UCRL-52186

769:

FLO W-REGIME CHARACTERIZATION FOR HORIZONTAL TWO-PHASE STEAM FLOW

Clarence A. Calder

October 5 , 1976

Prepared for U S Energy Research & Development .. Administration under contract No. W-7405-Eng-48

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UCRL-52186

FLOW-REGIME CHARACTERIZATION FOR HORIZONTAL TWO-PHASE STEAM FLOW

Clarence A. Calder

MS. date: October 5 , 1976

FLOW-REGIME CHARACTERIZATION FOR HORIZONTAL TWO-PHASE STEAM FLOW Abstract

The r e l i a b l e c h a r a c t e r i z a t i o n of t h e flow regime, given t h e f l u i d p r o p e r t i e s , flow rate, and piping c o n f i g u r a t i o n , would be a s i g n i f i c a n t h e l p i n t h e d e s i g n of instrumentation, energy-conversion machinery, and piping f o r two-phase geothermal flow. A r e l a t i v e l y s i m p l e model, using Baker parameters, is described and applied t o flow-regime d a t a generated by high speed photography of two-phase steam flow.

The experiments were conducted

a t t h e Geothermal Test F a c i l i t y (GTF) a t Lawrence Livermore Laboratory. Although r e s u l t s depend somewhat on t h e personal judgment and i n t e r p r e t a t i o n of t h e observer, t h e model was found t o g i v e a reasonable p r e d i c t i o n of t h e flow regime f o r t h e flow ranges a v a i l a b l e a t t h e GTF i n 1 and 2-in.-diam pipes.
r

Introduction
The r e l i a b l e p r e d i c t i o n of flow regimes i n h o r i z o n t a l two-phase flow

is v e r y d i f f i c u l t .
flow condition.

However, some i n d i c a t i o n of t h e expected type of flow

would be of c o n s i d e r a b l e v a l u e i n designing p i p e dimensions f o r a d e s i r e d For example, a sampling probe i n t h e flow should provide a reasonably good r e p r e s e n t a t i v e f l u i d sample f o r a homogeneous bubbly o r d r o p l e t flow, b u t it would g i v e u n r e l i a b l e information f o r a s t r a t i f i e d o r annular flow. Many models of varying complexity have been proposed and then compared t o experimental data f o r a s p e c i f i c l i m i t e d range of flow conditions. The technique u s u a l l y i n c o r p o r a t e s a two-dimensional map w i t h dimensioned o r dimensionless parameters as coordinates, which may o r may n o t be chosen on a r i g o r o u s t h e o r e t i c a l o r l o g i c a l b a s i s . The maps d e f i n e r e g i o n s o r zones The t r a n s i t i o n l i n e s are by t r a n s i t i o n l i n e s s e p a r a t i n g t h e flow regimes.

i n f a c t broad bands because of t h e d i f f i c u l t y i n c l a s s i f y i n g t h e flow near

a transition.
The v a r i o u s published maps are n o t i n good agreement. Apparently, t h i s

i s l a r g e l y due both t o the l a c k of a s t a n d a r d d e f i n i t i o n of t h e p o s s i b l e flow

-1-

regimes and t o t h e experimenters' d i f f i c u l t y i n d e s c r i b i n g t h e flow regime observed. Some methods are more g e n e r a l i n that t h e i r e x t r a p o l a t i o n t o flow Reference 1 c o n d i t i o n s o t h e r than those used i n t h e i r development i s p o s s i b l e .
in use today.

gives a c u r r e n t d e s c r i p t i o n of many o f t h e proposed flow-mapping techniques

One flow-mapping technique, developed by 0 .

in t h e e a r l y 1950s
This method i s

f o r two-phase gas-liquid flow i n t h e petroleum i n d u s t r y , w i l l be described

i n d e t a i l as t o i t s a p p l i c a t i o n i n two-phase steam flow.

simplest, most d i r e c t l y a p p l i c a b l e mapping techniques. 1-in.and 2-in.-diam-pipe

s t i l l widely used today f o r designing petroleum p i p e l i n e s and i s one of t h e P r e d i c t i o n s of t h e Baker method w i l l be compared w i t h experimental r e s u l t s from observation of h o r i z o n t a l flow of low q u a l i t y steam simulating

a geothermal source.

The d a t a presented are photographs from high speed

photography a t several framing rates w i t h image enhancement techniques employed t o b e t t e r d e f i n e t h e flow-density d i s t r i b u t i o n .

