Institute of Safety ResearchMHD department

Experiments on the magnetic field influence on gas-liquid metal two-phase flows

Chaojie Zhang, Sven Eckert, Gunter Gerbeth

Forschungszentrum Rossendorf

D-01314 Dresden, Germany

Sino-German Workshop on Electromagnetic Processing of Materials Shanghai, China, 11th-12th, October, 2004

Institute of Safety ResearchMHD department

Motivation

Background

• numerous applications of magnetic fields and bubble-driven flows in metallurgy

Our interest

• influence of external magnetic fields on the flow fields:

gas bubbles and the induced liquid motions

Institute of Safety ResearchMHD department

Measurements of local flow properties

Difficulties

• opaqueness, high temperature, poor wettability, chemically aggressiveness

Our approach

• application of the ultrasound Doppler velocimetry (UDV)

DOP2000 (model 2125, Signal Processing SA )

Institute of Safety ResearchMHD department

Ultrasound Doppler Velocimetry (UDV)

Pulse-echo method

information about the position

time of flight measurement

information about velocity

Doppler relation

(c - sound velocity, fD - Doppler frequency, f0 - ultrasound frequency)

ctx2

D

0

c fv

2 f

Institute of Safety ResearchMHD department

Ultrasound Doppler Velocimetry (UDV)

Advantages

• spatial-temporal velocity information

• non-intrusive method

Prerequisites

• ultrasound transmission• acoustic coupling• reflecting particles

Liquid metal applicationsMercury (Takeda, 1991. Nucl. Eng. Design. Vol. 126)

Gallium (Brito et al, 2001. Exp. Fluids. Vol. 31)

Sodium (Eckert & Gerbeth, 2002. Exp. Fluids. Vol. 32)

GaInSn (Cramer & Eckert, 2004. Flow Meas. Instrum. Vol. 15)

PbBi, CuSn, Al (Eckert & Gerbeth et al, 2003 Exp. Fluids. Vol. 35)

Institute of Safety ResearchMHD department

Test problem: bubble-driven flow

LDA

US Transducer

Present experiments:bubble driven flow in water and glycerin UDV & LDA measurement

Q=178mm3/s, 85% glycerin

UDV: (channel bubbly flow)

T.Wang: Chem. Eng. J., Vol. 92

Y.Suzuki: Exp. Therm Fluid Sci., Vol. 26

Institute of Safety ResearchMHD department

0.1 1 10 10010-4

10-3

10-2

10-1

100

term

ianl

bub

ble

velo

city

[m/s

]

equivalent bubble diameter [mm]

Haberman & Morton results in tap water Kubota results in 85% glycerin UDV results in tap water UDV results in 85% glycerin

Test problem: UDV results validation

0.00 0.02 0.04 0.06 0.08 0.10 0.12-0.02

0.00

0.02

0.04

0.06

Vel

ocity

[m/s

]height [m]

LDA results UDV results

single bubble rising velocity in stagnant liquids

LDA and UDV measured liquid velocity distributions along bubble chain centerline

Institute of Safety ResearchMHD department

Bubble motion in a liquid metal columnin a longitudinal D.C. magnetic field

coil 1

coil 2

US transducer

GaInSn

• GaInSn (melting point 10°C)

• singular Ar bubbles(de = 4...8 mm)

• longitudinal D.C. magnetic field

(Bmax = 0.3 T)

• magnetic interaction parameter N

ratio between electromagnetic and inertial force (N = 0 ... 1.3)

2el TN B L /( u )

Institute of Safety ResearchMHD department

Bubble terminal velocity in GaInSn (B=0)

e

l e

gd2u

d 2

water GaInSn mercury

Density 998 6361 13610

Surface tension

0.073 0.533 0.482

Dynamic

Viscosity9.8e-4 2.2e-3 1.55e-3

Mendelson equation:

Y.Mori: J. Heat. Transfer. Vol. 99

K. Schwerdtfeger: Chem. Eng. Sci., Vol. 23

1 2 3 4 5 6 7 8 910 2010

100

1000

u T [

mm

/s]

de [mm]

Mendelson equation for GaInSn Mendelson equation for mercury UDV measured results in GaInSn data from Mori et al. (1977) in mercury

