Nozzle Scaling Effects for the Thermohydraulic Performance of Microjet Impingement Cooling with Distributed Returns

Abstract Previous research studies showed that bare die liquid multi-jet impingement coolers with locally distributed outlets using silicon processing, mechanical micromachining, and additive manufacturing technology can achieve high cooling efficiency for high power electronic applications. The nozzle density is a crucial factor for thermal performance as well as for selecting the required fabrication technology. However, general design guidelines for the optimal nozzle density and cavity height are still missing in literature. In this paper, the impact of nozzle density on direct multi-jet impingement jet cooling is investigated using experiments and numerical modeling for an N × N nozzle array. The general scaling analysis with experimentally validated models is investigated based on three independent design parameters: nozzle density (N2/A), nozzle diameter (di) and cavity height (H). The objective is to find the optimal design parameters and to study the scaling trends. The experimental studies show that a very good thermal performance for the 8×8 jet array cooler with 1×1 mm2 cooling cells has be achieved as low as 0.13 cm2-K/W for a flow rate of 1,000 ml/min. The best cooler design, expressed as the cooler with the highest COP value, can be achieved in the middle range of the nozzle density between 30 to 300 nozzles per cm2 for the constant flow rate consideration. Comparisons in terms of constant cooler flow rate or constant pumping power will result in different optimal design parameter values.