Numerical Investigation on Submerged Jet Cooling for Avionics Devices

This study primarily aims to explore the flow distribution and heat transfer characteristics of single-phase submerged jet cooling and develop a new Nusselt number correlation for avionics devices. A 3-D numerical model was constructed to investigate the effect of various parameters such as hole diameter ( $D$ ), hole pitch ( $S$ ), Reynolds number ( ${\mathrm {Re}}_{\mathrm {jet}}$ ), and crossflow scheme on flow distribution and heat transfer characteristics of the avionics server module. The pressure drop, Nusselt numbers, total thermal resistance of dielectric fluid, and the maximum and average temperature of electronic elements were obtained from 64 simulation cases. The results of temperature and streamline distribution show that the flow structure of the avionics server module can be subdivided into flow convection region, jet impingement region, and crossflow region. Parameters studies show that the discrepancy of pressure drop and Nusselt number is less sensitive to variations in any $D$ at fixed $S/D$ = 4 or $S/D$ = 5 condition, but maximum temperature and total thermal resistance increase from 75.7 °C to 89 °C and from 0.186 °C/W to 0.4 °C/W, respectively. However, for $S/D$ = 2 or $S/D$ = 3 condition, the $D$ has a slight effect on the maximum temperature and total thermal resistance for the submerged jet cooling. With the ${\mathrm {Re}}_{\mathrm {jet}}$ increase, the maximum discrepancy of pressure drop, average temperature, Nusselt number, and total thermal resistance of different $S/D$ conditions was increased from 0.029 to 1.06 kPa, from 0.5 °C to 0.8 °C, from 0.25 to 1.85, and from 0.01 °C/W to 0.03 °C/W, respectively. The effect of various parameters on flow distribution and heat transfer characteristics of an avionics server module follows the order of ${\mathrm {Re}}_{\mathrm {jet}} > S/D > D$. Finally, we proposed a new correlation for predicting the average Nusselt number for the avionics server module with submerged jet cooling.