Effect of non-uniform magnetic field on non-Newtonian fluid and melting heat transfer characteristics of nanoparticles enhanced PCM within metal porous media

In this work, combined utilization of magnetic nanoparticles and non-uniform magnetic field on the ferrohydrodynamics (FHD) and latent heat storage of phase change material is numerically assessed during melting in a cubic cavity filled with metal foam. The non-uniform Kelvin force caused by magnetic field intensity gradient and temperature gradient are quantified in the mathematical model, and the non-Newtonian effect is described by power-law fluid model. The simulations are then performed for different governing parameters like Magnetic number (Mn), Rayleigh number (Ra), power-law index (n), and position coefficient (aX, aY and aZ). The main results illustrate that the magnetic field gradient is the main factor that dominates the magnitude and direction of the non-uniform magnetic force. Non-uniform melting and fluctuant phenomena are caused by the competitive effects of magnetic force and buoyancy force on the fluid flow, which can promote heat transfer and storage. Increasing the Magnetic number and decreasing the Rayleigh number can aggravate non-uniform heat transfer promotion. Negative effect on flow and heat transfer caused by increasing power-law index is more obvious in the presence of the magnetic field. Compared with the non-magnetic field case, the wire placed vertically on the left side can maximize heat storage efficiency by 51.3 %, while vertical placement on the right side inhibits heat transfer. The heat storage capacity and heat storage efficiency of the wire placed vertically on the left side are 0.88 % and 29.85 % more than those of horizontal placement.