Modelling and the feasibility study of a hybrid electrodialysis and thermal regeneration method for LiCl liquid desiccant dehumidification

Abstract

Liquid desiccant air conditioning systems are promising due to the efficient humidity control and the employment of renewable or waste heat sources. Electrodialysis is considered to assist in the regeneration of desiccant solutions in liquid desiccant air conditioning systems in the recent decade due to the easy control and energy-saving potential. However, the electrodialysis assisted liquid desiccant systems in the previous research were all designed in the batch mode, which ignored the water transfer by the electro-osmosis and the limit of concentration difference between the spent and regenerated solutions in the electrodialysis process. In this study, a hybrid method combining the electrodialysis and thermal regeneration method for liquid desiccant dehumidification is developed. This proposed system is designed in the continuous mode, which considers the limit of concentration difference, aiming to regenerate the liquid desiccant with a low-temperature resource. The feasibility study of the proposed system was carried out by simulations under three specific weather conditions and one week of tropic weather condition of Darwin, Australia. The results showed that the proposed system was able to work stably with a low-temperature resource. Electrodialysis accounted for around 85% of the total energy consumption of liquid desiccant regeneration due to the relatively high resistance of the ion-exchange membrane, which was the main constraint of the commercial implementation of electrodialysis in the liquid desiccant regeneration. Advanced ion-exchange membranes with a high ion conductivity and a low electro-osmosis coefficient are required to be developed for the specific application in the liquid desiccant dehumidification system.