Browsing by Author "Micka, Danny"
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Item Design, Development, and Testing of a Water Vapor Exchanger for Spacecraft Life Support Systems(46th International Conference on Environmental Systems, 2016-07-10) Izenson, Michael; Micka, Danny; Chepko, Ariane; Rule, Kyle; Anderson, MollyThermal 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.Item Performance of a Nafion Water Vapor Exchanger in an Amine Bed Test Loop(46th International Conference on Environmental Systems, 2016-07-10) Izenson, Michael; Micka, Danny; Quinn, Gregory; Papale, WilliamThermal 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 design considerations. This paper presents the results of testing a Nafion-based water vapor exchanger (WVX) in an amine bed test loop under conditions that simulate operation in a spacecraft life support system with a regenerative CO2 removal system. The WVX comprises an innovative assembly of Nafion tubes that achieves high water recovery (80-90%) with very low pressure losses (< 0.5 in. H2O). Nafion is an attractive material for this application because of its very high permeability for water vapor. However, Nafion is sensitive to poisoning by ammonia which is present in trace quantities in the outflow from amine-based CO2 removal beds. We measured the performance of a prototype WVX built by Creare in an amine-bed test loop at UTC Aerospace Systems. We found that water recovery efficiencies for short-duration tests were in the range 80-90%. These data come from tests run with flow rates and humidity levels that simulate the range of possible cabin conditions in future exploration spacecraft. These data are very consistent with the water recovery efficiencies measured in Creare’s laboratories without the amine beds. Pressure drop measurements by UTAS are also consistent with pressure drop data from Creare. These data are also consistent with separate effects tests in which we measured the water permeability of an unstructured Nafion tube bundle exposed to ammonia under accelerated test conditions. The accelerated tests can be used to extrapolate the lifetime of a Nafion WVX when used in conjunction with an amine bed.