A hydrophilic, antimicrobial coating has been developed for the condensing heat exchanger and filter assembly (CHXFA), part of the Environmental Control and Life Support System (ECLSS) of the Columbus Orbital Facility (COF), the European laboratory module of the International Space Station (ISS).
Condensing heat exchangers (CHX) are used in many applications, including space life support systems, to control temperature and humidity. In space, condensate from the air does not drain from the heat exchanger because of the absence of gravity. To overcome this problem, slurping condensing heat exchangers have been developed which combine a hydrophilic coating on the air flow passages, and an additional slurping section added to the air outlet of the heat exchanger to achieve efficient air-water separation.
For short missions such as those typical for shuttle flights, microbial proliferation in the coatings has not been a major issue, despite the fact that the coatings are continuously moist and a breeding ground for microbes. For longer missions, such as those proposed for the International Space Station, hydrophilic coatings containing biocides are required to prevent microbial growth and proliferation.
The COF CHXFA has a lifetime requirement of ten years. Accelerated testing of the hydrophilic, antimicrobial coating developed for this application has been performed to qualify its biocidal performance throughout a ten-year lifetime. Additionally, characterization of the coating physical properties has been performed. Results of the coating long-term evaluation are presented in this paper.