Designing a novel small-scale parabolic trough solar thermal collector with secondary reflector for uniform heat flux distribution

• Published in: Applied thermal engineering 2022-08, Vol.213, p.118660, Article 118660
• Main Authors: Shajan, S., Baiju, V.
• Format: Article
• Language: English
• Subjects: Computational analysis; Parabolic trough solar collector; Ray tracing; Response surface; Secondary reflector
• ISSN: 1359-4311
• DOI: 10.1016/j.applthermaleng.2022.118660

•A novel procedure for designing PTCs with secondary reflector is presented.•Best PTC configuration is found out for a targeted output power.•Significant enhancement of solar flux distribution around the receiver is possible.•The MCRT method is employed to calculate solar-energy flux on the receiver tube.•The design procedure can be extended to all small-scale PTCs. This paper presents a new stepwise approach to design a medium-temperature solar parabolic trough collector with a secondary reflector, which is the fastest growing technology among concentrated solar power technology. The goal of the design is to have a homogeneous concentrated solar flux distribution with maximal output power over the receiver tube. Tonatiuh, a Monte Carlo ray-tracing based optical simulation software, has been used to conduct the ray-tracing analysis of the secondary reflector. Response surface methodology has been used to examine and select the desirable configuration of the solar collector system, and the findings have been analysed using the analysis of variance. It is found that the use of secondary reflector improves the uniformity of heat flux distribution to 0.58, whereas it is 1.0836 for the solar collector without the secondary reflector. For a target output power of 5.5 kW, the most attractive configuration has a maximum desirability value of 0.974. The computational fluid dynamics analysis has been performed in the configuration with better uniform heat flux and the collector without a secondary reflector, using the flux distribution acquired from the ray-tracing analysis. Results show that the use of secondary reflector significantly reduces the thermal gradient, and the heat flux distribution is found to be homogenous. By determining configurations with the best heat flux distribution against a specific output power, the approach provided in this paper lays the groundwork for future research on the design of parabolic trough solar collector systems with secondary reflectors.