Investigation of the Mechanism of Boiling in Liquids

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P U R D U E U N IV ER SITY

THIS IS TO CERTIFY THAT THE THESIS PREPARED UNDER MY SUPERVISION

Paul Carl Zmola

BY

e n title d

M INVESTIGATION OF THE MECHANISM OF BOILING IN LIQUIDS

COMPLIES WITH THE UNIVERSITY REGULATIONS ON GRADUATION THESES

AND IS APPROVED BY ME AS FULFILLING THIS PART OF THE REQUIREMENTS

FOR THE DEGREE OF

Doctor of Philosophy

W

P

H

r o f e sso r

ea d

o f

S

in

C

h a r g e

ch o ol

o r

D

o f

T

h e s is

epa r tm en t

TO THE LIBRARIAN:----THIS THESIS IS NOT TO BE REGARDED AS CONFIDENTIAL.

/ XV/ REGISTRAR FORM 10—7 -4 7 — 1M

PROFESSOR LN CHARGE

AN INVESTIGATION OF THE MECHANISM OF BOILING IN LIQUIDS

A Thesis

Submitted to the Faculty

of

Purdue University

by

Paul Carl Zmola

In P a rtia l Fulfillment of the Requirements for the Degree

of

Doctor of Philosophy

June, 1950

ProQuest Number: 27714168

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To YERAM SARKIS TOULODKIAN

ACKNOW LEDGM ENT

I t is a p a rticu la r pleasure for me to acknowledge my indebtedness to the many friends who gave u nselfish ly of th e ir time and e ffo rts to help in the completion of th is work. I am grateful for the guidance and suggestions of Dr. Max Jakob, who shared with me some of his broad knowledge and experience in the f ie ld of boiling.

I t has

been a genuine pleasure to work under the direction of Dr. W . L. S ib b itt. I am p a rtic u la rly indebted to Professor John R. Clark who not only suggested using the M ultiplied-Deflection Potentiometer, but also directed i t s tion .

design and calib ra­

The help of Miss Gertrude Monhaut in the prepara­

tion of the thesis has been sincerely appreciated.

ABSTRACT

The mechanism of natural convection nucleate boiling from a f l a t horizontal surface was studied.

Apparatus was

constructed and techniques developed so th a t high speed motion pictures and single flash photographs as well as regular heat tra n sfe r information could be obtained* Photo­ graphic data were analyzed and found to check existing theory on bubble formation.

Comparison of heat tra n sfe r

data with published re s u lts showed that boiling conditions of which photographs were taken were representative* influence of heat flux, heater surface condition, tension, pressure,

The

surface

and subcooling on the growth and be­

havior of vapor bubbles was observed. A thermodynamic analysis of the growth and behavior of vapor bubbles in both ordinary and subcooled boiling is presented which depends upon the vapor within the bubble being in a metastable s ta te .

The conditions under which

a bubble will grow, collapse,

or remain the same size within

the liq u id bulk are given.

Results calculated on the basis

of these concepts compare favorably with experimental re ­ su lts •

TABLE OF CONTENTS P age INTRODUCTION ..........................................................................................................

1

Outline of the Field and Definition of Terms ............

1

Variables Involved in Boiling .............

7

Scope of the Work.....................................................................................

9

Objectives of the Work

.............................*...........................

10

SURVEY OF THE LITERATURE..........................................................................

12

Ordinary Boiling ........................................................................................

12

Subcooled Boiling

..................................................................................

l6

The Formation and Growth of Bubbles ....................................

17

PRELIMINARY CONSIDERATIONS AND PLANOF THE WORK

20

EXPERIMENTAL APPARATUS ................................................................................

21

TEST PROCEDURE.....................................................................................................

33

EXPERIMENTAL RESULTS .....................................................................................

35

Ordinary Nucleate Boiling ...............................................................

35

Subcooled Boiling .....................................................................................

45

ANALYSIS OF AND EVALUATION OF EXPERIMENTAL RESULTS . .

57

Ordinary Nucleate B o ilin g ..............................................................

57

Subcooled Boiling ...................................................................................

62

THEORETICAL CONSIDERATIONS OF THE MECHANISM OF BOILING................................................................................................................ The Thermodynamic Behavior of a Vapor Bubble in Ordinary Nucleate Boiling »..................

»

65 65

The Thermodynamic Behavior of a Vapor Bubble in Subcooled Boiling .........................................................................

71

CONCLUSIONS AND SUGGESTIONS..................................................................

78

TABLE OF CONTENTS - C o n tin u e d P age MEASUREMENT OF A-C POWER.......................................

82

M ultiplied-Deflection A-C P oten tiom eter.........................

82

Operation of the Potentiometer ..................................................

85

Accuracy and Precision of Measurements

88

APPENDIX A.

.............

Range and F l e x i b i l i t y .......................................................................... APPENDIX B.

91

MEASUREMENTOF TEMPERATURE ...............................

92

Fabrication and Calibration of Thermocouples «••••

94-

Accuracy

..........................................................................................................

96

APPENDIX C.

HIGH SPEED PHOTOGRAPHY............................................

97

High Speed Motion Picture Apparatus ....................................

97

The Western E lectric Fastax Camera .......................................

100

Lighting fo r Motion Picture Photography

102

S t i l l Flash Photography

..............................................................

105

Analysis of Photographs

........................................

109

Accuracy of Results ...............................................................................

Ill

Range and Limitation of Photographic Method . . . . . .

113

APPENDIX D. APPENDIX E.

B. C.

115

CALCULATION..........................................

117

Experimental C a lc u la tio n .......................................

117

Temperature Differences, Heat Flux, and Heat Transfer Coefficients ..........................................

117

Calculation of the Boiling Surface Temperature of a Ribbon Heater ...............................

118

Calculation of Bubble Volumes .................................

120

Part I A.

PRELIMINARYAPPARATUS ............................................

TABLE OF CONTENTS - C o n tin u e d P age Part II - Theoretical Calculations ......................................» A.

121

Natural Velocity of Rise for a Bubble on the Basis of Stokes Law ................

121

C ritic a l Bubble Size in Ordinary Nucleate Boiling .....................................................................

122

C.

Pressure Inside a SphericalVapor Bubble •»

124

D*

Bubble Growth and Collapse Rates

.......................

124

E*

I n i t i a l Bubble Velocity in Subcooled Boiling .............................................................................................

12?

B.

APPENDIX F.

NOMENCLATURE.........................................................................

129

APPENDIX G.

BIBLIOGRAPHY........................................................................

1]2

References on Boiling ..........................................................................

132

Related References ..................................................................................

137

References on Instrumentation APPENDIX H.

.............

LIST OF APPARATUS ...........................................................

13d l40

LISTS OF FIGURES AND TABLES

L ist of Figures Figure 1*

Page Variation of Liquid Temperature with Distance Above Heating S u r f a c e ...........................

3

Regions of Convection Heat Transfer Shown on the Boiling Curve .......................................................

3

3*

Cross Section of Boiling Apparatus ...........................

22

4*

General View of Apparatus and Instrumentation

5*

Boiler Assembly with Camera Arrangement for Flash Photography...............................................................

23

6*

Test Heater Assembly.................................................................

24

7•

Liquid Bulk Temperature Probe

.....................................

24

8.

Exploded View of Test Heater Assembly..................

25

9*

Cross Section of Main H e a te r ...........................................

26

10*

Power Supply Circuit Diagram for Boiling Apparatus .....................................................................................

28

11$

Control Panel ...................................................................................

29

12*

Top View of Apparatus Arrangement for Motion Picture Photography .............

31

Top View of Apparatus Arrangement for S t i l l Flash Photography...............................................

32

Comparison of Data for Water in Natural Convection Boiling at One Atmosphere

37

Ordinary Nucleate Boiling, Run 10B (Back Lighted) *....................................................................

L\.l

Ordinary Nucleate Bolling, Run 10B ( Si de Lighted) .......................................................................

l±l

17*

Ordinary Nucleate Boiling, Run 20 .............................

l±2

18.

Ordinary Nucleate Boiling, Run 21 .............................

l±2

2.

13# 14* 15* l6 .

23

L i s t o f F i g u r e s - C o n tin u e d F ig u r e

P age

19*

Ordinary Nucleate Boiling, Run 22

.....................

43

20*

Ordinary Nucleate Boiling, Run 2 3 ............................

43

21*

Ordinary Nucleate Boiling with Triton Added to Water, Run 13 (Back Lighted) .........................

44

Ordinary Nucleate Boiling with Triton Added to Water, Run 13 (Side Lighted) *......................

44

23*

Subcooled Boiling, Run P-l .................................................

50

24*

Subcooled Boiling, Run P-2 .................................................

50

25*

Subcooled Boiling, Run P - 3 .................................................

51

26 .

Subcooled Boiling, Run P ~ 4 .................

51

27.

Subcooled Boiling, Run 11 ...................................................

52

28*

Subcooled Boiling with Triton Added to Water, Run 12 .............................................................................................

52

Subcooled Boiling at Atmospheric Pressure, Run 2 5 .............................................................................................

53

Subcooled Boiling at Pressure of Two Atmospheres, Run 27 ..........................................................

53

Enlargement of Figure 29 Showing Bubbles Formed in Sub cooled Boiling, Run 2 5 ..............

54

Typical Formation of a Bubble Column from a Heated Surface ..................................................................

58

Volume of Vapor and Gas Bubbles When Breaking Off the Heater Surface ..................................................

60

34*

Frequency of Vapor B ubbles................................................

6l

35»

Sub-system Cycle Traced on Pressure Volume Coordinates (Low Heat Flux) ....................................

67

Sub-system Cycle Traced on TemperatureEntropy Coordinates (Low Heat Flux) ..............

67

Sub-system Cycle Traced on PressureVolume Coordinates (Higher Heat Flux)

68

22#

29* 30• 31 * 32* 33*

36. 37 *

****

L ist of Figures - Continued Figure 38.

Page Sub-system Cycle Traced on Temperature Entropy Coordinates (Higher Heat Flux) •••

68

Sub-system Cycle Traced on Pressure Volume Coordinates ...............................................................................

73

Sub-system Cycle Traced on Temperature Entropy C oordinates .........................................

73

Excess Pressure Developed in a Vapor Bubble Due to Surface T en sio n ..................................................

76

42•

C ircuit Diagram for A-C P otentiom eter...................

81j.

if3*

60 cps F i l te r Circuit ..............................................................

86

Ijjf•

Voltage Divider Network.........................................................

87

If5*

Thermocouples and Potentiometer C i r c u i t

93

if6.

Schematic Drawing of Rotating Prism Type High Speed Motion Picture Camera......................

99

Arrangement of a High Speed Motion Picture Camera U tilizing a Kerr Cell .................................

99

if.8.

Fastax Camera Power and Timing C i r c u i t ................

103

if9#

Relation of Speed, Time, and Voltage for 8 mm Fastax Camera.........................................................................

10lf

Variation of Light Inten sity with Voltage for GE Projector Spot Lamp ......................................

106

Si*

Wiring Diagram of Type R-if330 Flash Unit * ...

107

S2.

Early Design Heater Support Block Showing Thermocouples in Place .................................................

Il6

Cross Section of Test Heater Showing Symbols U sed .................................................................................................

