Experimental investigation on heat loss of semi-spherical cavity receiver

In this paper, experiments were performed to investigate the heat loss of semi-spherical cavity receiver applied for solar dish collector. Experiments were conducted for fluid inlet temperatures from 75 degrees C to 150 degrees C, receiver inclination angles of 0 (cavity aperture facing sideways), 15 degrees, 30 degrees, 45 degrees, 60 degrees and 90 degrees (cavity aperture facing down), and aperture size of 0.15 m, 0.2 m and 0.25 m. Total, conductive, convective and radiative heat loss were studied in low-temperature situations (75-150 degrees C) and extended to high-temperature situations (150-300 degrees C). Experimental correlations of Nusselt number as function of Grashof number were developed for different operating temperatures, inclinations and aperture sizes. Compared to numerical results of cavity receiver, the convective heat loss is higher in present work and with the reduction of inclination, the deviation is more obvious. (C) 2014 Elsevier Ltd. All rights reserved.