Experimental analysis of vacuum membrane dehumidifier: Hollow fiber module designs and dehumidification performance

Abstract

The aim of this study was to experimentally investigate the dehumidification performance of the vacuum membrane dehumidifier with the variance of the air-flow channel in hollow fiber modules. A prototype of a vacuum membrane dehumidifier consisting of five membrane modules was fabricated. The air-flow channel of membrane modules was adjusted by changing an aperture ratio of the module housing that facing the outer surface of hollow fibers. As indicators of dehumidification performance, humidity difference, moisture removal rate, and a pressure loss were considered. A total of 12 experiment sets were designed based on four cases of module configurations and three level of air flow rate to investigate dehumidification performance according to the module configurations. The pressure loss in accordance with the air flow rate for each case were also analyzed based on the additional test results. Finally, a multi-objective optimization analysis was conducted to derive optimal aperture ratios to achieve maximum dehumidification performance and minimum pressure loss. The results showed that the membrane dehumidifier presented 1.06–3.02 g/kg of humidity difference and 28.1–81.8 g/h of moisture removal rate according to the variance of aperture ratio and air flow rate. This indicates that the membrane dehumidifier with lower aperture ratio showed higher dehumidification performance but caused higher pressure loss owing to the longer contacting path between process air and membrane. Moreover, the optimum aperture ratio of membrane module was determined to be 0.2–0.271 m2/m2 when providing a higher weight to maximizing the dehumidification performance, while 0.502–0.586 m2/m2 aperture ratio is required when predominantly focusing on minimizing pressure loss.