Simulation of mixing process in viscous media by a turbulent mass diffusivity model in an impinging stream-rotating packed bed

Abstract

In this work, a three-dimensional numerical model is established to simulate the mixing process in viscous media in an impinging stream-rotating packed bed (IS-RPB). The realizable k–ε method is adopted to predict the turbulent flow, the high gravity environment is simulated by the sliding mesh model, and the turbulent mass diffusivity is calculated by the concentration variance $\overline{c^2}$and its dissipation rate ε_c formulations, so that the turbulent mass transfer process can be simulated without using empirical correlations. The simulated segregation index X_s is found to be in accordance with our previous experimental data. The fringe effect of the impinging stream is more pronounced in high viscosity systems, but it can be counterbalanced effectively by the RPB, leading to an enhancement in the mixing efficiency. Elevated liquid viscosity amplifies IS-RPB's liquid flow ratio sensitivity in mixing efficiency. Therefore, although IS-RPB demonstrates effective in viscous liquid mixing, the liquid impinging methodology optimization remains necessary to address the adverse effect on mixing when the liquid flow ratio is relatively high.