u r e s a t 0.59 Atmosphere Absolute

80-

-

,

%/*

I

0

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Other

component Styrene Styrene

50

0.053

X Styrene

l

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75 L? 50 iJ water

t A D

N u m b e r represents v o l u m e per c e n t of water Low q / A points replotted w i t h A t = plate temperature-water saturation temperature X 50% water V 75% w a t e r

N u m b e r represents v o l u m e per c e n t of water

0

60-

0

40-

20 -

0

0.0001

0.001

0.01

0.I

1.0

\\-ith Cichelli and Bonilla's correlations (2j. Iisecpt for styrene, the maximum heat transfer rate values for bhe pure components agree fairly ne11 (Figure 8). Except for water the critical temperature difference values for the pure components also agree (Figure 9j, particularly if the Cichelli and Bonilla curve is estcnded straight, as it might ~vellhave been from the original data ( 2 ) .

~

~

~

1118

INDUSTRIAL AND ENGINEERING CHEMISTRY

200,000-

Vol. 40, No. 6

pheric presure (Figure 10) xhere tht pressure is highest and thus vapor volume and agitation ale least, at 101' boiling rates and Kith equal or larger volume of water than of styrene a discontinuit,! exists in thc curve. This corresponds t r ' a critical rate above which the components mix more or less completely and LCIOTT-lvhich thcy separate. This phrnomenon could be obeerved visually, ac a t lo^ hoiling rates and high n-ater levels it could he seen that, styrene, KaF very seldom carried don-n to the heated

100,000

10,000

hoircvcr, it (1-cttd it y>referentially, di-

becamc licated Eurtlicr anct h > i l ( d riff At liigiiw boiling rates t h e 1,000 IO

1

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the temperature difference h t n - r c r i t h t plate and saturated natcr at the actua. At (TI Figure ,3. Boiling of Styrenepressure, the points obtainrd fnll fsirl: Water Mixtures at 0.053 Atmosphere close if not in the curve for pur(' water N u m b e r represents volume per cent of water Absolute (Figure lO)-which should start shifting to left at loT' p/L4--corroboratinf N u m b e r represents volume per cent of water this explanation. ;It the nest highesi pressure, 450 mm. (Figure ll), only orit uf the points oljtained was a t low enough boiling rate and higf Figures 10 through 13 give the results obtaincd x i t h styrene, enough water level to show this effect-iiaincly, the lolveat point r a t e r , and their mixtures (Table 11) a t the four prcssures ema t 50% of water. Using tho nater saturation temperature t,(m ployed. I t is apparent that the At values fcJr the mixtures arz considerably hipher than for the pure components, and the l e s , ~ compute A1 again checks the water curve. Figures 14 through 17 are plots a t constant total level ot ~ h r water the higher thcy are. ratio of the observed to the saturstion {ir rhrsretical At against This contrasts with the previously mentiuned results un 11thc theoretical At for styrene-water a t each pressurt'. Tlicse 1112,~ bury1 nlcohol and water, nhich showed little or no superheating 1 ~ i1,wfnl . in j>rcdicting approximatr artlml hoilirln t e m ~ ~ r : ~ t ~ ~ r + and for n.liich the At for the tno-phase equivolume mixture rtlways lay well betrveen that for the two pure coniponents separately ( 1 ) . and a t high boiling rat^^ was 1.0 " " ' " " " " ' ] less than either saturated layer by itself. At atlilo5I

At

1,000

Figure 12. Mixtures a t 0.184 Atmosphere A bsol Ute

IO

2oo

loo

0.9-

0.8-

i

0.8,

i

I

0

G6 *C -

2; 0.6-

0.5-

/

1 ,'

i

/

I

0.4 0'5:

I 0.31 0

Figure 15.

t

I

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Variation of

1

50

1

*

3

1

100

I

I

f

5

140

,htlTHE0 with Atrhea a t Constant Volume

Attheo

Percentage of Water and Styrene a t 0.59 Atmosphere Absolute N u m b e r represents volume per c e n t of water

N u m b e r represents volume per cent 0 50% water (by volume) 0 25% water (by volume)

of water

INDUSTRIAL AND ENGINEERING CHEMISTRY

lune 1948

1118

t

01

1

1

0

20 40 60 80 VOLUME PERCENT OF WATER

100

Figure 18. Variation of Theoretical Temperature Difference with Volume Per Cent of Water a t Constant Pressure for Styrene-Water Mixtures

’

04b

I

’

’

5 ’0

’

’

10 ’0

’

~ ~ T H E O Figure 16.

