Capillary-Driven Evaporation-Enhanced Heat Sink

Heat sinks with the same form factor but lower thermal resistance are desirable in many applications. For example, they would benefit electronics packaging by accommodating increased heat dissipation or enabling smaller overall system dimensions. An enhanced longitudinally finned heat sink that exploits evaporative cooling to significantly reduce its thermal resistance is conceptualized, modeled, fabricated, and tested. A wick in the form of a 1-mm-thick layer of (porous) sintered copper powder coated the (32 mm × 28 mm footprint × 14 mm tall) heat sink and (porous) sintered copper powder legs are immersed in an underlying water reservoir maintained at its base temperature. The assembly is placed in a wind tunnel in the fully shrouded configuration. Capillary forces maintained a film of evaporating water in the wick on the surface of the fins. The thermal resistance of the coated heat sink is 3.4-4.7 times lower than that of an uncoated heat sink of the same geometry. When (upstream) velocity equaled 2 m/s the conventional and enhanced heat sinks were tested for heat loads up to 20 and 60 W, respectively. At a heat load of 10 W, (upstream) velocity is varied from 1 to 4 m/s. External flow over a coated flat plate is investigated as well and similar reductions in thermal resistance observed.