Heat transfer of ferrofluids with magnetoviscous effects

Abstract

Ferrofluids have more excellent thermal performance than their carrier liquids, but the magnetoviscous effects under magnetic fields will increase the flow resistance to weaken this enhancement. We investigated the flow and convective heat transfer performance of ferrofluids in the tube under a magnetic field by the experimental method. A non-magnetic stainless-steel tube with 476 mm length and an inner diameter of 2.46 mm is used in our test. The maximum field intensity ranges from 22 to 97.2 kA/m. The friction coefficient and Nusselt number for water and ferrofluids are measured and compared under various conditions, including Reynolds number, nanoparticles concentration, magnetic field strength, heat flux, and magnets arrangement mode. The results indicate that the magnetoviscous effects induced by the external fields offset the possible convective heat transfer enhancement, which challenges the current view that ferrofluids can be used as a potential heat transfer medium, especially in a strong magnetic field.