An analysis of the combined conductive-radiative heat transfer between a surface and a gas-fluidized bed at high temperature

Abstract

A theoretical investigation of the combined conductive radiative wall-to-fluidized bed heat transfer is presented. The packet of emulsion is assumed to be an absorbing, emitting, and scattering nongray medium. Equations of energy and radiative transfer in the packet are solved simultaneously using an iterative numerical method. The bubble is modelled as a hemisphere of gas enclosed by the emulsion and the nongray heal transfer surface. Heat transfer coefficients were calculated for different bed systems in the temperature range 300–1000 °C. The predictions by the present analysis were in good agreement with available experimental data. The radiative contribution of as much as 35% varies directly with bed temperature, particle size and emissivity, surface temperature and emissivity. Both isotropic scattering and gray medium approximations were found to be acceptable for practical applications.