Natural Convection Heat Transfer Studies of Simulated and Actual Electronic Components Using Dielectric Liquids for Immersion Cooling
NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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Two experimental studies of the natural convection characteristics of heated protrusions immersed in dielectric liquids were conducted. The first study used a three by three array of simulated 20 pin dual-in-line chips which were made from aluminum blocks with foil heaters. The second set of experiments used a three by three array of thermal evaluation devices mounted on an alumina substrate. The devices were 8.9 mm square chips which contained resistors and a type of temperature sensing transistor. Both studies used an insulated Plexiglas enclosure with a top mounted heat exchanger maintained at a constant 10 deg C. Each array was mounted on a Plexiglas substrate, and spacers were used to vary the horizontal distance from the components to the enclosure wall. Five separate enclosure widths were used, with a maximum spacing of 40 mm. The vertically oriented aluminum blocks were tested with FC-71 and power levels ranging from 0. 115 Wchip to 2.9 Wchip. The non-dimensional data obtained was used to develop an empirical correlation which predicts Nusselt number as a function of Rayleigh number and enclosure width. The correlation was accurate to within 4 of the array averaged data, and the maximum uncertainty in the Nusselt number was 7.4.