118

Calculation of Volume for Bubbles with Rotational Symmetry .........................................................

120

39» lj.0* lj.1.

if7 •

50*

S3* 5if•

L i s t o f T a b le s T a b le

P age

1.

C lassification of Boiling Phenomena ...........................

7

2*

Summary of Experiments

...........................................................

36

3*

Summary of Experiments on Subcooled Boiling • •

lf6

If*

Time Required for Vapor Bubbles to Disappear in Sub cooled Liquid .............................................

ifÔ

5»

Photographic Information for Pictures Shown **

55

6*

Summary of High Speed Motion Picture Photography..................................................................................

$6

7*

Bubble Size D istribution in Subcooled Boiling

63

8,

Reynolds Numbers and Natural Rise Velocities for Bubbles in Subcooled Boiling .........................

62f

910*

Limiting Speeds for Various High Speed Motion Picture Cameras ....................................................................... 100 Focusing Infomation fo r Fastax Camera and Approximate M agnification

** 101

1

AN INVESTIGATION OF THE MECHANISM OF BOILING IN LIQUIDS

INTRODUCTION

The flow of heat to a boiling liq u id involves con­ vection complicated by a change in phase of the liq u id . An understanding of th is energy tra n sfe r from the heated surface to the liqu id on the basis of physical principles is

somewhat d if f ic u lt, not only because of the large

number of variables involved, but also because of the d iffic u lty in determining th e ir values.

The purpose of

th is study has been to investigate the origin, growth, and behavior of the vapor bubbles which arise in boiling in an attempt to understand the mechanism of nucleate boiling by examination of the hydrodynamic and thermo­ dynamic behavior of the bubbles.

Outline of the Field and Definition of Terms The tenu M boiling ” as used in the present study means the formation of a vapor phase in the bulk of the liqu id at the surface or wall through which the heat is being supplied. tio n i t

Boiling implies eb u llitio n .

With th is defin i­

is not s t r i c t l y correct to consider boiling as a

special case of evaporation since in so-called ”subcooled” boiling no net generation of vapor r e s u lts .

2

Consider a heating surface at temperature t H submerged in a pool or bulk of liquid at temperature tjj# boiling is

I f ordinary

taking place, the liqu id w ill be slig h tly super­

heated, i . e . ,

the liquid temperature w ill be slig h tly

higher than the saturation temperature corresponding to the pressure at which the boiling is taking place.

The tempera­

ture is necessarily uniform throughout the bulk of the liquid with the exception of a sharp temperature gradient which ex ists next to the heating surface*

The general form

of the variation of liquid temperature with distance above the heating surface is shown in figure 1*

The vapor

bubbles form on the heating surface ; grow rapidly in the superheated liq u id layer while s t i l l

attached to the heat­

ing surface; and, ultim ately, break away from the heating surface and rise in the liq u id bulk* I f the heat flux, qM , i s plotted as an ordinate against the temperature difference between the heater surface and the liquid bulk, tn - t^ , conditions, tained.

as the abscissa for a number of

a curve such as that shown in figure 2 is ob­

This curve can be divided into a number of regions

each of which have a slig h tly d ifferen t physical mechanism of heat tra n s fe r. Region I - Pure Convection In th is range there is no bubble formation at the heating surface.

I f the liquid bulk has a free surface.

3

ki 0

1 Is1 §

to

kj

L iQ U /O

T Æ Æ ftt& A T U R E

S A T C /Æ A 7YO/V

A t/A J U S

TE A JE E SPA TCS/IE

F/GJ VAR/AT/ON OF UQU/D TFMPFRAFORE W/TH D/S TANCE ABOVE F/EAT/A/G SURFACE Æ

o

LO(5 ( "bfj —E )

F/G. 2 REG/ONS OF CONNECT/IFF NEAT TRANSFER SNO A/A/ OA/ THE BO/UNG CURl/E

4 in terface evaporation w ill take place• mospheric pressure,

For water a t a t­

th is condition ex ists when the tempera­

ture difference between the heating surface and the liq u id bulk i s less than I4. degrees F* Region II - Ordinary Nucleate Boiling This i s the region of common "tea k e ttle " boiling or boiling of the so rt encountered in most powerplant boilers* I t is called nucleate boiling because the formation of the vapor bubble depends upon the presence of a nucleus of some nature; perhaps a so lid p a rtic le on the surface, gas ab­ sorbed in the liq u id , or gas adsorbed by the heating sur­ face.

A vapor bubble w ill not form spontaneously in a pure

liqu id.

For water at atmospheric pressure,

th is condition

exists when the heating surface - liq u id bulk temperature difference lie s between l\. and about 65 degrees F. Region I I I - P artial Film Boiling In both regions I and II the heat flux increases with the temperature; the steeper slope of the boiling curve in region I I i s due to the mixing action of the liquid pro­ duced by the bubbles•

However, a peak value is reached in

nucleate boiling because the bubbles become so dense they coalesce and form a vapor film over the heating surface* Since the heat energy must pass through the vapor by a combined mechanism of conduction and rad iatio n, n either of which is very e ffic ie n t in th is temperature range, the heat

5

flux decreases appreciably even though, the temperature d if ­ ference Is m aterially increased. is unstable; i t

In region I I I th is film

spreads over a p art of the heating surface

and then breaks down so that part of the surface is film boiling while the remainder is in violent nucleate boiling. For water at atmospheric pressure p a r tia l film boiling occurs at a temperature difference of 65 to ij.00 degrees F, Region IV - Film Boiling For s u ffic ie n tly high temperature differences,

the

film of region I I I becomes stable and the en tire heating surface is covered by a th in vapor blanket.

The energy

transfer through the vapor to the liq u id Is by conduction and rad iatio n.

For water at atmospheric pressure, film

boiling occurs at temperature differences in excess of lj.00 degrees F.

From a p ractical standpoint, film boiling has

severe lim itations because in many cases the melting point of the heating surface i s reached at a heat flux lower than th at obtained from the same heating surface in nucleate boiling near the maximum condition# In the foregoing discussion natural convection "pool" boiling was implied.

However, the boiling curve has the

same general shape for forced convection boiling although film boiling i s not often realized because the forced flow tends to wipe the vapor from the heating surface.

However,

i f a su ffic ie n tly high heat flux can be transferred to a

6

liq u id , bubbles w ill form a t the heating surface even though the liquid is considerably below i t s temperature.

saturation

Such boiling has been variously called sub­

cooled boiling,

local boiling,

and surface b oiling .

The

bubbles formed are considerably smaller than in ordinary boiling and most of them condense upon leaving the v ic in ity of the heater.

Very high flux ra te s can be transferred in

subcooled boiling; for water at atmospheric pressure, flux rates in excess of 2,000,000 B hr^ft""^ have been obtained. In forced convection 1^,000,000 B hr”^ f f 2 has been reached. The various c la ssific a tio n s of boiling are shown in table 1 with a re la tiv e indication of how much work has been done in each of the areas.

Some lib e rty has been

taken in c la s s ific a tio n since film boiling has not been observed in a subcooled liq u id ; however, the heating sur­ face does burn out at a su ffic ie n tly high flux which in ­ dicates that the surface must become vapor bound.

7 Table 1#

C lassification of Boiling Phenomena

Ordinary Boiling (Liquid temperature ap­ proximately equal to saturation temperature)

Nucleate Boiling Film Boiling

Subcooled Boiling (Liquid temperature less than saturation temperature)

Nucleate Boiling film Boiling

Natural Convection

Forced Convection

A

A

B

C

B

B

C

C

The l e t t e r s give a re la tiv e indication of how much work has been done in each of the areas. A.

Considerable work performed and information obtained.

B.

Some work performed but re la tiv e ly l i t t l e av ailable•

C.

No work performed.

information

Variables Involved in Boiling The variables influencing boiling which must be controlled in any study of the phenomenon can be divided into a number of classes. A.

Primary Variables In the operation of a specific piece of apparatus,

these variables must be known and controlled: 1.

Temperature of the liq u id bulk.

2.

Temperature of the heater surface.

3.

Heat flux being transferred to the boiling liquid from the heating surface.

if.

Pressure under which the boiling i s taking place.

5.

Velocity of the liqu id (for forced convection b o ilin g )•

6*

Pressure drop in boiling section (for forced convection b o ilin g )•

B.

Secondary Variables In order to understand the nature of the boiling

process, the influence of the following variables, in addition to the primary ones lis te d above, must be under stood* 1.

Physical configuration of the heating surface#

2.

Material from which the heating surface is made

3.

Nature of the heating surface (roughness, amount of adsorbed gas,

if.

e t c .) .

Surface tension (liquid-vapor,

solid-vapor,

and so lid -liq u id ). 5#

Thermal conductivity of the liqu id and vapor#

6#

Specific heat of the liqu id and vapor.

7•

Viscosity of the liqu id.

8#

Absorbed gases in the liq u id .

9.

Influence of scale and other contaminants.

10# 11*

Influence of mechanical ag itatio n . Density of liq u id and vapor.

9 Scope of the Work In considering the variables involved in boiling lis te d in the foregoing paragraph, i t becomes apparent that any single investigation must necessarily be quite a com­ promise as to which quan tities should be used as control variables#

In the present study the aim was to in v e s ti­

gate the mechanism of boiling; p a rtic u la rly the formation and behavior of the bubbles under various boiling condi­ tions, and the role played by the formation of bubbles in the heat tra n sfe r process#

Accordingly, the experimental

apparatus was designed with a view toward easy adaptation to investigation of most of the boiling variables with an intentional sa c rific e in a b ility to examine extreme values of some of these.

Since the work was part of a general

research plan being carried on in heat tra n sfe r in boiling, considerable e ffo rt was devoted to the development of ex­ perimental techniques. Experimental re su lts were obtained for d is tille d water in which natural convection nucleate boiling was taking place#

The heater m aterial was Chrome1 A#

and subcooled boiling runs were made#

Both ordinary

The influence of

pressure was investigated, Triton NE, a surface tension lowering agent, was added to the water in several runs to determine the influence of surface tension.

Both high

speed motion picture photographs and single flash photo­ graphs were taken and analyzed for the various boiling

10

conditions.

Film boiling was not investigated.

A th e o re tic a l investigation was made of the thermo­ dynamic and hydrodynamic aspects of bubble growth*

Thermo­

dynamic cycles of a bubble in both ordinary and subcooled boiling were traced.

Growth and collapse ra te s as well as

i n i t i a l v elo cities for bubbles in subcooled boiling were calculated.

The smallest size of bubbles which w ill grow

a fte r leaving the heating surface was obtained and compared with experimental evidence.

The general mechanism of heat

tran sfer in boiling from the heating surface to the liqu id was considered.

Objectives of the Work The specific objectives of the work were as follows : A.

The design of apparatus so that a long range

research program could be conducted on the study of the mechanism of boiling over a large range of variables with re la tiv e ly l i t t l e

change in physical apparatus and

technique. B.

The development of techniques by which visual ob­

servations of the boiling phenomenon could be analyzed and checked with existing theory. C.

To obtain experimental information on the origin,

growth and behavior of the vapor bubbles under various boiling conditions.

