NASA/TM--2001-210705 AIAA-2001-0767

Effects of Gravity on Cocurrent Two-Phase

Gas-Liquid Flows Through Packed Columns

Brian J. Motil

Glenn Research Center, Cleveland, Ohio

Vemuri Balakotaiah

University of Houston, Houston, Texas

Yasuhiro Kamotani

Case Western Reserve University, Cleveland, Ohio

Prepared for the

39th Aerospace Sciences Meeting and Exhibit

sponsored by the American Institute of Aeronautics and Astronautics

Reno, Nevada, January 8-11, 2001

National Aeronautics and

Space Administration

Glenn Research Center

February 2001
This report contains preliminary

findings, subject to revision as

analysis proceeds.

Available from

NASA Center for Aerospace Information

7121 Standard Drive

Hanover, MD 21076

Price Code: A03

National Technical Information Service

5285 Port Royal Road

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Price Code: A03

Available electronically at http: / / gltrs.grc.nasa.gov / G LTRS
EFFECTS OF GRAVITY ON COCURRENT TWO-PHASE GAS-LIQUID FLOWS

THROUGH PACKED COLUMNS

Brian J. Motil

National Aeronautics and Space Administration

Glenn Research Center

21000 Brookpark Road

Cleveland, Ohio 44135

Vemuri Balakotaiah

University of Houston

4800 Calhoun Road

Houston, Texas 77204

Yasuhiro Kamotani

Case Western Reserve University

10900 Euclid Avenue

Cleveland, Ohio 44106

Abstract

This work presents the experimental results of research

on the influence of gravity on flow pattern transitions,

pressure drop and flow characteristics for cocurrent gasliquid two-phase flow through packed columns. The

flow pattern transition data indicates that the pulse flow

regime exists over a wider range of gas and liquid flow

rates under reduced gravity conditions compared to

normal gravity cocurrent down-flow. This is illustrated

by comparing the flow regime transitions found in

reduced gravity with the transitions predicted by

Talmor. 1Next, the effect of gravity on the total pressure

drop in a packed column is shown to depend on the

flow regime. The difference is roughly equivalent to the

liquid static head for bubbly flow but begins to decrease

at the onset of pulse flow. As the spray flow regime is

approached by increasing the gas to liquid ratio, the

effect of gravity on pressure drop becomes negligible.

Finally, gravity tends to suppress the amplitude of each

pressure pulse. An example of this phenomenon is

presented.

Introduction

Long duration manned space activities will depend on

the development of regenerative life support systems

based on physicochemical and/or biological

technologies. NASA and the NRC have identified

through a workshop 2 and a commissioned study 3 that

multiphase processing of in-situ resources must be made

possible under conditions ranging from zero to partial

gravities (e.g., Mars, 0.38g, Lunar 0.17g), if NASA's

goals of Human Exploration and Development of Space

(HEDS) are to be achieved. One of the "enabling" unit

operations critical to many of these systems is the

packed (fixed) bed reactor with co-current flow of gas

and liquid.

In the typical operation of the packed bed reactor, gas

and liquid flow simultaneously through a fixed bed of

solid particles. The particles can be various shapes and

sizes and serve to force the two fluid phases through the

narrow channels connecting the interstitial voids. This

configuration provides for the intimate contact needed

between the phases to sustain chemical or biological

reactions. The packing may also serve as either a

catalytic site or as a surface for growing biological

material. NASA has flown two of these systems in a

microgravity environment with limited success. In both

systems, it was assumed the effects of a weightless

environment on the hydrodynamics were predictable

(even though prior to this study no experimental data

existed) and attention was focused on mass transfer.

NASA/TM--2001-210705 1
TheVolatileRemovalAssemblyFlightExperiment 4

(VRAFE)flewonSTS-89andSTS-96.Thisexperiment

involvedahightemperaturecatalyticoxidationprocess

as a final treatmentfor recycledwater.A lossof

chemicalperformancewas reportedalong with

increasedgasinclusion.Theothersystemattemptedby

NASA wasa biologicalreactorfor the primary

treatmentof wastewater andwasflownonNASA's

KC-135aircraft.Thepackedbedreactorapproachwas

abandonedafterit wasrecognizedthathydrodynamic

and phasedistributiondifferencesin a weightless

environment preventedthereactorfromfunctioningas

designed.

