Effect of Cavity Wall Temperature and Opening Ratio on the Natural Convection Heat Loss Characteristics of a Solar Cavity Receiver

The natural convection heat loss characteristics of a solar cavity receiver have been investigated by numerical simulation method. The results show that, the natural convection heat loss, the convection heat transfer coefficient and Nusselt number increase with the increment of opening ratio. However, due to the consideration of physical property variation of air in this study, the natural convection heat loss and the convection heat transfer coefficient increases with the elevation of cavity wall temperature while Nusselt number decreases as cavity wall temperature rises. Moreover, for a receiver with small opening ratio, the cavity wall temperature has extremely subtle effect on the convection heat transfer coefficient and Nusselt number, on the contrary, the cavity wall temperature variation will lead to notable change in the natural convection heat loss characteristics when the opening ratio becomes larger.