Pool boiling heat transfer with an array of flush-mounted, square heaters

Recent advancements in computers and electronics have driven the community toward ebullient liquid cooling systems for keeping LSI chips cool in the presence of ever-increasing power dissipation rates. However, the uncertainty about the initiation of boiling and an insufficient understanding about the conditions under which the peak nucleate boiling heat flux (Critical Heat Flux) is reached are impeding implementation of boiling heat transfer. In this paper, results of pool boiling heat transfer experiments with flush-mounted, square heat sources cooled in the electronic cooling fluid, FC-72, are presented. The fluid contains moderate levels of a dissolved, non-condensable gas. Each heat source has an aluminum oxide surface and a 25 mm² heated area. It is intended that these heaters simulate semiconductor chips. The results show that, in pool boiling, the incipience event is highly variable from case to case, even when the remainder of the boiling curve is repeatable. The effect of heating an element on the incipience of nearby elements is documented. Boiling from a heater below the test heater is shown to eliminate the excursion in temperature at incipience.