Thermo-hydraulic performance of magnetic baffles for cooling using magnetic nanofluid in a mini channel

Abstract

Thermal and flow performance under influence of magnetic field is studied numerically. A water based Fe3O4 nanofluid (2 %Vol. constant throughout the numerical study) is flowing in a 2-Dimensional channel at low Reynold’s number i.e., Re = 150, 170,190 and 210 and at different magnetic field strength ranging from 1200 G to 2000 G are applied. The heat sink with dimensions of 40 mm X 4 mm consists of magnets placed at two different locations. The magnetic field is acting as a vortex generator which enhance heat transfer for highly concentrated heat fluxes. The heat transfer enhancement due to the magnetic field at x = 15 mm and 25 mm is studied. Results show that there is an increment of 6.13 %, 16.23 % and 37.38 % when magnetic fields of strength 1200 G, 1500 G and 2000 G are applied respectively, at x = 15 mm and the values are increased to 7.12 %, 19 % and 47.64 % for same magnetic fields applied at x = 25 mm. However, this enhancement comes with an increase of pressure drop and back flow. This can be explained due to formation of vortices due to the flow separation caused by the force of magnetic field. Nevertheless, in some cases, there is a net decrease in the pressure drop with increase in heat transfer due to decrease in frictional pressure drop, which dominate the increase in pressure drop due to vortices formation. Results show the decrease in pressure drop by 11.53 %, 17.53 % and 10.05 % when magnetic field of strength 1200 G, 1500 G and 2000 G are applied respectively, at x = 15 mm. Similarly, 8.19 % and 4.78 % pressure drop decrement is shown for 1200 G and 1500 G while an increment of pressure drop by 44.32 % for 2000 G at x = 25 mm.