Flow Regimes
Flow p a t t e r n s are defined by t h e p o s s i b l e c h a r a c t e r i s t i c c o n f i g u r a t i o n s t h a t t h e two phases may assume under t h e v a r i o u s flow and piping c o n d i t i o n s of i n t e r e s t . There are no u n i v e r s a l l y accepted d e f i n i t i o n s of flow regimes Gravitational effects
To be

o r flow p a t t e r n s ; some a u t h o r s p r e f e r t o use a few b a s i c p a t t e r n s , while o t h e r s use much more d e t a i l e d regimes and subregimes t h a t occur.

are evident i n t h e h o r i z o n t a l flow p a t t e r n s , with t h e l i q u i d phase (tending t o

the lower l e v e l ) producing an asymmetric d i s t r i b u t i o n of t h e phases. used. 3'4
0

c o n s i s t e n t with t h e Baker c h a r t s , t h e flow regimes shown i n Fig. 1 w i l l be The seven flow p a t t e r n s o r regimes are defined as follows: I n bubbly flow, t h e l i q u i d phase i s continuous, w i t h t h e g a s phase d i s t r i b u t e d
in s m a l l , d i s c r e t e bubbles t h a t tend t o occur

Bubbly flow

toward t h e upper p a r t of t h e pipe.

0

Plug flow

Plug flow occurs when some gas bubbles approach dimensions of t h e o r d e r of t h e p i p e diameter and are elongated i n t h e axial d i r e c t i o n .

S t r a t i f i e d flow

I n t h i s p a t t e r n , t h e gas and l i q u i d phases are completely s e p a r a t e d ; t h e l i q u i d phase i s a t t h e bottom of t h e pipe and the gas a t t h e top. -2-

4
Bubble flow Slug flow

Plug flow
f I I f f I f

Annular f 1ow
I f
f f f

Iff

f I f f f

S t r a t i f i e d flow
D i spersed (mi st)

F1 ow
Wavy flow
Fig. 1. Flow p a t t e r n i n h o r i z o n t a l two-phase l i q u i d - g a s flow.
0

Wavy flow

Wavy flow i s a n extension of s t r a t i f i e d flow i n which a l a r g e r gas v e l o c i t y produces s u r f a c e waves i n t h e l i q u i d .

Slug f l o w

This p a t t e r n is an extension of the wavy flow

p a t t e r n i n which t h e gas v e l o c i t y i s g r e a t enough t o c a u s e s u r f a c e waves i n the l i q u i d t o reach t h e top of t h e pipe. Annular flow This produces flow segments t h a t are completely l i q u i d .
0

This regime i s defined by a l i q u i d annulus

(with an i n n e r gas c o r e ) a t t h e p i p e w a l l ; t h e annulus i s t h i c k e r a t t h e bottom of t h e

Dispersed d r o p l e t flow

Pipe This p a t t e r n o c c u r s when t h e gas phase i s continuous w i t h l i q u i d d r o p l e t s , dispersed throughout t h e flow ( a l s o c a l l e d fog o r m i s t flow).

-3-

Flow Regime Mapping

Most flow-regime maps are developed e m p i r i c a l l y by p l o t t i n g experimental observations of flow p a t t e r n s on a graph w i t h s u i t a b l y chosen axes, although r e c e n t e f f o r t s have been d i r e c t e d toward d e f i n i n g t h e regime boundaries on

a more r i g o r o u s t h e o r e t i c a l basis.'
rate t h e p o s s i b l e regimes.
o r dimensionless q u a n t i t i e s .

Then l i n e s o r bands are drawn t o sepa-

The c o o r d i n a t e s are u s u a l l y r e l a t e d t o t h e flow For h o r i z o n t a l flow, one of t h e b e s t known and Although

rates of t h e two phases o r t o flow r a t e and q u a l i t y , and may be dimensioned

s t i l l most widely used flow maps w a s developed by Baker i n 1954. 2s5

the Baker c h a r t i s not t h e most a c c u r a t e of t h e c u r r e n t l y used flow-regime mapping techniques, i t has gained wide acceptance because of i t s relative s i m p l i c i t y and ease of a p p l i c a t i o n . which are defined as follows5: The Baker c h a r t f o r h o r i z o n t a l flow i s

a log-log graph of two parameters c a l l e d t h e Baker parameters, Bx and B

0.333
Bx =

Y*

( p ; 7 u1 1 ; : ) t

)
i

B = 2.16 Y

wV

1/2 A(P1PV)

