Experimental investigation of buoyancy-driven convective heat transfer of Ag/Fe3O4 hybrid nanofluid inside an enclosure

With their superior heat transfer capabilities, hybrid nanofluids are gaining attention as advanced fluids, leveraging the enhanced properties of their individual components. This research investigates the combined effects of Ag and Fe₃O₄ nanoparticles for improving the thermal characteristics of traditional heat transfer fluids like ethylene glycol. Using a two-step methodology, the hybrid nanofluids are prepared and then characterized for their thermal conductivity and viscosity. The thermal conductivity of Ag/Fe₃O₄ shows an increase of up to 9.84% with respect to the base fluid. Similarly, viscosity rises with nanoparticle concentration with the highest viscosity increase of 23% at 0.2% particle loading, while a smaller enhancement of 2.05% occurs at 0.01% concentration. Zeta potential analysis indicated excellent dispersion stability, with values exceeding 30 mV, although stability decreased at higher concentrations due to particle agglomeration. An experimental study on buoyancy-driven convective heat transfer is conducted to evaluate the nanoparticle doping effectiveness. A cubic cavity filled with the hybrid nanofluid is used, and the heat transfer performance is measured by the Nusselt number and heat transfer coefficient. The results show significant improvements in both parameters compared to the base fluid. The Nusselt number increases by up to 7.03%, and the heat transfer coefficient reaches a maximum increase of 12.4% at an optimal nanoparticle concentration of 0.15%. These findings highlight the importance of optimizing nanoparticle concentration for enhanced heat transfer performance in practical applications.