CFD simulation of bubbling fluidized beds using kinetic theory of rough sphere

Flow behavior of particles is simulated using an Eulerian–Eulerian two-fluid model based on the kinetic theory of rough spheres. The interactions of the short and fast collisions of particles are incorporated to consider the redistribution of momentum and kinetic energy between the collision and friction interactions. The fluctuating kinetic energy by collisions of particles has taken the transfer of particle kinetic energy between the rotational and translational degrees of freedom and also the energy losses into account. Two coefficients, normal restitution coefficient and tangential restitution coefficient, are used to characterize the collisions of particles. The friction coefficient is used to predict the frictional stresses caused by the enduring contacts of particles. The collisional and frictional constitutive relations are used to predict the stresses of rough spheres. The solid pressure and viscosity are obtained in terms of the normal and tangential restitution coefficients and empirical friction constants. Distributions of concentrations and velocities of particles are predicted in the 2-D bubbling fluidized bed. The influence of bed temperature and particle diameter on fluctuation kinetic energy is analyzed in the bubbling fluidized beds. Simulated results are compared with measured axial velocity of particles and bubble diameter published in literature.

► A kinetic theory of rough spheres is proposed on the basis of the kinetic theory of granular flow.
► A frictional stress caused by the enduring contacts of particles is taken into account in the gas–solid two-phase model.
► The effects of tangential restitution coefficient on flow behavior of particles are analyzed in bubbling fluidized beds.