Thepurposeof this study was to gain insight into the

specific effects a reduced and high gravity environment

has on such gas-liquid fixed bed reactor hydrodynamic

parameters as flow patterns, phase distribution and

pressure drop. We refer to the test section as a packed

colunm or bed rather than a reactor since no mass

transfer or reactions are taking place. This paper first

presents a brief description of the flow regimes

encountered on earth and how they can be mapped to

include operation in reduced gravity. Pressure drop and

liquid holdup comparisons are then discussed along

with the effect of gravity on flow regime characteristics,

such as pulse amplitude.

Experimental

Test Apparatus

The Small Two-Phase Flow Experiment (STPFE) is an

existing two-phase rig designed to fly on NASA's

KC-135 aircraft. It was modified to accommodate the

packed bed test section and instrumentation. An

overview of the design is given by Motil 5 et al.

Figure 1 shows the test section which was a rectangular

colunm with a cross section of 2.54×5.08 cm. The

column was 60 cm long with 5 evenly spaced

differential pressure transducers and was made from a

clear polycarbonate material for viewing the phase

Packed Column

"res! Seclion

Abs, P

Recycle

Pump

Figure 1._Packed column test apparatus.

Pressure

Regulated

Gas

Venl

NASA/TM--2001-210705 2
distributionwitha highspeedSVHSvideorecorder.

Absolutepressuretransducerswere also located

oppositeof thefirstandlastdifferentialtransducers.

Bothphaseswerewellmixedjustpriorto theinletof

thecolumn.Thecolumnwasrandomlypackedwith

identicallysizedspherical gassbeads.

Test Conditions

The test conditions were designed to provide a wide

range of flow parameters as well as include the major

flow regimes. The gas phase was air and the liquid

phase was a water-glycerin mixture. Variations of

several orders-of-magnitude in the important

dimensionless numbers were obtained by varying the

packing size, gas and liquid flow rates, and the liquid

viscosity (by changing the weight percent of glycerin).

The ranges of dimensionless numbers, flow rates, fluid

properties and packing diameters used in these

experiments are given below:

0.18 < Re < 100

0.001 < We < 1.0

0.03 < O < 0.8 kg/(s m e)

3 < L < 50 kg/(s m 2)

1 <gL<20cP

= 68-72 dynes/cm

Dp = 2 and 5 mm

where G and L are superficial mass velocities of the gas

and liquid, gL is the liquid viscosity, cr is the surface

tension and Dp is the packing diameter. The two-phase

dimensionless groups (Reynolds and Weber numbers)

are defined as:

We = Dh (L + G)"v m

(7

(l)

Re - Dh (L + G) (2)

]-ILG

where

L/G 1

vL6 = v z + v G (3)

I+L/G I+L/G

L/G 1

]'/LG = ]'/L t- ]'/G (4)

I+L/G I+L/G

2eD

D h = (5)

2 + 3(1-e)(D/ Dp)

e is the packing bed void fraction, V G and V L are the

respective gas and liquid specific volume, and D is the

hydraulic diameter of the empty bed.

Over 250 different test conditions were recorded in

microgravity with a companion set of l-g tests to

provide a direct comparison of the two environments.

Flow Regimes

General Description

It is generally accepted that for non-foaming systems,

cocurrent gas-liquid downflow in packed beds on earth

can be operated within four basic flow regimes.

Weekman and Myers, 6 Charpentier and Favier, 7 and

Sato 8 et al. were among the first to provide detailed

descriptions of each regime, but many others can be

found in the literature. Two of the flow regimes can

further be classified as "gas continuous" because the gas

phase occupies most of the void space within the

column. At both low gas and low liquid flow rates,

trickle or channeled flow is observed. In this important

flow regime, the liquid phase trickles down the packing,

driven mainly by the draining force of gravity. The

liquid forms a laminar film that frequently does not wet

the entire packing surface and interaction between the

phases is relatively low. As the gas flow is increased,

the liquid film becomes turbulent and eventually the gas

flow is strong enough to suspend droplets of fiquid.

