Impact of Dish Structure on the Convective Heat Loss From a Parabolic Dish Solar Cavity Receiver
Parabolic dish cavity receivers achieve higher operating temperatures by using higher concentration ratios from larger dish structures, which in turn incur greater costs. Many studies have focused on understanding the heat loss from the cavity receiver in order to accurately predict the technical and hence economic performance of these systems. However, there is a lack of work on the influence of the dish structure on the wind and its subsequent effect on convective heat loss from the receiver. Hence, this work investigated the heat losses from a coupled dish-cavity receiver system. Convective heat losses from a cavity receiver (with a coupled dish) were determined numerically using computational fluid dynamics (CFD) for various wind directions and dish-receiver orientations. The heat losses were assessed considering wind velocities from 0 to 20 m/s, together with a range of wind incidence angles and dish tilt angles. The results show that the dish orientation in the flow field has a significant impact on the convective heat loss. It was found that at wind velocities less than 3m/s, the convective heat loss was lower than the natural convection heat loss (at 0 m/s). Further, the results indicate a significant reduction in heat loss (of between 15% to 40 % for winds between 3 m/s to 20 m/s) when including the presence of dish structure, compared to its absence. This finding highlights the need to consider the dish structure in the determination of thermal performance of these systems in order to avoid over design and excessive cost.