11

D*

To examine the formation of vapor bubbles In the

lig h t of basic thermodynamic and hydrodynamic principles in an e ffo rt to obtain more complete theo retical informa­ tio n on the process of nucleate boiling*

12

SURVEY OF THE LITERATURE

Considerable work has been done on heat tra n sfe r in boiling and there exists extensive lite r a tu r e on the sub­ ject*

Excellent reviews of the fie ld have been given for

ordinary boiling by Jakob (22, 25) (30), and Drew and Mueller (11)*

McAdams (lj.0), King General references on

subcooled boiling are not available although a reasonably comprehensive picture can be obtained from a number of a r tic le s by McAdams (^1, 45* 4&) ♦

No attempt has been

made here to cover the entire area; rath er, only those a rtic le s which were pertinent to a study of the mechanism of boiling and p a rtic u la rly , dealt with the rela tio n of vapor bubble formation to heat transfer in boiling were considered*

Ordinary Boiling Henning (1909) noticed th a t the temperature of b o il­ ing water was slig h tly g reater than that of the leaving steam*

In measuring the la te n t heat of steam Jakob (1928)

observed the same effect and in a la te r paper with F ritz ( 2 6 ) established the fact that the liqu id was superheated, Bosnjakovic (ij.) used th is fact in th eo retically

calculat­

ing the heat tran sfer to a bubble from the surrounding 1*

Numbers in parentheses re fe r to Bibliography, Appendix G*

13 liq u id .

He obtained an expression from which the heat

tran sfer coefficient to the bubble could be calculated. Jakob (21) and F ritz and Ende (15) performed experimental work, using a high speed camera, from which q u alitativ e agreement was obtained. When the bubble orig inates, the co efficien t, h^, is amazingly high. Values of about 4.0,000 B h r - l f f ^ p - l have been observed. Within 0.01 s e c ., however, h^ decreased to about 1|.000 B hr~lft~^F~l, and then r e ­ mained at about 3000 for the main part of the 1/5 sec. of observation in which the free water lev el, 2 in . above the heating surface was reached. (25) On the basis of an analysis of bubble formation in flo ta tio n by Wark (7 2 ), and using the method and tabular values of Bashforth and Adams (58) in calculating the volume of bubbles, F ritz

(13) obtained an empirical ex­

pression between the angle of c o n t a c t , , and the volume of the bubble, V ^, at the in sta n t the bubble breaks away from the heating surface In terms of the Laplace constant.

(1 )

The expression obtained by F ritz is

(2 )

Where

QT = surface tension

i4 ^

55 acceleration of gravity

^

= density of saturated water

^

= density of saturated steam

The expression is plotted in figure 3 3 .

The experimental

values for hydrogen were from Kabanow and Frumkin (29) and those for water from Jakob and co-workers* From photographic data Jakob (21) and Jakob and Linke ( 2 8 ) obtained a mean bubbles

bubble ris e velocity of

0 * 8 5 fps for

between 0 .Olj. and 0.32 inches in diameter. During

the in terv al in which the bubble adhered to the heating surface,

i t s center of gravity rose at about the same

velocity as did the bubble a fte r leaving the surface*

He

also noticed that at re la tiv e ly low heat loads the bubbles form column-like from favored spots on the heating surface* For bubbles which originated at a frequency of 20 per second,

a bubble existed on the heating surface for only

half of a period; i*e*,

a time interv al of h a lf of a period

lapsed before a new bubble started to develop*

A plot of

frequency against diameter of the bubble leaving the heat­ ing surface i s shown in figure 3 I4.. Jakob ( 2 I4.) showed that for heat loads in the order of 18,000 B h r”^ f t“^, less than 9 Per* cent of the he at trans­ ferred from the heating surface went into the formation of bubbles.

This confirmed the suggestions of a number of

investigators who f e l t that the essential role of the bubble in boiling was the agitation of the liquid*

15

Jakob and F ritz

(26) and Jakob and Linke (27 * 28)

investigated the effect of surface conditions (surface roughness,

etc*) on bubble formation and compared the heat

transfer from a v e rtic a l cylinder with that from a hori­ zontal f l a t plate. Although film boiling was observed by Leidenfrost 08)

in 1 7 5 6 and observed by investigators^ interested in

quenching media for heat treatment of metals, Nukiyama (49) appears to be the f i r s t investigator to obtain the entire boiling curve as shown in figure 2#

McAdams and co-workers

(44, 45) and Farber and Scorah (12) as well as other in­ vestigators have obtained boiling curves for a number of different conditions but re la tiv e ly l i t t l e

attention was

paid to the mechanism of the heat transfer.

Bromley (5)

derived a theoretical expression for the heat tran sfer co­ e ffic ie n t in film boiling based on conduction and radiation through the film and checked i t experimentally* McAdams (40) has summarized the re s u lts of a number of investigations on the influence of the various factors on heat transfer in boiling.

Relatively few of these have

been concerned with the mechanism of boiling*

2*

See, for example. Pilling and Lynch (50)*

16

Subcooled Boiling Mosciki and Broder (4-8) found in using a heated wire boiling apparatus that they could obtain about seven times the maximum heat flux (the flux at which the wire would bum out) i f the energy was dissipated to water at 20°C instead of saturated water as in regular boiling.

Although

they gave no explanation for the phenomenon, subsequent in ­ vestigators have found that the heater ebullates but that unlike ordinary boiling,

the vapor bubbles condense in the

bulk of the liquid* During the past five years,

considerable attention has

been paid to this type of boiling ( 2 , 1 8 , 3 3 * 34 -» 3 5 » 4-1 »

4-2 , 4-3 » 44 » 4-5 » 4-6 » 53 ) »

Flux rates as high as 2,000,000

and 4-»000*000 B hr~^ft"^ have been obtained in natural and forced convection boiling, respectively. has been done in forced convection*

Most of the work

Using high speed mo­

tion picture photographs obtained by McAdams, et al* (4-1) » Rohsenow and Clark ( 53 )

showed that the laten t heat of the

bubbles accounted by an even smaller part of the heat trans­ fer than in ordinary boiling and that the essential role of the bubbles i s the agitation of the liquid near the heating surface*

This has been suggested by other investigators,

Gunther and Kreith (18) conducted a photographic study of subcooled natural convection boiling and suggested a mechanism for the growth and collapse of the bubbles*

17

They checked a th eo retical calculation of the radial growth velocity of a bubble on the heating surface based on the growth of a spherical cavity caused by an underwater ex­ plosion.

The Formation and Growth of Bubbles The formation and growth of bubbles is important in a rather large number of technical and s c ie n tif ic processes. As a re su lt,

extensive work has been done in th is area

although much of the work cannot be applied in the study of boiling*

The papers considered here are only a few of the

more pertinent a r tic l e s . Cassel ( 6 ) investigated the formation of bubbles in connection with foaming in steam generation.

He considered

the s ta b i l i t y of "nuclei” from which bubbles form.

Cassel

as well as Dean (10) showed that the bubbles form more easily from cavities rather than from sharp projections on a heating surface. Considerable work has been done on bubble formation in the study of cavitation.

Kornfeld

and Suvorov (6 ?)

conducted experiments on the destructive action of small pulsating bubbles and verified that high pressures are de­ veloped within them. of cavitation bubbles.

Pies set (71) examined the dynamics He calculated the temperature change

in the water layer immediately next to a growing or con-

18

tr a c ting vapor bubble and found i t

to be of the order 1 , 8

degrees F. Harvey, McElroy and Whitely (62) and others have shown that when the nuclei! from which bubbles originate are eliminated, water will withstand very high tensions* The same process will also permit water to be highly super­ heated without boiling.

Kenrick, Gilbert, and Wismer (65)

were able to heat water to 270 degrees C* at atmospheric pressure i f

the water was f i r s t subjected to high pressure

for a short period* Mead (2) calculated the heat required to increase the diameter of a bubble from an i n i t i a l

size of 10 microns on

the basis of thermodynamic considerations*

Rohsenow and

Clark (53)# mentioned previously, performed the same cal­ culation in a s lig h tly d ifferen t manner. Larson ( 3 6 ) investigated the factors influencing eb ullitio n from a solid surface on the basis of thermo­ dynamic considerations.

In h is experiments he found that

the a b ility of a surface to i n i t i a t e boiling in a super­ heated liquid depended primarily upon the adhesion free energy or adhesion tension, which in turn is connected with the w ettab ility (angle of contact) of the surface.

In a

subsequent paper (3 7 ) he discussed the role of metastable states in boiling and condensation.

He considered only the

effect of superheated water in the case of boiling. Wigner (5 6 ) obtained expressions for the velocity of

19 bubble rise in a liquid and for the diameter of the bubble based on dimensional arguments#

20

PRELIMINARY CONSIDERATIONS AND PLAN OF THE W ORK

Since the object of the study was to investigate the mechanism of boiling and since the work was to f i t into a general research program on boiling, i t was decided to design and construct apparatus that would meet the follow­ ing q u alification s: 1.

Primarily suited to a photographic investigation

of bubble formation, growth, and behavior. 2.

Arranged so that ordinary heat transfer informa­

tion could be obtained provided i t was not obtained a t the expense of the photographic arrangement. 3.

Wherever possible,

constructed so that diverse

experiments could be performed with a minimum change in apparatus. With these qualifications in mind, a horizontal sur­ face was chosen so that the direction of bubble r i s e ,

the

general direction of flu id flow,

and the general direction

of heat flow would be the same.

A ribbon type heater was

used instead of a plate because too many bubbles in a line p a ra lle l to the axis of the camera lens would confuse the p ictu re. I n i t i a l experimental work was planned so that compari­ son could be made with existing information, p articu larly that of Jakob and co-workers.

21

EXPERIMENTAL APPARATUS

A cross section of the boiling apparatus is shown in figure 3 and a general view of the apparatus and in s tru ­ mentation is shown in figure 4 *

The u n it was composed of

a boiler assembly and a condenser.

The boiler assembly

was comprised of a steel box f i t t e d with four glass windows within which was mounted the t e s t heater,

two stainless

steel clad 1000 watt auxiliary immersion heaters, bulk temperature thermocouple probe*

and the

The condenser was

comprised of three sets of cooling tubes f i t t e d into a piece of 4 inch diameter glass pipe 2 feet long and the whole unit was mounted on top of the boiler assembly. A photograph of the te s t heater or main heater is shown in figure 6 .

The details of i t s construction are

shown in an exploded view in figure 8 and cross sections at the points of thermocouple junctions are shown in figure 9»

Both the t e s t heater and guard heater were 0*010 by

0.125 inch Chromel A ribbon.

The te s t heater was mounted

on a piece of adhesive glass tape to prevent boiling from the bottom surface.

The three t e s t heater the mo couple s

were placed on the bottom side of the glass tape at one inch interv als and centered with respect to the heater. The junctions of two d iffe re n tia l thermocouples were also placed at this level and located as indicated in figures 8 and 9*

Two layers of glass tape separated the second

22.

C O N D EN SER S E C T /O N

COOLING T U B E

N O TE N O T TO SC A LE

G L A S S P IP E LIQUID B U L K THERM OCOUPLE A U X IL IA R Y H EATERS

T E ST H EATER A SSE M B LY

G LA SS W IN D O W S

PO W ER LEAD S

F /a. 3 C R O S S SE C T /O N OF B O /L /N G APPARATU S

Pig*

General view of the apparatus and in stru - mentation with the Pastax camera in place*

Fig* 5* Boiler assembly with camera arrangement for flash photography.