Institute of Safety ResearchMHD department

160 140 120 100 80 60 400

50

100

150

200

250

300

1

2

3

4

5

6

78

9

10

11

12

13

14

15

1617

18 19

20

21

22

23

24

25

2627

28

29

30 31

32

3334

35

36

37

38

3940

41

42

43

44

45

46

47

48

49

50

51

52

53 54

55

56

57

58

59

6061

62

63

64

65

66

67

68

69

70

71

72

A

B

C

D

E

F

G

HI

J

K

L

M

N

O

PQ

R

S

T

UV

W X

Y

Z

AAAB

AC

AD

AE AF

AG

AH

AI

AJ

AK

AL

AM

AN

AO

AP

AQAR

AS

AT

AUAV

AW

AXAY

AZ

BA

BB

BCBD

BE

BF

BG

BH

BI

BJ

BK BL

BM

BNBO

BP

BQ

BR

BS

BT

a

b

c

de

f

gh

i

j

k

l

m

n

o

p q

r

s

t

u

v

w

x

y

z

aaab

ac

ad

ae

af

ag

ahai

aj

ak

alam

an

aoap

aq

ar

as

atau

av

aw

ax

ay

az

ba

bb

bc

bd

be

bf

bg

bh

bi bj

bk

bl

bm

bn

bo

bp

bq

br

bs

bt

B=0.19Tb

ub

ble

ve

loci

ty [

mm

/s]

depth [mm]

Bubble rising velocity evolutions in GaInSn

160 140 120 100 80 60 400

50

100

150

200

250

300

B=0

bu

bb

le v

elo

city

[m

m/s

]

depth [mm]

Institute of Safety ResearchMHD department

The magnetic field influence on the ensemble-averaged bubble velocity evolutions

160 140 120 100 80 60 40 20 00

50

100

150

200

250

300b

ub

ble

ve

loci

ty [

mm

/s]

depth [mm]

B=0 B = 0.19 T

Institute of Safety ResearchMHD department

Bubble drag coefficient modifications by the magnetic field

2egd

Eo

0.01 0.1 1 100.7

0.8

0.9

1.0

1.1

1.2C

D /

CD(N

=0

)

N

Eo=2.2 Eo=2.5 Eo=3.4 Eo=4.9 Eo=6.6

Institute of Safety ResearchMHD department

Bubble velocity oscillation frequency and amplitude modification by magnetic field

0.02 0.1 1 30.7

0.8

0.9

1.0

1.1

St /

St(

N=

0)

N

Eo=2.2 Eo=2.5 Eo=3.4 Eo=4.9 Eo=6.6

St = fde/uT.

0.02 0.1 1 3

0.6

0.7

0.8

0.9

1.0

1.1

A/A

(N=

0)

N

Eo=2.2 Eo=2.5 Eo=3.4 Eo=4.9 Eo=6.6

Institute of Safety ResearchMHD department

The magnetic field influence on the bubble wake

B=0

B0

A risinggas bubble

Wake region

US transducer

Bubble Eo=5.7

Institute of Safety ResearchMHD department

Magnetic field influence on the liquid velocity distribution in the container meridional plane

-50 -25 0 25 500

50

100

150

200

Radius [mm]

He

igh

t [m

m]

-50 -25 0 25 500

50

100

150

200

-35.0-30.0

-25.0

-20.0

-15.0

-10.0

-5.00

0

5.00

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.055.0

60.0

65.0

Radius [mm]

Q=20sccm

Institute of Safety ResearchMHD department

Summary

• UDV was validated for the capacity in the relatively low gas flow rate gas-liquid metal two-phase flow measurements.

• The static longitudinal magnetic field was found to have a damping influence on the single bubble non-steady motion by modifying the bubble wake structure trailing behind.

• Liquid metal flow driven by the bubble swarm in the meridional plane showed that the static longitudinal magnetic field elongated the flow structures along the field line direction and damped the re-circulating flow region near the free surface.

Institute of Safety ResearchMHD department

Acknowledgement

The research is supported by the Deutsche

Forschungsgemeinschaft (DFG) in form of the

SFB 609 “Electromagnetic Flow Control in

Metallurgy, Crystal Growth and Electrochemistry”.

This support is gratefully acknowledged by the

authors.