Experimental and Numerical Studies of Void Fraction Distribution in Rectangular Bubble Columns


Experimental and Numerical Studies of Void Fraction Distribution in Rectangular Bubble Columns

Krepper, E.; Reddy Vanga, B. N.; Prasser, H.-M.; Lopez De Bertodano, M.

Bubbly flow is encountered in a wide variety of industrial applications ranging from flows in nuclear reactors to process flows in chemical reactors. The presence of a second phase, re-circulating flow, instabilities of the gas plume and turbulence, complicate the hydrodynamics of bubble column reactors. This paper describes experimental and numerical results obtained in a rectangular bubble column with a cross-sectional area of 20 cm2. Images obtained from a high speed camera have been processed to calculate bubble velocities, bubble turbulence parameters and bubble size distributions. Gas disengagement technique was used to obtain the volume averaged gas fraction over a range of superficial gas velocities. A wire mesh sensor was applied, to measure the local volume fraction. Numerical calculations were performed with an Eulerian-Eulerian two-fluid model approach using the commercial code CFX.
The paper details the effect of various two-fluid model interfacial momentum transfer terms on the numerical results. The inclusion of a lift force was found to be necessary to obtain a global circulation pattern and local void distribution that was consistent with the experimental measurements. The nature of the drag force formulation was found to have significant effect on the quantitative volume averaged void fraction predictions.

Keywords: Bubble column; experiments; wire mesh sensor; high speed video camera CFD; drag bubble forces; non-drag bubble forces

  • Lecture (Conference)
    3rd International Symposium on Two-Phase Flow Modelling and Experimentation, 22.-24.09.2004, Pisa, Italy
  • Contribution to proceedings
    3rd International Symposium on Two-Phase Flow Modelling and Experimentation, 22.-24.09.2004, Pisa, Italy, paper MS11

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Publ.-Id: 6057