No abstract

Desiccant cooling systems, considered one of the sustainable air conditioning technologies, have been attractive for researchers to be studied for many years. In this paper, the modeling and simulation of a packed tower liquid dehumidifier and regenerator as well as a solid desiccant wheel are presented. The simplified equations that predict the air conditions after passing these systems are developed. This approach is quick and does not need a lengthy computer calculation and large memory capacity. Liquid and solid desiccant cooling cycles are presented and using this approach, the performance of these systems is calculated for weather data of a reference year and different climates in the United States. These systems are compared regarding their energy and water consumption based on this new approach. The first results show that liquid desiccant systems, without technology improvements, are relatively large but with low capacities and have lower coefficients of performance than solid desiccant cooling systems.

This paper describes an improved class of heat and mass transfer air cooler model. The model is based on the approach of Green [1]. It delivers a compact and fast model that is appropriate for year round simulations of air conditioning systems. The model is validated through a set of experiments in the laboratory with an air cooler of eight rows. The heat transfer coefficients have been derived from the standard relations. For a good agreement between the measurements of a wet cooler and the model solutions, a substantial correction in the heat transfer coefficients is needed. In addition, the results obtained from the measurements indicated that the heat transfer coefficient itself and the correlation between heat and mass transfer had to be adapted. Acceptable results were obtained when mass transfer coefficient was adjusted by a correction factor. The decrease in heat transfer has been observed with an increase in dehumidification and the same could be concluded from the coupling of heat and mass transfer. The fins are not completely wet, which implies that an analogy between sensible and latent heat only partly exists. The model does not take wetness of the pipe into account. To overcome this problem, the Lewis number is modulated, based on the degree of dehumidification. In other words, the smaller mass transfer coefficient, there is the higher the dehumidification.

In this paper the analytical and simulation modelling of the combined heat and mass transfer processes that occur in a solid desiccant wheel is carried out. Using the numerical method, the performance of an adiabatic rotary dehumidifier is parametrically studied, and the optimal rotational speed is determined by examining the outlet adsorption-side humidity profiles. An approach to compare the solutions for different conditions used in air dehumidifier has been investigated according to the previous published studies. Comparing the simulated results with the published actual values of an experimental work substantiates the validity of model. The model accuracy with respect to the key variables (outlet and inlet temperatures and humidity) is optimized to minimize margin of error. This method is useful to study and modelling of solid desiccant dehumidification and cooling system.

In this paper the analytical and simulation modelling of the combined heat and mass transfer processes that occur in a solid desiccant wheel is carried out. Using the numerical method, the performance of adiabatic rotary dehumidifier and enthalpy wheels are parametrically studied, and the optimal rotational speed is determined by examining the outlet adsorption-side humidity profiles. A comparison of solutions for different conditions used in the air dehumidifier has been investigated according to the previously published studies. These approaches have been developed for enthalpy wheels. The simulated results have been compared with the published actual values of an experimental work. This substantiates the validity of the model. In addition, the effect of wall thickness on outlet water content and the wheels efficiency for different rotation speeds and different sorption characteristics are taken into consideration. The model accuracy with respect to the key variables (outlet and inlet temperatures and humidity) is optimized to minimize margin of error. This method is useful to study and model solid desiccant dehumidification and cooling systems.