HOTSPOT COOLING PERFORMANCE FOR SUBMERGED CONFINED TWO-PHASE JET IMPINGEMENT COOLING

Jet impingement can be particularly effective for removing high heat fluxes from local hotspots. Two-phase jet impingement cooling combines the advantage of both the nucleate boiling heat transfer with the single-phase sensible cooling. This study investigates two-phase submerged jet impingement cooling of local hotspots generated by a diode laser in a 100 nm thick Hafnium (Hf) thin-film on glass. The jet/nozzle diameter is similar to 1.2 mm and the normal distance between the nozzle outlet and the heated surface is similar to 3.2 mm. Novec 7100 is used as the coolant and the Reynolds numbers at the jet nozzle outlet range from 250 to 5000. The hotspot area is similar to 0.06 mm(2) and the applied hotspot-to-jet heat flux ranges from 20 W/cm(2) to 220 W/cm(2). This heat flux range facilitates studies of both the single-phase and two-phase heat transport mechanisms for heat fluxes up to critical heat flux (CHF). The temporal evolution of the temperature distribution of the laser heated surface is measured using infrared (IR) thermometry. This study also investigates the nucleate boiling regime as a function of the distance between the hotspot center and the jet stagnation point. For example, when the hotspot center and the jet are co-aligned (x/D = 0), the CHF is found to be similar to 177 W/cm(2) at Re similar to 5000 with a corresponding heat transfer coefficient of similar to 58 kW/m(2).K. While the CHF is similar to 130 W/cm(2) at Re similar to 5000 with a jet-to-hotspot offset of x/D approximate to 4.2.