Heat transfer, entropy generation, economic and environmental analyses of linear Fresnel reflector using novel rGO-Co3O4 hybrid nanofluids

Abstract This work aims to enhance the heat transfer of a small prototype linear Fresnel reflector by using rGO-Co3O4/water hybrid nanofluids at a location in Blida region, in Algeria. Hybrid nanofluids, with varying concentrations (0.05, 0.10, and 0.20 wt.%) and temperatures (20-60 °C), are prepared. For 0.2 wt. % of rGO-Co3O4 nanofluids, the viscosity and density increased by 70.83%, and 0.47%, respectively, while the specific heat decreased by 0.17% at a temperature of 60 °C over the base fluid data. The receiver pipe energy balance equations are solved using MATLAB software. With the use of 0.2 wt.% of hybrid nanofluid, the mean thermal efficiency enhanced by 2.75% to 31.95%, the mean exergy efficiency improved by 23.67% to 2.27%, and the mean temperature increased by 9.42 °C, while, the receiver pipe temperature decreased by 2.69 °C. In addition, the mean heat transfer coefficient, mean thermal conductivity, Nusselt number, and the performance evaluation criteria were improved by using rGO-Co3O4/water nanofluid at 0.2 wt. % by 309.67%, 19.31%, 254.75%, and 240.92%, respectively, while the mean entropy generation and electrical energy consumption decreased by 59.48% and 20.30%, respectively, as the CO2 emission mitigation was 253.94 kg.