Numerical and ExperimenNumerical and Experimental Investigations on the Performance Improvements of Parabolic Trough Solar Thermal Collector for Medium Temperature Applicationstal Investigations on the Performance Improvements of Parabolic Trough Solar Thermal Collector for Medium Temperature Applications

Abstract

The environmental repercussions of harmful emissions caused by conventional energy fuels such as petroleum and coal are a significant concern in today’s globe. A parabolic trough collector (PTC) is a promising solar energy harvesting technology that provides thermal energy. In conventional PTC receivers, solar fluxes are significantly non-uniform, which can cause high local temperatures and large temperature gradients, posing serious challenges to safety and efficiency. One approach for increasing the service life and dependability of a PTC is to reduce the receiver tube’s circumferential temperature difference that increases with the concentration ratio. This study investigates the design and development of a PTC with a secondary reflector for medium temperature applications and its experimental performances. Tonatiuh, a Monte Carlo ray-tracing based optical simulation tool, is used to obtain the power output and heat flux profiles on the receiver tube surface. Response surface methodology has been used to examine and select the desired configuration of the solar collector system, and the findings have been analysed using ANOVA. The results showed that the uniformity of heat flux distribution has significantly enhanced after the secondary reflector is installed in its most suitable location, compared to the solar collector without the secondary reflector. Therminol® 55 (TH55) oil-based hybrid nanofluids with graphene nanoplatelets and alumina nanoparticles are prepared by two-step method with different concentrations. Compared to the base fluid, the hybrid nanofluid appears to have an 18.72% increase in thermal conductivity at 65°C. A CFD analysis results show that at 0.1 kg/min mass flow rate, the hybrid nanofluids average convection heat transfer coefficient has enhanced by 21.88%. The experimental results revealed that the efficiency of the PTC with the secondary reflector obtained a greater than 6.0 % improvement over conventional PTCs. With a flow rate of 7.5 lpm, the PTC using hybrid nanofluid demonstrated an increase of 4.05 % in average thermal efficiency compared to the PTC using TH55. Overall this study proposes a new design approach of a solar PTC and a new hybrid nanofluid as its heat transfer fluid for efficient operation of PTC systems