Fig. 6 . Test Heater Assembly

Fig* 7• Liquid Bulk Temperature Probe

V/EW

OF

TEST HEATER

ASSEMBLY

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27

junctions of the d iffe re n tia l couples from the f i r s t tions and another single layer separated these, from the guard heater*

junc­

in turn,

The guard heater had two addi­

tional layers of glass tape attached underneath i t ,

the

bottom one of which was screwed to the la v ite support block.

The t e s t heater was held in place by clamping i t s

ends between the lav ite support block and the copper end supports*

The current was conducted to the heater through

the end supports* The t e s t heater thermocouples were located so that for 3/ l 6 of an inch on either side of the junction, the leads ran p a ra lle l to the te s t heater its e lf *

The thermo­

couples were made of No* 30 copper and consta n tan wire* The thermometric arrangements are given in greater detail in Appendix B. The liquid bulk thermocouple probe is shown in figure 7*

The junction was located l / 4 inch from the tip of the

probe.

The probe i t s e l f was located about one inch above

the te s t heater when the apparatus was in operation* The power supply circ u it diagram for the apparatus is shown in figure 10*

A-C resistance heating was used

throughout* An A-C potentiometer was used to determine the voltage drop across the t e s t heater. I4. inches long,

Although the te s t heater was

the te s t section was only 3 inches long to

obviate end effects*

28

A-CPOTENT/OA/ETER AUX/ l / ARY HEATER-i B O /L E R

A U X /L / A R Y H E A T E R RO W E R SU R R L Y

|_

GUARD HEATER POWER SUPPLY

A 1AMMETER

T E S T HEATER POWER SUPPLY

F/G. /O P O W E R S U P P L Y C /P C U /T D /AG PAM FOP BO /L/N G A PPA R A TU S

P ig . 1 1 o C o n tro l P an el

The potential leads, which were No. 30 Chromel wire, were spark welded to the top of the te s t heater surface and actually defined the t e s t length. can be seen in figure 6 .

The potential leads

The measurement of power and the

construction of the potentiometer are discussed in Appendix A. The tube bundle in the condenser section was made in three separate sections which were connected to the cooling

30

water line in parallel*

Five-sixteenths inch diameter

copper tubing was used* All steel parts of the boiling apparatus were cadmium plated to prevent corrosion and the formation of rust p a r tic le s . Figure 12 shows the arrangement of apparatus employed in taking high speed motion picture photographs.

Lighting

was accomplished by over volting ten or more sealed beam spot lamps*

Figure 13 shows the apparatus arrangement

used in flash photography.

The photographic apparatus and

techniques are described more completely in Appendix C* Descriptions of the preliminary apparatus used in exploratory runs and the boiling apparatus before modifica­ tion are given in Appendix D.

I il i &ï 1

y

1

f~\ % Q

F/G. 13

TOP FOR

V/EW OF APPARATUS ARRANGEMENT ST/LL FLASH PHOTOGRAPHY 32

33 TEST PROCEDURE

Upon assembly, the boiler was pumped to about one inch of mercury, absolute ; and since th is was not es­ se n tia lly a vacuum apparatus,

it

was considered su fficien tly

free from leaks i f more than one hour was required for the unit to leak to about atmospheric pressure* The unit was f i l l e d with d i s t i l l e d water by evacuat­ ing the boiler and permitting a ir pressure to force the water through a valved opening in the bottom*

The auxil­

iary heaters were turned on and the water was boiled for about two hours to purge adsorbed gases*

In an early run

preliminary degassing of the system and water were trie d by pumping them for 80 and 50 hours,

respectively; but

since no benefit was observed from th is t ime- consuming pro­ cedure, i t was eliminated* After degassing,

the te s t heater was turned on and

the other controls were adjusted to obtain the setting de­ sired*

A steady s ta t e condition was considered existent

when no steady change could be observed within one-half hour in both the liquid bulk and the heater temperatures* The duration of run was varied over a rather large range*

Runs as long as 84 hours and as short as 5 minutes

were made.

With the exception of the formation of deposits

on the heating surface, which, of course,

could never be

considered at any "representative" condition, non-control

34 variables were found to remain constant for even the longest runs.

As a re su lt,

2-hour runs in which four read­

ings were taken at ^.0 -minute intervals were considered s a t­ isfacto ry . For a given reading, the procedure was to read the temperatures, pressure,

and e le c tric a l quantities in the

order given and then in reverse order.

The average of the

two values so obtained was the value used for that reading* Since conditions did not change appreciably from one read­ ing to another,

values for the run were obtained by simply

averaging the four individual readings.

The "up and back”

technique for individual readings was not used in cases of questionable r e l i a b i l i t y

(in a b ility to adjust guard heater

or boiling at the thermocouple junctions).

In these cases

a reading consisted of a single determination. Photographs were taken during the time between read­ ings,

Ordinarily,

one high speed motion picture photograph

and two flash photographs were taken during a run.

35 EXPERIMENTAL RESULTS

Experimental resu lts were both quantitative and q u a lita tiv e .

A summary of experiments performed is pre­

sented in table 2.

The method of calculating the heat

transfer quantities is

shown in Appendix E, part I-A»

The

correction described in Appendix E, part I-B was not ap­ plied to these values. Figures 15 through 31 are representative photographs of the conditions investigated.

Specific technical informa­

tion on photography i s given in tables 5 and 6 at the end of th is section.

In table 5 is l i s t e d information on photo­

graphs included here.

Table 6 presents information on the

high speed motion picture photographs.

Ordinary Nucleate Boiling In figure llf data obtained in runs 20, 21, and 22 are compared with those of Farber and Scorah (12) for O.Oit-O inch diameter Chromel A wire and with the mean value given by number of investigations a l l using horizontal f l a t heating surfaces but not a ll using the same material. Run 23 was not plotted because boiling was taking place at the junctions of a ll themocouples which were used to de­ termine the surface temperature.

This comparison shows

that photographic info ma t i on was being obtained for rather

36

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47

leaving tlie heating surface•

Because of th e ir small size,

a l l bubbles encountered in subcooled boiling were spherical. The influence of the surface tension lowering agent in the water was to decrease the bubble size# Influence of Subcooling An increase in subcooling, the bubble size. obtained,

Atjj = tg - t%,, decreased

Although quantitative values were not

visual observations indicated th a t the bubble

size decreased rapidly at f i r s t with increasing subcooling and la te r much less rapidly. Influence of Pressure The influence of pressure on bubble size was found to be appreciable#

Figure 29 shows subcooled boiling at

atmospheric pressure.

Figure 30 shows boiling at 2 atmos­

pheres a t the same heat flu x and about the same degree of subcooling; here the bubbles are hardly v is ib le . early run at 0.2 atmospheres, inches in diameter.

In an

some bubbles grew to 0.15

This run was not s t r i c t l y comparable,

however, since subcooling was not the same* Behavior of Bubbles in the Liquid Bulk As might be anticipated, most of the small bubbles formed in subcooled boiling condensed in the liquid bulk. However, the condensation process did not take place as rapidly as one might suspect.

Values for the time required

for bubbles to disappear under two conditions are given in

48

table If.

The values of the half-tim e may be in error since

they were obtained by visual estimate.

Time zero was taken

at the in stan t the heater was turned o ff. the heater was less than one second.

Thermal lag of

In ordinary boiling,

by comparison, the liq u id bulk was completely cleared of bubbles within two or three seconds a fte r the heater was turned o ff. Table if*

Time Required fo r Vapor Bubbles to Disappear in a Subcooled Liquid Time required for one-half the bubbles to disappear

Condition 1. q" = 216,000 B h r - lf t- 2 125 degrees subcooled d is tille d water 2. q" = 215,000 B hr”I f t ”2 1 2 5 de­ grees subcooled d is tille d water plus 0.05% Triton by volume

Time required for a ll bubbles to disappear

-

15 sec.

5 sec.

^

,

1■ 50 sec.

IfO sec.

The term "disappear" instead of "condense" has been used because about 5 or 10 percent (visual estimate) of the bubbles did not condense but rose to the liqu id surface just as the larger bubbles in ordinary nucleate boiling. These bubbles were representative of the entire bubble size spectrum.

With the thought th at these few may have been

bubbles of gas in solution or of adsorbed gas on the heater surface, the same boiling condition was reproduced a fte r

49 3 0 0 hours of operation; however, the effect was the same» I t would appear th a t these were actually vapor bubbles. Heater Surface Conditions A cleansing action of the bubbles on the heater sur­ face was noticed in subcooled boiling»

In run number 11,

for example, the whitish deposit that had formed in over 100 hours of ordinary boiling was almost completely gone a fte r 8 I4. hours of sub cooled boiling*

5o

EFFECT OF INCREASING HEAT FLUX IN SUBCOOLED BOILING

Fig. 2 4 * Subcooled boiling, y/' = 520,000 B Run P-2*

51

EFFECT OF INCREASING HEAT FLUX IN SUBCOOLED BOILING (Continued)

Fig. 25. pJ^Cp°^ed boiling, q" = 930,000 B h r ^ f f 2*

Fig. 26. Subcooled boiling, qM= 1,5000,000 B hr“l f t “2. Run P-lf.

52

EFFECT OF LOWERING SURFACE TENSION IN SUBCOOLED BOILING

Fig# 27# Subcooled boiling, qw = 216,000 B R un 1 1 .

F ig *

28* S u b c o o le d b o i l i n g w it h T r i t o n a d d ed t o w a t e r , q" = 2 1 6 ,0 0 0 B h r - l f t - 2 . Run 1 2 .

EFFECT OF PRESSURE ON SUBCOOLED BOILING

Fig. 29. Subcooled boiling at atmospheric pressure q" =7770,000 B h r " lf t- 2 . Run 25.

Fig. 30. Subcooled boiling at pressure of two atmospheres, q” = 770,000 B h r-lft~ 2 . Run 27.

54

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88

known and from t h i s

the most s u i ta b l e m u ltip ly in g f a c to r

can be s e t . 3«

The voltage adjustment i s manipulated u n t i l a

minimum i s

reached on the o s c illo s c o p e .

in cre ase d i f 4»

necessary#

The phase adjustment i s

mum i s reached.

3

Steps n u ll

and

4-

The Y gain i s

manipulated u n t i l

a mini­

again adju sted i f necessary.

are repeate d a l t e r n a t e l y u n t i l an e s s e n t i a l l y

reading i s

5#

The Y gain i s

obtained#

The voltm eter reading a t t h i s

duct of the p o t e n t i a l d iffe re n c e

condition i s

a pro­

across the leads and the

m u ltip ly in g f a c t o r of the d iv id er c i r c u it #

Accuracy and P re c is io n of Measurements

The potentio m eter method lends i t s e l f voltage measurement i n

very well to

r e s is ta n c e heating because the

h e a te r i t s e l f

can be made longer than the t e s t len g th and,

consequently,

the end e f f e c t s

p o ten tia l none at

le a d wires carry only a very small

a ll,

they can be very small r e l a t i v e

of the h e a t e r . due to the

can be o bviated.

