Enhancement of single-phase heat transfer and critical heat flux from an ultra-high-flux simulated microelectronic heat source to a rectangular impinging jet of dielectric liquid

Experiments were performed to investigate single-phase and boiling heat transfer from smooth and microstructured (micro-groove and micro-stud) surfaces having equal platform areas of 12.7×12.7 mm², to a jet of dielectric Fluorinert FC-72 liquid issued from a thin rectangular slot into channels confined between the surface of the heat source and the nozzle. The micro-groove and micro-stud surfaces augmented the single-phase heat transfer coefficient and CHF substantially due to the increased surface area. The micro-groove surface outperformed the other two surfaces, reaching CHF values well in excess of 160 W/cm² at jet velocities less than 2 m/s, and producing a virtually isothermal surface under single-phase as well as boiling conditions. CHF dependence on subcooling for the micro-groove surface exhibited a transition from decreasing to increasing CHF with increasing subcooling. The unusual trend in the low subcooling regime is attributed to the increased void fraction causing significant flow acceleration and mixing with the bulk liquid along the chip surface. Fluxes in excess of 400 W/cm² were achieved with the micro-groove surface with a combination of high jet velocity and large subcooling. The results of this study demonstrate that the use of a jet-impingement cooling scheme and structurally enhanced surfaces, coupled with phase change, can easily and reliably remove very high heat fluxes such as those anticipated with future microelectronic devices.