The conductive and radiative heat transfer to the walls of a Fluidized Bed Combustor are calculated. As a simplified model, the coal and ash particles are assumed to be spherical and the bed is considered to be vigorously bubbling. The analysis is one dimensional and is based on a gas film-emulsion packet model. The problem is formulated in terras of a non-linear partial differential equation assuming the gas film to be radiatively transparent and the emulsion packet to radiate as layers of black bodies. The solution is obtained numerically by the Crank-Nicolson method. The conductive and radiative specific heat fluxes and heat transfer coefficients for the emulsion and bubble phases are calculated at different fluidizing velocities, bed temperatures and particle sizes. The analytical results are shown to be in good agreement with the results reported in literature. © 1974.