Thermal performance investigation of the newly shaped vacuum tubes of parabolic trough collector system

Abstract

The parabolic trough collector (PTC) system is currently the most mature technology for concentrator solar power (CSP) plants. However, the huge radiative heat loss under high temperatures is one of the major obstacles restricting its thermal efficiency and development to the higher temperature. To reduce the radiative heat loss, this study proposes a newly shaped tube (NS-tube) with flatted upper and lower surfaces based on the Negative thermal-flux region theory. By considering different opening angles and tracking errors of the shaped tubes, an optical simulation is developed to analyze the heat flux distribution, and a heat transfer model is established to investigate the heat loss and thermal efficiency. Results show that the thermal efficiency of the NS-tube with optimum opening angles can be improved by 0.62%–4.64% compared to the original tube. The improvement effect is more obvious at high operating temperatures and low Direct Normal Irradiance. Additionally, the thermal stress variation is also analyzed by Ansys fluent. The result shows that the thermal stress of the NS-tube is even smaller than that of the original tube due to the uniform thermal flow effect caused by the flattened lower surface.