A review of liquid desiccant air dehumidification: From system to material manipulations

Abstract

This paper provides a comprehensive literature review of the latest research on liquid desiccant air dehumidification, with an emphasis on manipulation methods from components, systems to materials. Energy comsuption for indoor humidity control is significant, especially in tropical and subtropical areas. Liquid desiccant dehumidification can independently remove moisture from the supply air. It has many advantages, including effective humidity control, utilization of low-grade thermal energy, higher supply air quality and energy storage potential. With the development in recent decades, this technology and its economic value are close to being viable in practice. However, the system still faces some limitations due to the use of corrosive desiccants with low heat capacity and insufficient wettability on packing columns. This paper firstly summarized the bottlenecks of liquid desiccant dehumidification in practical applications, including droplet carrying problems, low liquid/air contact area due to poor wettability, large temperature change during heat/mass transfer, and large heat requirement, etc.Then the optimization methods for improving the system feasibility and performance were reviewed, from these three aspects: 1) Component optimization: New type of dehumidifers/regenerators, including the hollow-fiber membrane dehumidifiers, electrodialysis and vacuum regenerators; 2) System optimization: Combined with solar collector, vapour compression, heat pump or waste heat recovery; 3) Material optimization: Modification of desiccants and membrane materials, and modifications of packing/plate surfaces. This review will help to identify research gaps and explore new pathways to further improve the practical feasibility of liquid desiccant air dehumidification.