NUMERICAL MODELING OF NANOFLUID UTILIZATION IN A FLAT-PLATE SOLAR COLLECTOR ENHANCED WITH KOCH FRACTAL GEOMETRY

The surface temperature of flat-plate solar collectors must be maintained within an optimal range to ensure efficiency. This study enhances the thermal performance of a flat-plate solar collector using Koch fractal structures. The first three iteration models-Model-1 (triangle), Model-2 (star), and Model-3 (snowflake)-were placed beneath the collector surface. A water-Al2O3 nanofluid (NF) mixture served as the working fluid, improving heat transfer by increasing the surface area. The novelty of this study lies in employing Koch strips of varying geometries with NF under the collector. The system was evaluated under constant heat flux and Reynolds numbers (Re) of 10,000-20,000 using ANSYS Fluent for numerical simulations. Results indicated that the Koch snowflake structure (Model-3) outperformed the other designs. The fractal strip induced complex flow patterns thus enhancing fluid mixing but increasing the pressure drop and friction factor. At lower Re, the thermal performance factor (eta) was higher, reaching a maximum of 1.08 at a Re number of 10,000 and a strip diameter of 0.015 m. Model-3 demonstrated superior heat transfer, with improvements of 6.4% and 9.2% compared to Model-2 and Model-1, respectively. The findings highlight the potential of Koch fractal structures combined with NFs to improve the thermal efficiency of flat-plate solar collectors.