Heat Transfer Analysis of a Cavity Type Solar Receiver-Experimental validation and Design Improvement

This paper presents results of our numerical and experimental research to reduce heat losses, avoid hot spot problem, and achieve more uniform temperature distribution in a cavity type solar receiver designed and manufactured by our research group. The numerical model was developed by considering the dominant heat transfer mechanism in the system including: absorption of solar radiation entering through the aperture, radiation heat transfer between internal surfaces of the cavity, convection between gas and inner cavity walls, radiation losses through the aperture, and heat losses to the surrounding through the outer cavity walls. Validation of the numerical model is accomplished by comparing the calculated and measured temperatures at different points of the receiver radiated by 7 kW high flux solar simulator. The model is then served as a base line to evaluate different solutions to improve heat transfer in the system. Numerical results showed that higher temperatures can be achieved by changing the geometry of the receiver’s front flange, since it has a significant contribution on heat losses to the surrounding. Unless this solution is more effective than increasing the insulation thickness, it does not improve the temperature profile inside cavity receiver. Further simulation results indicated that by increasing the cavity length, more uniform temperature distribution is achieved inside the receiver. Based on these findings, a new solar receiver geometry is proposed to achieve higher temperature and avoid hot spots.status: publishe