This flow regime is generally called spray or mist flow.

At higher liquid flow rates and relatively low gas flow,

the continuous phase is now liquid and the gas phase is

uniformly dispersed in small bubbles throughout the

colunm. This regime is called bubbly flow. Finally, an

interesting flow regime exists for a specific range of gas

and liquid flow rates called the pulse flow regime. This

flow regime can be observed as the liquid flow is

increased beyond trickle flow until pulses (traveling

waves) of liquid can be observed, The waves quickly

grow until they span the entire cross section of the

column. Pulses are first observed at the bottom of the

column and their initial formation appears to move

upward as the liquid flow is increased. A great deal of

mixing between phases frequently makes this the

desired flow regime for effective mass transfer despite

the fact that the actual mechanism of pulse formation

NASAfrM--2001-210705 3
andthetricklingto pulsingtransitionis stillanactive

areaofresearch. Thetransitiontopulseflowmayalso

occurfromtheliquidcontinuousbubblyflowregimeby

increasingthegasflowrate.Whilemanyl-g studies

focusedonthetricklingtopulsingtransition,verylittle

work hasbeenreportedon the bubblyto pulse

transition.Sincetheformertransitiondoesnotexistin

0-gandthelatterexistsin bothl-gand0-g(aswellas

highorintermediategvalues),studyingtheinfluenceof

gravityonthistransitionisusefulinunderstanding the

rolegravityforceshaveonalltransitionboundaries.

Flow Maps

Many attempts have been made to predict where the

transitions between flow regimes will occur. Models

based on hydrodynamic stability theory have been

proposed as well as flow maps using dimensionless and

even dimensional parameters. The variables influencing

the flow pattern transitions are the gas and liquid

densities, viscosities, and velocities. In addition,

interfacial tension, gravitational acceleration and the

packing and column diameters must be considered.

These ten variables give rise to seven dimensionless

groups. To make it possible to correlate experimental

data, these are normally combined into two groups.

Figure 2 shows such a dimensionless map by Talmor J

based on prior work by Oshinowo and Charles. 9 His

objective was to create a generalized flow map in terms

of some useful coordinates that can be scaled over

several orders of magnitude. One of these coordinates,

the Froude number, includes the effect of gravity. The

Talmor map was tested using multiple experimental

studies conducted in normal gravity for non-foaming

systems including air-water/glycerin, CO2-Hexane,

Freon-Silicon Oil, and Natl. Gas/CO2/Lube Oil. The

map is generally accepted with some noted limitations.

The basis for the map is that a driving-to-resistance

force ratio can be developed for two-phase flow through

a packed column similar to two-phase flow through an

empty tube. The driving forces are inertia and gravity

while the resistance forces are viscous and surface

tension. By normalizing the inertia forces and using

two-phase Froude, Weber and Reynolds numbers,

Talmor derives the force ratio as:

1 + (1 / Fr)

We + (1/ Re)

Inertia + Gravity

Interface + Viscous

(6)

where

[(L + G)v m ]2

Fr -- (7)

gD_

This flow map can then be applied to a microgravity

environment by neglecting the gravity force term.

I

fla.

IO0

10

0,1

Spray or Mist Flow

_ulsing and Pulsing-__._ _ _ Trickling FlOgubbling w

0.1

: : : ::::] : : : : :::;[ : ; : : ::::_

1 10 100

[1 +(1/Fr)] / [We ÷ (1/Ro)]

Figure 2.--Talmor flow regime map.

