Experimental dataset for heat transfer with hybrid magnetic nanofluid in transition and turbulent regime

Results show that Fe₃O₄/ZnO-DIW with an 80:20 HMR achieved the highest thermal conductivity enhancement (31.28%) and lowest viscosity at 50°C, ensuring an optimal balance. Fe₃O₄/TiO₂ (18 nm)-DIW exhibited the highest electrical conductivity (4.23 mS/cm) at 50°C. Temperature emerged as a critical factor influencing thermal conductivity, highlighting MHNFs' potential for advanced cooling applications, such as proton exchange membrane (PEM) fuel cells.</p><p><br></p><p dir="ltr"><b>Phase 2: Heat Transfer Performance</b><br>This phase examines the heat transfer capabilities of Fe₃O₄/TiO₂ fluids across Reynolds numbers and volume fractions.

Significant enhancements in the convective heat transfer coefficient (CHT) were observed, with optimal performance at lower concentrations:</p><ul><li>0.0125 vol.%: 26.33% improvement</li><li>0.00625 vol.%: 24.30% improvement</li><li>Higher concentrations (e.g., 0.3 vol.%) showed diminishing returns in CHT while inducing higher pressure drops.</li></ul><p dir="ltr">The Total Efficiency Index (TEI) peaked at 0.0125 vol.%, signifying the ideal balance between heat transfer improvement and hydraulic resistance.</p><p dir="ltr"><b>Phase 3: Transition Flow Dynamics</b><br>Focusing on Fe₃O₄/MgO MHNFs, this phase revealed distinct thermal transport behavior.

Results indicated delayed transition at higher Reynolds numbers compared to DIW. At 0.0125 vol.% and 0.00625 vol.%, maximum thermal transport enhancements of 31.6% and 30.2%, respectively, were achieved, offering a practical trade-off between efficiency and pressure loss.</p><p dir="ltr"><br></p><p dir="ltr"><b>Phase 4: Influence of Magnetic Fields</b><br>The final phase investigates the impact of magnetic field strength and waveforms on Fe₃O₄/TiO₂ nanofluids.

Magnetic waveforms—sine, square, and triangular—enhanced heat transfer by 27.87%, 28.21%, and 26.74%, respectively, at 0.0125 vol.%. Optimal performance was observed at 60 Hz frequency and 4V voltage, demonstrating the potential of magnetic fields to significantly boost thermal performance.</p><p><br></p><p dir="ltr"><b>Implications and Applications</b><br>These findings contribute to the understanding of MHNFs in forced convection heat transfer, offering actionable insights for energy-efficient thermal management in power generation, HVAC systems, and chemical processing.

MHNFs demonstrate the ability to enhance heat transfer efficiency while minimizing pressure losses at low concentrations, presenting promising opportunities for advancing heat exchanger and thermal system design.</p>