Experimental investigation into heat transfer and flow characteristics of magnetic hybrid nanofluid (Fe3O4/TiO2) in turbulent region

Extensive research and empirical evidence demonstrate the superior thermal performance of nanofluids compared to DIW. Magnetic hybrid nanofluids, such as Fe3O4/TiO2, are currently being explored for their enhanced thermal properties. This study evaluates Fe3O4/TiO2 nanofluids for heat transfer and hydraulic resistance across Reynolds numbers from 3200 to 5300 and volume fractions from 0.00625 % to 0.3 % vol. UV-Vis spectroscopy shows that lower volumetric fractions correlate with decreased sedimentation. Over 30 days, nanofluids with 0.3 % vol, 0.2 % vol, and 0.1 % vol exhibited high sedimentation factors (SF) of 31.79 %, 11.88 %, and 11.44 %, respectively, while 0.00625 % vol, 0.0125 % vol, and 0.025 % vol demonstrated better stability with SFs of 8.89 %, 9.82 %, and 10.24 % respectively. Volume fractions significantly impact heat transfer, with CHT coefficients increasing by 11.42 % at 0.3 % vol, 14.03 % at 0.2 % vol, 18.04 % at 0.1 % vol, and 19.98 % at 0.05 % vol. The greatest enhancements are at lower concentrations: 22.91 % at 0.025 % vol, a peak of 26.33 % at 0.0125 % vol, and 24.30 % at 0.00625 % vol. Pressure drops are highest at 21 % for 0.3 % vol at Re 5018, decreasing with lower concentrations: 13.10 % at Re 5144.4 (0.2 % vol), 11.94 % at Re 5041.6 (0.1 % vol), 9.82 % at Re 5112.2 (0.05 % vol), 7.67 % at Re 5258.7 (0.0125 % vol), and 10.29 % at Re 5094.0 (0.00625 % vol). These results highlight that higher nanoparticle concentrations increase pressure drop, impacting energy efficiency. Lower concentrations (0.0125 % Vol and 0.00625 % Vol) provided better heat transfer with lower pressure losses. Total Efficiency Index (TEI), The optimal nanoparticle concentration for maximum thermal efficiency was approximately 0.0125 % Vol. TEI values were highest at this concentration, indicating enhanced heat transfer with minimal thermal resistance and pressure drop. Higher concentrations (0.2 % Vol and 0.3 % Vol) showed lower TEI values, suggesting reduced thermal efficiency due to increased flow resistance. These findings highlight the importance of selecting an appropriate nanoparticle concentration to optimize thermal performance in heat transfer systems, balancing the benefits of enhanced heat transfer with the drawbacks of higher-pressure losses.