Experimental investigation of heat transfer characteristics of magnetic nanofluids (MNFs) under a specially designed revolving magnetic field effect

Abstract

This study investigated the heat transfer characteristics of magnetic nanofluids (MNFs) under external magnetic field effects. Magnetic nanofluids used in the experiments were synthesised with Fe3O4 (iron oxide) nanoparticles (at mass ratios of 0.5, 1, and 2 %) in deionised water. Then, the thermal conductivity and viscosity values that directly affect the heat transfer results were measured after a comprehensive study on the stability of magnetic nanofluids. A unique set of experiments was designed to determine the effects of magnetic fields on different magnetic nanofluids. This system, which creates a rotating magnetic field effect, can be used stationary and with the effect of revolution at a certain speed. Heat transfer experiment results were evaluated considering average Nusselt numbers obtained from 3500 to 15,000 Reynolds numbers. The magnetic field acting on the magnetic nanofluids in heat transfer experiments was investigated for three circumstances. It was determined that the increasing rates of average Nu numbers in magnetic nanofluids with mass ratios of 0.5, 1 and 2% under the influence of constant magnetic field effects were 25, 38, and 60%, respectively, compared to deionised water. Moreover, when the magnetic field effects were constant, the increasing rates of average Nu numbers obtained 15, 20, and 33% in nanofluids with mass ratios of 0.5, 1, and 2%, respectively, compared to the case without magnetic field effects.