Numerical Estimation of View Factors for Simple Roof Enclosures with Five Surfaces

M. Pubudu G. Sirimanna, Amarasinghage T.D. Perera, and Rahula A. Attalage


View factor, Roof enclosure, Differential area


View factor (form factor, shape factor, configuration factor) is an essential parameter for surface to surface radiant heat exchange formulations. Radiant heat exchange of a roof is a regularly encountered major engineering application where estimation of view factor becomes challenging. Orientations of the roof surfaces in 3D space and varying dimensions require special methods to this estimation. A general formulation based on vector representation and numerical procedures to estimate view factors in such scenarios are presented in this paper. The numerical solution for a generic five surface roof enclosure was obtained and verified using a specific case where analytical solution is possible, and the result showed 1.0 % error for 108 iterations. Five view factors were estimated for each considered roof configuration in order to carry out complete thermal analysis of roof enclosures. Finally, numerical results for different roof angles and length/width ratios of considered roof configuration were estimated and presented in graphical format for convenient use.

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