Effects of applying uniform and non-uniform external magnetic fields on the optimal design of microchannel heat sinks

A numerical study is performed to investigate the effects of an external uniform and non-uniform magnetic field on the optimal geometric design and thermal performance of a microchannel heat sink. Fe3O4 nanoparticles suspended in water is used as the cooling fluid. The optimization process has been utilized for three cases: (1) in the absence of the magnetic field, (2) in the presence of a uniform magnetic field, and (3) in the presence of a non-uniform magnetic field generated by a current-carrying wire. The numerical results are validated with existing experimental and numerical works. The results indicated that; for the off-design (non-optimal) geometries, imposing a uniform magnetic field decreased the thermal resistance up to 21% and improved the heat sink performance. However, for the on-design (optimal) geometries, no significant improvement was achieved by applying a uniform magnetic field. In this case, imposing the magnetic field did not change the optimal geometry of the heat sink compared to the reference case (in the absence of a magnetic field). On the other hand, imposing a non-uniform magnetic field improved the heat sink performance up to 10% for the on-design geometries. In this case, the optimal geometry of the heat sink changed in comparison with the reference case.