On the influence of boundary conditions and thermal radiation on predictive accuracy in numerical simulations of indoor ventilation

Room ventilation is a well studied field, whereby ventilation is either mechanically driven or reliant on buoyancy forces driven by thermal gradients. In office spaces, where occupant comfort is important, the latter (termed displacement ventilation) is sometimes used. In many existing studies, computational methods used to simulate ventilation cases use a number of general engineering assumptions. These can include neglecting heat transfer through the walls, assuming that internal radiative transfer is negligible, or by modelling radiative sources as additional heat loads. In this study, these assumptions are systematically examined by selectively modelling certain phenomena in the simulations. In this way, the accuracy and suitability of such assumptions can be examined with reference to previous experimental work. The variation of radiative absorptivity upon the vertical temperature profile has also been investigated in order to determine the contribution of thermal re-distribution by surface radiation alone, and in addition to radiative participation from the air.