Comparison between the cooling performances of micro-jet impingement systems using liquid metal and water as coolants for high power electronics

Abstract

Liquid metals are attractive coolants for MEMS with a high heat flux. However, most existing studies on liquid metals were focused on micro- and mini-channel heat sinks. In the present work, we applied liquid metals into three micro-jet impingement systems, i.e., jet impingement surface cooling (JISC), jet impingement body cooling (JIBC) and hybrid body cooling (HBC) systems. Analytic and numerical models were established, based on which the thermal resistances of these systems using water and liquid gallium (Ga) as coolants were compared and analyzed. The results indicated that the systems using liquid Ga always achieved a smaller thermal resistance compared to water, showing a maximum decrease of 29.8% in thermal resistance and a largest drop of 12.6 K in chip temperature. The minimum thermal resistance using liquid metals reaches as low as 0.033 K/W. In addition, JIBC system always had the smallest thermal resistance when water was used. However, in the case of liquid Ga, HBC system performs best at small flow rates. The influences of geometry parameters on the system cooling performance were analyzed. It was shown that an optimal nozzle spacing of 4.7 mm existed. Moreover, the thermal resistances of the three systems increased with an increasing nozzle diameter, and the thermal resistance of JIBC system would exceed that of HBC system at an enough large nozzle diameter (e.g., ∼0.28 mm for Ga). Regardless of the coolant used, the thermal resistances of JIBC system kept nearly constant with the variation of side gap height. For HBC system, the thermal resistance increased obviously with an increasing side gap height when water was used as coolant, while barely changed for liquid Ga. The findings in this study provide a guidance for the design and operation of micro-jet impingement systems employing liquid metals as coolant.