1000

NASA/TM--2001-210705 4
Flow Regimes in Reduced Gravity

As mentioned earlier, the trickle flow regime exists

because of the draining force of gravity. It seems

reasonable, therefore, to expect trickle flow not to exist

in microgravity. Instead, within the limitations of the

experimental flow rates and 20 second microgravity

durations, pulse or bubbly flow was observed at very

low liquid and gas flow rates. Rather than draining, the

liquid tends to spread in a radial (as well as axial)

direction until a sufficient amount of liquid has plugged

a cross sectional area. Depending on the gas flow rate,

the plug will either continue to fill the column until it is

the continuous phase or at slightly higher gas flow rates,

it will become the start of a liquid pulse. The other

extreme of the gas continuous flow is spray or mist

flow, which occurs at a very high gas-to-liquid ratio.

This flow regime was observed in only a few of our

microgravity experiments, but as expected, the

transition boundary and pressure drop were found to be

nearly independent of gravity because this transition is

dominated by inertia.

Based on the discussion above, our study focuses on

the pulse and bubbly flow regimes. Figures 3 and 4

show typical pressure traces for bubbly and pulse flow

respectively. Below each trace is the corresponding

normalized frequency response, which is calculated

using a Fast Fourier Transform (FFT) algorithm. The

frequency response was considered along with a

review of the high-speed video in determining the

flow regime.

25-

20-

13..

v

'-' 15-

£

"O

= 10-

0 i

1

0.10 --

0.08

0.06 --

0.04 -

0.02 -

0.00 -

PRESSU RE TRACE

I I I I 1 I I

12 13 14 15 16 17 18

time (sec)

NORMALIZED FREQUENCY RESPONSE (FF'I')

test 224022 (11 to 18 sec)l

,,,,i,,,,i,,,,i,,,,i,,,,l_',,,l,,,,i,,,,l,,,,l,,,,i,,,,i,,,,i,,,,i,,,,i,,,,i

0 2 4 6 8 10 12 14

frequency (Hz)

Figure 3.--Typical bubbly flow.

NASA/TM--2001-210705 5
A

t_

n

Ck

"O

_0

25-

20-

15-

10-

5 m

0 -

PRESSURE TRACE

I I I I I I I

9 10 11 12 13 14 15 16

time (sec)

0.10 -

0.08 -

0.06 -

0.04 -

o.oo.II I

I''''I''''

0

NORMALIZED FREQUENCY RESPONSE (FFT)

L I . [test 228019 (9 to 16 sec)l

,,,,l,,,,l,,l,l,,,,l,,,,l,,,,l,,,,l,,,,l,,,,l,,,,I,,,,l,,,,l,,,,l

2 4 6 8 10 12 14

Hz

Figure 4.mTypical pulse flow.

Figure 5 shows the transition boundaries between these

two regimes using Talmor's coordinates. The dashed

line represents the transition in normal gravity and is in

agreement with our l-g data. For clarity, we leave the

1-g data off of the map. The solid line represents the

flow regime transitions in 0-g. If the ratio of forces

proposed by Talmor is correct, the plot should still hold

after the absence of gravity is accounted for through the

Froude number. Instead, pulse flow was observed at a

much lower volumetric gas to liquid ratio than

predicted. One possible reason for this shift in the flow

regime transition may be due to the enhanced role of the

capillary forces in determining the amplitude of the

waves that exist on the liquid film surrounding the

particles. In addition, the wetting of the particles by the

liquid in 0-g is different than in 1-g since the

gravitational draining force is not present in 0-g. We

present some data in a later section which shows that for

the same gas and liquid flow rates, the pulse amplitude

is larger in 0-g than in l-g.

Pressure Drop and Liquid Holdup

Background

Total pressure drop is an important design parameter in

two-phase gas-liquid packed beds. It determines the

operational power and is used as a correlating variable

to estimate mass transfer rates (Gianetto _° et al.).

Another important design parameter, related to pressure

drop, is the liquid holdup in a column. Liquid holdup

refers to the amount of liquid that is retained within the

non-porous packing and is classified as static or

dynamic. Static holdup is the easier of the two to

determine experimentally and is directly related to the

competing gravitational and surface tension forces. It is

usually measured by flooding the colunm with a known

amount of liquid and then allowing the column to drain.

The difference is considered the static holdup.

