Effective thermal conductivity with radiation is analyzed by the homogenization method. This method can precisely represent the microstructure of a packed bed. In this study, the effects of parameters such as the radiation emissivity, temperature and particle size of the packed bed on the conductivity have been estimated to clarify the mechanism of complex packed structure. For example, heat transfer by radiation does not dominate if the material has voids of less than 1 mm in size. Moreover, by comparing a conventional model and the homogenization method, applicability of their models were shown for estimating the effective thermal conductivity. (C) 2014 Elsevier Ltd. All rights reserved.