A combined conductive and radiative heat transfer problem is analyzed in two-dimensional rectangular enclosure and axisymmetric cylindrical duct. Especially, the media are two-phase consist of gas and solid particles, which considered with an emphasis on the thermal radiation, i.e., the radiation by both gas and particles. A complex form of nonlinear integro-differential radiative transfer equation is solved by the discrete ordinates method (or called $S_N$ method) in the two geometry described above. The effect of variation of gas and particle absorption coefficients is mainly investigated, and other parameters are also studied, such as wall emissivity, particle emissivity, etc. The results come out from the analysis are various. Most of all, the two-phase radiation plays very important role in combined heat transfer problem. In practical problems, because the absorption coefficient of gas is generally bigger than that of gas, the temperature of particles varies faster than gas and thus it occurs more heat transfer than there is gas-only medium.
