Design models to handle radiative and convective exchange in a room.

The traditional handling method of handling heat exchange in a room for design purposes was to suppose that all heat from the plant, radiative as well as convective, was input at a so called "air temperature". This is an evident misnomer, since air temperature as such cannot drive longwave radiation as themodel actually assumed. The "environmental temperature" concept has been introduced in the UK to get round the difficulty. This paper presents an analysis of when an approach along these lines may be logically acceptable. The surface to surface system of radiant exchange is first reduced to a surface-to-star point exchange by a least squares fit. It is then shown that the space-averaged o observable radiant temperature can be approximated by the value of the temperature generated at when the radiant output from heating appliances and casual gains is taken to act. Now it is normally assumed that convective gains can be treated as though input at the space averaged air temperature,. Thus we can set up a "binary star" model, formed from theradiant star pattern centred on T and the convective star pattern centred on T can be set up. It pro provides an attractive model for the internal exchange of heat in a room. An equivalence theorem can be demonstrated, and it serves to show that the binary star system, based on T and T, can, in certain well-defined conditions be replaced by a single star system, centered on an index temperature, (the "rad-air" temperature). T in fact serves the same function as did "air temperature" in the old fashioned sense. The model based on T is workable but it is physically unattractive, and a model that handles convection and radiation separately may provide a better design procedure.Environmental temperature is a form of T but the logic of setting it up is seriously flawed.