CFD simulation of dynamic characteristics in liquid–solid fluidized beds

A simple two-fluid model is used to predict the hydrodynamics of liquid–solid fluidization after a step change in liquid velocity. Based on the inviscid model A of Gidaspow (1994), the effect of the particles dispersed on the momentum equations is considered in this model. Numerical simulations are conducted in the platform of CFX 4.4, a commercial CFD code, together with user-defined FORTRAN subroutines. Predicted overall bed voidage in this work is much closer to the experimental measurement than that based on the kinetic theory of granular flow in the literature (Cornelissen et al., 2007). The results show that the computational bed heights in the expansion process fit in with the idealized curve except at the transitional stage, which leads to actual response time slightly greater than its corresponding idealized value. Non-uniform liquid velocity inlet condition has a strong effect on the transient solid volume fraction within the bed and the response time of bed surface. In the contraction process, however, the transient bed height and response time follow exactly the idealized predictions for either uniform or wave-shaped liquid inlet condition.

Graphical abstractThe fluid dynamics of liquid–solid fluidized beds are predicted by an inviscid two-fluid model combined with additional forces in the momentum equations of liquid and particle phases. Both the transient solid volume fraction and response time are greatly affected by the non-uniform liquid inlet velocity for the expansion process, while they follow the idealized predictions for the contraction process.Figure optionsDownload full-size imageDownload as PowerPoint slide