Influence of the specularity coefficient on hydrodynamics and heat transfer in a conical fluidized bed combustor

In this paper, the hydrodynamics and wall-to-bed heat transfer of gas-solid flow in a conical fluidized bed were simulated using the Eulerian-Eulerian model. Sand with a diameter of 560 μm was used as bed material where its properties were calculated by applying the kinetic theory of granular flow (KTGF). Different amounts of slip between particle and wall were given by varying the specularity coefficient. The effect of different values of specularity coefficient (0, 0.2, 0.5, and 1.0) on hydrodynamic and wall-to-bed heat transfer at superficial gas velocity of 0.65 m/s was investigated. It was found that the wall-to-bed heat transfer coefficient decreases with increasing specularity coefficient. The specularity coefficient had no clear effect on the bed pressure drop. Different values of specularity coefficient resulted in almost the same hydrodynamic behavior near the wall and the center of bed.