Thermal analysis of a packed bed of two types of particles is conducted using the homogenization method. Using a thermal radiation coefficient, sigmoidal curves are obtained as functions of the Nusselt number in the same way as for a unary bed, even when the two types of particle have different emissivities and thermal conductivities. The emissivities are contributing terms to the Nusselt number, and the parameters that express the shape of the sigmoidal curve are determined mainly by the ratios of particle number and thermal conductivity between the two types of particle. The data show that thermal radiation analysis in more complex packed beds could be simplified, and the present technique is expected to contribute to reductions in computational costs. (C) 2019 Elsevier B.V. All rights reserved.