/Itact

Variation of

Boiling a t 4000 6.t.u. per hour X square foot On a horizontal plate a t a depth of 2.5 inches Number represents pressure in atmospheres absolute

’

roo,000~ ,

120

,

I I 1 I I l l

1

I

with 1ttl,.. a t Constant

-\[the?

Volume Percentage of Water and Styrene a t 0.184 Atmosphere Absolute Number represents volume per cent of water

II

0.9

30,000-

0.8

20,000-

0.61 I0,Ooo

I

”,

90

Variation of

Atact ~

with

Atthe0

,

, , , ,,

,

150

At

A~THEO. Figure 17.

,

200

0

( O f 7

Figure 19. Boiling of ButadieneWater Mixtures a t Constant Volume

Aftheo

Percentage of Water and Styrene a t 0.053 Atmosphere Absolute Number represents volume per cent of water

and vapor superheat under these conditions. S o reason is knon-n for the agreement in Figure 15 bctn-cen 25 and 50yo of water. The positive slope clearly indicates the improved mixing and loiver actual Imiling teinpera~urcol,taiii(.jat high boiling rate4, and the discontinuity on the higher pressure curves s h o w in yet another way the shift in boiling nieclinnisni from unmixed to mixed constituents. To analyzc further what occurred, the “smoothed” values in Table I11 (page 1121) have been computed from Figures 10 and 14, for n boiling rate of 20,000 B.t.u. per hour X square foot, lyhich cuts across the lines on both sicks of the discontinuity. The starred plate temperatures are practically the same as that for water, as vould be expected with the water separated a t the bottom. With increasing volume.? of styrene misecl in with the water the required plate temperature similarly increases, from 0

\ i l “70 nttr

n

10 12 5 33.3 33.3 33.3 50 66.6 8i.5

Prt..ui* itm. 4 08 4 08 ti 12 4 08 4.05 4 08 4 08 4 06

Y attr De5tb, Inches 0.313 0.313 0.G25

0.623 1.258 1 230 1 230 2 183

t u 100‘; styrm,. This i~ grobalil! clue to the preferential neitirig of the plate by tlic \tyrci,c, previousl! mentioned. The liquid temperatures niai,ketl x are even higher than the boiling point of water. This must he because the thermocouple we]. averagez the temperatuws o i the globules of water and styrent that touch it, and the latter can rise directly from the plate, where because of their preferential wetting their cores have been heatec up before their release to temperatures probably approaching the

boiling point of styrene. U7ithout n high temperature hear source a different situation might develop. In general, however. it seems that coiisiderahle superheating may be expected 5vvher two imiiiiscible liquids are boiled. I-ndoubtetlly tile reasor. butanol-n-ater tivo-phase systems did iiot show this effect is thai their mutual solubility permits each phase t o boil, appreciably, a i or near their common boiling point, whirh cannot occur wit]

1120 practically insoluble liquids. (At the boiling point the water layer has 2.5 mole % butanol and the “oil” layer 58 mole %water.) Keplottirig Figures 10 through 13 as q ) A against the observed At values moves the curves for the three mixtures t o the left and decreases their slopes, as could be predicted from Figures 14 through 17. At, the three lower pressures the curves for the mixtures are brought Tvithin 20% of the ill of each other, and all intersect the styrene curve near q,‘A = 10,000. At atmospheric pressure the agreement is poorer, but, the average result is the same.

INDUSTRIAL AND ENGINEERING CHEMISTRY Table 1 1 .

Kiln

NO. 843 844 84; 846 847 848 855

860 86 1 862 863 864 866

867 868 869 870 871 872 673 874 876 876 877 878 879

Water, 5% by YO].

-.

_ii 0J-

---_ -_

Absolute Pressure, Atm. 1

1

10 13 iJ

1 1

75

1

75 75 75

75 75 75

75 75

75 75

1

1

1 1 1 1 1 11m. 460 430 450 430 450 4io 140 140 140 140 140

q A,

Boiling of Mixtures of Styrene and Water

R.t.u./Hr. X Sq. Fr.

