Natural Convection of Magnetic Nanofluid in a Cavity Under Non-uniform Magnetic Field: A Novel Application

Natural convection of the water-Mn0.6Zn0.4Fe2O4 magnetic nanofluid was evaluated in a square cavity under a nonuniform magnetic field. The top and bottom walls of the cavity were assumed to be adiabatic, while the left and right walls were maintained at high and low temperatures, respectively. The magnetic field was applied such that upward magnetic force is applied to the nanoparticles near the hot wall and vice versa near the cold wall. The two-phase Euler–Lagrange method was used for simulation. Investigations were performed at different magnitudes of the magnetic field gradient, concentrations, and particle sizes. Velocity of the nanofluid is increased near the walls by applying the magnetic field. Isotherms become more curved by application of the magnetic field, which is indicative of the increased heat transfer between the fluid and the walls. This increment becomes more prominent when magnitude of the magnetic field gradient is increased. With particles enlargement, the intensity of the streamlines increases, which indicates an enhanced convection of the nanofluid in the cavity. This is because the larger particles experience greater magnetic force. Meanwhile, increasing concentration of the nanoparticles enhances the velocity near the walls and local Nusselt number as well. The results demonstrate that using the magnetic nanofluids along with application of the magnetic field can be applicable in controlling natural convection heat transfer.