As much as 40% of the total load on air conditioning systems can be attributed to condensation dehumidification. However, new water vapor-selective membranes present a unique opportunity to greatly reduce the power requirements for moisture removal by avoiding phase change and have thus been ranked as a top alternative to traditional HVAC systems. To date, however, all such systems have relied on the assumption of constant temperature, even terming the technology “isothermal dehumidification.” This work proposes a membrane-based air cooling and dehumidification approach, referred to as the Active Membrane Energy Exchanger (AMX), which is the first to provide simultaneous, yet decoupled, air cooling and dehumidification. The suggested AMX configuration uses two vapor-selective membrane modules with a water vapor compressor in between them, using the second membrane module to reject vapor into the exhaust stream. Cooling and heating coils in each membrane module channel move heat between the air streams using a vapor compression cycle. A detailed steady-state, thermodynamic model is presented for the AMX integrated within a 100% outdoor air conditioning system. The AMX’s limiting parameters and design considerations like compressor efficiency are systematically analyzed for a broad range of outdoor air conditions and compared against standard and state-of-the-art dedicated outdoor air systems. This new high efficiency approach is found to outperform all other standard and state-of-the-art systems, achieving 1.2–4.7 times the COP over conventional dedicated outdoor air treatment. Lastly, a building simulation case study predicted cooling energy savings as high as 66% in hospital buildings with 100% outdoor systems in hot, humid climates.


This is the author-accepted manuscript of Fix, A.J., Braun, J.E. and Warsinger, D.M., 2021. Vapor-selective active membrane energy exchanger for high efficiency outdoor air treatment. *Applied Energy*, *295*, p.116950.. Copyright Elsevier, it is made available here CC-BY-NC-ND, and the version of record is available at DOI: 10.1016/j.apenergy.2021.116950.


membrane, dehumidification, vapor-selective, air treatment, outdoor air

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