11,320 16,750

25,700 29,500 47,000 57,900 35,200 51,530 20,800 28,000 36,900 15.200 20,600 11,550 ?3,100

40,000 46,700 50,000 10,820 6,730 16,050 22,100

Vol. 40, No. 6

-

(Total liquid depth 2.5inchen) k B.t.u.:’fIr. !!oits B.t.u. Per Hr. Plate Cor. btr!reo, x Sq. F t . X Gross F. input Losses Temp., F. 0 F. 216.0 85 18.0

15.0 35.6 43.1 66.8 90.4 41.4

85 57 103 115 148 102

216.9 233.6 241.1 264.8 288.4 239.4

2i.4 38.6 47,l 55.3

86

219.4 236.6 249.6

42.6 31.3 48,l il.6 80.9

370 577 Film boiling

a23 479 986 1575 1792

F. 7.6 10.2 31.0 39.4 62.2 O

85.7

36.4 13.9

113

253.3

34.2 51.6 55.1

78 70

214.0 203.3 220.1 243.6 252.9

35.1 24 0 40,s 63.6 73.5

99 110

483 362 522

Ataet,

82 98 106

htset Ahheo

0.422 0.537 0.871 0,892 0.931 0.947 0.88 0.bb 0.886 0.913 0.996

0.824 0.767 0.841

0.88

0.91 is , . Figure 18, plotted for a q / A 75 0.825 2 9 9 51 160’. 3 4i2 3’6.3 298 75 value of -10,000, clearly shon-s 20.5 0 . 7 , i i 157.4 292 49 207 32.4 75 39.0 0,842 172.2 59 638 75 318 46.3 the rrlative effect of composi48.0 0 . 855 181.2 66 866 595 75 56.2 59.8 0.g07 189.0 t,ion. Evidently a t about one1100 io 75 28,500 G6.0 432 67.1 0.912 198,6 76 488 1380 75 140 36,000 73.6 third water by vclume and 73.2 0.916 206.5 81 540 1639 43,200 75 140 80.0 76.8 0.934 207.4 82 1870 75 140 82.4 600 49,500 tFo-thirds styrene the heat 880 Film boiiing 73 140 58,000 48.8 0,908 137.8 transfer is poorest for a total 205 433 3i 882 75 40 11,000 i3.8 43.6 0.991 131 .O 45 883 75 11,450 44.0 469 260 40 depth of 2.5 inches. The 54.4 0,944 144.6 741 43 333 40 884 76 19,300 57.6 62.2 0,902 155.8 51 583 885 376 40 75 25,800 68.8 reason for the particular loca0.553 70.7 161.2 1180 54 420 75 40 886 31,200 74.2 0,954 68.6 tion and for the constancy of 158.9 887 1180 52 31.300 71.9 435 75 40 this minimum at different presAim 48.2 0 . 7 7 124 260.7 sures is not apparent. 793 50 381 985 1 23,900 62.7 65.9 0 . 8 1 279.3 1855 142 47,500 50 1 793 583 81.3 The effect of pressure on 71.6 0.82 150 285.6 675 2285 50 87.6 1 59,200 796 10.2 0.51,5 217.8 6 89 800 50 1 840 89 16,620 15.8 temperature difference for the 12.4 0.605 218.5 92 822 801 50 i 20.5 985 20,200 43.2 0 . 8 1 251.2 mixtures is less than half that 802 50 1 455 982 107 24,200 53.2 0.75 46. 259.0 467 1154 124 50 1 61 803 28,600 for the pure components (Fig49.8 0.76 263.6 1 507 1330 128 50 65.6 804 33,300 0.43 7.2 214.8 89 807 50 1 16.8 601 463 10,100 ure 6’)-i.c., At is approxi8.9 0 475 ,>5 4 216.8 50 583 808 1 18.8 90 12,830 33.5 0.1.1 241.4 mately proportional to P-0.1 a t 110 632 50 1 343 809 43.4 15,000 40.7 0.80 249.0 50 1 815 118 379 810 51.0 19.300 constant q / A . This cwnpares 43.5 0.13 257.6 122 I 1000 811 50 408 39.G 24,300 57.8 0.88 264,O 50 I 6fi 0 537 127 1407 33.400 812 with an exponent averaging 1Im about -0.25 found by Cichelli 7.3 0.608 187. 430 67 50 4,900 12 408 819 and Bonilla for niiscible binary 29.0 0.591 221.8 90 460 820 50 10,150 49 208 33.2 0.632 mixtures in this pressure range 102 234.7 821 50 16,800 62 2i1 450 49.2 0.683 110 245.2 50 430 25,200 72 350 82 2 as well as for pure compo56.2 0.711 251.7 116 50 450 73 464 36,700 823 64.7 0 . 7 5 2 25s.g 121 450 82 4 50 560 48,300 86 nents. 0.768 71.4 265.6 126 57,000 50 430 825 613 93 91.2 0.748 286.0 50 122 145 450 631 77,000 826 Plotting the ratio of the 0.83 101.1 678 295.4 50 450 I57 82,900 122 827 actual observed i l t values in111.3 0.831 306.9 91,500 828 50 4.50 682 173 134 0,772 64.8 259.4 116 50 430 84 588 49,400 829 stead of the equilibrium ones 42.7 0.562 247.1 450 50 107 24,300 76 830 450 30 92,000 831 yields a slope close t,o -0.25, O.Cib4 8.7 139.4 832 50 14.4 39 140 1,230 Thus the reason for the slope 14.7 0.504 154.2 30 50 3,650 29.2 833 140 22.7 0.528 168.1 83 4 50 6,150 43.0 54 140 of -0.1 is probably that at 32.8 0.635 1i6,6 50 10,600 51.6 59 110 835 47.4 0.715 191.3 30 R6.3 17,050 68 140 836 loxer pressures for a given g / r l 62.6 0.886 203.6 30 25,500 78 70.6 837 140 77.4 0.849 the vapor volunie is larger, 50 83 216.1 140 91.1 35,500 838 0.863 88.8 227.2 50 103 95 46,700 140 839 giving better agitation and 0 . 744 57.3 75 50 201.9 140 77 22,200 840 0,877 101.9 104 240. , 5 50 $6,000 116 140 841 decreasing the superheat par50 140 1,000 842 i6.i 0.G36 108.8 p0 40 1.8clO ii.3 18 849 tially to counteract the normal 21.7 0 . 5 i 9 124 5 a0 27 850 40 37.5 4,200 rise in At due to increasing 36.2 0.718 50.4 50 40 137.4 3.i SS1 7,670 0 , iS9 46.0 147.6 50 40 37 872 11,870 60.6 vapor volume with one rom0.837 62 1 163 1 .50 50 853 1410 18,800 74.1 0,888 177 0 80 50 58 140 26,300 854 90.0 ponent alone. 0.916 9i .7 BO 193 7 140 41,900 106.7 67 855 The maximum boiling rate 110.7 n 925 836 50 40 206 8 .&,900 119.8 78 122.1 0,530 837 :0 40 217 3 131.5 70,600 86 values obtained Kith styrene40 50 828 i1,oon .. water mixtures have been (Continued on p a g e 21Zf) entered on Figure 8, based on both critical pressures. 30 consistent agreement isnoticed. The butanol-ivater value ( 1 ) based on the critical pressure of metal of the surface ( f ) , and cannot be directly used with confithe denser phase agrees fairly F\ ell, horvever, as might have been dence in design with other surfaces. Butadiene-Water. Figure 19 shows the results obtained hoped. The critical temperature differences plotted in Figure 9 against (Table IV) with butadiene-water mixtures a t 60 pounds per square inch absolute, the lowest pressure regularly obtainable the reduced pressure of the lighter phase give poorer agreement. These At values mould be expected to vary considerably with the with the cooling water available. The At, based on the equilib!

