Gravity Independent Capillary Condensing Heat Exchanger

The designs of condensing heat exchangers (CHXs) for life support aboard exploration spacecraft are challenged by the unearthly complications of microgravity fluid phenomena coupled with the perpetual requirements of light, small, safe, silent, rugged, long life, etc. In this paper we review how heritage designs such as the Extravehicular Mobility Unit (EMU) and International Space Station Common Cabin Air Assembly (CCAA) CHXs have both succeeded and failed from a microgravity fluid physics perspective. We then present new passive designs that exploit recent advances in capillary fluidics research combining the additional effects of surface tension and complex 3D-printed system geometry to achieve robust CHXs that do not require coatings of any kind, are not limited to materials choice, perform their own passive condensate-air separation, achieve high-efficiency dropwise condensation, and offer physical barriers to condensate carry-over without mass, volume, and performance penalties. In summary, we note that such advances provide significant cross-cutting design options for myriad variable-gravity fluids management operations relevant to life support aboard spacecraft.