The assumption that the spectral absorption coefficient is independent of frequency in problems involving radiant energy transfer in hot gases is examined. A particular case, that of the hypersonic wake, is treated in some detail, and a non-gray transfer equation involving two mean coefficients is developed. One mean absorption coefficient is related to emission, and the other to absorption.
The problems arising from lack of chemical equilibrium are discussed, and a modification of the equations used for prediction of the spectral absorption coefficient (for diatomic species) is suggested, wherein two distinct temperatures are utilized. Sample calculations for one nitrogen band have been made and the results presented graphically.