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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]

The entrainment and flow of a thin film of liquid on a vertically rotating disc partially immersed in a liquid bath has been investigated experimentally and modelled numerically. The Volume of Fluid (VOF) Computational Fluid Dynamics (CFD) modelling approach has been employed to characterise the shape and stability of the thin film thickness profile. The thickness of the rotating disc plays a significant role in the thin film profile and this is confirmed through the comparison of simulation with the experimental results. Other factors determining the film thickness were identified as the rotational speed and the fluid viscosity where the film thickness profile increases with the increase of the rotational speed and also the viscosity. A correlation equation to predict the film thickness as a function of angular position, radius, rotating speed, viscosity and surface tension is proposed. The results given in this study specifically report on the thin film thickness variation with the angular direction and the film entrained into the liquid. In both the simulation and experimental results, it is noted that the film thickness stabilises following a rotation of 15° after drag out of the liquid, and remains so until 10° before being dragged back in. [ABSTRACT FROM AUTHOR]