Study On Different Operation Conditions Of Temperature And Humidity Independent Control System In Train Station Waiting Hall

In recent years, the temperature and humidity independent control system has been applied to several large passenger spaces in China because of its high energy. Among them, the combined system of liquid desiccant fresh air unit + floor radiant is the most common system form in large space application. While the liquid desiccant fresh air unit + dry fan coil system is less in practical application in large spaces, because of its large fan energy consumption. Liquid desiccant fresh air unit + radiant floor air conditioning system has a different consideration in application: firstly, even if temperature and humidity independent control is applied, the supply air volume increases significantly compared to conventional primary air system and the fan energy consumption increases; secondly, under part load conditions, the energy consumption of air volume adjustment modes contradicts with indoor comfort. This paper mainly revolves the above two contradictions.This paper takes a train station waiting hall model in hot summer and cold winter area as an example to study different fresh air strategies of temperature and humidity independent control system under part load conditions: 1) the design calculation method and the sizing of the air terminal; 2) special considerations in summer design condition and adjustment methods in part load condition; 3) distribution characteristics of indoor thermal environment for different control strategies of part load conditions.Firstly, investigations have been conducted on the types of terminals as well as HVAC systems that are applied at home and abroad in recent years. Then, a large train station waiting hall model has been established in Energy Plus according to the previous survey, to acquire the summer cooling load and winter heating load.Secondly, the design calculation method of solution dehumidifier + dry coil temperature and humidity control system, the determination of state points and the parameters of dry fan coil unit supply air have been discussed. The air volume of terminals, the sensible load supplied by fresh air units, and the total cooling capacity of fresh air under different CAV/VAV approach have been compared. It is revealed that compared to conventional primary air systems, the total air volume of liquid desiccant fresh air unit + dry fan coil system increases 34~63%. Then, by taking a section of the waiting hall as an example, the sensible cooling capacity of fresh air units as well as dry fan coil units has been calculated. And further on the psychometric chart, it is proved that fresh air units provide equal sensible cooling capacity under CAV/VAV strategy. But during most of the summer air conditioning time, the total cooling load of fresh air units under CAV condition is larger than that of VAV condition.Thirdly, by CFD simulation, the indoor thermal environment of part load conditions under CAV/VAV strategies has been compared. Results show that the ADPI under constant fresh air volume is about 20% higher than that of variant fresh air volume control. And the inhomogeneous coefficient of temperature and humidity ratio under variant fresh air volume is about 50% higher than that of constant fresh air volume strategy.This paper aims at the load fluctuation and long air-conditioning time of large train station waiting halls, and studied the energy efficiency and indoor thermal environment of temperature and humidity independent control system with liquid desiccant fresh air units, to provide some reference in the application of such systems in large train station waiting halls.