Magnetic-thermal-fluidic analysis for cooling performance of magnetic nanofluids comparing with transformer oil and air by using fully coupled finite element method

Magnetic-thermal-fluidic analyses were conducted to assess the cooling performance of magnetic nanofluids by comparing the performance with that of transformer oil and air using the fully coupled finite element method (FEM) considering the magnetoconvection phenomena. Magnetic nanofluids (MNFs) have been studied extensively for bio-and nanotechnology applications. In particular, some studies reported that the MNF has good characteristics for thermal management and electric insulation in experiments. With this motivation, this study focused on the cooling performance of MNFs including the experimental and numerical approaches. Until now, research on the cooling effect of MNF has focused mainly on heat propagation without any real magnetic system, in which the magnetic force plays a key role in driving fluidic flow. This flow driven by the magnetic force density was related to the magnetoconvection effect. To analyze this effect quantitatively, a coupled analysis technique should be developed using the magnetic-thermal-fluidic equations. To validate the cooling performance of MNFs numerically, the numerical results were verified by a comparison with those from the experimental tests in the air, transformer oil, and MNF. After confirming the numerical setup, some experiments were conducted with a vertical solenoid coil immersed in a MNF with different volume fractions of magnetic nanoparticles. The temperature at the inside part of the coil decreased dramatically by approximately 5° C in the 7 vol. % MNF compared to the transformer oil. These temperatures were also predicted well using the proposed numerical setup.