Studying the characteristics and energy performance of a composite hollow membrane for air dehumidification

Vacuum-based membrane dehumidification (VMD) unit is an energy-efficient alternative to the conventional mechanical vapor compression air-conditioning technology. Since the latent component of the cooling load can be independently handled by the VMD unit, the energy cost for cooling is substantially reduced. In this work, we investigate the dehumidification potential of a hollow membrane for VMD application. The hollow membrane offers higher dehumidification density and is more compact when compared to the flat-sheet types, thereby leading to a smaller air-handling unit (AHU) requirement. The developed hollow membrane is constructed from a polyetherimide (PEI) substrate and coated with PVA/LiCl active layers. Its apparent water vapor permeance and selectivity are 3395 gas permeation units (GPU) and 4240, respectively. During the lab-scale experimental study of a 3 m2 hollow membrane with varying air flowrates spanning 3 to 36 m3/h, it is observed that the attainable percentage of moisture removal of the membrane module is up to 86%, and the maximum dehumidification COP is 1.9. In contrast to a flat-sheet membrane module with a similar effective membrane area, the hollow membrane module is just half the size but displays the same dehumidification performance.