Performance study of a solar-assisted hollow-fiber-membrane-based air humidification-dehumidification desalination system: Effects of membrane properties

Hollow-fiber membrane humidifiers were used in solar-assisted and membrane-based air humidification-dehumidification desalination systems (SMHDD) because of their greater packing density and thus better transfer efficiency. A dynamic mathematical model containing the major components of this system was established, including the membrane humidifier, dehumidifier and solar heating unit. The model was validated with test data from an experimental platform where three kinds of membranes with different membrane thickness, heat conductivity, etc., were tested. To understand the role of membrane characteristics in the proposed desalination system, the effects of the membrane moisture diffusivity (D-m), heat conductivity (lambda(m)), membrane thickness (delta(m)) and membrane area (A(tot)) on the system performance were analyzed numerically. Of the three factors, D-m and A(tot) show the most significant effect on the accumulated freshwater production (AP) and coefficient of performance (COP), and the effects of delta(m) on the system performance are far less pronounced than that of D-m and delta(m). In summary, membranes with higher moisture diffusivity and smaller thickness can improve system performance without much attention to the heat conductivity. However, further raising D-m above 3.0 x 10(6) m(2)/s has a slight benefit to the performance improvement. Findings in this paper are useful in guiding the preparation of membranes used for application-scale membrane-based desalination systems operating in real-world environmental conditions. (C) 2019 Elsevier Ltd. All rights reserved.