Experimental flow and heat transfer analysis of electronics cooling with impinging jet and channel crossflow: The effects of nozzle geometry

Abstract

This study experimentally investigates the effects of crossflow interaction with jet flow emerging from jet nozzles with various geometrical forms on the heat transfer characteristics of a prismatic electronic module. Various jet nozzle exit forms, including circular, square, elliptical, and rectangular, with aspect ratios ($\text{AR}$) varying between 0.33 and 3 are tested. The dimensionless jet-to-target plate distance ($H/D$) is maintained at 3, while the jet-to-crossflow velocity ratio ($V_r$) varies from 2.5 to 10 in the analysis of crossflow and jet interaction. Surface temperature contours are obtained using infrared thermography, and the resulting heat transfer coefficients are expressed in terms of local and average surface Nusselt number distributions. The dimensionless pressure loss coefficient derived from pressure readings is also reported. The findings indicate that crossflow significantly influences the temperature distribution on the module surface, particularly at low $V_r$ values. 47.8 % increase in the mean Nusselt number is obtained at $V_r=3$ for elliptical nozzle with 0.33 aspect ratio (EAR0.33) and rectangular nozzle with 0.33 aspect ratio (RAR0.33) compared to the circular nozzle. The rectangular nozzle forms enhance the heat transfer performance while minimizing the increase in the pressure loss coefficient, especially at higher $V_r$ values. The square nozzle results in a 20.3 % increase in the loss coefficient while the mean Nusselt number exhibits an enhancement of 20.1 % in returns compared to the circular one at $V_r=10$. These values are obtained as 13.4 % and 22.5 % respectively, for RAR0.33. The findings show nozzle forms with low aspect ratios can mitigate crossflow deflection and be used effectively in crossflow environments.