As a r e s u l t ,

not only i s

t h e i r attachment to the heatin g

d is ta n ce

current or to the siz e

the disturbance

surface

between the p o t e n t i a l leads

Since the

small,

but

can be measured

to an accuracy w ithin the p re c is io n of the power measure­ ments.

By t h i s method the

test

len g th i s

c a r e f u ll y defined.

89

In th e instrument used,

the coarseness of the

voltage

and phase c o n tro l powerstats appeared to be the l i m i ti n g f a c t o r in r e p r o d u c ib ility # readings a t lie

the same power s e t t i n g ,

w ithin a 0 * 6

The p a r t of t h i s is

For a number of consecutive

not known#

the readings would a l l

per cent band over most of the range* s c a tte r

th a t was due to l in e

In any event,

order as the accuracy of

t h i s sca tte rin g

voltage changes i s of the same

the voltmeter#

The accuracy i n the measurement of power both fo r the potentiom eter used and f o r the potentiom eter method as a whole can be e a s i l y examined# the t e s t

The power,

P, r e le a s e d in

s e c tio n is given by :

P = EaI = EVI

(A-l)

where Ea = a c tu a l p o t e n t i a l s e c tio n , v o l ts Ev = p o t e n t i a l I

d ifferen ce across the t e s t

d iffe re n c e across

a current passing through t e s t

the voltm eter, sec tio n ,

v o lts

amperes

R]_ = r e s i s t a n c e across a s e c tio n of the voltage d iv id e r r e s i s t o r s as s e t on the s e l e c to r switch, ohms Rg = r e s i s t a n c e across the e n t ir e l i n e of voltage d iv id e r r e s i s t o r s , ohms D ifferencing the power fun c tio n ; termwise,

by the function i t s e l f ;

dividing

the r e s u l t ,

and taking

the absolute

values of the terms the maximum percentage e r r o r i s obtained.

90

% error 100

Ap

_

A

_

P

Tli© r e s i s t o r s

I

I

A Ey Ev

+

The p re c is io n of the r a t i o

p re c i s i o n of the i n d iv id u a l r e s i s t o r s For

(A-2)

Ri r2

are considered to g eth e r because they always

appear in a r a t i o *

v alu e•

a ïï5

the p otentio m eter used,

% error =

| 0 *[j. |

+

ammeter

| 0 J4 |

+

voltmeter

and not the

i s the s i g n i f i c a n t

these values are :

| 0*2 |

= 1 *0 ^

re sisto rs

The estim ate of e r r o r f o r the r e s i s t o r s

is

a somewhat

p e s s im is tic one and i s based upon the nominal m ultiplying f a c t o r s f o r th e voltage d iv id e r c i r c u it * resistan ces

A ctually ,

these

can be measured to fiv e places a c c u ra te ly at

a given tem perature.

By using the a c tu a l m ultiplying

f a c t o r s the p re c is io n of the instrument could be made e s ­ s e n tia lly

the sum o f the p re c is io n s of the voltage and

current re a d in g s.

However,

to f u l l y r e a l i z e

such pre­

c is io n , major changes would have to be made in the power source sin ce l i n e voltage f lu c tu a ti o n s

are a t l e a s t

of t h i s

order* As a good general estim ate,

p re c is io n of 1 per cent

can be a t t a i n e d i n the measurement of power by the po­ ten tio m e te r method w ithout s p e c ia l precautio ns ; p re c is io n of g r e a t e r

than 1 p er cent i s

d iffic u lt

to a t t a i n because

the following f a c t o r s must be determined or c o n tr o lle d :

91

le

Harmonics c o n trib u tin g to the power*

2#

Voltage f lu c tu a tio n *

3*

Limiting p re c is io n o f the voltmeter and ammeter*

Range and F l e x i b i l i t y

The p r i n c i p a l d i f f i c u l t y r e s i s t a n c e heatin g difference*

is

of measuring power in

the measurement of the small p o t e n t i a l

The lower l i m i t of th e potentiom eter used was

1 0 m illiv o lts;

th is

is a lso about the lower l i m i t of t h i s

type of instrument*

The upper l i m i t of the potentiom eter

was 135 volts*

The cu rren t

range covered was 0*4 to I4.OO

amperes but these values do n o t represent l i m i t i n g

condi­

tions® It

bears re p e a tin g th a t

the m u l t i p l i e d - d e f l e c t i o n

p otentio m eter method of measuring power is not r e s t r i c t e d to a pure r e s i s t a n c e t iv e

load*

and c a p a c itiv e loads

of precision*

I f a wattmeter i s used, can be measured without

induc­

s a c rific e

92

APPENDIX B

MEASUREMENT OF TEMPERATURE

Copper-constantan thermocouples were used f o r a l l temperature measurements t h a t were made w ithin the b o i l e r . The lo c a tio n s o f the various thermocouples have been d i s ­ cussed p re v io u s ly and are mocouple e .m .f.

shown i n fig u re s 8

arrangement i s

shown in fig u re

ence ju n ctio n was used; and the tie s

Ther­

was measured with a Leeds and Northrup

p o rta b le p r e c i s i o n type potentiom eter. of the

and 9*

switching

however,

A c irc u it

diagram

A common r e f e r ­

the nature of th e c i r c u i t

arrangement obviated any of the d i f f i c u l ­

sometimes experienced with a common refere n ce ju n ctio n

lea d . The thermal e .m .f.

of the t e s t h e a t e r and l i q u i d bulk

thermocouples was measured in the standard manner. the d i f f e r e n t i a l

thermocouples,

the reference

To read

jun ctio n was

shorted out by means of the double pole double throw switch. The re fe re n c e

ju n ctio n compensator on the potentiom eter was

then s e t up to some a r b i t r a r y value and the thermocouple was balanced i n the

the re g u la r manner.

s e t t i n g on the re fe re n c e

The d iffe ren c e between

jun ction

compensator and the

reading of the main s l i d e wire was the value req u ired . guard h e a t e r was

adjusted to bring

The

t h i s value to a minimum*

08000000000 I +

"

h + 7ll1 tt I I I I I

J V

ll

^ W J L ^

id

K

k

g

I 1

E

\ * I

E

vl

I k

i=

1

I I

1

1! I

FIG. 4-5

Wx S>

THERMOCOUPLES AND POTENTIOMETER

CIRCUIT

93

9k F a b ric a tio n and C a lib r a tio n of Thermocouples

With the exceptio n of the re fere n ce which were No* 2i^ gauge g la ss

jun ctio n leads

in s u la te d duplex c a l i b r a te d

copper and const ant an wire and the l i q u i d bulk thermo­ couple leads

which were of s im i la r No* 28 gauge wire,

a ll

of the thermocouple wires were No* 3 0 gauge copper and constantan c a l i b r a t e d enameled wire* t io n and th e

The reference

junc­

l iq u i d bulk thermocouple ju n c tio n were spark

welded under o i l by the "mercury pool" method. jun ctio ns were b u t t welded by means of bank of condensers.

A few of the f i r s t

All o th e r

a discharge from a thermocouples were

made i n an atmosphere of n itro g e n although i n c a l i b r a t i o n no d iffe re n c e was n o tic e d between these and o th ers made in air*

If

peening or trimming of the

junctions was re q u ire d ,

they were subsequently annealed by heatin g them up with a match and p erm ittin g

them to

cool in air*

This was found

to be a simple and most s a t i s f a c t o r y method of annealing*

is

A photograph of

the l i q u i d bulk temperature probe

shown i n fig u re 7*

The thermocouple ju n ctio n was

lo c a te d 1/% inch from th e t i p

of the probe and the wires

were lead out through the c en ter o f the tube* VVeatherhead f i t t i n g the b o i l e r wall* h e ig h ts

was used to c a r ry the probe through

The probe could be adjuste d to various

and p o s itio n s

Since the

A modified

with regard to the t e s t heater*

e n t i r e range of temperatures encountered

95 in the study lay roughly between 100 F and 300 F, i t was considered sufficient to calibrate the thermocouples in a hypsometer at the steam point only.

The thermoelectric

c ir c u it used in calibration was the same one used in the actual tests* For the steam point determination a modified form of the equation of Blaisdell and Kaye (7^-) was used.

Their

equation was

tg = 100 + 0.0368578 (pa - 760) - 0.000020159 (pa-76o)2 + 0.00000001621 (pa - 7 6 0 ) 3

(B-l)

where tg = saturation temperature (steam point) correspond­ ing to p&, in degrees C Pa = atmospheric pressure in millimeters of mercury The f i r s t three terms more than gave sufficient accuracy for this study.

The modified equation was

t i = 212 + 0.936 (pa - 29.92) - 0.0130 (p' - 29.92) (B-2) where tg = saturation temperature (steam point) correspond­ ing to pa, in degrees F = atmospheric pressure in inches of mercury Most of the thermocouples checked the steam point within the accuracy of the conversion tables used.

Since

in no case was the difference between the true steam point and the corresponding reading on the thennocouple greater

96

than Oo5 degrees F, this difference was used as an algebraically additive constant over the whole range the thermocouple was used*

To simplify the determination of

temperature, the values from the Standard Conversion Tables for L and N Thermocouples (84) were plotted and used in graphical form*

Accuracy The accuracy of temperature measurement was examined with reference to the temperature differences encountered* The temperature differences ranged from about 5 degrees for low flux ordinary nucleate boiling to about 130 degrees for subcooled boiling at high flux r a t e ,

although about 20 de­

grees was, perhaps, a more significant upper value*

In

most cases the thermocouple e.m.f* could be determined within 0 * 0 0 4 m illivo lts which corresponded to 0 * 1 5 degrees F.

For the low flux range,

of about 3 per cent.

this corresponded to an accuracy

Over the largest part of the range

an accuracy of better than 2 per cent was easily maintained* The values considered above were the raw temperature read­ ings*

Adjustments required due to the geometry of the

heater are discussed in Appendix E, part I-B.

97

APPENDIX C

HIGH SPEED PHOTOGRAPHY

Since high speed photography i s very specialized, nearly as many cameras have been devised as there are applications•

Watson (82) cites and b riefly describes a

number of these photographic methods and a rather exten­ sive bibliography i s presented in a book by Edgerton and Killian (77)• the area.

No attempt will be made here even to outline

Only the methods applicable to photographing

bubble formation will be b rie fly discussed and the arrange­ ment, operation,

and general range of the methods used in

this study w ill be presented. In the present study both high speed motion pictures and s t i l l flash photographs of the boiling process were taken. High Speed Motion Picture Apparatus High speed motion picture cameras d iffe r from the regular type in a number of respects.

They do not u ti li z e

shutters and the film does not stop while the photograph is being taken.

The elimination of interm ittent motion

makes film speeds in excess of 100 feet per second possible. The cameras operate on either of two principles.

The f i r s t

type u ti l i z e s a rotating prism placed between the lens and

98

the film to cause the images to move along with the film* The Pastax Camera (8 l ,

85) is one of this type and i t s

arrangement is schematically shown in figure second type depends upon high inten sity,

The

short duration

flash lamps of the type developed by Edgerton to expose the film in a time su ffic ien tly short so that neither the film nor the image of the object being photographed moves enough to blur the film*

Knapp and Hollander ( 6 6 ) and

Knapp (78) describe cameras operating on this principle

r which have been used for cavitation and general underwater studies• One advantage of the rotating prism type camera i s that i t ever,

can be used with a continuous lig h t source.