I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY

June 1948 Table I I .

Run SO.

1020 1021 1022 1023 1024 1023 1026 988 989 990 991 992 993 994 995 996 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016

K a t er , by

7. T 01.

Absolute Pressure.

htm.

2.5 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 2 .i 25 25 25 25 25 25 25

natural convection from horizontal cylinders was computed from the usual equation (6) for the same diameter and At. The resulting ratio mas 187. The approximate equation h = 0.38 ( A 0 0 25 for natural convection of air from a hot horizontal surface facing upward ( 4 ) n as then multiplied bv 187 and equated to 40,00O/At. Solving for At gave 160” F., in good agreement with 150’ F., an average value for rnoLqtof the runs.

Boiling of Mixtures of Styrene and Water (Continued) (Total liquid depth q/A, B.t.u./Hr. X Sq. Ft.

At.hea,

OF

11,100 5,630 27,800 18,650 28.800 ioi700 33,900 12,900 30,100 42.000 12,950 9,500 5,260 19,810 9,570 3,640 18,270 9,800 6,350 18,900 51,300 18,850 18,900

1 1 1

1

1 1 1 450 450 450 450 450 450 450 450 450 450 450 450 450 450 450 140 140 140 140 140 140 140 40 40 40 40 40 40

= 2.5 inches)

cor.

~ . t . ~ j j ’ ~Heat, ~ . xB.t.u. per Hr. Sq. X Gross Plate, Atact, F. imput Loase5 Temp.,’ F. O F.

Ft.