The s u b s c r i p t s 1 and v r e p r e s e n t t h e l i q u i d and gas phases, W i s mass flow 3 rate i n l b / h r , p i s d e n s i t y i n l b / f t , v is v i s c o s i t y i n c e n t i p o i s e , u is t h e s u r f a c e t e n s i o n i n dynes/cm, and A i s t h e p i p e c r o s s - s e c t i o n a l area i n 2 I f X = Wv/(Wv W) i s t h e q u a l i t y and Q = Wv 1 W1 t h e t o t a l flow rate ft

f o r t h e two-phase flow, Eqs. 1 and 2 can b e more conveniently w r i t t e n f o r t h e p r e s e n t a p p l i c a t i o n as

B = 2.16 Y

Q X

112

(4)

The Baker c h a r t i s shown i n Fig. 2.

The two-phase flow h a s been assumed

isothermal, t u r b u l e n t i n both t h e l i q u i d and vapor phases, and steady ( i n

-4-

Bubble or froth
a J
CC aJ
fu
Y

Stratified

5 L
fu

b lo3P

t
1O21 lo-'
I

1 I 1

1o2 Baker parameter, B X

10

I o3

Fig. 2. B a k e r c h a r t f o r flow-regime p r e d i c t i o n . flow c o n d i t i o n s f o r tests reported.)

( I n d i c a t e d d a t a p o i n t s are

t h a t t h e r e i s no s l i p ) ; p r e s s u r e l o s s i s assumed i n s i g n i f i c a n t . of temperature are r e q u i r e d .

To apply

t h e Baker c h a r t , t h e v i s c o s i t y and s u r f a c e t e n s i o n of water as a f u n c t i o n P l o t s of t h e s e q u a n t i t i e s are shown i n Figs. 3 and 4, where t h e d a t a f o r t h e temperature range from 300 t o 500F h a s been e x t r a c t e d from p l o t s over an extended temperature range given i n Ref. 6 .

n V

30 -

20300

b
350 400 450 Temperature - O F
f 1

Temperature

- "F

Fig. 3. Dynamic v i s c o s i t y vs temperature f o r w a t e r a t 300-500F.

Fig. 4. Surface t e n s i o n vs temperat u r e f o r water a t 300-500'F.

-5-

Flow-Visualization Experiments
The Geothermal T e s t F a c i l i t y (GTF) w a s employed t o provide a steam source f o r flow-visualization experiments. described i n d e t a i l . 7
The f a c i l i t y w a s constructed t o

support development of t h e geothermal t o t a l flow concept'

and has been

B a s i c a l l y , i t i s a hot-water g e n e r a t o r from which t h e The q u a l i t y of t h e mixture is

p r e s s u r i z e d w a t e r i s f l a s h e d t o a d e s i r e d two-phase p r e s s u r e (or temperature) low q u a l i t y c o n d i t i o n f o r test purposes. c o n t r o l l e d by t h e s e l e c t i o n of t h e p r e s s u r i z e d water temperature where a c o n s t a n t enthalpy expansion t o t h e two-phase f l u i d s t a t e is assumed. c o n d i t i o n s f o r t h e hot-water generator are 50F 5' flow rates of about 2.5 l b / s p o s s i b l e . The flow rate t o t h e test s p o o l i s a c c u r a t e l y determined by using an orifice-meter measurement taken b e f o r e f l a s h i n g t h e p r e s s u r i z e d water. Temperature and p r e s s u r e of t h e water are a l s o recorded using conventional strain-gage p r e s s u r e transducers and thermocouples. Temperature of the f l a s h e d two-phase steam i s measured a t t h e inlet and o u t l e t of t h e test spool by using thermocouples i n t r i n s i c a l l y mounted on t h e o u t e r w a l l s u r f a c e of t h e s t a i n l e s s - s t e e l p i p e w i t h a l a y e r of i n s u l a t i o n over t h e thermocouple. Pressure, although dependent on t h e two-phase temperature, w a s a l s o recorded

Maximum

and 1000 p s i a w i t h long term

as a check n e a r t h e i n l e t and o u t l e t of t h e spool by using p r e s s u r e t a p s on

t h e top of t h e pipe. system.
A l l d a t a are recorded on a Kaye d i g i t a l d a t a - a c q u i s i t i o n

The thermocouple temperatures are given d i r e c t l y i n degrees c e n t i The 5O-in.-spool s e c t i o n is designed

grade, b u t t h e p r e s s u r e output i n v o l t s must be converted t o p s i a by using the appropriate s e n s i t i v i t y factor. t o permit t h e t e s t i n g of a v a r i e t y of p o s s i b l e two-phase i n s t r u m e n t a t i o n 9 techniques; flow v i s u a l i z a t i o n is one.
The two-phase thermodynamic state p r o p e r t i e s i n t h e spool t e s t - s e c t i o n

are evaluated w i t h t h e use of an i n t e r a c t i v e computer program c a l l e d "SPOOL."