How­

a prism-less camera, such as th at made by General

Radio Corporation, can be used with a continuous lig h t source i f

a Kerr cell is placed between the ligh t source

and the camera*

By reversing the polarity of the Kerr c e ll,

the lig h t i s alternately blocked or transmitted*

The ar­

rangement u tiliz e d by Gunther and Kreith (18) is shown schematically in figure 4?»

A comparison of the various

cameras is made in table 9 *

In every case the film speed

is the limiting factor in the number of pictures that can be taken per second.

Photographic rates as high as 5 million

frames per second have been obtained (8 3 ) but in these cases the film has been fastened to a rotating drum or disc and

9?

F/LM

-SP R O C K E T

i FRONT APERTU RE

REAR \ APERTU RE REFERENCE

8!

F /S . 46 SC H E M A T/C D RAW /M G O F R O T A T /N G P R /S A f T Y P E H /G H SP E E D M O T /O N P /C T U R E CAM ERA. FA S T A X CAMERA

GENERAL

GENERAL R A D /O CAM ERA

F L E C T P /C A-H6 LAMP

PO LA R O /D S

-K E R R CELL O B J E C T B E /N G P H O TO G R A P H E D

C O N D E N SE R LENS

A /R COOLED LAMP H O U S/NG RE FEREN C E / S

F/G . 47 A R R A N G E M E N T O F A H/GH S P E E D M O T /O N P /C T U R E C A M E R A U T /L /Z /N G A K E R R CELL

100

represents re la tiv e ly few actual photographs# Table 9»

Limiting Speeds for Various High Speed Motion Picture Cameras Maximum Speed frames/second

Camera

Frame Size Height (in*) Width (in*)

Fastax 8 mm

8,000

0*15

0,21

Fastax l6 mm

4,000

0,30

General Radio (with flash lamp)

20,000

o#o6

0*42 1.00

General Radio (with Kerr cell)

20,000

0,06

1.00

The Western Electric Fastax Camera In the present study, a l l motion picture photographs were made with an 8 mm Western Electric Fastax Camera#

The

construction and operation of this camera has been described by Smith camera

(8 1 )

(8 5 )#

focal length,

and in the instruction bulletin for the For most of the photography an coated Wollensak lens was used#

f

2, 2-inch Various com­

binations of Kodak Portra Lenses were used to increase the image to object r a ti o .

Focusing information and approxi­

mate magnification are given in table 10*

In some of the

e a r lie r photographs d iffic u lty was experienced in analysis because the bubbles were of the order of the aberration and not a great deal larger than the grain size of the film. Aberration due to the prism is one of the disadvantages of

/Oi

TA B LE /O FO CU S/A/G /NFORMA T/O/V FOR F A STA X CAMERA AND APPROX/M ATE M AGA//F/CA T/O N LENS ARRANGEM ENT DISTANCE S E T T /N G O F CAMERA LENS (F EET)

2 " F /. L E N S 35M M e "f / l e n s W/TH S E PORTRA FH. W/TH S e PORTRA LENS ATTACHMENT LEN S ATTACH M ENT a"E /

2 .5

O/STANCE FROM FRONT OF LENS SOCKET R/NG E G .7 TO O B JE C T (/NCHES)

a s

oo

2 .5

CO

/S

Ô.4

/O H

G.7

7 .4

/4 2

H E /G H T (/NCH ES)

//S '

030

0 .4 5

0 .2 3

o .a a

/.O

W /D T H (/N CH ES)

/.G

0 .4 .2

O.G3

0 .3 2

0 30

/ 4

APRROX/MATE DEPTH 3 .0 O F F /E L D (/NCHES)

0 /3

025

0 /3

OH9

2 3

R A T /O O F /M A G E S /E E TO O B J E C T s /z e (m a g n / f / ca t / o n )

OHS

o .s o

0 33

O. G S

0 .5 4

0 /5

APPROX/MATE MAGN/F/CAT/OH WHEN PR O ­ JE C T E D TO S O D/~ AM ETERS

4-

/G

4 5

F/E LO

/S

/O

2 0

102

th is type of camera so that even with the most favorable lens se ttin g i t is not possible to obtain photographs of the same c la rity as with standard motion picture cameras* I t was noticed that although the camera was f i t t e d with an f 2 lens, the effective aperture was less than f I4..5 because of the prism arrangement.

In addition,

the

prism absorbed some of the lig h t so that i t was p ra ctica lly impossible to over-expose the film*

The exposure time per

frame is approximately 27 per cent of the reciprocal of the frames per second or roughly one-quarter of the cycle time* A diagram of the Fastax Camera power and timing c i r ­ cuit is shown in figure ï±8o

The camera u tiliz e s an argon

lamp to mark the film every 1/120 of a second; however, since the camera was operated at voltages which were too low to f ir e

the lamp, a powerstat was used to step up the

voltage to about line value.

The speed, time, and voltage

ch aracteristics for the Fastax camera are shown in figure 4.9e

The camera was operated on alternating current only* Detailed information on focusing, loading, and

general operation of the camera is given in the instruc­ tion b u lletin (85)*

Lighting for Motion Picture Photography Since a continuous lig h t source i s used with a

s

r

| IL~i

e

L

P

II AND

r \

POWER

j

CAMERA

I

R

s

T/M/NG

e

k

!

15

to

I

J

FASTAX

C/PCU/T

|

/76T. 4-8

/03

D Z S */93& /lJ.O /cJ cC 733dS

V&3WVD

00

% !

R

§ 8

is

5 3

5

| |I ? E V

V&3WVD H 5>ÛOà/HJ- S S V d O l AY 7/3 30 1300/ 303 SO N O D 3S ' N / 033/0033 3/V /l

105

Fastax. Camera, the only problem was to get su ffic ien t lig h t concentrated on the object being photographed.

I t was

found that ten G*E, sealed beam projector spot lamps rated

150 watts at 120 volts would provide sufficient lig h t over the entire operating range of the camera i f they were operated at about 200 volts.

To minimize burning out the

lamps, they were connected across the secondary of a 2 2 0 volt Powerstat and were operated at 200 volts only long enough to take the photographs.

All preliminary adjusting

of the lamps and focusing of the camera was done at about 100 volts.

I t was found th a t the lamps could stand an

appreciably higher voltage i f they were permitted to warm up at 80 volts for about ten minutes.

The resu lts of a

perfunctory check on the increase in lig h t in te n sity due to over-volting are shown in figure 50•

Over-volting also

causes a noticeable s h ift toward blue lig h t which is a favorable condition.

About ij. KVA was required for lightin g.

S t i l l Flash Photography Since the camera and the lighting are really a single unit in high speed flash photography, they will be considered together.

The light source was a Sylvania Type

R-4330 f la s h lamp placed in a parabolic re fle c to r.

A

diagram of the c ir c u it used for firin g the lamp is shown in figure 5l*

The duration of flash for a lamp of th is

/06

ÇL X

X

k k

N

8 I g Ê % is I & I

X I

§

6

s

S

M

(AJ./A/n S V A /3 M J . A O e / J.V A J./$N 3J.N f) A JL /SN 3J.A // JL /iV /7 3 A /J .V 7 3 &

O

k

I? I §g * R

/C’7

LEG END Z - 2 2 0 0 VOLT T R A N S F O R M E R Tg-/5t OOO V O L T T R A N S F O R M E R Vt i Vs - 2 x 2 A R E C T /F /E R Ct ,C z - O J M F D - 2 0 0 0 V O LT C O N D E N S E R Cs - S O M F D - 2 5 0 0 VOL T C O N D E N S E R C f - Z O M F D - 7 5 VOL T C O N D E N S E R Z M E G O H M - 0 . 5 W R E S /S T O R Re - 0 .2 7 M E G O H M - 0 .5 W R E S /S T O R W -R -4 3 S O F L A S H T U B E

F/S. 57 W /R/NG D/AGRAM OF TYPE R - 4 3 J O FLASH U N IT

106

design is about 200 micro seconds, although the duration of the peak intensity is much shorter.

The principle of

operation of these lamps has been extensively described in the l i t e r a t u r e

(7 3 , 7 5 , 7 6 ) ®

back lighting were employed.

Both side lighting and

The firin g was controlled

manually. A number of cameras were used with equal success : 120 Kodak with an f

6.3

lens;

a

3 1/4

a

by 4 1/4 in. Graflex

Super D with an f 4*5 lens; and a 9 by 12 cm. Welta view camera with an f 4*5 lens.

In fact,

any camera with a

reasonably good lens and a shutter with a "time” setting could have been used.

The photographic procedure was as

follows :

1.

The camera was focused and loaded,

was set for "time.”

and the shutter

Portra lenses were used to get as

large an image as possible. 2*

The flash equipment was turned on and the room

lig h ts were turned off.

3. discharged,

The camera shutter was opened, the fla sh lamp was and the camera shutter was closed.

The

photographs were necessarily taken in a darkened room to prevent fogging of the film during the time the shutter was open. The settings differed slig h tly for the various cameras and had to be determined by t r i a l .

However, the flash

109

lamp provided sufficient l i g h t ; for example, with the 120 Kodak using Super XX film, best resu lts were obtained with lens openings between f l 6 and f 32o

The rather small

openings were desirable since they resulted in a large depth of focus •

When back lighting was employed,

a sheet

of tracing paper was placed between the lamp and the object being photographed to diffuse the light*

The film develop­

ment was standard.

Analysis of Photographs A number of methods of examining the photographs were tr ie d and the projector method was found to be most s a t is ­ factory.

When the film was viewed under a microscope,

imperfections in the film base, d i r t ,

and other ir re g u la ri­

ti e s appeared at least as prominent as the emulsion, when su ffic ien tly low magnification was used. film was projected,

even

When the

i t was found that the effect of many

of these ir r e g u l a r iti e s was attenuated and the image was more d efin ite.

A number of projection devices were used:

a 3 5 mm. slide projector; an enlarger; and a microfilm viewer. graphs,

The projector was used for motion picture photo­ the enlarger was used for s t i l l photographs, and

the microfilm viewer was used for both.

110

M o tio n P i c t u r e

P h o to g r a p h s

The Image was projected on a white surface at a magnification of 15 to 30 diameters♦

To determine bubble

volumes, the outlines of the bubbles were traced on white paper and the volumes were evaluated by the method outlined in Appendix E, part I-Ce

To determine bubble growth and

formation frequency, bubble images were traced every 10 frames or so and the change was noted*

Markings at the

side of the film made by the argon flash lamp every 1 /1 2 0 second permitted calculation of the incremental time be­ tween images*

I f the size and the depth of f ie ld permitted,

a scale of some nature was included in the f ie ld of the camera.

When a scale could not be included in the photo­

graph, information from table 10 was u tiliz e d to determine actual dimensions.