Charpentier 7 et al. first presented a correlation, which

NASA/TM--2001-210705 6
®

lO0

lO

o.1

+• Bubbly PulseFFlow ow

• •• • • • • [Upperand LowerBoundary

•, • ,, •, •" • * * /forBubbly/Pulse FlowPredicted

",_ - • ••• • • • • /byTalmor

•"4. ,==•*'A t •t. / /

:.." ,%. ", ,.

Obs_e_edfor Bubbly/PuLseFlowI

in MicrograviD/ J

0.1 1 10 100 1000

[We+(1/Re)]-1

Figure 5.--Flow map in microgravity.

was improved on by Saez and Carbonell," between the

static holdup and the ratio of these forces using the

Eotvos (or Bond) number.

Eo- pLgDp

_L

(8)

In these correlations, the limiting value of static hold-up

is 11% as Eo approaches zero. This in fact does not

hold for the microgravity environment. In the absence

of gravity, the flooded column does not drain and the

static liquid holdup is 100%.

Comparison to Reduced Gravity

In this section, we compare the effect of gravity on total

pressure drop for both the bubbly and pulse flow

regimes.

At low gas and liquid flow rates, figure 6 illustrates the

pressure drop varies linearly with the liquid flow rate

for both normal and reduced gravity. This is consistent

with the well-known Darcy relationship

_u

-VP=---_ o (9)

Dynamic holdup is more difficult to determine

accurately. Correlations between pressure drop and

dimensionless groups such as the Re and We have been

attempted with some success. Measurement techniques

such as stopping the flow and measuring the amount

drained before the flow becomes static are used as well

as many attempts to directly measure the total liquid

holdup during actual flow and then subtracting the static

component. Obviously, it is difficult not to introduce

significant experimental error.

There are two basic types of hydrodynamic models used

to estimate pressure drop. One approach uses empirical

correlations (Sato 8 and Midoux l" et al.) the other uses a

modified Ergun equation (Saez 11and Holub 13et al.).

where K is the permeability of the packing and u o is

the average filter (packing) velocity vector. The Darcy

model gives a good correlation for single-phase liquid

at low velocities. However, as the liquid velocity is

reduced to a flow rate that would produce trickle flow

in normal gravity, bubble flow is still observed in the

reduced gravity case.

Another important observation is the slope of both

curves in figure 6 is nearly the same. The difference is

roughly equivalent to the liquid static head.

Figure 7 spans both the bubbly and pulse flow regimes

with a constant liquid flow. In this plot, it can be seen

that the pressure drop difference between l-g and 0-g

NASA/TM_2001-210705 7
10"_

_-8-

n

Q.

_o

6-

_m

¢9

.m

r_4--

_2--

0_

+ Normal Gravity I

<> Microgravity ]

Water, 5mm Packing

-3 2

G= 3.6x 10 g/(s cm )

I I I

1 2 3

2

L (g/s cm )

Figure 6.--Average pressure drop for bubbly flow.

¢5

Q.

v

v

¢}

_D

10-

_

m

Water, 5mm Packing

2

k = 1.5 g/(s cm )

%

\ \

_ _. Spray

x

S I+N_0='Ora l

+,t Bubbly "

I I I I

20 40 60 80

G (g/s cm 2)

Figure 7.--Average pressure drop for pulse flow.

I

-3

100x10

NASA/TM--2001-210705 8
-3.0-

-3.5 -

-4.oh

o. 4.5-

-5.0 -

-5.5

(1 psi = 6.89 kPa)

Ik _ I IVicr°grm4tYl =- _

/ '

i I i , i , [ i , i i I i i i , I i i i l l ' ' i i I i I i i i ¢ ]

10 20 30 40

seconds

Microgravity High Gravity Difference

( 10-18 s) (32-40 s)

Average Pressure Drop 28.61 kPa 32.75 kPa 4.14 kPa

Pulse Amplitude 15.3 ! kPa 11.65 kPa 3.66 kPa

Figure 8.mEffect of gravity on pulse amplitude.

begins to decrease as the inertia forces begin to

dominate the flow. If the data is extrapolated into the

spray flow regime, the difference becomes negligible.