This program u s e s a l a r g e set of s u b r o u t i n e s f o r t h e c a l c u l a t i o n of s t e a m p r o p e r t i e s based on an i n t e r n a t i o n a l l y agreed-upon set of equations c a l l e d t h e "1967 IFC Formulation f o r I n d u s t r i a l Use"." The program assumes a c o n s t a n t enthalpy expansion from t h e compressed water state t o t h e two-phase

steam state, and r e q u i r e s an i n p u t of t h e measurements of t h e water p r e s s u r e

and temperature, t h e orifice-meter zero flow and t h e test-flow d e l t a press u r e , and t h e test-spool temperature and pressure. The o u t p u t provides t h e two-phase c o n d i t i o n s of enthalpy, flow rate, q u a l i t y , s p e c i f i c volume, and
-6-

average flow v e l o c i t y , as w e l l as r e p e a t i n g t h e measured spool temperature and comparing t h e corresponding s a t u r a t e d p r e s s u r e w i t h t h e measured pressure. Flow-visualization experiments w e r e conducted using t r a n s p a r e n t g l a s s

s e c t i o n s of both 1 and 2411.

i.d.

sandwiched between Schedule 80 304 Figure 5 shows t h e g l a s s s e c t i o n , 24 i n . long, i n place. A high speed 16-mm camera, e i t h e r a Hycam

stainless-steel p i p e o f t h e same corresponding diameter.

test-spool s e c t i o n w i t h t h e 1-in. t e f l o n s h e e t served as a d i f f u s e r . 7242, was used i n a l l runs.

I n a l l cases, t h e g l a s s s e c t i o n w a s l i g h t e d from t h e back and top; a o r a Milliken, was p o s i t i o n e d as shown; high speed Ektachrome f i l m , EF type A mirror below t h e g l a s s p i p e w a s positioned

i n some r u n s t o g i v e a bottom view of t h e flow, while i n o t h e r cases i t w a s

simply angled t o r e f l e c t t h e top f l o o d l i g h t f o r bottom l i g h t i n g and f o r a

more uniform l i g h t i n t e n s i t y .
A closeup view of t h e 5-in.-long, spacer p i p e appears i n Fig. 6. Invar t i e r o d s shown. 2.0-in. i . d . by 2.7-in. 0.d. glass The spacer p i p e w a s held i n place by t h e A similar arrangement 0.d. g l a s s

The a n g l e i r o n used f o r alignment and s t i f f e n i n g mini1.0-in. i . d . by 1.3-in.

mized t h e bending moment c a r r i e d by t h e g l a s s s e c t i o n .

is shown i n Fig. 7 f o r t h e 24-in.-long,

process pipe. rods were n o t necessary. number on t h e f i l m .

This p i p e has c o n i c a l ends f o r mounting t o t h e f l a n g e , so t i e The d i g i t a l i n d i c a t o r w a s used t o provide a run

The i n d i c a t o r , flood l i g h t s , and high speed motion

camera were remotely a c t u a t e d so t h a t a test series could be conducted witho u t personnel in t h e area when t h e g l a s s s e c t i o n was pressurized. o p e r a t i n g p r e s s u r e before t h e i r use i n the experiments. I n a d d i t i o n t o t h e black-and-white i n t e n s i f i c a t i o n schemes. photographs taken from s e l e c t e d frames of t h e 1 6 mm f i l m , t h e d a t a w a s a l s o analyzed w i t h t h e use of two imageThe f i r s t produces a three-dimensional photograph The from t h e n e g a t i v e o r photograph i n which t h e t h i r d dimension is p r o p o r t i o n a l t o the d e n s i t y of t h e f i l m d a t a a t any p a r t i c u l a r l o c a t i o n on t h e film. ranges. second method is similar, but v a r i o u s c o l o r s r e p r e s e n t c e r t a i n f i l m d e n s i t y Both glasss e c t i o n designs were t e s t e d a t o p e r a t i n g temperature and t h r e e times

In most cases, flow p a t t e r n s were found t o be more e a s i l y defined

An example of t h e

using t h e s e methods over t h e conventional photograph.

image i n t e n s i f i c a t i o n r e s u l t is demonstrated i n Fig. 8 f o r 2-in.

p i p e flow

with the average q u a l i t y and v e l o c i t y of 18.2% and 18.7 ft/s, r e s p e c t i v e l y .

