Hotspot Cooling Performance of a Submerged Water Jet via Infrared Thermometry

Liquid jet impingement is one of the most effective methods for dissipating local hotpot heat fluxes in microelectronics. Due to its normal incident flow-field, jet impingement cooling can achieve heat transfer coefficients (HTCs) approaching ≈1 MW/m
²
·K due to its ability to thin the local thermal boundary layer in the stagnation region. This experimental study presents HTC data for water jet impingement cooling of a laser heated Hafnium (Hf) thin-film on glass. A laser diode induces local hotspots for either a steady- or pulsed-laser operation mode. The hotspots have areas ranging within 0.04 mm
²
to 0.2 mm
²
and heat fluxes up to ≈3.5 MW/m
²
. A submerged jet impingement configuration is pursued with an inlet jet diameter of ~1.2 mm, jet nozzle to hotspot/surface distance of ~3.2 mm, and the jet Reynolds Number of ~2004. The HTCs are measured using infrared (IR) thermometry using a 1.5-5 μm spectral resolution FLIR camera. Also investigated is the spatial dependence of the HTC relative to the offset between jet/wall stagnation point and the center of the local hotspot. For example, for impinging jets that are co-aligned with the hotspot center, HTCs of ~650 kW/m
²
·K and ~470 kW/m
²
·K are measured for steady and pulsed-modulated laser heating (respectively), whereas, for offsets beyond ~6 mm (x/D >5), the measured HTCs are <; 100 kW/m
²
·K.