Two-flux spherical harmonic modelling of two-dimensional radiative transfer in furnaces

Abstract A new two-flux model for two-dimensional radiation fields in axisymmetrical furnaces has been derived from radiative transport equations based on the P 1 spherical harmonic approximation by assuming radial polynomial variation of some radiation parameters, and applying an averaging procedure. The new model has been applied to the prediction of the thermal behaviour of an idealised radiant cell of a multipass process gas heater, and the results have been compared with previous values obtained using the zone method of analysis, and with limited experimental data from an operating heater. Satisfactory predictions are obtained for gas and surface temperature distributions, and for the overall thermal behaviour of the cell. This predictive accuracy, coupled with their computational simplicity and economy compared with the zone method of analysis, suggests that two-flux models of this type should prove to be useful tools for approximate thermal design calculations for axi-symmetrical furnaces and combustors.