The Effect of Permanent Magnet Location on The Performance of Ferrofluid Based Spncml

Abstract

Ferrofluids are suspensions of ferromagnetic nanoparticles (iron, cobalt, nickel, magnetite, hematite, etc.) dispersed in non-magnetic base fluids. They have application potential in many fields due to the tunable thermophysical properties and the manipulation capability of the ferromagnetic nanoparticles under the influence of an external magnetic field. This numerical study investigates the effect of external magnetic field location on the performance of ferrofluid-based single phase natural circulation mini loop (SPNCmL) in which the driving mechanism is resulting buoyancy forces of density gradient caused by temperature difference. Since the working fluid exhibits higher magnetization at low temperatures, effects of the magnetic field have been investigated for the low-temperature side of the SPNCmL by placing a permanent magnet at the cooling-end outlet and heating-end inlet. The steady 3D numerical model was developed in the COMSOL Multiphysics by coupling three different physics: magnetic field (no current), heat transfer in fluid, and laminar flow. The performance of the SPNCmL working with water-based Fe3O4 ferrofluid under an external magnetic field was evaluated in terms of the maximum temperature (T-max), the temperature difference between heater inlet and outlet (Delta T-heater), the effectiveness (epsilon), and the flow distribution. In addition, the magnetic field effect on the fluid flow was visualized by velocity and the temperature distributions at the critical cross-sections.