The Treatment of Nongray Properties in Radiative Heat Transfer: From Past to Present

Radiative heat transfer in high-temperature participating media displays very strong spectral, or “nongray,” behavior, which is both very difficult to characterize and to evaluate. This has led to very gradual development of nongray models, starting with primitive semigray and box models based on old experimental property data, to today's state-of-the-art k-distribution approaches with properties obtained from high-resolution spectroscopic databases. In this paper a brief review of the historical development of nongray models and property databases is given, culminating with a more detailed description of the most modern spectral tools.