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

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, 11 th -12 th , October, 2004.

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

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  1. 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

  2. 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

  3. 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 )

  4. 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)

  5. Ultrasound Doppler Velocimetry (UDV) Advantages • spatial-temporal velocity information • non-intrusive method Prerequisites • ultrasound transmission • acoustic coupling • reflecting particles Liquid metal applications Mercury(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)

  6. Test problem: bubble-driven flow Present experiments: bubble driven flow in water and glycerin UDV & LDA measurement LDA US Transducer UDV: (channel bubbly flow) T.Wang: Chem. Eng. J., Vol. 92 Y.Suzuki: Exp. Therm Fluid Sci., Vol. 26 Q=178mm3/s, 85% glycerin

  7. Test problem: UDV results validation single bubble rising velocity in stagnant liquids LDA and UDV measured liquid velocity distributions along bubble chain centerline

  8. Bubble motion in a liquid metal columnin a longitudinal D.C. magnetic field • 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) coil 1 GaInSn coil 2 US transducer

  9. Bubble terminal velocity in GaInSn (B=0) Mendelson equation: Y.Mori: J. Heat. Transfer. Vol. 99 K. Schwerdtfeger: Chem. Eng. Sci., Vol. 23

  10. Bubble rising velocity evolutions in GaInSn

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

  12. Bubble drag coefficient modifications by the magnetic field

  13. Bubble velocity oscillation frequency and amplitude modification by magnetic field St = fde/uT.

  14. The magnetic field influence on the bubble wake A rising gas bubble B=0 Wake region US transducer Bubble Eo=5.7 B0

  15. Magnetic field influence on the liquid velocity distribution in the container meridional plane Q=20sccm

  16. 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.

  17. 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.

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