An idealised model for room radiant exchange.

In order to arrive at a simple design procedure to handle heat transfer in a room, certain fairly complicated expressions for radiant exchange are needed, and moreover the further operations that have to be performed on them are involved and lead to non-exact relations. The corresponding operations for radiant exchange between patches which form part of a spherical cavity are elementary and exact,and lead to results which are quite close to those for a cubic enclosure. Thus a consideration of radiant exchange in a sphere illustrates the principles of radiant exchange in a room, elegantly and with little of its complexity.