Gas-Liquid Two-Phase Flow Simulation Of Bubble Columns

Bubble column reactors are widely used for many industrial processes, such as petrochemical, biochemical, energy conversion and environmental engineering, due to numerous advantages of geometrically simple and excellent interfacial mass and heat transfer. Through understanding of the hydrodynamic behavior in such reactors is critical for an optimal design and operation of a bubble column reactor. Computational Fluid Dynamic (CFD) is a viable approach to the simulation of gas-liquid flow of a bubble column. In this paper, the Euler-Euler two-fluid model is applied in the modeling of the hydrodynamics in rectangular bubble columns. Upon comparing with experiment results reported in the literature, the gas-liquid turbulence closure model, the bubble size model and the strategy of boundary condition setup are established for a reasonable prediction of hydrodynamic behavior of such kind gas-liquid flow systems.3-dimensional simulations were performed for a rectangular bubble column, the hydrodynamic characteristics, such as the gas holdup, plume oscillations period, and gas-liquid flluid velocities in the column were simulated and compared with experiment results. Three turbulence models (the Standard k-ε, RNG-k-ε, and Realizable k-ε models) are tested in the frame of RANS simulation, respectively. It was found that RNG-per-phase k-ε was able to predict a higher shear strain rate, a higher turbulence dissipation rate and a lower plume oscillations period, which is in close agreement with the value of measurement.2-dimensional simulations were perfomed for a thin rectangular bubble column, which was systematically measured by PIV technique within L.S. Fan Group. Two Inlet velocity conditions:i.e.:(1) actual inlet velocity of3D bubble column;(2) the averaged inlet velocity combined diffusion; were setup, respectively. The results showed the oscillations period can only be predicted with the averaged inlet velocity combined diffusion setups. It was also found that Reynolds Stress Model (RSM) is superior to the RNG-k-εturbulence closure model in the2-dimensional modeling.In order to simulate the gas-liquid hydrodynamics in heterogeneous bubble regimes, three bubble size models:i.e.:the single-sized bubble model, the large-small bubble-sized model and the Population Balance bubble Model (PBM) model were tested, respectively. The simulated results were compared with experimental data reported by L.S. Fan group. The large-small bubble model was found to be able to predict the hydrodynamic behaviors in heterogeneous bubble regime with reasonable agreements.