Numerical investigations on the heat transfer characteristics of pin-fin heat sink for power converters in more electric aircraft

Efficient cooling of high-power density converters is critical for the aerospace industry. This study investigates a 40-kW aviation power converter and examines the heat transfer (HT) characteristics of pin-fin heat sinks under specific operating conditions. The effects of the height-to-diameter ratio ($r_h$), relative spanwise spacing ($r_s$), relative streamwise spacing ($r_x$), and Reynolds number (Re) on HT performance are analyzed. When the pin-fin diameter is fixed, the average Nusselt number ($\overline{\mathrm{Nu}}$) of the pin-fin surface (PFS) is consistently 40 %–70 % higher than that of the end wall. Both $\overline{\mathrm{Nu}}$ levels on the PFS and end wall increase as Re increases. The thermal performance index (TPI) and improved thermal performance index (TPI’) both initially increase and then decrease with increasing $r_h$ when $Re$ ≤ 10,000, while they consistently decrease with increasing $r_h$ when 15,000 ≤ $Re$≤25,000. Additionally, the friction coefficient and resistance enhancement coefficient increase as $r_h$ varies from 4 to 20. The optimal heat sink structure is identified as having a pin-fin diameter of D = 6 mm, a height-to-diameter ratio of $r_h$ = 10, a relative spanwise spacing of r_s = 3, and a relative streamwise spacing of $r_s$ = 3 and $r_x$ = 2.5, respectively.