The black-and-white
photograph, three-dimensional image i n t e n s i f i c a t i o n , and c o l o r image i n t e n s i f i c a t i o n can be compared f o r t h e same 16-mttt frame. -7-

The

I 03 I

Fig. 5. Two-phase instrumentation-development test spool showing 1-in.-diam glass section for flow visualization.

Teflon d i f f u s e r
...
,..

Fig. 6 . Glass s p a c e r p i p e (2-in.-diam) f o r flow v i s u a l i z a t i o n . about two-thirds f u l l of water a t t i m e of photograph.)

(Pipe w a s

numbers on the c o l o r chart i n Fig. 8c g i v e t h e relative d e n s i t y ranges f o r each c o l o r band, black being t h e most dense. The f i e l d of view of t h e blackand-white photograph i s s l i g h t l y shortened on t h e r i g h t s i d e .

-9-

. . . .l."C.- - -

Fig. 7 .

Glass process p i p e (1-in.-diam)

f o r flow v i s u a l i z a t i o n .

Results
Table 1 g i v e s a summary of t h e 1-in.and 2-in.-diam tests f o r which With t h e exception

flow-visualization d a t a are t o b e presented.

The l o c a t i o n on t h e Baker c h a r t

f o r t h e flow c o n d i t i o n of each run i s shown i n Fig. 2.

of runs 1 and 2, a l l d a t a are f o r approximate f i e l d conditions of 200 p s i a ,

18%q u a l i t y , and varying flow rates.

The d a t a f o r t h e 2-in.-diam

p i p e were

taken b e f o r e t h e i n s t a l l a t i o n of a higher c a p a c i t y pump, s o t h a t maximum flow

rate on a continuous b a s i s w a s about 1.6 l b / s .

t e s t i n g i n 2-in. spools a t over 2.0 l b / s .

The new pump should permit

The 1-in.-diam

pipe r u n s w e r e

taken with t h e high c a p a c i t y pump i n s t a l l e d , b u t t h e flow choked a t about

1.8 l b / s .

-10-

F1 ow

Side view

Bottom view

0 0

Relative density range

(c)
Fig. 8. Two-phase flow visualization. Comparison of a regular photograph with three-dimensional and color image-intensification results taken from the same 16-mm frame. Flow was 18.2%quality at average velocity of 18.7 ft/s i n the 2-in.-dim pipe. (a) black-and-white photograph; (b) three-dimensional image intensification; (c) color image intensification. -11-

Table 1. Framing r a t e/ s h u t t e r speed 1000/ 1000/

Summary of flow-visualization d a t a . Average velocity (ft/s) 60.4 6.3 9.2 30.0 39.5 129 42.7 143
.

Run

Pipe diameter (in.) 2a 2b 2b 2b

lb lb

Temp. (OF) 334 434

38 9

&%A)
109 361 218

Flow rate (lb/s) 1.59 11 . 1 0.48 1.51 0.51 1.55 0.53 1.78

Quality

(%I
18.7 7.6 17.9 18.5 18 .O 18.7

2500 1
1 2500

1 loo/ 4000
loo/ 4ooo

389 388 38 6 37 9 382

218
215 210 193 201

1 250/ 12,000 1 250/ 12,000 1000/ 3000/

1 2500

la
la

18 .O
18.5

1 7500

Side v i e w only.

bSide and bottom view.

Flow-visualization results f o r t h e 2-in. f o r l-in. flow i n Figs. 13-16.

flow appear i n Figs. 9-12 and

The 2-in. runs i n c l u d e t h e image enhancement A s w i t h Fig. 8,

r e s u l t s f o r t h r e e dimensional and c o l o r image i n t e n s i f i c a t i o n and g i v e a d i r e c t comparison w i t h t h e conventional flow photograph.

the black-and-white

photograph on Figs. 9, 10, and 12 h a s a shorted f i e l d Although image enhancement w a s done f o r t h e runs, Flow v e l o c i t i e s were s u f f i c i e n t l y high

of view on t h e r i g h t s i d e .

t h e s e r e s u l t s are n o t included s i n c e they d i d n o t s i g n i f i c a n t l y improve t h e i n t e r p r e t a t i o n from t h e photograph.

i n t h e l-in.

cases t o g i v e well-mixed flow and small d e n s i t y v a r i a t i o n s .

