This chapter describes the fundamental behavior of desiccant materials. You'll find information about both liquid and solid desiccants, including their composition and typical sorption capacity when at equilibrium with air at different relative humidities. It's basically a discussion of material properties, but the chapter also relates fundamental desiccant behavior to the way those materials are used in dehumidifiers.

Solid desiccant materials used in dehumidifiers are quite durable, allowing a five-year warrantee by most manufacturers. But if there are large volumes of viscous particulate in the air stream, the some of the desiccant surface could become clogged, reducing its moisture sorption capacity. In this study, the U.S. Department of Energy's National Renewable Energy Laboratory tested typical silica gel desiccant matrices under conditions roughly equivalent to a home environment, with smokers who consume 70 cigarettes per hour, continuously, for a year.(6 mg/m3 particulate concentration) The performance degradation varied between 10 and 35%, depending on the rotation speed of the matrix.

Desiccant components can be combined with evaporative components to form a cooling device rather than a dehumidifier. This theoretical paper investigates and describes the optimal sorption behavior for desiccants being considered for use in a cooling system.

Desiccant sorption performance at equilibrium is only a small part of what makes a given material commercially useful. It's rate of sorption, and the temperature and total amount of energy it needs for rapid desorption from the matrix are much more important. This paper shows how a relatively simple, reversing-flow test rig can generate empirical data that, when loaded into a computer model, will be a useful predictor of full-scale dehumidification performance in a rotating wheel dehumidifier.

During the late 1980's and early 1990's, the Gas Research Institute funded research managed by ASHRAE to determine the pollutant-removal characteristics of desiccant materials when they are exposed to air streams at different relative humidities, mixed with varying concentrations of typical pollutants. This brief volume summarizes the results of five years of research. Four additional volumes provide much more detail for those who need it.

This paper summarizes the results from the project described above, for just the liquid desiccants commonly used in commercial dehumidification systems. Over time, the TEG solutions tested were somewhat more effective at removing pollutants than lithium chloride, perhaps because of reactions with the desiccants.

Solid desiccants used for dehumidification can also collect radon. This paper, based on the extensive research described above, outlines the sorption behavior of two desiccant materials for radon gas, mixed in varying concentrations with air at different relative humidities. At higher relative humidities, the desiccants tested are less effective at adsorbing radon.