Magnetic field effects on the thermal performance of Fe3O4 nanofluids in a forced convection system

This study experimentally investigates the effects of magnetic field strength, Reynolds number, and nanoparticle concentration on the unsteady heat transfer characteristics of a Fe₃O₄-water nanofluid. The nanofluid was prepared by dispersing nanoparticles in water at concentrations of 0 %, 0.08% v/v and 0.16% v/v, using a stabilizer to maintain dispersion. A double-pipe system, encased in a copper coil (solenoid), was employed to facilitate heat exchange between tap water and the nanofluid under magnetic field. The solenoid exerts the desired magnetic field. The Taguchi method was utilized for experimental design and analysis. Results indicate that the Reynolds number, magnetic field strength, and nanofluid concentration all enhance the heat transfer rate; however, their effects differ due to distinct mechanisms of action. Analysis of variance reveals that the Reynolds number has the most significant impact although at low Reynolds only. This is while the effects of nanoparticle concentration and magnetic field strength are comparable. The findings suggest that even a magnetic field aligned with the fluid flow can serve as an auxiliary factor to enhance heat transfer in ferrofluids, particularly when increasing nanoparticle concentration is constrained by rising pressure drops and the risk of agglomeration.