Finite-element heat-transfer computations for parallel surfaces with uniform or non-uniform emitting

Abstract

Radiation heat transfer has very many applications in building physics. In such studies, one has to deal with radiant energy exchanges between surfaces of different orientation and aspects. Two principal cases that may be cited here are exchanges between (i) surfaces that share a common edge and are at an angle to each other, and (ii) surfaces that are parallel to each other. Examples that may be cited here are walls of buildings and also ceiling and floor areas. In a previous work, the authors presented a generalised, numerical-oriented solution for analysing radiant exchange that belongs to case (i) cited above. In the present article, a generalised treatment for case (ii) is presented. A software tool is also provided for analysing the radiant exchange for surfaces that are parallel to each other and have uniform or non-uniform reflectivity, incident irradiation and/or emission. As a demonstration of the applicability of the present work, calculation of incident reflected irradiation on the walls of urban street canyons with varied orientation and non-uniform reflectivity is presented. Finally, the application of the presently developed tools for enhancing building design has been highlighted.