PERFORMANCE ENHANCEMENT OF A FLAT PLATE SOLAR COLLECTOR USING AL₂O₃–CU HYBRID NANOFLUIDS

This study examines the thermal performance enhancement of a flat plate solar collector (FPSC) using Al₂O₃–Cu hybrid nanofluids as the working fluid. Hybrid nanofluids, formulated by combining metal-oxide and metallic nanoparticles, offer superior thermophysical properties compared to conventional fluids. In this work, Al₂O₃ and Cu nanoparticles were dispersed in distilled water at low volume concentrations (0.05–0.15%) using ultrasonication, and their thermal conductivity, viscosity, and stability were characterized. Experiments were conducted under real-time solar radiation to evaluate useful heat gain and instantaneous thermal efficiency of the FPSC. Results show that hybrid nanofluids significantly enhance heat transfer, with thermal conductivity increasing by up to 22% compared to water. The collector’s useful heat gain improved by 18–28%, and the instantaneous efficiency increased by 12–20% depending on nanoparticle concentration. These improvements are attributed to enhanced thermal conductivity, intensified convective heat transfer, and synergistic effects between the nanoparticles. The findings demonstrate that Al₂O₃–Cu hybrid nanofluids are promising next-generation heat transfer fluids for high-performance solar thermal systems.