Investigating the performance of direct contact membrane distillation for liquid desiccant regeneration and freshwater production: A CFD-based study

Abstract

Liquid desiccant air conditioning (LDAC) systems offer a promising solution for enhancing indoor thermal comfort, air quality, humidity control, and energy efficiency. This study focuses on the critical aspect of regenerating liquid desiccants in LDAC systems, which has the potential to enhance system efficiency and performance significantly. Using computational fluid dynamics (CFD) to model direct contact membrane distillation (DCMD) for liquid desiccant regeneration and freshwater production, this research paves the way for improving the performance of LDAC systems. The DCMD process, which involves mass transfer across a membrane driven by a temperature gradient between the permeate and feed channels, is a key area of exploration in this study. The findings of this study have significant implications for the design and operation of LDAC systems. The impact of feed inlet velocity and temperature on vapor flux for liquid desiccant regeneration is substantial, with increasing the feed inlet temperature leading to a fourfold increase in water vapor flux. Similarly, increasing the feed inlet velocity boosts flux due to enhanced convective heat transfer. Membrane characteristics, such as porosity and thickness, are key determinants of system performance. These findings underscore the importance of optimizing these parameters for efficient liquid desiccant regeneration and freshwater production in LDAC systems, thereby enhancing their overall performance and energy efficiency. Finally, a mathematical model for water vapor flux was developed to investigate water vapor flux as a function of key factors such as inlet temperature, velocity, liquid desiccant concentration, and membrane characteristics.