Performance and Sizing of Vacuum Membrane Dehumidification in Varied Building Types and Climate Zones

Abstract

Conventional condensation dehumidification requires significant energy, which can be drastically reduced by rejecting water vapor without phase change. Perhaps the most efficient method to do so is vacuum membrane dehumidification with a compressor between two membranes, dubbed the dual-module humidity pump (DMHP) setup. However, little is known about the design and sizing of vacuum dehumidification, limiting implementation. This work provides the membrane sizing requirements and annual energy savings potential for DMHP, while considering 4 building types, both common membrane types, and location analysis across the continental US. The analysis uses a partial pressure-driven ε-NTU framework of the DMHP system with flat sheet membrane (FSM) module and hollow fiber membrane (HFM) module configurations. The simulation models for FSM and HFM configurations are validated against experimental results, achieving a prediction accuracy within a 5% error range. Annual weather data and building indoor loads are obtained from an EnergyPlus simulations and are incorporated into the DMHP system thermodynamic model. The effect of ventilation ratio on membrane sizing and energy savings, which depends on the outdoor and building indoor conditions, is also analyzed. For medium office buildings in the United States, membrane area per total floor area requirement for FSM can vary from 0 to 0.25 m2·m-2, depending on the specific location and climate zones. The energy saving potential for restaurants can be up to 12.16 kWh/m2 due to the restaurant’s larger latent load gains compared to other building types. Thus, this framework can serve as a valuable tool for sizing membrane-based dehumidification systems and understanding the energy savings.

Keywords: Membrane Dehumidification, DMHP, ventilation, air conditioning, Sizing