AC-02-04-3 -- Developing a Standard Method of Test for Packaged, Solid-Desiccant-Based Dehumidification Systems

A draft method of test (MOT) has been proposed for packaged, air-to-air, desiccant-based dehumidifier systems that incorporate a thermally regenerated desiccant material for dehumidification. This MOT is intended to function as the "system" testing and rating complement to the desiccant "component" (desiccant wheels and/or cassettes) MOT (ASHRAE 1998) and rating standard (ARI 1998) already adopted by the industry. This draft standard applies to packaged systems that

• use solid desiccants for dehumidification of conditioned air for buildings;
• use heated air for regeneration of the desiccant material;
• include fans for moving process and regeneration air;
• may include other system components for filtering, pre-cooling, post-cooling, or heating conditioned air; and
• may include other components for humidification of conditioned air.

The proposed draft applies to four different system operating modes depending on whether outdoor or indoor air is used for process air and regeneration airstreams. Only the "ventilation" mode, which uses outdoor air for both process and regeneration inlets, is evaluated in this paper. Performance of the dehumidification system is presented in terms that would be most familiar and useful to designers of building HVAC systems to facilitate integration of desiccant equipment with more conventional hardware.

Parametric performance results from a modified, commercial desiccant dehumidifier undergoing laboratory testing were used as data input to evaluate the draft standard. Performance results calculated from this experimental input, results from an error-checking/heat-balance verification test built into the standard, and estimated comparisons between desiccant and similarly performing conventional dehumidification equipment are calculated and presented. Some variations in test procedures are suggested to aid in analytical assessment of individual component performance.

Units: Dual