(1)变风量比 (1) the air quantity ratio 空调系统全年大部分时间运行在部分负荷工况下，也就是说，变风量系统的风机、风道以及末端的风量大部分时间都处于最大风量和最小风量两种极限状态之间。根据经验，如果在这两种极限状态下不发生问题，那么基本上可以保证系统大部分时间运行正常。最小设计风量与最大设计风且之比定义为变风量比(KV)，一般地，房间的变风量比KV值最好不要小于0.4—0.5，否则容易导致房间气流组织恶化、噪声和通风问题；系统的KV值最好也不要小于0.4—0.5，否则会导致系统新风严重不足以及控制不稳定等问题。 Air conditioning system for most of the time running under partial load conditions, that is to say, the variable air volume system fan, air duct, and most of the time at the end of the air volume in the maximum and minimum air volume between the two limit state. By experience, if you don't have a problem in these two limiting states, you can basically guarantee that the system is running normally for most of the time. Minimum design air volume and the ratio of the largest wind and defined as variable air volume ratio (KV), in general, variable air volume of the room than the KV value should not less than 0.4-0.5, otherwise easy to cause the deterioration of room air distribution, noise and ventilation problems; The KV value of the system should not be less than 0.4 to 0.5, which will cause the new wind in the system to be severely inadequate and control instability. 不论是房间还是系统，变风量比都是表征变风量系统一个比较重要的动态特性参数； Whether it is a room or a system, the variable air volume ratio is a more important dynamic characteristic parameter of the variable air flow system; (2)新风问题 (2) new wind problems 在过渡季，通过调节新风，回风和排风三个阀门的开度来改变新风、回风和排风三个阀门的开度来改变新风量以维持一个混风温度。这种做法是为了缩短冷机的开启时间，这里姑且不谈经济循环系统在定量系统中能否正常运行。 In transition seasons, by adjusting the fresh air, return air and exhaust valve opening to change fresh air and return air and exhaust valve opening to change the new air volume in order to maintain a mixed air temperature. This is an attempt to shorten the opening time of the cold machine, which is a good example of how the system can operate in a quantitative system. 对于采用混风的空调系统，不论是定风量系统，还是变风量系统，新风量在各个房间是按负荷分配的。也就是说，即使总新风量达到要求，有的房间也会有新风不足的问题。对于变风量系统，由于送入房间的风量是变化的，所以房间的新风量必然也是变化的。如果为了满足这些房间的要求，总新风量将会增加，甚至在有的时候可能超过需要的送风量。为此ASHRAE标准62—1989提出，在一定的新风量下，总回风中二氧化碳的含量不一定超标，可以利用回风以减少总新风量。 In the case of air conditioning system, the new air quantity is distributed according to load in different rooms. That is, even if the total amount of new air is required, there will be a shortage of new winds in some rooms. In the case of variable air volume system, the new air volume of the room must also change due to changes in the amount of air that is sent into the room. In order to meet the requirements of these rooms, the total new air volume will increase and may even exceed the required air supply. The ASHRAE standard 62-1989 suggested that, under certain new winds, the amount of carbon dioxide in the total return wind is not necessarily high, and can be used to reduce the total new air volume. ASHRAE标准62—1989只回答了如何确定总新风量问题。可是，对于变风量系统，送入房间的风量是变化的，房间的新风量必然也是变化的，新风的问题就更加突出了。所以，在新风要求很高的场合，可能要单独敷设新风道。这样，风道占用建筑的空间就要增加了。 ASHRAE standard 62-1989 only answered how to determine the total new air volume problem. However, to change the wind quantity system, the wind quantity that send room is changed, the new wind quantity of room also must be change, the problem of new wind is more outstanding. As a result, there may be a new wind in the new wind. In this way, the space of the wind tunnel occupies the building to increase. 所以，变风量系统中，新风主要存在三方面的问题：总新风量的控制，总新风量的确定和新风的分配。 Therefore, in the system of variable air flow, the new wind has three main problems: the total new air volume control, the determination of the total new air volume and the distribution of the new wind.