Employing nonuniform magnetic fields to improve energy transfer of flow after a sudden expansion inside a miniature channel: A hydrothermal study

This study aims to use single/multiple dipoles to control the flow field after a two‐dimensional milli channel, including a sudden expansion. The study is done numerically and using a finite volume based software. First, a single dipole is positioned under the lower boundary of the channel located after the step (which is heated), and the influences of the different locations of the dipole under the heat transfer and pressure drop are analyzed. The same analysis is done for a dipole located on the opposite wall. The results show that the best performance is achieved when the dipole is located under the heated wall, where it enhances local heat transfer by 700%. The study also reveals that when multiple dipoles are used in the domain, some enhancement happens in the local Nusselt number, but the resulting pressure loss is so high. For example, when three dipoles are used, the local heat transfer enhances by 15% in specific places, but the pressure drop increases by five times. The higher strength of the dipoles also results in a much higher pressure drop. Also, the study of the inlet flow Reynolds number shows that magnetic effects on the flow decrease as the Reynolds number rises.