The effect of position-dependent magnetic field on nanofluid forced convective heat transfer and entropy generation in a microchannel

This paper presents a numerical analysis of Al2O3-water nanofluid forced convection and entropy generation in a microchannel. The nanofluid is subjected to the position-dependent magnetic fields arising from electrical current through wires. The governing equations considering Lorentz body forces are discretized using SIMPLE-based finite volume approach. The effects of Hartmann number, axial position and number of magnetic sources and Reynolds number on heat transfer enhancement are explored. Moreover, frictional, magnetic, heat transfer and total entropy generation are computed for Hartmann number ranging from 0 to 1000. Results show that hydrodynamic and thermal behaviors of nanofluid in the microchannel are alerted considerably by the application of position-dependent magnetic field. It is observed that due to Lorentz forces vortices are generated near the magnetic sources and number and strength of vortices depend strongly on Hartmann number. For multiple magnetic sources heat transfer enhancement depends on number and relative position of magnetic sources. Second law analysis indicates that total entropy generation rate declines as Hartmann number increases.