Heat transfer enhancement of a parabolic trough solar collector using innovative receiver configurations combined with a hybrid nanofluid: CFD analysis

The present study investigates the thermal performance of three novel parabolic trough receiver configurations and compares the performance of two different heat transfer fluids: Syltherm800 and MWCTN-TiO2/Syltherm800 hybrid nanofluid. Numerical simulations were conducted using computational fluid dynamics in ANSYS Fluent software. The model was validated by comparing the numerical results with experimental results from Dudley's study. Simulations were performed for various inlet velocities and temperatures to evaluate parameters including the Nusselt number, friction coefficient, performance evaluation criterion, temperature gradient, and thermal efficiency. Among the three configurations, Configuration 3 demonstrated the highest thermal performance. The MWCTN-TiO2/Syltherm800 hybrid nanofluid exhibited better thermal performance compared to Syltherm800. The maximum variation in parameters comparing new configurations with the smooth receiver is: Nusselt number increased by 60 %, 55.1 %, and 149 %; thermal efficiency increased by 2.55 %, 1.86 %, and 5.12 %; friction factor increased by 2.7, 3.8, and 6.5 times; temperature gradient decreased by 29.67 %, 23.9 %, and 47.4 %, for configurations 1, 2, and 3, respectively. When comparing the MWCTN-TiO2/Syltherm800 hybrid nanofluid to Syltherm800: Nusselt number increased by 4.9 %, 3.6 %, 4.9 %, and 3.5 %; thermal efficiency increased by 2.7 %, 1.98 %, 2.5 %, and 2.56 %; friction factor increased by 8.48, 7.123, 11.62 and 9.88 times; temperature gradient decreased by 3.1 %, 6.8 %, 6.3 %, and 6.4 %, for the smooth receiver and configurations 1, 2, and 3, respectively. The findings highlight the potential of using tabulators and the MWCTN-TiO2/Syltherm800 hybrid nanofluid for improving thermal performance and reducing thermal stresses in parabolic trough receivers.