Enhanced Thermal Performance of Shell-And-Tube Heat Exchangers Using Fe<sub>3</sub>O<sub>4</sub> and Al<sub>2</sub>O<sub>3</sub> Nanofluids: A CFD-Based Comparative Study

Shell-and-tube heat exchangers (STHEs) are widely used but limited by the low thermal conductivity of conventional fluids. This study uses CFD simulations to compare the thermal performance of Fe3O4-water and Al2O3-water nanofluids in an STHE under laminar flow. Nanoparticle concentrations of 5–20% and Reynolds numbers of 200-1000 were tested. Model validation showed deviations within ±8%. Results reveal that both nanofluids enhance heat transfer, with Fe3O4 consistently outperforming Al2O3. At ϕ = 20% and Re = 1000, Fe3O4 achieved a maximum heat transfer coefficient of 306.95 W/m²·K, about 318% higher than water and 40% above Al2O3. Temperature contours confirmed thinner boundary layers and greater heat removal for Fe3O4, highlighting its superior thermal capability for compact heat exchanger applications.