State-of-the-art on liquid desiccant dehumidification systems: Components, performance, challenges and integration with evaporative cooling systems

Air-conditioners manage both the sensible as well as the latent heat loads for human thermal-comfort. However, they consume 37 % of the overall energy usage in buildings throughout the world. It is therefore imperative to seek alternative, more energy-efficient technologies, one of them being the Liquid Desiccant Dehumidification System, which can operate the latent heat load. This technology largely operates using low-grade waste/solar heat and requires significantly less electrical energy. The present review paper discusses the working of two major types of such open-cycle dehumidifiers, namely the adiabatic and the internally-cooled/heated as well as their variants and flow-configurations. Various desiccants and their desirable properties are also discussed along with their impact on indoor air quality. An exhaustive list of performance parameters and their definitions are provided for both types of dehumidifiers. Furthermore, experimental studies are reviewed involving several desiccants and novel systems. A back-calculation procedure is presented to calculate the idealized regeneration temperature of the liquid desiccant. Next, to realize a complete air-conditioning system, sensible heat must be handled as well. Therefore, due importance is also given to studies that integrate liquid desiccant dehumidifiers with evaporative cooling technologies, both direct and indirect. Challenges due to corrosion and strategies to mitigate it are discussed as well. Lastly, the conclusions and future work suggested may help researchers identify research gaps, the work towards which would hopefully result in LD-DS's widespread commercial adoption.