Long-Life, Hydrophilic, Antimicrobial Coating for Condensing Heat Exchangers

Environmental control systems for manned exploration spacecraft and lunar/planetary bases will need a condensing heat exchanger (CHX) to control humidity in crew habitat modules. Antimicrobial coatings are needed to prevent growth of microbes and formation of biofilms on the condensing surfaces inside the CHX and maintain a healthy spacecraft environment. Creare has developed a highly adherent, hydrophilic, antimicrobial coating that can be applied to heat exchanger surfaces. However, recent studies have shown that the lifetime of this coating may be limited in prototypical environments. We propose to develop an improved coating process that builds on our prior coating development but adds features to extend the lifetime, potentially to ten years. In Phase I we will prove the feasibility of our approach through theoretical studies of coating stability, deposition of trial coatings, analysis of the coatings, and measurement of coating performance after exposure to prototypical environments. In Phase II we will scale up and refine the process, produce prototypical CHX cores with the hydrophilic and antimicrobial coating, and demonstrate performance after extended exposure to prototypical environments.

Efficient and reliable condensing heat exchangers will be needed for fuel cell generators or fuel reforming systems for portable electric power generation or onboard vehicular fuel cells or reformers. These heat exchangers are required for water-neutral operation and hydrophilic and biocidal surfaces are needed for long-term reliability of the system. The coating process developed in the proposed program will be ideal for these applications.

The condensing heat exchanger is a critical component for control of humidity and maintenance of a healthy environment on manned spacecraft. Any spacecraft or lunar/planetary base intended for long duration operation with closed-loop life support will need a CHX. Applications include future lunar or Mars bases and manned interplanetary spacecraft. The coating will also be useful for potential upgrades to the environmental control system on the International Space Station, which has experienced degraded operation due to failure of hydrophilic coatings on condensing heat exchangers.

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