Thermal Performance Enhancement of Flat Plate Solar Collectors Using Hybrid Nanofluids: A Review of Channel Geometry Effects

The thermal performance degradation caused by elevated operating temperatures remains a major challenge in flat plate photovoltaic/thermal (PV/T) solar collectors, directly affecting electrical efficiency and long-term system reliability. While channel geometry modification and the utilization of hybrid nanofluids (HNFs) have independently demonstrated significant potential for enhancing heat transfer, their coupled thermo-hydraulic and economic interactions have not yet been systematically evaluated within an integrated design framework. This study presents a comprehensive review and analytical assessment of the combined effects of flow channel geometry and HNF thermophysical properties on the heat transfer characteristics and overall performance of flat plate PV/T collectors. Recent experimental and computational fluid dynamics (CFD)-based investigations involving various channel configurations-including straight, multi-pass, zigzag, spiral, and ribbed geometries are critically analyzed with respect to thermal efficiency, pressure drop, pumping power consumption, and electrical output. In addition, the synergistic impact of low-volume fraction hybrid nanofluids on temperature uniformity and convective heat transfer enhancement is examined from a thermo-electro-economic perspective. The results indicate that although complex channel geometries significantly increase Nusselt number and temperature uniformity, the associated rise in viscosity-induced pressure drop may offset performance gains in the absence of cost-aware optimization. A performance-to-cost ratio (PCR) framework is introduced to identify optimal design windows that simultaneously maximize thermal and electrical efficiencies while maintaining economically acceptable pumping power requirements. The analysis reveals that hybrid nanofluids at volume fractions below ۰.۱%, when combined with optimized multi-pass or zigzag channel geometries, can achieve notable cell temperature reduction and overall efficiency enhancement without compromising system-level economic feasibility. These findings provide practical engineering guidelines for next-generation PV/T collector design based on integrated thermo-electro-hydraulic optimization.

کلیدواژه ها:

Hybrid nanofluid ، Flat plate solar collector ، Channel geometry ، Heat transfer enhancement ، Solar thermal systems