A Comprehensive Study of Silicon Micropillar Based Biporous Evaporator

Abstract

-Silicon micropillar based evaporators were proven to be good candidates in advanced vapor chambers, due to their high permeability, excellent capillary performance and ease of control over the fabrication process. In this paper, biporous silicon micropillar based evaporator with microchannels to shorten the fluid transportation distance was studied comprehensively. Semianalytical model in predicting the dryout heat flux of biporous evaporator was developed. Evaporator samples with different microchannel widths were fabricated and tested. Sample with geometries of d = 3.4 μm, h = 9.00 μm, l=6 μm, l i =101.0 μm, w = 58.5 μm was able to demonstrate a dryout heat flux q''= 55.9 W/cm 2. This has a difference of only 9.0 % compared to the model predicted dryout heat flux. The biporous evaporator was found to have a gentle drop of heat transfer coefficient after dryout, owing to the existence of microchannels that can shorten the fluid propagation distance. Samples with wider microchannels were found to have larger superheat values, due to the smaller thin film evaporation areas of these sample. This paper provided great insights into the investigation of biporous evaporators and can serve as important design guidance for biporous evaporator utilized in advanced vapor chamber.