OPEN CYCLE SOLID DESICCANT COOLING -- COMPONENT MODELS AND SYSTEM SIMULATIONS

The performance of open cycle desiccant air conditioning systems with rotary components is investigated. A key component, the rotary dehumidifier, is extensively studied.;The finite difference model is used to determine the effect of the desiccant sorption isotherm shape, the heat of sorption, the maximum sorbent water content, sorption isotherm hysterisis, matrix moisture diffusivity, and matrix thermal capacitance on the performance of a counterflow rotary dehumidifier. The results are applied to determine the influence of dehumidifier properties on the performance of an open cycle desiccant cooling system.;The performance of a counterflow dehumidifier in which part of the dehumidifier air stream is purged and recirculated to the regenerating period of the dehumidifier is studied using both analogy and finite difference solutions. Two purge geometries that result in a spatially nonuniform inlet condition in the regenerating period are considered. The results are interpreted in terms of the design point performance of desiccant air conditioners.;Computer simulation of long term system operation is used to analyze the performance of the ventilation and recirculation cycle desiccant air conditioners. Current generation and improved performance systems are considered for gas fired, solar/gas and solar fired operation in three representative U.S. locations. The thermal and electrical energy requirements for each system are determined and expressed in terms of an equivalent fossil fuel or primary energy use. A commercially available vapor compression air conditioner is also simulated to provide a reference for energy consumption and room comfort.;The numerical accuracy of two approximate and computationally fast methods for estimating the outlet states of a rotary dehumidifier is determined by comparison with a finite difference solution. Both approximate methods rely on an analogy to the solution for a rotary heat exchanger. The numerical comparison is made for a silica gel dehumidifier with convection controlled heat and mass transfer. The effect of matrix properties on the accuracy of the analogy solutions is considered. The long term operation of a desiccant air conditioning system is simulated using the analogy and finite difference dehumidifier models to determine the utility of the analogy solutions for this application.