Investigation on the effect of magnetic field on forced convection heat transfer of liquid metals in a microchannel heat sink

A strong magnetic field provides a new method of heat transfer with high heat flux. A numerical simulation for a heat sink with high heat flux under an external uniform magnetic field in three different directions is used to investigate the flow field and displacement heat transfer between liquid metal and hot surfaces. Due to its high density and large thermal and electrical conductivity coefficients, gallinsten liquid metal has been used as a working fluid. Discretization of the Navier-Stokes equations is performed by the upstream second-order finite volume method. The results show that the effect of applying a magnetic field in the Y and Z directions (perpendicular to the flow axis) on the heat sink with a Hartmann number of 88, improves the displacement heat transfer coefficient by 15% and 8%, respectively. The best efficiency in increasing the heat transfer was obtained by applying the magnetic field in the Y direction. By applying the magnetic field in the Y direction to the heat sink, the displacement heat transfer coefficient was increased by 11.9% for Hartman number of 44, 15% for Hartman number of 88, and 17.7% for Hartman number of 132, compared to zero Hartman number. By applying the magnetic field in Z direction to the heat sink, the displacement heat transfer coefficient was increased by 4.3% for Hartmann number of 44, 8% for Hartmann number of 88, 11.4% for Hartmann number of 132 and 22.1% for Hartmann number of 330, compared to Hartmann number of zero. Also, the results show that the effect of applying a magnetic field perpendicular to the flow axis has increased the velocity gradient. As a result, the pressure drop and friction coefficient of the heat sink have increased.