Effect of thermal comfort conditions on radiant wall heating panel design

This study investigates heat transfer characteristics of a wall-heating hydronic radiant panel model. A cost analysis has also been studied for a number of variation in thickness of the aluminum foil, which serves as an extended surface, and for different values of pipe spacing.Numerical solutions have been carried out by means of a widely used computational fluid dynamics (CFD) flow modeling software, ANSYS FLUENT. Firstly, 3-D models of the radiant panel having different pipe spacings have been created; then numerical solutions have been obtained for each pipe spacing changing thickness of the aluminum foil. Pipe spacings of 50, 100, 150 and 200 mm and aluminum foil thickness of 0.1, 0.3, 0.5 and 0.7 mm, that is, sixteen models in total have been taken into account. Inlet temperature of water is set to 30, 35 and 40 oC, respectively, for each foil and pipe-spacing combination. Change in panel surface heat flux with respect to different aluminum foil thickness and pipe spacing and their combined effect on cost per unit heat gain is investigated. Results have shown that increasing thickness of the folio enhances the temperature distribution over the panel surface. However, it is found that additional cost of increasing folio thickness is not compensated by the increase in panel heat flux; since rate of increase in cost is larger than that in heat flux for each case. Therefore the most economical option is using aluminum folio of the smallest thickness as possible.Furthermore, effect of insulation thickness and conductive heat transfer coefficient of insulation material on panel heat transfer is investigated. Additional solutions have been obtained for insulation thicknesses of 20 mm and 40 mm and conductive heat transfer coefficients of 0.031 and 0.034 W/mK.Finally, thermal medium in the model room is investigated with respect to predetermined criteria concerning global and local thermal comfort in case of employing radiant panels with various values of pipe-spacing and of water inlet temperature, while foil thickness is held constant.