Analytic approach to analyzing the performance of membrane dehumidification by pervaporation

Abstract

As life quality has been greatly improved recently, the importance of humidity control has increased. Various kinds of humidifiers and dehumidifiers have been developed and utilized widely in our daily lives and industrial processes. In this work, we focused on dehumidification facilitated by a pervaporation system that employs a nonporous membrane. The system mainly consists of two parallel chambers separated by the membrane and a vacuum pump that constantly drives moisture removal. The membrane-pump couple sets out a vapor concentration gradient across the membrane to permeate water vapors from the feed chamber of ambient wet air to the low-pressure permeate. The experiments were performed in a constant temperature and humidity chamber to supply the constant concentration of vapor to the feed chamber. We measured the outlet humidity and the water vapor transport rate, the mass of vapor permeated through the membrane, under various experimental conditions of different feed flow rates and feed chamber heights. As the flow rate increases, the outlet humidity is decreased, whereas the water vapor transport rate is increased. However, they are independent of the height in our experiment range. Combining the mass transport theory of the membrane and volume conservation of an infinitesimal control volume, we have established theories of the outlet humidity and the water vapor transport rate. The experimental data points are entirely consistent with our theory curves. Comparing the experimental results to the theories, we also have derived the membrane coefficient.