Liquid Desiccant Air Conditioners (Emerging Technologies‪)‬

Liquid desiccant air conditioners are an approach to effectively manage humidity under challenging conditions such as buildings with high outdoor air (OA) requirements located in humid regions. They remove moisture and latent heat (and, possibly, sensible heat) from process air via a liquid desiccant material, such as lithium chloride (LiCl) or halide salts. (1,2) Liquid desiccant AC has two essential components, an absorber and a regenerator. In a basic configuration, strong (i.e., concentrated) and cooled liquid desiccant flows into the absorber and down through a packed bed of granular particles (or other enhanced mass transfer surface or packing). Counterflowing return air passes up through the bed, transferring both moisture and heat to the liquid desiccant. The water absorbed from the air dilutes the liquid desiccant leaving the bottom of the packed bed, and flows into the regenerator. In the regenerator, a heat source (gas- or oil-fired, waste heat, solar, etc.) heats the weak liquid desiccant solution, increasing the vapor pressure of the water. When the weak desiccant is sprayed on another packed bed, the absorbed moisture migrates to a counterflowing scavenger air stream to regenerate a concentrated liquid desiccant solution. Subsequently, the return feed from the regenerator passes through a cooling tower or chiller to remove the heat input from the regenerator. Finally, the cooled liquid desiccant solution returns to the absorber to complete the cycle.