A protractor was used to measure the

angle of contact of the vapor bubble surface with the heat­ ing surface at maximum volume* S t i l l Flash Photographs Since flash photographs were taken at the same b oil­ ing condition for which motion pictures were taken, the flash picture could be considered a "representative frame" of the motion picture photographs. were inherently clearer;

The flash photographs

and inhere doubt existed about a

part of a motion picture image, q ualitative information could often be obtained from the flash picture that would

I ll

permit more significant interpretation of the motion picture photographs.

Measurement techniques were essenti­

ally the same as for motion pictures.

For the determina­

tion of the nature of the bubble population in subcooled boiling,

the image was projected on a ruled grid with suf­

f ic ie n tly small squares so that the number of bubbles of a given size could be determined by counting the number in each of the squares and summing over the squares for the t o t a l in the fie ld of vision.

An enlarger was found most

useful in this work*

Accuracy of Results The nature of measurement from photographic data is such that the accuracy varies rather widely.

However,

a few general remarks can be made regarding the measure­ ment of the various quantities© In the discussion of accuracy below, the estimates are based on what the camera recorded and not any average value for the variables.

In other words,

the accuracy has sig­

nificance only in terms of the photograph which was being analyzed. The information that was obtained from photographs was as follows : lo

Bubble diameters (subcooled boiling)

2o

Bubble volumes

112

3o

Time intervals Bubble velocities

5o

Bubble populations

Bubble Diameters The accuracy of a lin ear measurement on a photographic image depends greatly on the sharpness and the actual size of the image on the film* accuracy is possible,

Slightly better than 5 per cent

but 10 to 15 per cent would be a

b etter estimate for most photographs* Bubble Volumes Since the bubble volume depends on three linear di­ mensions, the third one of which is only a reasonable guess, the maximum accuracy i s in the order of 60 per cent*

This

indicates why the cube root of the volume instead of the volume i t s e l f is used in correlations whenever possible. Time Intervals This measurement has significance for motion picture photographs only. the film s t r i p , little

Using the argon flash lamp markings on

2 per cent accuracy was maintained with

d if f ic u lty .

Bubble Velocities Since a velocity i s the quotient of a distance and a time in te rv a l,

1 5 per cent.

the accuracy for this measurement was about

113

B u b b le P o p u la t i o n This was simply a counting of various sized bubbles that existed at the particular instant the photograph was obtained, and accuracy in i t s usual sense has l i t t l e

sig­

nificance for th is process•

Range and Limitation of the Photographic Method The factors determining the lim itation of the photo­ graphic method are the lighting,

the size of the bubbles,

and the size and configuration of the heating surface» In the present study,

s t i l l flash photographs recorded

bubbles in the order of 0 * 0 0 1 inches diameter, although the diameters could not be measured.

For motion picture photo­

graphs with the Fastax camera, 0*001 was a limiting value which could not always be achieved; and also, the depth and size of fie ld was quite small (see table 10)* heater arrangement used,

For the

lighting was not p articu larly d if­

f i c u l t since more lig h ts could have been added i f i t had been necessary.

Back lighting gave a brighter image for

the same in ten sity lig h t; however,

since essentially

silhouette images resulted, overlapping bubble images created a problem.

Also, small diameter bubbles were more

d i f f i c u l t to photograph with back ligh tin g. Camera speed appeared to be quite adequate except for the i n i t i a l stages of bubble growth.

Even at l^OOO

ii4

frames per second a bubble of appreciable size could be seen on a surface which one frame before was free of bubbles »

115 APPENDIX D

PRELIMINARY APPARATUS

Before a l l of the apparatus described in the main text was designed and constructed, were made using a l / 8

some preliminary runs

inch wide Chrome1 A heating strip

suspended between two support rods and backed with spun glass adhesive tape to prevent boiling from the bottom side• A chromel-alumel thermocouple was welded directly to the heater to obtain the surface temperature.

The whole as­

sembly was placed in a 4-000 ml. beaker which was f i l l e d with d i s t i l l e d water.

The beaker was placed on a hot

plate which provided auxiliary heating*

Runs made with

this apparatus are prefixed P in tables 2 and 3 *

The photo­

graphs in figures 23 through 2 6 were obtained with this ap­ paratus.

Among the information obtained,

it

was found that

thermocouples welded onto the boiling surface of the heater were not very satisfactory* Figure $2 shows an early design heater support block that was used in the main apparatus.

The heater,

again a

1/8 inch Chromel A s tr ip , was cemented into the center groove with sauer-eisen*

The temperature very close to the

bottom side of the heater s t r ip was obtained by means of the three thermocouples shown in the pictu re.

In spite of

preliminary t e s t , d if f ic u lty was experienced because the sauer-eisen did not provide a su fficiently strong bond to hold the heating s t r i p in place.

The lines on the side

of the support block ruled every 1 / 1 0 inch were for photo­ graphic reference*

Fig* 52.

Early Design Heater Support Block Showing Thermocouples in Place. Heating s tr ip has been removed*

117

APPENDIX E

CALCULATIONS^-

Part I - Experimental Calculations A* Temperature Differences, Heat Flux, Coefficients

and Heat Transfer

Temperature differences were calculated from average values obtained in each run.

tg and t jj were recorded

values and tg was the steam table value of saturation temperature for the environmental pressure, pg*

Quantities

computed were :

A t = t g - tL

(E-l)

A t s = t g - tg

(E-2)

= tg -

(degrees of subcooling)

(E-3)

The heat flux was computed by means of the expression

1

3.413 EaI * area of t e s t section

(E-4)

The heat transfer coefficient was obtained from the familiar expression (E-5)

4.

Symbols used are tabulated and defined in Appendix P.

118

B. Calculation of the Boiling Surface Temperature of a Ribbon Heater For the t e s t heater arrangement used in the apparatus, the temperature obtained by the thermocouples when the guard heater was adjusted properly was that of the nonboiling surface of the resistance heater.

The boiling sur­

face temperature can be obtained rather easily i f one di­ mensional heat flow i s assumed*

For the heater used, th is

was a v alid assumption*

t/Q l/Z D

ffO /l /A/G-

U.JLJL J i J L l JlJg

y= Fig* 53»

o j

t=t0

Cross Section of Test Heater Showing Symbols Used

A heat balance in the y direction for this element shown in figure 5 3 resu lts in the equation

2 dy + q 1 *1 Ady

kA

=

0

(E-6 )

dy2 where t is the temperature at any point, Let

y, in the heater.

119

& = t - tL ;

0g = t 0 - t L ;

= ^

=

t 0" U t

Substituting for t and simplifying

+

dy2

a ^ . o k & 1935; English review Mech. Eng. , vol. 58, pp . 59, 1936.

29.

Kabanow, B., and Frumkin, A., ”TJber die Grosse elektroly tisch entwickelter Gasblasen,” Z eitschrift fur Physikalische Chemie A., Vol. 1657 PP* 433*4^2, Vol. I 6 0 , pp. 3 I 6 - 3 1 7 > 1933*

30.

King, W . J . , "The Basic Laws and Data of Heat Trans­ mission," Mech. Engineering, Vol. 54> PP* 560-565, 1932.

31.

King, W . J ., Refrigeration Engineering, Vol. 25, P* 8 3 , I 9 3 3 ; Discussion of the paper of Cryder, D. S. and Gilliland, G. R.

135

32.

Klusener, 0 ., "Form and Grosse von Dampfblasen, ” Forschung anf dem Gebiete des Ingenieurwesens. Vol. 5, pp. 1 1 8 - 1 2 0 , May, June, 193ft*

33*

Knowles, J. W., nHeat Transfer with Surface Boiling,,f Canadian J. Res. Sec. A. J Vol. 26, pp. 268-278, !9ft8.

3ft*

Kreith, F ., and Sommerfield, M., "Pressure Drop and Convective Heat Transfer with Surface Boiling at High Heat Flux: Data for Aniline, N-Butyl Alcohol, and Water," Heat Transfer and Fluid Mechanics I n s t i ­ t u t e , A.S.M.E., pp. 127-138, June, lftftft.

35*

Kreith, F ., and Sommerfield, "Heat Transfer to Water at High Flux Densities with and without Surface Boiling," Trans. Am. Soc. of Mech. Engrs. , Vol. 71, pp. 805-8l£, October, lQft9*

36.

Larson, R. F ., "Factors Affecting Boiling in a Liquid," Ind. Eng. Chem. , Vol. 37, pp. 100ft-1009, 19ft5*

37*

Larson, R. F ., "Occurrence of Metastable States of Liquid and Vapor," Ind. Eng. Chem., Vol. 37, No. 10, pp. 1 0 1 0 - 1 6 , October^ 19ft5*

38.

Leidenfrost, J. G., De aquae communis nonnullis qualit atibus tra c ta tu s . Duisburg, 1756.

39«

Linden, C. M. and Montillon, G. H., "Heat Transmission in Experimental Inclined Tube Evaporator," Trans. Amer. In s t, of Chem. Engrs. , Vol. 2ft, pp. 120-lftl, 1930.

ftO.

McAdams, W . H., Heat Transmission, Second Edition, McGraw-Hill Book Co., New York, pp. 29 ft-339, 19ft2.

ftl.

McAdams, W . H., et al "Investigation of Heat Transfer at High Flux Density from Metal to Water," Informal Monthly Reports of Massachusetts In s titu te of Technology Project DIG 1-6ft89, 19ft8.

ft2.

McAdams, W . H., "Some Recent Developments in Heat Transfer," Purdue Engineering Experiment Station Bulletin, No. 10ft, pp. 23-ftO, Lafayette, Indiana, 1 9 ft8 .

ft3.

McAdams, W . H., "Heat Transfer," Chemical Engineering Progress, Vol. ft6 . No. 3, PP* 121-130, March, 1956•

ftft.

McAdams, W . H., Addoms, J. N., Rinaldo, P. M., and Day, R. S., "Heat Transfer from Single Horizontal Wires to Boiling Water, " Chemical Engineering Progress, Vol. ftft. No. 8 , pp. 6 3 9 , 19ft8.

McAdams, W. H . , K e n n e l , W. E . , Addoms, N* J . , M in d e n , C, S. and Gamel, C* M*, "High Densities of Heat Flux from Metal to Water," Heat Transfer Lectures, NEPA 80ft-IER-10, Vol. 1, pp. 17-ftl, Dec., 19ft8, A.E.C., Oak Ridge, Tennessee. McAdams, W. H . , K e n n e l , W. E . , M in de n, C. S . , R u d o l f , C . , P i C o r n e l l , P. M . , Dew, J . E. , "Heat T r a n s f e r a t H i g h R a t e s t o Water w i t h S u r f a c e B o i l i n g . " I n d . and Eng. Chem. . V o l . f t l , p p . 19ft5, S e p t . , 194-9• M a dsen, D. H . , "Heat T r a n s f e r from C y l i n d e r s to Boiling Liquids," M SM E Thesis, School of Mechanical Engineering, Purdue University, 19ft8. M o s c i k i , I . , and B r o d e r , J . , R o c z n i c k i C h e m j i * V o l . 6 , p p . 319*“35ft, 1 9 2 6 ; C o m p le t e E n g l i s h T r a n s l a t i o n on f i l e a t E n gin eering R esearch Laboratory E xperim ental S t a t i o n , E. I . duPont deNemours & C o . , W i l m i n g t o n , D elaw are. Nukiyama, S., "Maximum and Minimum Values of Heat Transmission from Metals to Boiling Water under Atmospheric Pressure," Journal Society of Meclianical Engineers, Japan, Vol. 3 6 37, pp. 3 6 ft-37ft, 193ft, Abstract in English, S5>3-S5ft; Complete English Translation (F-TS-713-RE, Feb. 12, 19ft7) on f i l e at AAF Wright Field, Dayton, Ohio. P illin g, N. B., and Lynch, J. D., "Cooling Properties of Technical Quenching Liquids," Am. In s t. Mining Met. Engrs., Vol. 62, pp. 6 6 5 - 6 8 8 , 1920.

