Exploring ferrofluids for heat transfer augmentation

We explore the potential of ferrofluids for heat transfer augmentation, via numerical simulations using water-based ferrofluids flowing between parallel plates (laminar flows; Reynolds number (Re) <1 0 0), exposed to external magnetic fields, produced by single and multiple magnetic line dipoles. Two water-based ferrofluids having different magnetic and thermo-physical properties owing to their different solid volume fractions of magnetic nanoparticles are considered. It is shown that the presence of the non-uniform magnetic field produced by the dipoles induces an attractive magnetic body force on ferrofluids, which disturbs the flow locally, thus augmenting local Nusselt number. While flow strongly gets affected by the magnetic field at Re = 25, magnetic field does not affect the flow significantly beyond Re >= 75 which shows the dominance of inertial forces over magnetic forces, at a given external magnetic field strength. A detailed parametric study is performed to investigate the effect of single and multiple dipole placements, the solid volume fraction of magnetic nanoparticles and Reynolds number on heat transfer enhancement. It is concluded that forced convective heat transfer can be enhanced by applying external magnetic field compared to no magnetic field case, only under certain boundary conditions.