The p r e d i c t e d flow state i s i n d i c a t e d i n each case on an expanded s e c t i o n of t h e Baker c h a r t . -12-

Run 1

P
Q

= 109 psia = 1.59 lb/s

X = 18.7 %

Vave = 60.4 f t / s

Baker c h a r t

F1 ow

Fig. 9. Flow visualization (%in. pipe), run 1. (a) photograph of typical frame, s i d e view; (b) three-dimensional enhancement; (c) color enhancement.

-1 3-

Run 2
P = 361 psia

Q = 1.11 lb/s
X = 7.6 %
,V ,
= 6.3 f t / s
I
I

I I I \ I

I I

F1ow

Baker chart

T i e roid image

Fig. 10. Flow visualization (2-in. pipe), run 2. (a) photograph of typical frame, s i d e view; (b) three-dimensional enhancement; (e) color enhancement.

-14-

Dispersed

Run 3
P = 218 psia
Q = 0.48 l b / s

Bubble

X = 17.9 % Vave = 9.2 f t / s

Baker c h a r t T i e rod image Side view

F1ow

Bottom view

.
Fig. 11. Flow visualization (2-in. pipe), run 3. (a) photograph of typical frame; (b) three-dimensional enhancement; (c) color enhancement. -15-

Run 4
P = 218 psia
Q = 1.51 lb/s

X = 18.5 %
\Iave = 30.0 f t / s

Baker c h a r t

F1 ow
Side view

Bottom view

Fig. 12. Flow visualization (2-in. pipe) run 4. (a) photograph of typical frame; (b) three-dimensional enhancement; (c) color enhancement. -16-

Run 5 P = 215 psia

Q = 0.51 lb/s

Dispersed Bubble

X = 18.0 %

v,,

= 39.5 f t / s

Baker c h a r t

F1ow
Photograph o f t y p i c a l frame

Side view Bottom view

Fig. 13.

Flow visualization (1-in. pipe), run 5.

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Run 6
P = 210 psia
Q = 1.55 l b / s

.Dispersed Bubble Annular

X = 18.7 %

Vave = 129.0 f t / s
Baker chart

___t

F1ow

Side view

Bottom view

Photograph o f t y p i c a l frame

Fig. 14.

Flow visualization (1-in. pipe), run 6 .

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Run 7
P = 193 p s i a Q = 0.53 l b / s

X = 18.0 % Vave = 42.7 f t / s

Baker c h a r t

Photograph o f t y p i c a l frame
'\

- side

view

Fig. 15.

Flow visualization (1-in. pipe), run 7.

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Run 8
P = 201 p s i a

Dispersed Bubble

Q = 1.78 l b / s

X = 18.5 % V ,,
= 143.0 f t / s

Baker c h a r t

Photograph o f t y p i c a l frame - s i d e view Fig. 16.

. Flow visualization (1-in. pipe), run 8

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Discussion
Typical f i e l d two-phase c o n d i t i o n s a t flow rates o b t a i n a b l e i n t h e GTF l e a d t o flow regimes concentrated i n t h e annular region of t h e Baker c h a r t f o r 2-in. f o r l-in. pipe flow. p i p e flow. The upper annular and dispersed r e g i o n s were obtained Although a b s o l u t e flow p a t t e r n s w e r e not e a s i l y i n t e r -

preted from t h e 16-mm f i l m o r t h e corresponding s i n g l e frame photographs, t h e general flow n a t u r e w a s approximately defined by t h e Baker c h a r t prediction. I n a l l cases, some l i q u i d flow a t t h e i n n e r w a l l boundary w a s noted, w i t h a g r e a t e r c o n c e n t r a t i o n of l i q u i d flow near t h e pipe bottom. Some runs a c t u a l l y showed reverse flow f o r t h e o u t e r l i q u i d annulus, while o t h e r s i n d i c a t e d a churning o r screw motion of t h e f l u i d . uniformly fog o r m i s t flow. Figures 9 and 1 0 show s i d e views of flow p r e d i c t e d by t h e Baker c h a r t t o be i n t h e annular regime but tending towards dispersed flow. w a l l e v i d e n t i n both cases. the l i g h t i n g configuration. This i s a reasonable d e s c r i p t i o n of t h e flow p a t t e r n found, w i t h l i q u i d flow near t h e The flow d e n s i t y i s noted t o be g r e a t e r near These r u n s used a r e f l e c t i n g m i r r o r a t t h e t h e bottom of t h e p i p e , as expected, b u t t h i s may be misleading because of underside of t h e p i p e t o achieve n e a r l y uniform l i g h t i n g , but t h i s arrangement s t i l l tends toward higher l i g h t i n g i n t e n s i t y near t h e top of t h e pipe. Thus, t h e g r e a t e r flow d e n s i t y i n d i c a t e d near t h e lower p a r t of t h e pipe may be somewhat influenced by t h e l i g h t i n g technique. evident. The flow i s s u f f i c i e n t l y t r a n s p a r e n t i n run 2, Fig. 10, f o r t h e image of a t i e rod t o be c l e a r l y I n no case w a s t h e flow considered i d e a l l y dispersed o r i n a s t a t e t h a t would be c a l l e d

