Thermo-hydraulic performance of magnetic baffles for removal of concentrated heat fluxes in a heated mini channel

Abstract

The present computational study is focussed to remove highly concentrated heat flux at low Reynolds number in the presence of external magnetic field. To accomplish this task, magnetic force is used as a source of vortex generation to create turbulence to enhance heat transfer. A water based Fe3O4 magnetic nanofluid (2 vol%) is flowing in a two- dimensional heated channel at low Reynolds number (Re = 150–250). Different magnetic field intensities ranging from 1200 G to 3000 G are applied. The heat sink consists of magnets placed at four different locations. Results show that there is an improvement of maximum 26% in heat transfer using magnetic nanofluid without magnetic field as compared to pure water. When compared with the nanofluid flow without magnetic field, there is a heat transfer enhancement of 5–15% when a magnetic field of strength 1200 G is applied and even around 62–135% at strong magnetic field of strength 3000 G. However, this enhancement comes with an increase of pressure drop and back flow. This can be explained due to formation of vortices caused by the force of magnetic field. However, in low magnetic fields, i.e., 1200G-2000G, there is a net decrease in the pressure drop by 5–10% due to decrease in frictional pressure drop, which dominate the increase in pressure drop due to vortices formation. The thermal enhancement factor for all the cases is more than one, which proves that applying magnetic field increase the effectiveness of heat transfer.