Secondary Reflector and Receiver Positions for Uniform Heat Flux Distribution in Parabolic Trough Solar Thermal Collector

Abstract

The distributions of heat flux over the circumference of the receiver tubes have an immense influence on the performance and reliability of the parabolic trough solar thermal collectors. The location of the receiver tube and the secondary reflector configuration may largely influence the performance of the system. Therefore, in this study, the effect of receiver tube position and parabolic secondary reflector configuration has been analyzed, and the non-uniformity of solar flux distribution, heat gradient, and power output has been compared. The results of the Monte Carlo ray-tracing analysis to homogenize the receiver tube flux distribution and maximize the output power, making the use of the cutting edge solar optical simulation tool Tonatiuh, has been presented. A parabolic trough collector with a rim angle of 80 deg and aperture area of 40 m2 have been used for the analysis. It has been confirmed that the circumferential heat flux gradient and the local hot spot could be greatly diminished, while the power output tended to reduce slightly due to the shading effect of the secondary reflector. Under the conditions investigated in this work, although the output power decreased by 4.83%, flux gradient reduced significantly, and the non-uniformity of flux distribution has reduced from 0.9757 to 0.5176. A simple design procedure for receiver tube position and secondary reflector configurations to homogenize the receiver tube temperature distribution has also been proposed.