Assuming the frictional pressure loss is the same for

both gravity environments, the difference in pressure

drop between the two is a direct measurement of the

dynamic and static head on the column. From this, the

dynamic liquid holdup can be determined.

Pulse Characteristics

The pulse amplitude is also affected by the relative

strength of the gravitational forces. Figure 8 illustrates a

typical pulse flow in which we continued to record the

pressure trace beyond the microgravity segment of the

aircraft trajectory. As the aircraft begins to pull out of

the microgravity "dive", the experiments on board

experience an increased downward acceleration

(relative to the experiment) of about 1.8 times that of

normal gravity.

From the pressure trace, it is clear that not only does the

average pressure drop shift as we discussed above, but

the pulse amplitude decreases with increasing

downward acceleration. In this case, the amplitude

decreases by 3.66 kPa.

This observation provides insight into the apparent shift

of the flow regime transitions seen in the Talmor map. As

shown earlier, pulse flow occurs at a much lower G/L in

the absence of gravity than predicted. This indicates that

gravity has a stronger influence over the bubbly-pulse

transition than previously thought.

Conclusions

We have presented in this work only some preliminary

results of an ongoing study. Based on these results, two

important conclusions can be drawn. First, the flow

regimes and the transitions that exist are different in

reduced gravity than in normal gravity. In reduced

gravity, the trickle flow regime becomes either pulse or

bubbly flow and the pulse flow regime is observed over

a much wider range of conditions. Second, the total

pressure drop in zero gravity is higher than normal

gravity cocurrent downflow. If the frictional pressure

drop is assumed to be nearly the same, or only slightly

higher, the difference between these two can be used to

estimate the dynamic liquid holdup in normal gravity

cocurrent downflows. In addition, this study

demonstrates the utility of reduced gravity experiments

in the understanding of normal gravity multiphase

flows. For example, by fixing the gas and liquid flow

rates and varying only the gravity level (from 1-g to 0-g

and 1.8-g) we can estimate the influence of gravity on

any common transition boundary, the true frictional

pressure drop, and the dynamic liquid holdup in a given

flow regime. This will be pursued in more detail in

future work.

NASA/TM--2001-210705 9
,.)

3.

4.

5.

6.

References

Talmor, E., "Two-Phase Downflow Through Catalyst

Beds," AIChE J., vol. 23. no. 6, pp. 868-878 (1977).

Singh, B.S., "Workshop on Research for Space

Exploration: Physical Sciences and Process

Technology," NASA/CP-- 1998-207431, ( 1998 ).

Committee on Microgravity Research Space Studies

Board, commission on Physical Sciences, Mathematics,

and Applications National Research Council,

"Microgravity Research in Support of Technologies for

the Human Exploration and Development of Space and

Planetary Bodies," National Academy Press (1998).

Holder, D.W., and Parker, D.S., "Volatile Removal

Assembly Flight Experiment and KC-135 Packed Bed

Experiment: Results and Lessons Learned," 30th

International Conference on Environmental Systems,

SAE# 2000-01-2251 (2000).

Motil, B.J., Green, R.D., Nahra, H.K., and

Sridhar, K.R., "Two-Phase Flow in Packed Columns and

Generation of Bubble Suspensions for Chemical

Processing in Space," 30th International Conference on

Environmental Systems, SAE# 2000-01-2239 (2000).

NASA/TM--2000-210212.

Weekman, V.W., and Myers, J.E., "Fluid-Flow

Characteristics of Concurrent Gas-Liquid Flow in

Packed Beds," AIChE J., vol. 10, no. 6, pp. 951-957

(1964).

8.

9.

I0.

II.

12.

13.

Charpentier, J.C.. and Favier, M., "Some Liquid Holdup

Experimental Data in Trickle-Bed Reactors for Foaming

and Nonfoaming Hydrocarbons," AIChE J., vot. 21, no.

6, pp. 1213-1218 (1975).

