Natural convective heat transfer of magnetite/graphite slurry under a magnetic field

This paper presents a numerical analysis of the natural convective heat transfer of magnetite/graphite slurry non-Newtonian ferrofluid in a square enclosure under a variable external magnetic field. A heat source with variable temperature distribution is located at the bottom of the enclosure. The left and right walls of the enclosure are at a relatively low temperature. The top wall and part of the bottom wall are thermally insulated. Experimental results are used to obtain the non-Newtonian behavior of graphite slurry and to obtain the properties of its temperature function. The governing equations take into account the effects of ferrohydrodynamics, magnetohydrodynamics, and non-Newtonian fluid behavior. The effects of the Rayleigh number, magnetic number, and Hartmann number on the heat transfer and fluid flow are studied. The results show that, at low Rayleigh numbers, the increase in the Hartmann number does not have any effect on the heat transfer. At high Rayleigh numbers, the heat transfer decreases as the Hartmann number increases. This decrease becomes less significant at higher Rayleigh numbers. The results also show that the strength of the applied magnetic field (the Kelvin force) should reach a certain value (Mn∗f≥104) so that it can affect the heat transfer