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Computational Fluid Dynamics(CFD) has become an alternative method to experiments for understanding the fluid dynamics of multiphase flow.A two-fluid model,which contains additional terms in both the gas-and solid-phase momentum equations,is used to investigate the fluidization quality in a fluidized bed.A case study for quartz sand with a density of 2,660 kg/m3 and a diameter of 500 μm,whose physical property is similar to a new kind of catalyst for producing clean fuels through the residue fluid catalytic cracking process,is simulated in a two-dimensional fluidized bed with 0.57 m width and 1.00 m height.Transient bubbling and collapsing characteristics are numerically investigated in the platform of CFX 4.4 by integrating user-defined Fortran subroutines.The results show that the fluidization and collapse process is in fair agreement with the classical theory of Geldart B classification,but the collapse time is affected by bubbles at the interface between the dense phase and freeboard.
Computational Fluid Dynamics (CFD) has become an alternative method to experiments for understanding the fluid dynamics of multiphase flow. A two-fluid model, which contains additional terms in both the gas-and solid-phase momentum equations, is used to investigate the fluidization quality in a fluidized bed. A case study for quartz sand with a density of 2,660 kg / m3 and a diameter of 500 μm, whose physical property is similar to a new kind of catalyst for producing clean fuels through the residue fluid catalytic cracking process, is simulated in a two-dimensional fluidized bed with 0.57 m width and 1.00 m height. Transient bubbling and collapsing characteristics are numerically investigated in the platform of CFX 4.4 by integrating user-defined Fortran subroutines. The results show that the fluidization and collapse process is in fair agreement with the classical theory of Geldart B classification, but the collapse time is affected by bubbles at the interface between the dense phase and freebo ard.