Sato, Y., Takahashi, F., and Hashiguchi, Y., "Flow

Pattern and Pulsation Properties of Cocurrent GasLiquid Downflow in Packed Beds," J. Chem. Eng.,

Japan, vol. 6, no. 4, pp. 315-319 ('1973).

Oshinowo, T., and Charles, M.E., "Vertical Two-Phase

Flow, Part I, Flow Pattern Correlations," Can. J. Chem.

Eng., vol. 52, pp. 25-35, (' 1974L

Gianetto, A., Baldi, G., Specchia, V., Sicardi, S.,

"Hydrodynamics and Solid-Liquid Contacting

Effectiveness in Trickle-Bed Reactors," AIChE J.,

vol. 24, no. 6, pp. 1087-1104 (1978).

Saez, A.E., and Carbonell, R.G., "Hydrodynamic

Parameters for Gas-Liquid Cocurrent Flow in Packed

Beds," AIChE J., vol. 31, no. 1, pp. 52-62 (1985).

Midoux, N., Favier, M., and Charpentier, J.C., "Flow

Pattern, Pressure Loss and Liquid Holdup Data in GasLiquid Downflow Packed Beds with Foaming and

Nonfoaming Hydrocarbons." J. Chem. Eng., Japan, vol.

9, no. 5, pp. 350-356 (1976).

Holub, R.A., Dudukovic, M.P., Ramachandran, P.A.,

"Pressure Drop, Liquid Holdup, and Flow Regime

Transition in Trickle Flow," AIChE J., vol. 39, no. 2, pp.

302-321 (1993).

NASA/TM--2001-210705 10

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1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE ! 3. REPORT TYPE AND DATES COVERED

February 2001 Technical Memorandum

4. TITLE AND SUBTITLE

Effects of Gravity on Cocurrent Two-Phase Gas-Liquid

Flows Through Packed Columns

6. AUTHOR(S)

Brian J. Motil, Vemuri Balakotaiah, and Yasuhiro Kamotani

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration

John H. Glenn Research Center at Lewis Field

Cleveland, Ohio 44135-3191

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration

Washington, DC 20546-0001

5. FUNDING NUMBERS

WU- l 01-53--00-00

8. PERFORMING ORGANIZATION

REPORT NUMBER

E-12636

10. SPONSORING/MONITORING

AGENCY REPORT NUMBER

NASA TM--2001-210705

AIAA-2001-0767

11. SUPPLEMENTARY NOTES

Prepared for the 39th Aerospace Sciences Meeting and Exhibit sponsored by the American Institute of Aeronautics and

Astronautics, Reno, Nevada, January 8-1 l, 2001. Brian J. Motil, NASA Glenn Research Center; Vemuri Balakotaiah

University of Houston, 4800 Calhoun Road, Houston, Texas 77204; Yasuhiro Kamotani, Case Western Reserve

University, 10900 Euclid Avenue, Cleveland, Ohio 44106. Responsible person, Brian J. Motil, organization code 6712,

216--433-6617.

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13. ABSTRACT (Maximum 200 words)

This work presents the experimental results of research on the influence of gravity on flow pattern transitions, pressure

drop and flow characteristics for cocurrent gas-liquid two-phase flow through packed columns. The flow pattern

transition data indicates that the pulse flow regime exists over a wider range of gas and liquid flow rates under reduced

gravity conditions compared to normal gravity cocurrent down-flow. This is illustrated by comparing the flow regime

transitions found in reduced gravity with the transitions predicted by Talmor. Next, the effect of gravity on the total

pressure drop in a packed column is shown to depend on the flow regime. The difference is roughly equivalent to the

liquid static head for bubbly flow but begins to decrease at the onset of pulse flow. As the spray flow regime is

approached by increasing the gas to liquid ratio, the effect of gravity on pressure drop becomes negligible. Finally,

gravity tends to suppress the amplitude of each pressure pulse. An example of this phenomenon is presented.

14. SUBJECT TERMS

Microgravity; Two-phase flow; Packed bed; Porous media

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NSN 7540-01-280-5500 Standard Form 298 (Rov. 2-89)

Prescribedby ANSI Std, Z39-18

298-102