直接蒸发冷却式变风量空调模拟系统是在节能现状分析的基础上，提出的具有节能潜力的新型系统形式，该系统将直接蒸发冷却变频制冷系统的蒸发器，应用于变风量空调系统的空气处理箱，取代了水为载冷剂的二次能耗环节，制冷剂直接蒸发对变风量空气进行热湿处理，最终实现制冷系统与变风量空调系统有机结合、协调控制和稳定运行。本模拟系统设计主要包括模拟负荷设计、变风量空调系统设计、直接蒸发冷却制冷系统设计和模拟系统控制系统设计四部分内容。同时，本模拟系统的建立也将为空调负荷模拟、变风量空调系统、直接蒸发制冷系统及相结合系统的多方面的课题研究提供实验平台。

在测控方面，模拟系统借鉴集散型控制系统的思想，融合课题科研要求，自行设计了模拟系统的自动控制软硬件系统。本文建立了针对变风量空调和变频制冷系统的多组控制环节，主要有模拟系统电气控制、模拟负荷热湿发生器控制、送风静压控制、房间温度控制、最小新风量控制、过热度控制、过冷度控制、送风温度控制和冷凝器进口空气温度控制九个环节。软件在Windows Xp环境下，利用Microsoft公司Visual Basic 6.0开发，很好的实现了各控制环路的硬件通信、数据采集、数据保存、趋势曲线、算法库资源、网络监视发布和二次开发等多项功能，为模拟系统的稳定运行和实验研究提供了友好的应用平台。

基于建立的模拟系统实验台，本文又对直接蒸发冷却式变频制冷系统应用的有效控制进行实验探讨。在对过冷度控制单回路实验中，发现有贮液器的变频系统，过冷度受冷凝风机转速影响不明显，控制冷凝压力对系统性能发挥有现实意义；在对过热度单回路控制实验中，采用改进的PID数字控制方法实现了对电子膨胀阀的调节，对过热度的良好控制，使过热度的控制性能得到改善；在对送风温度控制实验中，本文提出了一种组合控制策略，并通过实验验证了该策略对制冷系统的综合控制效果，实现了直接蒸发变频制冷系统最终控制参数——送风温度的良好控制，控制精度在±0.2℃，同时使直接蒸发变频制冷系统的性能处于较优化的工况范围。该综合控制策略提供了一种解决“直接蒸发制冷系统应用于变风量空调系统的关键技术——送风温度有效控制”的方法，该实验参数和结果可以直接为直接蒸发冷却系统在定风量或变风量空调系统中应用，提供实际指导。

On the basis of the analysis for the energy consumption conditions, the direct expansion refrigeration & VAV simulated system which has been offered is a new type of systems. The evaporator of the direct expansion variable frequency refrigeration, taking the palace of the air-conditioner cooled by water, was put into VAV’ s AHU to handle the air in order that the combined system (DER & VAV) can be run stably and controlled efficiently. There are four parts of the designs of the simulated system—— the sensible simulated heat & moisture load generation system, VAV system, direct expansion refrigeration system and data acquisition & control system. Furthermore, the built combined simulated System (DER & VAV) will provide the experimental station for the future studies on these four systems.

In view of the demands of multi-purpose experimental studies, The data acquisition and control system hardware and software have been designed, used the idea of Total Distributed System (TDS) for reference. The built control system hardware has totally 9 control circles, including the electric control circle, the sensible simulated heat & moisture load control circle, the supply air static pressure control circle, the simulated room temperature control circle, the minimum outdoor air flow rate control circle, the refrigerant degree of superheat control circle, the refrigerant degree of sub-cooling control circle, the supply air temperature control circle and the temperature of air entering the condenser control circle. The Software, which has been programmed with VB 6.0, has actualized many kinds of functions, such as the hardware communication, data acquisition & save, operational characteristic curves/performance data display, several control strategies resources and so on. The software also provides a platform of experimental study and reprogramming for an end-user of the experimental station.

Based on the built combined simulated System (DER & VAV), the experiment of Controllability of the direct expansion variable frequency refrigeration has been carried out . The refrigerant degree of sub-cooling has been affected little by Rotate speed of the condenser fan , it is more significance to control the condenser refrigerant pressure for promoting the refrigerant efficiency in the control experiment for the refrigerant degree of sub-cooling circle. In the control experiment for the refrigerant degree of superheat, the modified control methods gained the better control effects than digital PID by adjusting the electronic expansion valve; The supply air temperature has been maintained by the integrating control strategies, the control accuracy is to ±0.2℃ ,and the reasonable condition of the refrigerant system has also been attained at the same time in the corresponding experiment. The experimental results & data can be provided a reference for the application of the system.