Effect of powder size on capillary and two-phase heat transfer performance for porous interconnected microchannel nets as enhanced wick for two-phase heat transfer devices

Abstract

In order to enhance the performance of vapor chamber heat spreaders, porous interconnected microchannel nets (PIMNs) were developed as an enhanced capillary wick by traditional copper powder sintering and wire-electric machining methods. The capillary performance of the PIMNs was characterized using a novel IR-thermal imaging method. The experimental results indicated that the gravitational effect was negligible at the initial capillary rise stage but became increasingly influential at the intermediate stage, implied by the transition of capillary rise kinetic from H(t)∼t1/2 to H(t)∼t1/3 where H(t) is the capillary height. The sample of 50–75μm powders exhibited the best capillary performance possibly due to the good balance between the capillary pressure and permeability. The two-phase heat transfer performance of the enhanced wicks was further characterized by pool boiling tests, which revealed that the sample of 50–75μm also maximized the heat transfer coefficient, and could be an optimum structural design of the PIMNs. Comparative studies with other enhanced wicks justified that the PIMNs yielded competitive capillary performance, making it a promising alternative as enhanced wick for two-phase devices.