Critical heat flux in subcooled flow boiling of fluorocarbon liquid on a simulated electronic chip in a vertical rectangular channel

Experiments are performed to correlate and model CHF during subcooled flow boiling of dielectric fluoro~rbon (FC-72) liquid on a smooth 12.7 x 12.7 mm* sirn~at~ electronic chip inside a vertical rectangular channel. Two distinct CHF regimes are established based on flow visualization and experimental data. At low flow velocities, CHF is accompanied by the formation of a continuous vapor blanket and the dryout of a liquid sublayer between the blanket and the chip. Higher velocities reduce the thickness of the vapor blanket and maintain partial contact of subcooled liquid from the core with the chip, leading to the formation of discrete vapor blankets much smaller than the boiling surface of the chip. Experimental data obtained in the lower velocity regime display excellent agreement with predictions of a new CHF model which accounts for the effects of the liquid velocity profile, liquid subcooling and flow geometry.