Thermal efficiency improvement of parabolic trough solar collector using different kinds of hybrid nanofluids

In this paper, the use of eight hybrid nanofluids to improve the thermal efficiency of a parabolic trough solar collector (PTSC) is investigated. The analysis is performed with the thermal model developed and validated with Sandia National Laboratory's experimental data using pure Syltherm 800. The developed model results prove a good agreement with the experimental study with an average error of 1.92% and 2.34% to calculate the outlet temperature and thermal efficiency. The simulation results showed that PTSC thermal efficiency could achieve its maximum improvement of 2.8% using hybrid nanofluids evaluated and an average improvement of PTSC thermal efficiency of 1.6% under the operating conditions of the examined tests compared to Syltherm 800. All hybrid nanofluids achieve a better PTSC's thermal efficiency than the base fluid, and the difference between them is insignificant due to keeping the total concentration constant (phi= 3%) for all of them. This improvement of PTSC's thermal efficiency using hybrid nanofluid is explained by the most significant increase and improvement of heat transfer coefficient and Nusselt number compared to pure Syltherm 800. This paper is beneficial to researchers focused on applying and improving the PTSC's thermal performance based on the improvement of heat transfer fluids.