Thermal performance enhancement of microchannel heat sinks under an oblique magnetic field for electronic cooling applications

Abstract

Efficient thermal management of microchannel heat sinks (MCHSs) is essential for high-power electronic systems. This numerical study examines the influence of a magnetic field with variable angles on the flow structure, heat transfer, and hydraulic performance of a rectangular MCHS cooled by $${\text{A}\text{l}}_{2}{\text{O}}_{3}-\text{w}\text{a}\text{t}\text{e}\text{r}$$ nanofluid. The effects of the magnetic field angle ( $$0^\circ \le \alpha \le 90^\circ$$ ), Hartmann number ( $$0\le \text{H}\text{a}\le 40$$ ), and Reynolds number ( $$250\le \text{R}\text{e}\le 2000$$ ) are systematically analyzed and compared with the transverse and no-field cases. The performance evaluation criterion (PEC) is used to quantify the trade-off between heat transfer enhancement and pressure losses. Results indicate that, compared to the no-magnetic field case, an oblique magnetic field at $$\alpha =45^\circ$$ yields the maximum enhancement in the mean heat transfer coefficient (up to 86%) and reduces thermal resistance by 52%; however, this improvement is accompanied by a notable increase in pumping power at higher $$\text{H}\text{a}$$ . The conventional transverse configuration ( $$\alpha = 90^\circ$$ ) consistently yields PEC values below unity across the examined $$\text{H}\text{a}$$ and $$\text{R}\text{e}$$ ranges, highlighting its limited effectiveness. In contrast, an oblique magnetic field at $$\alpha = 15^\circ$$ yields the highest PEC, exceeding the $$\alpha = 90^\circ$$ and $$\alpha = 45^\circ$$ cases by 70.9% and 20.2%, respectively, highlighting the dominant role of magnetic field orientation in governing MCHS performance.