Experimental and numerical simulations of compound heat transfer in an internally circulating fluidized bed

Abstract

In this paper, the compound heat transfer of convection and radiation in an internal circulating fluidized bed for low temperature oxidation of pulverized coal was numerically simulated. The numerical prediction about the compound heat transfer characteristics and its relationship of convection and radiation was compared with the experimental measurements of low temperature radiation. The discrete ordinate model (DOM) was employed to investigate the radiation heat transfer in the low temperature oxidation internally fluidized bed, and user-defined function (UDF) was compiled by considering the effect of the particle flow emissivity on radiation heat transfer. The convection heat transfer coefficient increases with the increase of gas inlet volume flow rate and initial bed material height, however, thermal radiation coefficient was opposite. An increase of the thermal flux results in an increase of the surface temperature of the fluid and the heater surface, and the thermal transfer coefficient between bed material and heater surface is also increased. The results have the application reference to complex thermal transfer design of circulating fluidized bed systems wherein thermal radiation transfer must be considered as a significant mode.