This chapter describes the two basic types of desiccant dehumidification equipment: liquid and solid. The graphics describe their configuration and their performance, and how that performance is affected by changes in key operating variables. The chapter also discusses the equipment's operating, maintenance and commissioning considerations. Finally, it describes several brief examples of where and why desiccant dehumidifiers are applied in commercial and industrial buildings.

Working with this generic, java-based applet will help you develop your own intuition with respect to desiccant wheel performance [Go to Estimator]

With the rising concern about mold in buildings, many have become interested in dehumidification performance of air conditioning systems. This article shows and describes three commercial equipment configurations currently used for drying ventilation air: active desiccant, passive desiccant and mechanical dehumidifiers. It also proposes a simple method of evaluating their performance at the more common "off-peak" performance point.

Not all buildings are candidates for desiccant subsystems, and both benefits and costs of controlling humidity with desiccants vary by application. This article summarizes some of the key issues to consider when evaluating the potential benefits and potential costs of using desiccant systems in commercial buildings. It provides a table comparing operating costs and humidity performance for active and passive desiccant technologies in 7 applications.

Parametric Analysis of Variables That Affect the Performance of a Desiccant Dehumidification System [Purchase]
Vineyard, Sand & Durfee
ASHRAE Transactions, 2000, 8 pages

Desiccant systems used in commercial buildings are usually delivering air at mid-range dew points rather than at the much lower dew points typical of industrial applications. These papers show measured results for one particular commercial-style desiccant unit, and show the effect on performance of changes in inlet conditions, wheel rotation speed and reactivation temperature. In the second paper, the measured data is extended through parametric analysis. While the equipment tested is no longer manufactured, these results illuminate the basic relationship between the key performance variables for rotating, heat-reactivated (active) desiccant wheels.

It is not practical to physically test all possible combinations of equipment at all points of operation. So computer-based performance models are useful in evaluating the many combinations which might make up a desiccant system. This article describes one such multi-component model. It allows the user to "click and drag" components together, define their key operating characteristics, and simulate of behavior of the resulting system at different inlet conditions.

The Effect of Absorber Design on the Performance of a Liquid Desiccant Air Conditioner [Planned PDF availability - Jan 2004]
Lowenstein & Gabruk
ASHRAE Transactions, 1992. 9 pages

The Effect of Regenerator Performance on a Liquid Desiccant Air Conditioner [Planned PDF availability - Jan 2004]
Lowenstein & Gabruk
ASHRAE Transactions, 1992. 9 pages

Liquid desiccant systems are very flexible. Their conditioners (the part of the system which dries and cools the supply air) can be configured in many different ways, depending on the goal for the application. Similarly, the regenerator can be arranged in many different ways. This paper explains some of the trade-offs in air flow configuration, liquid desiccant flow rate and in the mechanical characteristics. For readers interested in designing liquid desiccant equipment itself, these two papers provide an excellent technical foundation.

Optimal Design of Liquid Desiccant Cooling Systems [Purchase]
Jain, Dhar & Kaushik
ASHRAE Transactions, 2000, 8 pages

One of the important advantages of liquid desiccants is their ability to remove great quantities of moisture from air using very low-temperature (therefore low-cost) heat for desiccant regeneration. This is especially helpful when using the equipment primarily for cooling, where high-temperature heat used for regeneration will reduce the unit's cooling capacity. This paper proposes a theory of optimal characteristics for such a desiccant-based cooling unit, based on climate conditions typical of Delhi, India.