Ferrohydrodynamic and Magnetohydrodynamic Effects on Jet Flow and Heat Transfer of Fe₃O₄-H₂O Nanofluid in a Microchannel Subjected to Permanent Magnets

In the present study, the two-dimensional jet flow of Fe3O4-H2O nanofluid was numerically investigated in a microchannel. The main objective of this article was to study the impact of permanent magnets on both ferromagnetic hydrodynamic and thermal behavior. A ferromagnetic hydrodynamic model, which includes the Brown effect and thermophoretic effect, was applied to simulate the problem through solving momentum, energy, and volume fraction equations. In this regard, different results, including the velocity vector, temperature distribution, and Nusselt number, were analyzed. Moreover, the influence of Kelvin force, inlet opening, permanent magnets position, and Reynolds number were studied on the jet flow and heat transfer. The obtained results demonstrate these factors significantly affect the jet flow and heat transfer of Fe3O4-H2O nanofluid in the microchannel. Moreover, it was found that the magnetic field originating from permanent magnets can effectively solve the problem of local high temperature on the wall at low inlet opening. The heat transfer gain was the most obvious when the position of the permanent magnet was close to the microchannel entrance. When inlet opening and permanent magnets position are 1/4 and 1, respectively, the heat transfer gain was largest, reaching 35.2%