Radiative heat transfer in a two dimensional square enclosure containing gray absorbing/emitting and nonscattering media is studied using the second order discrete ordinate method which has been reformulated from the conventional discrete ordinate $(S_N)$ method.
Discretization equations were obtained by the linear interpolation method, and results were compared with the zonal computations and the conventional SN solutions.
The linear interpolation method is free from negative coefficients in the discretization equations, thereby no physically unrealistic result occurs. However, numerical diffusion may occure and overall energy balance may be broken when the ordinate do not coincide with grid points(so that linear interpolation is employed in the calculation process). For $S_2$, the result agrees fairly well with the conventional $S_2$ solution because linear interpolation is not employed in this case. Ray effect with the dependence on ordinate and grid is discussed.