Low-Flow Liquid Desiccant Air Conditioning: General Guidance and Site Considerations

Abstract

AHU air handling unit ASH anti-sweat heater CDD cooling degree day cfm cubic feet per minute COP coefficient of performance DB dry-bulb (temperature) DD design day DOAS dedicated outdoor air system DOE U.S. Department of Energy DP dew-point (temperature) DX direct expansion EER energy efficiency ratio gpm gallons per minute HR humidity ratio HVAC heating, ventilation, and air conditioning LDAC liquid desiccant air conditioning LDDX liquid desiccant direct expansion LiCl lithium chloride MCDB mean coincident dry bulb (temperature) NREL National Renewable Energy Laboratory psi pounds per square inch RH relative humidity RSHI regeneration specific heat input RTU rooftop unit scfm standard cubic feet per minute WB wet-bulb (temperature) vi This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications. Nomenclature product or process airstream Air that leaves the conditioner and will eventually be introduced into the building as supply air. The product air may go through other equipment or processes before it is introduced into the conditioned space. regeneration specific heat input The amount of thermal energy consumed by a desiccant regenerator to remove one pound of moisture from the air, in kBtu/lb (ASHRAE 2007a). The typical range of RSHI values for single stage liquid desiccant regenerators are between 1.25 and 2.1 kBtu/lb. Two stage regenerators can achieve RSHI values as low as 0.9 kBtu/lb. The RSHI does not include the energy from the regenerator's pump(s) and fan.