Hydrodynamic modeling of particle rotation in bubbling gas-fluidized beds

Abstract

A kinetic theory for flow of dense, slightly inelastic, slightly rough sphere (KTRS) is proposed on the basis of kinetic theory of gases and kinetic theory of granular flow. The fluctuation kinetic energy of particles is introduced to characterize the random motion of particles as a measure of the translational and rotational velocities fluctuations. The kinetic energy transport equation is proposed with the consideration of the redistribution of particle kinetic energy between the rotational and translational modes and kinetic energy dissipation by collisions. The models for solid pressure, conductivity of fluctuating energy and viscosity are presented in terms of the tangential restitution coefficient and normal restitution coefficient. Thus, present kinetic theory for rough spheres (KTRS) has the same structure as that for frictionless spheres, i.e., only conservation of mass, mean translational velocity and fluctuation energy are considered. The partition of the kinetic energy of inelastic rough particles between rotational and translational modes is shown to be affected by the particle roughness and inelasticity. Hydrodynamics of gas–solid bubbling fluidized beds are numerically simulated on the basis of the kinetic theory for flow of rough spheres. Computed profiles of particles velocity are in agreement with the experimental measurements in a bubbling fluidized bed. The effect of tangential restitution coefficient on the distribution of energy dissipation, fluctuation kinetic energy and viscosity of particles is analyzed.