MODELING RADIATIVE HEAT-TRANSFER IN PACKED-BEDS

A comprehensive approach for modelling dependent radiative heat transfer in beds of large (geometric range) spherical particles is presented. Such a system of large spheres lies in the dependent range even for large porosities. We show that the dependent properties for a bed of opaque spheres can be obtained from their independent properties by scaling the optical thickness while leaving the albedo and the phase function unchanged. The scaling factor is found to depend mainly on the porosity and is almost independent of the emissivity. We show that such a simple scaling for non-opaque particles is not feasible. The transparent and semi-transparent particles are treated by allowing for the displacement across an optical thickness (because of transmission through a particle) while solving the equation of radiative transfer. When combined with the scaling approach, this results in a powerful method of solution called the dependence included discrete ordinates method (DIDOM). The results obtained from the DIDOM give good agreement with the results obtained from the Monte Carlo method.