关键词:

液固流化床, 固含率, 时空分布特性, CFD模拟

Abstract:

Spatio-temporal evolution of solid holdup in the liquid-fluidized bed was predicted by Brandani and Zhang model, which includes additional terms in both the liquid- and solid-phase momentum equations based on the two-fluid theory by considering particle-fluid interactions under a quasi-equilibrium state.Numerical simulations were conducted in the platform of commercial Computational Fluid Dynamics (CFD) code, CFX4.4, by adding user-defined Fortran subroutines.Based on the independences of mesh, time step and convergence criterion obtained, the effects of the physical properties of liquid-solid system and the operational conditions on the solid holdup profiles were investigated numerically in the 0.5 m (long)×0.1 m (wide) 2D fluidized bed.The computational results show that the solid holdup profile within the stable bed transfers to a new equilibrium state once the physical property of the system or the operational condition is changed.The bed surface decreases and the average solid holdups increase in all the vertical planes, due to the downward acceleration of particles, when particle density or size is increased.The similar phenomenon is observed with a decrease of liquid density or viscosity.When the liquid inlet velocity is abruptly increased, however, the motion of each particle accelerates upwardly and solid holdups decrease in the bed.Both liquid density and viscosity reduce with an increase of temperature, which leads to downward motion of particles and solid holdups increase.The above simulated data can be explained reasonably by the forces acting on particles.

Key words:

液固流化床, 固含率, 时空分布特性, CFD模拟