Design and Optimization on Linear Integrated Triangular Cavity Absorber for Parabolic Trough Solar Concentrator

A linear integrated triangular cavity absorber based on black cavity principle was proposed and designed, and efficiency factor and heat removal factor for the cavity absorber were deduced. The oil was applied as the working fluid to test the influence of direct radiation and flow rate on the thermal performance of the cavity absorber. The results showed that the heat loss coefficient decreased with the increasing of tilting angle of the cavity absorber and increased with the increasing of operating temperature, and the thermal efficiency increased with the increasing of the flow rate of working fluid and the direct radiation. The thermal efficiency was 40.5% when the direct irradiance was 900W/m². The experimental results of efficiency factor and heat removal factor were 0.857 and 0.849 at 104.9℃ of working fluid. The proposed cavity was optimized, and it was found that the thermal efficiency of the optimized cavity was comparable to evacuated tube when the temperature of working fluid was under 220℃. The temperature of working fluid could be arriving 300℃ with the optimized cavity absorber in operation, and the working fluid was 140℃, the thermal efficiency of the optimized cavity was 48.6%.