A ray tracing formulation is described for the solution of the radiative heat transfer equation in absorbing, emitting and non-scattering real gases. The Goody and the Malkmus statistical narrow band models and the Edwards wide band model are used for calculating the radiative dissipation and the wall fluxes in a series of planar configurations containing inhomogeneous, non-isothermal H2O/N-2 mixtures bounded by non-reflecting walls. Comparisons between these models are performed and their sensitivity on the sets of the band parameters is investigated. The accuracy of the results obtained by considering correlated and non-correlated solutions is also discussed.