Radiation is a major component of heat transfer in the modeling of furnaces. In the present work, transient coupled radiative and conductive heat transfer problems are analyzed in two-dimensional irregular geometries with a simple Cartesian practical method named the blockedoff. By this technique, Cartesian coordinate-based raytracing algorithm can be applied to the geometries with inclined or curved boundaries. The S-N discrete ordinates method used to solve the radiative transfer equation and finite difference method by applying the Taylor series for solving the energy equation to obtain the transient temperature distributions inside the participating medium. The walls of the enclosures are opaque, diffuse, and gray with specified temperatures. The medium was considered to be absorbing-emitting and linear anisotropic scattering with variable thermal conductivity, variable density, and variable specific heat, as a function of temperature. In the case of constant thermophysical gas properties, results have been compared with those reported in the literature, and good agreement was found.