Wetting improvement of plastic working plate for liquid desiccant dehumidification systems

Abstract

Liquid desiccant dehumidification is promising because it removes extra excess effectively and environmentally. By affecting the contact area between desiccant and air, the mass transfer performance is significantly influenced by the wettability on inner working surfaces of the dehumidifier. Non-metallic surfaces such as plastics are considered as good alternatives due to their anticorrosion characteristics. However, poor wetting properties severely limited the application. In this study, a silica super-hydrophilic coating on pre-etched plastic surfaces was developed by the sol-gel method to enhance wetting performance. Coating properties were test on samples made of acrylic with a 40% LiBr solution and deionized water. Results showed that with the pre-etching and super-hydrophilic coating, water droplets could completely spread within 3 seconds, which means that the contact angle could be reduced to about 0 degrees. Furthermore, the durability test showed that after 48 hours of continuous scouring under 0.01 Mpa water pressure (approximately 1000 times that of that in common liquid desiccant systems), the droplet could fully spread within 22s and the contact angle remained was maintained at 0°. Therefore, the novel coating on pre-etched surfaces developed in this study could effectively increase the wetting performance on plastic surfaces, which is helpful to the mass transfer of liquid desiccant dehumidification systems.