Application Study Of Liquid Desiccant In Dedicated Outdoor Air System

Traditional air-conditioning design method has exposed xatoqwkn problems in its development. That is, the coupling control of temperature and humidity brings about great energy dissipation, it's hard to adjust to the variations of the indoor temperature and humidity, the bacterial contamination is created by the wet surface of fan-coil unit and the failure clean of the fresh air filter, and so on. The forms of air-conditioning system has become hot issue, especially after the wreak havoc of SARS(Severe Acute Respiratory Syndromes) virus in 2003. As a result, the dedicated outdoor air system created by Gershon Meckler has gradually been concerned by the whole society. The system adopts new wind operation, without mixing with return air. Therefore, it avoids air cross-contamination and greatly improves the building environmental security. The system needs to select the ice storage air conditioning system, because the chilled water needed will be lower than conventional system on temperature. But the ice storage air conditioning system is still at an early stage in China. In addition, the system needs inducing tuyere with high induction ratio. But the inducing tuyere is rare and expensive in China. To cope with the two problems, the author envisages leading in the liquid desiccant technology, which accomplishes the desiccant link, instead of the ice storage air conditioning system and inducing tuyere.The liquid desiccant technology uses dehumidifying salt solution as cycle fluid. The driving source is the difference of the partial vapor pressure of air and vapor pressure of salt solution surface's saturate boundary layer. The system nonuse the refrigerating fluid of CFCs to destruct the ozone layer, so it's a green and environment-protective system. Due to lower regeneration temperature, lower-grade heat sources have great value in use, such as solar energy, geothermy, industry waste heat, and so on. The uniting of liquid desiccant technology and dedicated outdoor air system has certain superiority in system operation energy consumption and indoor air environment safety.Firstly, this paper elaborates the principle of the dedicated outdoor air system based on the liquid desiccant technology, analyses and summarizes the structural style of the main component part of this system. And then it establishes the mathematical model of dehumidifier by bringing in the concept of the total heat exchange efficiency and the moisture exchange efficiency. Based on the dehumidifier model, this article has launched the design calculation relatively specific, pointing out the difference on load calculation compared with conventional air-conditioning system, discussing how to determine the inlet water temperature when the fan coil system works in dry-type. Moreover, this article analyses the cold source selection and discusses the advantages and disadvantages of the combining forms of chilled water system. Especially, by analyzing the ground sink direct cooling dry-type fan-coil system, it describes the special form of dry-type fan-coil chilled water system providing the conditions of using natural cooling source. Moreover, this paper makes a simulation to observe the comfort in the software of'fluent'. On the base of the partition for the state points of outdoor air, an operational control strategy of summer and transition seasons is proposed. Finally, through contrastive analysis with general cooling dehumidifying system in the case of the mentioned building, this paper forms the conclusion that the system has higher initial cost, but greatly cuts down on the operation cost.The research work of this paper will contribute to the effective promotion to the dedicated outdoor air system.