Studies on the use of radial jet reattachment nozzles as active heat sinks for electronic component boards

Thermal management of high power electronic components (chips) with dissipation ratings of over 2-3 W/cm² clearly demands non-traditional means to be successful. Many different approaches have been attempted in the past with varying degrees of success. In the last 8 years radial jet reattachment (RJR) has been proven in the laboratory to be a novel and effective mechanism for high surface heat removal rates with negligible downward force as compared with the commonly-used impinging open jets or in-line-jets. We propose in this report the use of these nozzles, either singly or in a array to cool PCB´s from the top or from the bottom. Two typical arrangements for radial nozzle applications are fully discussed here in view of surface pressure and heat transfer characteristics. The discussion is supplemented with experimental work carried out at IIT to provide needed data. Our investigation indicates that high heat transfer rates are indeed achieved using radial nozzles. In general, RJR nozzles produce highest heat transfer rates when placed very close to a surface and for a wider area than for ILJ nozzles, with negligible downward (positive) forces. Typical maximum heat transfer coefficients are for gases, 300-500 W/m ²-K, and, although the experiments were performed with air, for liquids (no evaporation) the values (based on experimental Stanton numbers) range between 10000 to 50000 W/m²-K, depending on the fluid