Discrete·ordinates S2' 54, 56 and 58 approximations arc used to study radiative transfer in athree-dimensional furnace with complex geometry including cooling-pipes in the combustion chamber. Theability of the discrete-ordinates method to model highly-directional shadowing effects caused by the internalpipes is illustrated. Predicted values for incident wall flux and net radiative transfer to the pipes are shown tocompare well with experimental data. The large energy sink produced by the pipes minimizes the sensitivityof results to variations in wall emissivity. The 54 approximation is shown to produce results of adequateaccuracy except in cases where detailed modeling of the pipe shadows requires the higher order 56 and 58approximations. Results from mesh densities of 76.000, 388,000 and 815,000 cells show different mesh sizesdo not significantly alter incident flux or net heat transfer predictions,