Banded radiative heat transfer analysis

Recent work has shown that many ceramic fibres which are increasingly used to line industrial furnaces have highly spectral-dependent emissivities. This paper presents an extension to the standard zone method for radiative heat transfer calculations which directly models spectral variation in surface and gas properties. A short description of the zone method is given along with a summary of the weighted sum of grey gases model. This is often used as a means of representing the temperature dependence of total gas properties brought about because of the spectral non-uniformity of these properties. When surfaces as well as the gas are non-grey, a new approach is required. The method of this paper is based on dividing the spectrum into a number of bands and treating the properties as constant within each band. This method can be used directly if the boundary conditions specify ail the zone temperatures. However, if some temperatures are unknown, then an iterative solution technique is required. Results of some sample calculations are presented, These illustrate the importance of directly modelling the spectral behaviour of gas and surface properties. (C) 1997 John Wiley & Sons, Ltd.