Current research supports requirements for fresh air ventilation standards with continuous supply and increased amounts of building ventilation to help assure safe and healthy indoor air environments (ASHRAE 1999). Off-the-shelf, packaged rooftop equipment used to air condition most facilities are not designed to handle the increased or continuous supply of outdoor air necessary to comply with building ventilation codes written to this new standard Integration of a rooftop, unitary air conditioner with an active-desiccant module (ADM) allows the use of a standard rooftop air conditioner with a thermally regenerated active desiccant component to provide a compact, cost-effective, and simple-to-use packaged system for efficiently pre-treating and supplying ventilation air adequate to ensure healthy indoor environments. By designing a combined vapor-compression/active-desiccant system with the desiccant component positioned after a conventional cooling coil, the dehumidification effectiveness of the desiccant is significantly enhanced because it operates on cold, saturated, or nearly saturated, air leaving the evaporator. "Post-coil" rather than the normally used, "pre-coil" desiccant arrangement also minimizes the regeneration temperature required for the active-desiccant, allows for partial by-pass for recombination with and post-cooling of the desiccated air, and a dramatically decreases overall size for the pre-conditioning unit.
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