Effect of Roof Profiles on Wind Heat Loss Coefficient for Roof Top Solar Collectors in the Gulf Region

Nowadays solar collectors are constructed on roof tops very frequently for water heating, air heating or photovoltaic power generation. At a location the wind velocities increase as the elevation from the earth increases and its variation follow one-seventh power law. This variation plays a crucial role in determining the efficiency of roof mounted solar air heating collectors. Unglazed collectors are more affected by the wind than glazed collectors. Previous studies either neglected wind effects or used relations based on experiments conducted on flat surfaces to predict these losses. The subject matter of this paper is to predict the wind velocity induced thermal top-losses on roofs of different configurations through the use of computational fluid dynamics software. Wind data for the Arabian Gulf region in terms of wind velocity and direction has been used for the calculation of thermal top loss. Reynolds number of the order of 5x105 -2x106 is considered for the simulation. Several factors contribute for the heat loss coefficient from the roof surface. The results help in estimating the performance of solar collectors installed on roof tops and to choose the right type of roof.