Numerical investigation of the effect of the location of an immersed tube in a fluidized bed on heat transfer of surface-to-bed

Abstract

The study of heat transfer characteristics within an external heat exchanger (EHE) in circulating fluidized bed (CFB) boilers for the treatment of municipal solid waste (MSW) is of great significance for improving energy utilization. An Eulerian-Eulerian approach coupled with the kinetic theory of granular flow (KTGF) was used in this work and the effect of the immersed tube location on hydrodynamics and heat transfer characteristics in a gas-solid fluidized bed was investigated. The model accuracy was validated by the reference result. It was shown that the tube location has a significant effect on heat transfer of surface-to-bed, with increasing height of the tube from 0.2 m to 0.5 m, the average heat transfer coefficient (HTC) of the immersed surface decreased from 302 to 274 W/(m2K). Meanwhile, the specific process of particle renewal on the tube surface and the impact of the particle renewal mechanism on heat transfer were investigated.