The effects of outlet size, shape, and location on spatial temperature distribution reduction via direct jet impinging in power electronics

Power electronics are used daily in a wide range of applications. Overheating is a major problem associated with power electronic chips. Direct jet impingement on silicon-based chips has emerged as a promising technique for power electronics cooling. However, this technique results in variations in spatial temperature between the center of the jet and the jet outlet location. This paper introduces a jet outlet design that facilitates a more uniform spatial temperature distribution. To this end, a numerical model is developed for a jet impingement configuration featuring four top circular outlets and experimentally validated using a thermal test chip with a jet Reynolds number of 7000. The resultant data show that reducing the outlet size by 30% results in a 31% decrease in the spatial temperature variance between the stagnation point and hot spot locations. Five outlet configurations are also investigated: eight circular top outlets; eight circular side outlets; four square top outlets; eight square top outlets; and eight square side outlets. Analysis of the temperature profiles of these designs reveals that the configuration featuring eight top circular outlets produces the highest spatial temperature difference, while the configuration featuring four top circular outlets (1.4 mm diameter) produces the smallest difference. Specifically, the four top circular outlet design enables a 42 % reduction in the spatial temperature difference, with a 3.8 % decrease in the pressure drop between the main inlet and outlet. Additionally, the findings show that this configuration produces a higher increase in the hot spot heat-transfer coefficient compared to the eight top circular outlet configuration (from 18,500 to 22,300 w/m2 °C, an increase of 20.5 %), thus flattening the spatial heat-transfer coefficient radially.