Reduced incipient superheats in boiling of fluids which hold dissolved gas

Recently, boiling of dielectric fluids, such as Fluorinert (FC series by 3M), was proposed as a promising cooling mechanism for high-end computer chips and other high-heat-flux power sources. Boiling is a very effective mode of heat transfer, thus, initiation of boiling at the lowest possible heat flux is desirable. Concern over the large superheat values (excess in temperature above the saturation temperature) needed for initiation of nucleate boiling has arisen, however. Incipience superheat is reduced by increasing the radii of embryojic bubbles which serve as nuclei for boiling heat transfer. Two methods for increasing ebryonic radii are evaluated herein for cases where the working fluid is gassy. They both employ mixing for raising the gas partial pressure near the heated surface and slowing condensation of vapor within existing bubbles. When gas is available to the near-wall region, the wall superheat at boiling incipience is sharply decreased. Under this condition, the excursion in wall superheat, which often accompanies high superheat values and is a frequent characteristic of boiling with electronic cooling fluids, is nearly eliminated.