Numerical Study of Wall-to-Bed Heat Transfer in a Gas- Solid Bubbling Fluidized Bed by CFD

Due to the effective heat transfer in fluidized beds, these systems have been wieldy used in many thermal processes. There are limited published papers in the literature regarding heat transfer in fluidized beds, because of complexities existing in these systems. In the present study, a gas-solid bubbling fluidized bed including the spherical particles with diameter of 280 µm is simulated by a Eulerian-Eulerian Two-Fluid Model incorporating the kinetic theory of granular flow (KTGF). Influence of two important drag models of Gidaspow and Syamlal as well as some hydrodynamics parameters, namely, particle-particle restitution coefficient and solid wall boundary conditions are studied. Both drag models predict the behavior of the bubble passage through the bed reasonably. Although both drag functions show the same trend with the experimental data, Gidaspow drag model predicts the better results than the Syamlal one. The CFD results reveal that the modeling parameters of specularity coefficient, particle-particle and particle-wall restitution coefficients have a significant effect on the heat transfer coefficient between the wall and particles.