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For the simulation of industrial-scale bubble column reactors, while modelling the gas distributor as uniform inlets oversimplifies the inhomogeneity introduced by inlets, the direct simulation of the full geometry of gas distributor or sparger brings about enormous pre-processing work and huge computational cost. A new inlet model is therefore proposed in this paper to simplify the modelling of gas distributor and meanwhile maintain the simulation accuracy. The new inlet model is validated by the comparison of the model prediction with experiments and the CFD simulation incorporating the full geometry of gas distributor for bubble columns of small or large diameters. Comparisons of three different inlet boundary conditions, i.e., the direct simulation of gas distributor, the uniform inlet, and the new inlet model, are made in the simulation of the total gas holdup, the radial profiles of gas holdup at different cross-sections along the column height, and the axial velocity of liquid at various superficial gas velocities. The results indicate that the new inlet model is capable of achieving a good balance between simulation accuracy and computational cost for the CFD simulation of large-scale bubble column reactors. [ABSTRACT FROM AUTHOR]

Traditionally, bubble shapes have been assumed to be spherical in breakup models such as the one developed by Luo and Svendsen in 1996. This particular breakup model has been widely accepted and implemented into computational fluid dynamics (CFD) modeling of gas–liquid two-phase flows. However, simulation results from this model usually provide unreliable predictions about the breakage of very small bubbles. The incorporation of bubble shape variation into breakup models has rarely been documented in literature but the bubble shape plays an important role in the interactions with the surrounding eddies, especially when the effects of bubble deformation, distortion, and bubble internal pressure change are considered during the events of eddy-bubble collision. Thus, the assumption of spherical bubbles seems to be no longer appropriate in reflecting this phenomenon. This study proposes and implements a modified bubble breakup model, which accounts for the variation of bubble shapes when solving the population balance equations for CFD simulation of gas–liquid two-phase flows in bubble columns. The key parameters predicted by the modified breakup model have been compared with the ones predicted by the original model. The simulation results of interfacial area and mass transfer coefficient for larger bubbles have been greatly enhanced by the modified breakup model. [ABSTRACT FROM AUTHOR]