Enhancing Thermal and Exergy Efficiency of Evacuated Tube Solar Collectors Using Hybrid Fe₂O₃/MgO Nanofluid and Porous Medium Integration

Evacuated tube solar collectors (ETSCs) are advanced solar thermal systems that efficiently capture and utilize solar energy, even in low-temperature and diffuse radiation conditions. Integrating nanofluids enhances their thermal performance by improving heat transfer properties. This combination offers a promising solution for applications requiring high thermal efficiency and improved energy conversion. This investigation experimentally performed the ETSC function by combining hybrid nanofluid and porous material integration. For the hybrid nanofluid with a mix of iron oxide (Fe₂O₃) and magnesium oxide (MgO) nanoparticles in equal share (1:1 ratio). Moreover, the hybrid nanofluid was studied under various volume concentrations of about 0.5vol.%, 1vol.%, and 2vol.%. The result of the hybrid Fe₂O₃/MgO nanofluid at 2 vol.% experienced a maximum thermal parameter value with porous medium conditions. At 2 vol.% Fe₂O₃/MgO nanofluid concentration with porous medium, the fluid temperature peaked at 92.3°C, the heat gain reached 757.1 W, and the thermal efficiency improved to 86.9%. Also, the exergy efficiency increased to 19.2% under similar conditions. Moreover, the enviro-economic analysis was carried out and the energy output rose to 1697.5 kWh, achieving a CO₂ reduction of 22.7 tons. The study concluded that integrating hybrid Fe₂O₃/MgO nanofluid (2 vol.%) with the porous medium in evacuated tube solar collectors significantly enhanced thermal performance and highlighted its potential for sustainable and efficient solar energy applications.