As a g e n e r a l r u l e , t h e flow w a s noted t o be c l e a r e r a t t h e lower

flow rates and lower flow q u a l i t y . near t h e bottom.

As would be expected, run 2 shows t h e

g r e a t e s t d e n s i t y v a r i a t i o n , being t r a n s p a r e n t a t t h e top and h i g h l y opaque

1 Runs 3 and 4 i n Figs. 1 and 12 show f i e l d - c o n d i t i o n runs a t moderatly

low and moderately h i g h flow rates t h a t show up as an annular flow regime on t h e Baker c h a r t . These runs had t h e m i r r o r on t h e underside of t h e t r a n s parent p i p e s e c t i o n angled t o provide a simultaneous bottom view of t h e flow. This arrangement r e s u l t s i n a s l i g h t l y b r i g h t e r image a t t h e top p o r t i o n of t h e s i d e and bottom views; t h i s must be considered when analyzing d e n s i t y v a r i a t i o n s i n t h e flow f i e l d . The lower flow-rate condition of run 3 l e a d s -21-

t o a more t r a n s p a r e n t flow, and t h e tie-rod image from t h e curved g l a s s s e c t i o n i s c l e a r l y evident. lower p o r t i o n of t h e pipe. The flow i n run 3 appears t o be a combination The higher flow rate of run 4 l e a d s t o a more of s t r a t i f i e d and annular, as t h e r e i s a d e f i n i t e l a y e r of l i q u i d i n t h e uniform flow d i s t r i b u t i o n , as p r e d i c t e d by t h e Baker c h a r t . The corresponding three-dimensional and c o l o r enhancement photographs i n Figs. 9-12 provide a clear r e p r e s e n t a t i o n of t h e d e n s i t y v a r i a t i o n s i n t h e flow; t h e l i q u i d c o n c e n t r a t i o n s n e a r e r t h e bottom of t h e pipe are e v i d e n t

i n a l l runs.

These techniques, of course, are l i k e w i s e influenced by t h e They a l s o i n d i c a t e

s l i g h t l y uneven l i g h t i n g used f o r t h e flow photography. flood lamp i n t e n s i t y w a s not evenly d i s t r i b u t e d .

a b r i g h t e r l i g h t i n g area (hot s p o t ) near t h e c e n t e r of t h e flow because t h e

S i m i l a r flow-visualization d a t a f o r t h e 1-in. spool i s shown i n Figs. 13-16. I n t h e s e cases, much h i g h e r v e l o c i t i e s are obtained f o r t h e flow; t h e s e higher The flow

same flow rate when compared with t h e 2-in.-spool

v e l o c i t i e s result i n a more evenly d i s t r i b u t e d flow p a t t e r n .

regime i n d i c a t e d by t h e Baker c h a r t f o r runs 5 and 7 i n Figs. 13 and 1 5 i s annular, b u t very c l o s e t o t h e annular-dispersed flow-regime border. by t h e Baker c h a r t .

Runs

6 and 8 i n Figs. 14 and 16 l i e w e l l w i t h i n t h e d i s p e r s e d flow regime p r e d i c t e d

Both s i d e and bottom views were taken w i t h r u n s 5 and The same comments on

6, b u t only s i d e views w i t h r u n s 7 and 8 as shown.

s p o t i s even more evident.

l i g h t i n g - i n t e n s i t y d i s t r i b u t i o n apply f o r t h e 1-in. flow; t h e c e n t r a l h o t The two r u n s a t t h e lower v e l o c i t i e s show l i q u i d flow a t t h e w a l l i n an annular flow f a s h i o n p r e d i c t e d by t h e Baker chart. The high v e l o c i t y flow c o n d i t i o n s are much more dispersed, as expected.

