Design optimization of hollow fiber membranes for passive air dehumidification in drying applications

Dehumidification and drying processes significantly contribute to energy consumption in air conditioning and dry material manufacturing. Conventionally, water is removed by cooling the airstream below its dew point, demanding substantial energy for phase change and reheating. Vapor-selective membranes mitigate these energy penalties by selectively separating water vapor without condensing it, offering notable energy savings for transitioning to sustainable drying processes with heat pumps. However, efficient membrane dehumidification requires a large surface area, necessitating innovative designs for high efficiency and compactness. This study proposes a new drying cycle combined with vapor-selective membranes, focusing on the design optimization of hollow fiber membrane-based energy recovery ventilators. Hollow fiber membrane properties, geometry, and pressure drops are integrated into a model of the partial pressure-driven epsilon-NTU method. The simulation is validated within a 10% error range against experimental data. Global sensitivity analysis emphasizes that membrane geometries significantly influence dehumidification performance more than physical properties. Design optimization is then conducted with four competing objectives: water vapor removal, fan power consumption, sensible heat loss, and compactness. The optimized design demonstrates a compactness of 13.05 cm(2)& sdot;cm(-3) and an exceptional equivalent coefficient of performance of 16.8 under nominal conditions. Compared to the baseline, this optimized design showcases a 20% increase in compactness and an impressive 460% increase in coefficient of performance, even under varying operating conditions. Scale-up design guidance suggests that employing multiple small units in parallel is more efficient than a single large unit when dealing with dehumidification at high air flow rates.