Optimized Liquid Impinging Jet Arrays for Cooling CPU Packages

Abstract

This study investigates optimization of the thermal-hydraulic performance of liquid impinging jet arrays for cooling of concentrated heat sources with an integrated heat spreader (IHS), mimicking a typical high-powered CPU package. Three heat source sizes were investigated, namely $10\times 10$ mm2, $15\times 15$ mm2, and $20\times 20$ mm2, all with a 1.3 mm thick copper heat spreader. An automated optimization workflow was developed in a computational fluid dynamics (CFD)-based environment to determine the ideal geometric design parameters of the impinging jet array heat exchangers, with the objective functions chosen to minimize hydraulic power consumption and/or minimize the overall thermal resistance, representing both single and multiobjective optimization strategies. The analysis showed that for maximizing the heat transfer performance only, the design tended to favor fewer closely spaced and higher velocity jets that targeted a concentrated region within the footprint on the heat spreader that was commensurate with the heat source. This focused the high convective intensity of the impinging jets on the central region of the heat spreader where the highest heat flux levels exist. However, the high jet velocities incurred a comparatively high hydraulic pumping power penalty. Conversely, when minimizing both thermal resistance and hydraulic power consumption simultaneously, the design favored a much higher population of lower velocity jets in order to mitigate the pressure drop and reduce the hydraulic power. Here, despite the lower convective cooling intensity of the lower velocity jets, the designs leveraged a much larger surface area of the heat spreader, which tended to maintain high heat transfer performance with disproportionately lower hydraulic penalties.