Using a Nonuniform Magnetic Field to Enhance Heat Transfer Before a Sudden Compression in a 2d Milli-Channel

Abstract

The advancement of electronic devices has made heat dissipation challenging, but heat convection shows promise as a solution. However, obstacles like resistors in the way of a straight channel can slow the flow and weaken heat transfer, particularly where the horizontal and vertical walls meet at sudden compression. This study examines numerically using nonuniform magnetic fields to enhance thermal energy transfer in the mentioned critical regions in a sudden compression inside a two dimensional milli-channel. The study includes placing single or multiple dipoles either beneath the lower heated wall (where the compression occurs) or over the upper wall. The effects of number, the longitudinal and vertical locations of dipoles, and the inlet flow Reynolds number are examined. The ferrofluid used in this study is EMG-805. The findings of this study demonstrate that heat transfer improves when single or multiple dipoles are positioned downstream of the step wall on the heated wall. The location of dipoles is critical. For example, the best minimum local Nusselt number (70.7% increase with respect to the base case) is achieved when the single dipole is at <i>a</i> = 49 mm (from the inlet). Increasing the number of dipoles in the thermally weak region improves heat transfer. For instance, by having three dipoles of equal strength in that area, the minimum local Nusselt number is enhanced by 90.1%, resulting in a Nusselt number before the step that surpasses the Nusselt number immediately after the step. Furthermore, as the Reynolds number increases, the effects of the magnetic field disappear.