Experimental Study of Combined Natural Convection and Radiation Heat Loss from a Solar Cavity Receiver

فاقد چكيده فارسي

Heat losses affect the performance of solar cavity receivers. Convective and radiative losses form the major contributions to the heat losses. In this paper, an experimental study of the steady-state natural convective loss from a new model of solar cavity receiver is performed. For this purpose, an electrically-heated solar receiver which consists of two cylindrical cavities of different diameters, with aspect ratio (length to diameter) of 1, was constructed and tested at different inclination angles from −90° (upward-facing) to +90° (downward-facing) with an increment of 30°. The cavity surface was exposed to a constant heat flux of 1360 W/m2. The results show that by increasing inclination angles from 0° to +90° the stagnant zone increases which results in decreasing convective loss. The maximum convective loss and the minimum surface temperature of cavity occur roughly at −30° inclination and the minimum convective loss occurs at +90° which means maximum stagnant zone.