P r i d g e o n , L. A. and B a d g e r , W. L . , " S t u d i e s i n E v a p o ra to r D e s i g n , " I n d . Engr. C h e m istr y , V o l. l 6 , p p . ft7ft-ft78, 1 9 2 ft. R h o d e s , R . H. and B r i d g e s , G. H . , "Heat T r a n s f e r t o B o i l i n g L i q u i d s , " T r a n s . Am. I n s t . Chem. E n grs *, V o l . 35, p p . 73-95, 1939; I n d . Eng. Chem. , V o l . 30, pp. ifto i-ifto 6 , 1938. R o h se n o w , W. M. and C l a r k , J . A . , "A S t u d y o f t h e M echanis m o f B o i l i n g H e a t T r a n s f e r , " R e p o r t N o . 1 f o r th e O f f i c e o f Naval R e se a rc h , M a ssa c h u se tts I n s t i t u t e o f T echnology, D i v i s i o n o f I n d u s t r i a l C o o p e r a t i o n , F e b r u a r y 1, 1950• S a u e r , E. T . , C o o p e r , H. B. H . , A k i n , G. A. and McAdams, W. H., "Heat Transfer to Boiling Liquids," Mech. Eng., Vol. 6 0 , pp. 6 6 9 - 6 7 5 , 1938.

Sieder, E» N«, and Tate, G r. E., ’’Heat Transfer and Pressure Drop of Liquids in Tubes,” Ind. and Eng. Chem. , Vol. 28, pp. llj.29-35, 1936. Wigner, E. P., "Rate of Rise of Bubbles, ” AEG Document - 193® Oak Ridge, Tennessee, August, 19^8• Related References Adam, N. K., Physics and Chemistry of Surfaces, Oxford University Press, London, 1938. Bashforth, F. and Adams, J . , Cambridge, 1 8 8 3 .

Capillary Action,

Dorsey, N. E., Properties of Ordinary Water Substance, American Chemical Society Monograph, No. 8 l , 194-0. Fisher, J • C., "The Fracture of Liquids,” Journal of Applied Physics, Vol. 1 9 , pp. 1 0 6 2 -1 0 7 1 » Nov., 1948• Fowle, F. E ., Smithsonian Physical Tables, Eighth Revised Edition, Smithsonian In stitu tio n , Washington D. C., 1934. Harvey, E. N., McElroy, W . D., and Whiteley, A. H., "On Cavity Formation in Water," Journal of Applied Physics, Vol. 18, pp. 162-172, 1947. Keenan, J. H., Thermodynamics, John Wiley and Sons, New York, 1941* Keenan, J. H., and Keyes, F. 0 ., Theimodynamic Properties of Steam, John Wiley and Sons, New York, T93&: Kenrick, F. B., G i l b e r t, C. S., Wisraer, K. L . , "The Superheating of L iq u id s," Journal of Physical Chemistry, Vol. 28, pp. 1305, 1924*

Knapp, R. T., and Hollander, A., "Laboratory Investiga tion of the Mechanism of Cavitation," Trans. A.S.M.E Vol. 70, pp. 419-435, July, 1948. Kornfeld, M., and Suvorov, L ., On the "Destructive Action of Cavitation," Journal of Applied Physics, Vol. 15, PP. 495-506, June, 1944* Lewis, G. N. and Randall, M., Thermodynamics, McGrawHill Book Co., New York, 1923®

138

69#

Maxwell, J* C., f1Capillary Action,” Encyclopaedia Britanica, Ninth Edition, Vol. V, pp. 56-71* 1900.

70o Pease, D. C. and Blinks, L. R., "Cavitation from Solid Surfaces in the Absence of Gas Nuclei," Journal of Physical and Colloid Chemistry, Vol. 51* PP.“5^6-567, 1947. 71 * Plesset, M. S., "The Dynamics of Cavitation Bubbles," Journal of Applied Mechanics, Trans. A.S.M.E., Vol. 71, pp. 277-202, 1949. 72.

Wark, I . W., "The Physical Chemistry of Flotation," Journal of Physical Chemistry, Vol. 37* Part I, pp. (523 - 61+4 , Part I I , p . 797, Part I I I , p. 805, Part IV, p. 815, 1933.

References on In strum entation

73»

Anik, B., "Spark Photography," M. S. Thesis, Purdue University, 1948.

74-

Blaisdell, B. E., and Kaye, J . , "The Location of the Normal Sulfur and Mercury Boiling Points on the Thermodynamic Temperature Scale," Temperature, I ts Measurement and Control in Science and Industry, Reinhold Publishing Corp., New York, p. 130, 1941.

75#

Carlson, F. E., "Flash Tubes," Journal of the Society of Motion Picture Engineers, Vol. 4^* NoT 5* pT- 395* May, 1947 #

76.

Carlson, F. E. and Pritchard, D. A., "The Characteris­ t i c s and Applications of Flash Tubes," Ilium. Engr. Vol. 42» No. 2, pp. 235-248, Feb., 1947.

77#

Edgerton, H. E., and Killian, J r . , J * R., Flash, Hale, Cushman, and Flint, Boston, 1939*

78.

Knapp, R. T., "Special Cameras and Flash Lamps for High Speed Underwater Photography," Journal of the Society of Motion Picture Engineers, Vol. J4.9 . No. 1, pp. 64-82, July, 1 9 4 7 *

79.

Marshall, R. B., "A Multiplying-Deflection A-C Potentiometer," M. S* Thesis IOO3 6 , Purdue Univer­ s ity , 1941*

139

80#

Roeser, W . P., "Thermoelectric Thermometry," Temperature, I t s Measurement and Control in Science and Industry, Reinhold Publishing Corp., New York, p. i d o , 1 9 4 1 •

8 l*

Smith, H. J . , "8000 Pictures Per Second," Journal of the Society of Motion Picture Engineers, Vol. No. 3 , p. 171, Sept., 1945'.

82.

W a tson , E. M., " A id s f o r P i c t o r i a l l y A n a l y z i n g H ig h Speed A c t io n ," Journal o f the S o c i e t y o f M otion P i c t u r e E n g i n e e r s , V o l . 43» No. I4., p . 2 6 7 , O c t . , 1944*

8 3 © "High Speed Camera," Mech. Engineering, Vol. 69s PP* 1045-1046, Dec., 1947! 84.

Standard Conversion Tables for L and N Thermocouples, Standard 31031» Leeds and Northrup Company, Philadelphia, Pa.

85*

"Western Electric Fastax High-Speed Motion Picture Camera," Instruction Bulletin, No. 1079» Bell Telephone Laboratory.

lij.0

APPENDIX H

LIST OF APPARATUS !•

7*5KVA Powerstat, Type 125& Variable Transformer Superior Electric Co. Range: 230/115 Volts

Used ij.

2.

2.0 KVA Powerstat, Type 1126 Variable Transformer Superior Electric Co. Range : 115 Volts

Used 3

3*

0.4 KVA Powerstat, Type 20 Variable Transformer Superior Electric Co. Range: 115 Volts

Used 5

4#

Cathode Ray Oscilloscope, Type 24? Allen B. Dumont Laboratories Range: 115/230 Volts, 40 to 60 cycles, A-C Voltmeter, Type P-3 General Electric Range: 150 Volts

6.

A-CVoltmeter, Type P-3 General Electric Range : 7 5 Volts

7*

A-C Voltmeter, Type P-3 General Electric Range : 15 Volts

8.

A— C Ammeter, Type P-3 General Electric Range : 100 Amperes

9.

A-C Ammeter, Type P-3 General Electric Range : 20 Amperes

H O

5e

A-C Ammeter, Type P-3 General Electric Range : 10 Amperes

300 watts

141 11,

12

.

13.

A-C Ammeter, Type P-3 General Electric Range: 5 Amperes Portable Precision Potentiometer Leeds & Northrup Co. Fastax Camera, 8 mm. Western E l e c tr ic Co.

Lens : f f Speed:

2 , 2 inch f . 1 . 2, 35 mm, f . l . 300 to 8000 frames p er second

14.

120 Roll Film Camera, Kodak Autographic Eastman Kodak Co. Lens : f 6 . 3 Shutter: 1/300 to 1 second

15.

9 x 12 cm. View Camera 'Welta

Lens : f 4*5» 13.5 cm, f . l , Steinheil Shutter : 1/200 to 1 sec. Compur

16.

3 1/4" x I4. 1/4" R. B. Super DGraf lex Lens : f lj.,5 Ektar 152 mm. f . l . Shutter: 1 / 3 O to l/lOOO focal plane Graflex Incorporated

17.

Portra Lenses, Kodak Series V and VI Power: 2+, 3+

18 ,

High Speed Flash Lamp Sylvan!a. Type R-4330 Sylvania Mfg. Co.

19.

Projector Spot Lamp, sealed beam 150 watts, 120 volts General Electric Co.

20

.

Bourdon Tube Pressure Gage 6 inch. Range : 100 psi American Steam Gage and Valve Mfg. Co.

21

.

22

.

23.

Mercury Manometer Range : 0 to 32 inches of mercury Thermometer Range: 30 F to 120 F

Thermometer Range: «4^ F to 120 F

35 mm. F ilm S l i d e P r o j e c t o r 1 0 0 W a tts A rgu s E lw o o d E n la r g e r L en s: f 6 .3 M ic r o f ilm R e a d e r S p e n c e r L en s C o. 1 1 5 V o l t , 100 W att

143

VITA

Paul Carl Zmola was bom in Chicago, I l l in o i s on November 21, 1923#

He was reared in Berwyn, I l l i n o i s ,

and in 1938 he was graduated from the Komensky Grammar School in that c ity . in Cicero, I l l i n o i s ,

He attended J. S, Morton High School from which he was graduated in 194-1 •

In 194l he entered Purdue University and, with the excep­ tion of the summer of 1 9 4 2 during which he worked as a draftsman at the I llin o is Tool Works in Chicago, I l l i n o i s , remained u n til April, 1944» when he received the degree of Bachelor of Science in Mechanical Engineering.

From

May, 1 9 4 4 to July, 1943» he was employed as a manufactur­ ing engineer connected with the manufacture of high fre ­ quency vacuum tubes by the Western Electric Company in Chicago, I l l i n o i s .

In July, 1945» he returned to Purdue

University as a member of the full-time s ta ff and was engaged in teaching and Army Air Forces research.

He

received the degree of Master of Science in Mechanical Engineering in June, 1947®

In July, 1948» he resigned

his position as Instructor in Mechanical Engineering to accept a Westinghouse Research Fellowship which he cur­ rently holds.