Conclusions
Flow v i s u a l i z a t i o n provides an e x c e l l e n t method of e v a l u a t i n g t h e flow regimes p r e s e n t f o r v a r i o u s flow c o n d i t i o n s . The information i s e s p e c i a l l y Knowing t h e flow regime u s e f u l i n designing instrumentation and sampling techniques t h a t may be h i g h l y influenced by t h e d i s t r i b u t i o n of t h e flow. energy-conversion machinery. f o r given c o n d i t i o n s should a l s o be i n v a l u a b l e i n t h e design of nozzles and
The Baker c h a r t , based on t h e l i m i t e d flow

c o n d i t i o n s used i n t h i s study, appears t o g i v e a reasonable p r e d i c t i o n of

-22-

t h e flow p a t t e r n o r regime expected f o r any given flow conditions. a l s o a r e l a t i v e l y simple method t o apply.

It i s

I n p r e p a r a t i o n f o r p o s s i b l e f u t u r e flow-visualization s t u d i e s i n t h e l a b o r a t o r y and e s p e c i a l l y i n t h e f i e l d w i t h a c t u a l geothermal flow, several recommendations are made as a r e s u l t of t h i s work: e The Baker c h a r t provides a reasonable quick-look method of p r e d i c t i n g t h e flow regime f o r given c o n d i t i o n s .

o The u s e of c o l o r f i l m , a t least w i t h clean water, does n o t appear t o

have any advantages over black-and-white s p o t s i n t h e flood lamps. parent section. film. e Recorded flow d e n s i t i e s are influenced by t h e l i g h t i n g method and h o t This would be reduced by shadowgraph (back f i l m could be used t o l i g h t i n g only) and by l o c a t i n g t h e flood lamp f a r t h e r from t h e transHfgher speed black-and-white account f o r t h e decreased l i g h t i n g i n t e n s i t y .
0

Three-dimensional c o l o r image-enhancement techniques provide a u s e f u l a d d i t i o n t o conventional photography f o r t h e e v a l u a t i o n of flow p a t t e r n s and flow-density v a r i a t i o n s .

Glass process p i p e has a s u f f i c i e n t f a c t o r of s a f e t y f o r use a t

c o n d i t i o n s considerably above r a t e d o p e r a t i n g p r e s s u r e and temperature. Beaded g l a s s p i p e i s recommended f o r f u t u r e work, s i n c e alignment i s n o t c r i t i c a l , and t h e t i e r o d s used i n t h e 2-in. necessary s e c t i o n would n o t be

Although g l a s s i s s l i g h t l y s o l u b l e i n s t e a m , several hours o f o p e r a t i o n produced no v i s i b l e deter-ioration i n t h e o p t i c a l q u a l i t y of t h e g l a s s test-sections.

Acknowledgements
The a u t h o r would l i k e t o acknowledge t h e a s s i s t a n c e of J i m Kuhlman and

Leo Meisner i n t h e design, f a b r i c a t i o n , and t e s t i n g of t h e s p o o l s f o r t h e

flow-visualization studies. motion-picture coverage. Gary Carter provided t h e image-enhancement r e s u l t s , and Jm Caywood was t h e photographer f o r t h e s t i l l and high speed i

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References
1.
Y. Taitel and A. E. Dukler, AIChE. J. 22, 47 (1976). 0. Baker, &Z Gus J. 53, 185 (1954). G. F. H e w i t t and N. S. Hall-Taylor,

2.
3.
4. 5. 6.

AnnuZar Two-Phase n o w (Permagon

P r e s s , New York, 1970).

G. W. Govier and K. Aziz,

The n o w of CompZex Mkctures i n Pipes (Van

Nostrand-Reinhold, New York, 1972).

R. Kern, Chem. Eng. (New York) 82, 145 (1975).
C. L. Yaws and H. S . N. S e t t y , Chem. Eng.

(New York) 8 l , 67 (1974).

7.

H. Weiss, GeothermaZ Two-Phase Flow Test FaoiZity, Lawrence Livermore

Laboratory, Rept. UCRL-76409, P r e p r i n t (1975).

8.

A. L. Austin, G. H. Higgins, and J. H. Howard, m e Totaz FZozd Concept

f o r Recovery of Energy from GeothermaZ Hot Brine Deposits, Lawrence

Livermore Laboratory, Rept. UCRL-51366 (1973).

9.
10.

C. A. Calder, Instrumentation for !Two-Phase GeothemnaZ Flow, Lawrence

Livermore Laboratory, Rept. UCID-16806 (1975).

R. B. McClintock and G. J. S i l v e s t r i , CaZcukztion o f Properties of Steam

(American Society of Mechanical Engineering, New York, 1968).

.
WTW/ c/ l a /mla s

GPO 789-038/8
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