231 149 343 311 397 228 429 220 39 1 461 220 180 122 279 192 107 293 1RG 155 266 493 258 255 345 423 199

48 38 81 !203 47 79 59 77 91 59 53 43 71 50 34 64 50 41 71 104 73 74.1

503 291 1132 783 1155 484 1350 560 1190 1630 557 428 268 747 427. 5 204.2 758 433 305 778 1960 778 751 1159 1567 571 509 289.8 751 459 854 1298 49 1 274 1665

101 88 129 109 119 98 127 92 104 115 90 85 78 32 82 72.5 82 81 76 96 107 98 68 77 85 68 62.0 52.5

245.8 236.2 279.0 258.2 270.5 245.0 277.2 232,4 249.3 263.0 231.3 225.3 214.9 242.7 221.9 206.7 236.0 221.5 213.0 243.2 275.9 244.6 204 211.8 221.9 194.8 188.2 173.4 200.5 E3,9 171.0 186.7 156.3 139.5 192.9

33 25.6 51.2 39.2 51. 29.4 62.6 36.0 56.4 70.0 34.9 29.7 22.6 44.7 24.1 11.7 39.7 26.3 19.4 46.6 81.3 50.7 46.8 58.7 69.2 41.1 35.2 23.0 46.0 41.1 59.1 75.5 43.9 28.8 79.6

1121

&L-! Attheo

0.69 0.67 0.63 0.65 0.70 0.625 0.79 0.61 0.733 0.77 0,592 0,561 0.525 0.63 0.482 0.344 0.620 0.526 0.473 0.638 0.781 0.693 0.631 0, 675 0.713 0.588 0.559 0.479 0.605 0.614 0,704 0,755 0.636 0,544 0,752

CONCLUSIONS

In the boiling of mixtures of cornponcnts that are not mutuallv soluble the necessary At, based on the saturation tcmperature in cach case, will 30,000 87 be appreciably larger than for 41,100 9: either component alone a t the 70 13,920 63 197 12.400 same q / A . By560 137 48 70.0 76 249 18;900 I n the boiling of relatively 39 67 174 11,650 50 shallow depths of the order 265 84 22,250 58 344 100 34,350 of magnitude of 2.5 inches of 41 181 69 12,460 28.5 131 53 6,950 mixtures of insoluble liquids. 63 .O 420 106 44,500 considerable superheating of the mixture may be expected, with an “avwage” temperature possibly exceediiig the boiling point of the loner boilrium temperature, required to boil the mixture is much higher ing constituent. This contrasts with the boiling of two-phase than for either pure component (Figure 20). Visual observation mixtures of partially soluble liquids, in which it is probable from showed that in none of the butadiene-water runs, even up to 50,GOO previous work that no significant superheatin? of the mixture will B.t.u. per hour X square foot, did the water start boiling. The occur. highest plate temperature in these runs Tas several degrees belorr the saturation temperature of TTater a t the pressure of the run. Instead, hot 11-ater rose from the plate by natural convection and caused the butadiene layer to boil strongly without intermixing with it. This effect might aln-ays tie expected a t Ion. q / A when thv lower boiling liquid has a lon-er density than the high boiler. I n this case the extreme difference in the boiling poiuts (105’ C. at atmospheric pressure) has meant that the full heat fluxes employed could be carried by natural Convection alone. The following observations also evidence this mechanism: ~~

The change in At a t constant qld that occurred on going from 60 to 90 pounds per square inch absolute (Figure 19) is negligible, or a t least considerably smaller than would have been expected in the boiling of either a single liquid or mixed immiscible liquids. Using the boiling temperature for water at the given pressure to compute Af gives values considerably hipher than those obtained on water boiling alone a t these heat transfer rates (Figure 20). Shallower depths of water give on the average progressively lower plate temperature and At values (Figure 19), whereas in simple boiling no such effect would be espected. Employing several assumptions, a value of It at q / A = 40,000 was computed for natural convection through the water layer which roughly agrees n-ith that observed (Figure 20). First the ratio of thr heat transfer coefficients for water and for air b>-

Table I I I . Boiling of Styrene-Water Mixtures a t Atmospheric Pressure and 20,000 B.t.u. per Hour X Square Feet from a Chromium-Plated Horizontal Surface

7Z water hv volume Approu. t s a t n , 0 F. Condirion of layers l o ) , F.

Attheo LFieure plate,

*A

*ttheo Atact,

tlisuid,

F.

(Figure 14)

F. F.

-,-J

100 212

9

221

2’