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Abstract:
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Current passive cooling methods of aerospace and military , high heat -flux electronics include the use of thermal planes made of exotic metal alloys , which have been designed , at a great expense , to have high thermal conductivity and low density (i .e . light weight ) . Also , phase change modules composed of a metal matrix saturated with a solid phase change material are being employed for systems requiring a transient cooling scheme such as expendable weapons . This method requires the heat to be transferred from the source location , through the metal matrix (typically a porous aluminum foam ) , to the available phase change material . Preliminary empirical evaluations performed at Raytheon's Space and Airborne Systems indicate that wick -based coldplates including a non -metallic porous medium , saturated with fluid may be much more effective . This wick -based method allows the capillary action of the wick to passively transport liquid from liquid -rich areas to the point of need , a much more efficient process . The objective of this research was to characterize the mass and heat transport of this proposed non -metallic , wick -based coldplate . Mass transport was characterized by measuring the wickability (liquid penetration into porous media ) between the proposed working fluids and porous medium . This was accomplished by employing the two most common techniques , the height and weight approaches . The height approach requires the measurement of distance penetrated by the liquid into the porous medium , while the weight approach tracks the mass gained by the pores due to imbibition . Experimental data was analyzed through Washburn's Theory . Heat transport was characterized by measuring the transient cooling capacity and the steady state thermal resistance of the proposed wick -based coldplate . For these evaluations , an aluminum oxide based ceramic served as the porous medium with the following working fluids : water , methanol , ethanol , methanol -water mixtures , ethanol -water mixtures , and a fluorinert liquid FC -72 . |