Numerical study of surface radiation and combined natural convection heat transfer in a solar cavity receiver

Purpose - The purpose of this paper is to present the numerical solutions of surface radiation and combined natural convection heat transfer in a solar cavity receiver. The paper aims to discuss sundry issues that take place in the saidmodel. Design/methodology/approach - The numerical solutions are developed by means of second-order upwind scheme using the SIMPLE algorithm. Findings - The effects of physical factors such as Rayleigh number (10(4) <= Ra <= 10(6)), inclination angels of insulated walls (0 degrees <= theta <= 10 degrees) and the wall surface emissivity (0 <= epsilon <= 1) on natural convection-surface radiation heat transfer rate are analyzed. Impact of sundry parameters on flow quantities are discussed and displayed via graphs and tables. Stream lines and isothermal lines have also been drawn in the region of cavity. The numerical results reveal that increasing the Rayleigh number, wall surface emissivity and inclination angels of insulated walls in an open cavity enhances the mean total Nusselt number. The variations of the surface radiation and natural convection heat transfer mean Nusselt numbers are very small to the inclination angle of theta, while a significant change is noted for the case of Rayleigh number and emissivity. Originality/value - To the best of authors' knowledge, this model is reported for the first time.