Development of an Advanced Radiation Exchange Module for Use in Simulation of Spaces with Radiant Systems

The surface temperature of radiant systems can be significantly different than the temperature of other room surfaces; therefore, radiation heat exchange often becomes the dominant mode of heat transfer. It is necessary to accurately predict the surface temperature of radiant systems and to model radiative heat fluxes in detail, in order to evaluate the thermal environment and the impact on energy and comfort. This paper presents the development of a radiation exchange module that can be used to predict the performance of rooms with radiant systems with and without the presence of solar radiation. The module is based on radiosity theory in enclosures and includes detailed computation of window projections of the floor (sunlit area) which are treated a separate surface in an 8-surface enclosure. A comparison between heat fluxes calculated with currently accepted models (i.e. constant, linearized, and non-linear heat transfer coefficients) and with the developed model is presented for variable surface temperature differences.