Optimization of Finned Thermal Collectors in Solar Water Systems: A Study on Al2O3/Water Hybrid Nanofluid

Solar water heating systems (SWHS) offer a sustainable solution for reducing reliance on conventional energy sources; however, their performance is often limited by insufficient heat transfer within the collector. This study presents a CFD-based numerical investigation on the optimization of finned thermal collectors in a solar water heating system using Al2O3/water hybrid nanofluid. The effects of nanoparticle volume fraction (1–3%), fin geometry (triangular and hexagonal), and mass flow rate (5–20 kg/h) on the thermal and heat transfer performance of the system were analyzed. Key performance indicators including absorber/PV temperature, outlet fluid temperature, convective heat transfer coefficient, thermal efficiency, and improved daily efficiency were evaluated under transient operating conditions. The results show that increasing Al2O3 concentration enhances heat transfer and thermal efficiency due to improved thermophysical properties of the working fluid. Fin geometry significantly influences thermal behavior, with hexagonal fins generally producing higher outlet temperatures and thermal efficiency of 65%, while triangular fins provide higher daily efficiency improvement under optimized conditions. The convective heat transfer coefficient increased with both nanoparticle concentration and flow rate, reaching peak values during mid-day hours corresponding to maximum solar input. The study confirms that combining optimized fin structures with Al2O3/water nanofluids provides an effective strategy for improving the thermal performance of solar water heating collectors, while CFD modelling offers a reliable approach for system design and performance prediction.