CFD simulation of a fluidized bed using the EMMS approach for the gas-solid drag force

Abstract

Drag force is one of the main contributing factors in describing the hydrodynamics of gas-solid flow systems. In fact, the drag force is the primary coupling force between the fluid and particulate phases. Therefore, accurate prediction of the drag is the goal of the present study. Flow of particulate solids in gas-solid flow systems is inherently heterogeneous due to different attraction and repulsion forces between the particles. The assumption of a homogeneous system leads to unrealistic predictions of system characteristics for different gas-solid regimes, e.g., bubbling fluidized beds and circulating fluidized beds. In the literature, several approaches have been developed to encounter the effect of heterogeneities inside the system, e.g., EMMS (Energy Minimization Multi-Scale) and subgrid filtering approaches. In this study, an EMMS approach was applied to a fluidized bed operating at the ranges between the bubbling regime and packed bed. The result of 2D simulations in a fluidized bed was compared with both experimental data and homogeneous models. Simulation results using the EMMS approach showed very good agreement with the Krishna [20] bed expansion experimental data, while the modeling using homogeneous drag force diverged considerably from the experimental data.