Passive, Durable, Gravity-independent Condensing Heat Exchangers for PLSSs

We propose a 3D-printed, light, durable, passive, gravity-independent condensing heat exchanger (CHX) to meet the rigorous requirements of EVAs in long-duration space exploration missions. The proposed 3D-printed CHX relies on an innovative dual-plane gradient wick structure combining in- and out-of-plane capillary action to capture, collect, and recover the humidity exhaled and perspired by astronauts during EVAs. Unlike current condensers that share a common surface for both droplet nucleation/growth and condensate removal, the out-of-plane gradient wick decouples the nucleation/growth surface from the condensate removal for enhanced humidity condensation and delayed flooding. The in-plane gradient wick then directionally and passively transports the condensed humidity to a capillary reservoir for later drainage upon completion of the EVA. This enables full passive condensate management by preventing flooding and ensuring efficient removal to a reservoir. Previously, we successfully demonstrated the concept of the in-plane gradient wick condenser for enhanced flow condensation of pure dielectric/refrigerant vapors (i.e., no air). Building on this experience, the proposed project conceptualizes and demonstrates a novel dual-plane gradient wick topology for varied g-fields. Phase I deliverables will include: 1. Detailed modeling and simulation results demonstrating the optimal pore size distribution of the dual-plane gradient wick structure will be delivered. 2. A functional prototype of the proposed dual-plane gradient wick CHX complemented with detailed design documents will be delivered. 3. Detailed experimental results demonstrating that the proposed dual-plane gradient wick CHX meets the project’s performance metrics will be delivered. 4. A detailed design for a full-scale dual-plane gradient wick CHX will be delivered. Also, a detailed assessment of its potential integration into future PLSSs for lunar and Martian missions will be conducted.
Benefits: NASA seeks passive, coating-free, durable, and reliable water recovery solutions for humidity control in life support systems. The proposed 3D-printed CHX with a dual-plane gradient wick enables efficient, compact, light, durable, and gravity-independent condensation, eliminating the need for coatings and active mechanisms. Building on prior research, this technology enables next-generation CHX technologies for Portable Life Support Systems (PLSSs) and spacecraft Environmental Control and Life Support Systems (ECLSSs). Beyond space exploration, the proposed CHX technology has significant potential in HVAC systems, industrial dehumidification, and military applications. For instance, the passive, coating-free design makes it ideal for commercial heat pumps, air conditioning units, and water recovery systems in both residential and industrial settings. Additionally, its durability and efficiency offer high-value opportunities for military aerospace and defense systems, where reliable, gravity-independent heat exchangers are critical in variable conditions particularly in high g-forces experienced by aerial firefighting aircraft.