Design, Development, and Testing of a Water Vapor Exchanger for Spacecraft Life Support Systems

Date

2016-07-10

Journal Title

Journal ISSN

Volume Title

Publisher

46th International Conference on Environmental Systems

Abstract

Thermal and environmental control systems for future exploration spacecraft must meet challenging requirements for efficient operation and conservation of resources. Maximizing the use of regenerative systems and conserving water are critical considerations. This paper describes the design, development, and testing of an innovative water vapor exchanger (WVX) that can minimize the amount water absorbed in and vented from regenerative CO2 removal systems. Key design requirements for the WVX are high air flow capacity (suitable for a crew of six), very high water recovery, and very low pressure losses. We developed fabrication and assembly methods that enable high-efficiency mass transfer in a uniform and stable array of Nafion tubes. We also developed analysis and design methods to compute mass transfer and pressure losses. We built and tested subscale units sized for flow rates of 2 and 5 ft3/min. Durability testing demonstrated a stable core geometry that was sustained over many humid/dry cycles. Pressure losses were very low (< 0.5 in. H2O total) and met requirements at prototypical flow rates. We measured water recovery efficiency across a range of flow rates and humidity levels that simulate the range of possible cabin conditions. We measured water recovery efficiencies in range 80-90%, with the best efficiency at lower flow rates and higher cabin humidity levels. We compared performance of the WVX with similar units built using an unstructured Nafion tube bundle. The WVX achieves higher water recovery efficiency with nearly an order of magnitude lower pressure drop than unstructured tube bundles. These results show that the WVX provides uniform flow through flow channels for both the humid and dry streams and can meet requirements for service on future exploration spacecraft. The WVX technology will be best suited for long-duration exploration vehicles that require regenerative CO2 removal systems while needing to conserve water.

Description

United States
Creare LLC
Creare Inc.
NASA Johnson Space Center
103
ICES103: Thermal and Environmental Control of Exploration Vehicles and Surface Habitats
Vienna, Austria
The 46th International Conference on Environmental Systems was held in Vienna, Austria, USA on 10 July 2016 through 14 July 2016.
Michael G. Izenson, Creare LLC, USA
Daniel J. Micka, Creare LLC, USA
Ariane B. Chepko, Creare LLC, USA
Kyle C. Rule, Creare LLC, USA
Molly S. Anderson, NASA Lyndon B. Johnson Space Center, USA

Keywords

water management, membrane mass exchanger, regenerable life support systems

Citation