1、1、 外文原文（复印件）VAV SYSTEM ANALYSISXue Zhifeng,Chen Feng and Jiang YiTsinghua UniversityBeijing+100084 ChinaxuezhfABSTRACTThere are two kind of supply fan rotation speed control methods , one is the static pressure control method, the other is the float pressure control method. Simulation shows that the
2、y have different working point along the whole year. The supply air fan controlled with float pressure control method need low rotation speed and works on high efficiency, so the float pressure control method need only 30% fan operation energy of the static pressure control method .The layout of the
3、 air duct may influence the fan control method.INTRODUCTIONAs the VAV system is getting popular in China, many problems are rising from the design, the operation as well as controls (Jiang 1997).According to investigation on several VAV systems in Beijing, the energy consumption changes in the range
4、 as large as between factors 1 to 1.5 due to different in design and control.The supply fan rotation speed control method is one of the important factor that influence the VAV systems energy consumption. There two kind of control methods, One is the static pressure control method, which is set a sta
5、tic pressure at the fan export or at one point on the supply air duct. The other is the float pressure control method, using this mehthod , the supply air fan pressure head is just eaquel to the resistance of the supply air duct. The float pressure control method need the communication of the VAV bo
6、x, so it is difficult to realize. Most of the VAV systems in the comercial buildings in Beijing are using static pressure control method. But some research work consider the float pressure control method should be used(Sun,1997).There are two kinds of supply air duct layout, one is the tree type, an
7、d the other is the looping type (Goswami 1986 and I. Khoo 1997).Different duct layout influences the operating effect of static and float pressure control method.These former researches on the VAV systems control method and air duct layout are combined with the controller(for example PID),and they o
8、nly give some qualitative result. To guide the operation of VAV systems, this pape compare the different fan speed control stratergy with fan pressure head, rotation speed, efficiency and opration energy according to simulations. And also comparing the simulation result of looping and tree duct layo
9、ut.Table 1 Information of standard floorFigure 1 is the drawing of a commercial building in Tianjin of China. The middle is the machinery room, the around are office rooms. Each standard floor includes outer space and inner space. The depth of office room is about 15 meter. There are 30 floors in th
10、is building altogether. Table 1 shows the information of the building(standard floor).The external wall of the whole building is glass curtain wall.THE SUPPLY AIR AMOUNT AND THESUPPLY AIR TEMPERATUREUsing simulation software DeST (Chen,1999 and Jiang 1991),based on the whole year weather data, we ca
11、n calculate the whole year cooling and heating load of the building. The VAV systems have a variable supply air amount, so the supply air temperature varied also. The optimal temperature is the most energy saving. Knowing the cooling load and the supply air temperature, then we can get the supply ai
12、r amount of the whole year.The whole year supply air volume of outer space shows in Figure 2,the max min and ave represent the maximum minimum and average supply air volume of the same day from 8:00 in the morning to 17:00 in the afternoon.Figure 2:Supply air volume of the whole yearIn winter and su
13、mmer, some rooms in the building (for example north rooms in summer and south rooms in winter)have the large cooling or heating load of the all rooms, but the load of other rooms are little. In order to satisfy the room in each orientation, the supply air temperature can not be too high in winter an
14、d too low in summer. Figure 3 shows the whole year supply air temperature, the highest temperature is 32 C, and the lowest is 16 C.In winter and in summer, the difference with the supply air and the room temperature can not be very large. Then the coldest room of the building will need very large am
15、ount supply air volume .In the spring and the autumn, the situation is different, the cooling load difference of all the rooms are very little, so the supply air volume is between the maximum and minimum. In spring and autumn, the outdoor temperatures are between winter and summer, so the supply air
16、 volume is smaller than winter and summer. So in winter and summer the whole buildings supply air volume gets the maximum values. In spring and autumn the supply air volume is betweenthe winter and summer.Picture 3:Supply air temperature of the whole yearFigure 4 shows the supply air volume of the s
17、outh and the east orientation rooms. The largest supply air volume appears at different date.Figure 4:Supply air volume of the south and eastrooms of the buildingIn the following paper, we will compares the differen fan speed control strategy and supply air duct layout of this building combined with
18、 the supply air volume simulation results.FAN CONTROL STRATEGY OF TREEDUCTPicture 5 shows the one type supply air duct layout of the building refers in above paragraphs.Where AHU is the air-handling unit,1,2,39,10 are supply air duct number.With the known supply air volume, using simulation method,
19、we can get the fan pressure head of the whole year.Figure 6 shows the fan working point with three different control strategies.Figure 6:Fan working point with different control strategy of tree duct layoutWhere float present the float pressure control method. Static presents the static pressure con
20、trol method with static pressure point setting at the fan export .The part-sta present the static pressure control method with static pressure point at two part of the whole supply air duct(in Figure 5,it is at the export of duct 6).Where G present the supply air volume, P present the fan pressure h
21、ead.According to simulation results, we can see running in the same air volume, three different kinds of fan speed control strategy need different pressure head. The float pressure control methods pressure head is the lowest, while the static pressure control method with the static pressure setting
22、at the fan export needs the highest pressure head. The method with static pressure point setting at the two-part of the whole supply air duct needs fan pressure head between the other two kind methods.Different fan working points have different running efficiency. Choosing one kind of centrifugal su
23、pply air fan, using simulation method can get the fan efficiency for each working point according to the relation between the air volume, pressure head and fan running efficiency.The fan performance curve and fan efficiency curve also show in Figure 6.They come from the next formulas.Where:P is the
24、fan pressure head.G is the fan supply air volume.is the fan efficiency.n0 is the design fan rotation speed.n is the variable fan rotation speedIn Figure 6,some fan working point locate in the high efficiency area, others not. The area include most of the point working with static pressure point sett
25、ing at two-part of the whole air duct, some of the point working with float pressure control method, and only little part of the point working with static pressure point setting at fan export .Figure 7 shows the percentage of the fan working point locating in the high efficiency area for three diffe
26、rent fan rotation speed control strategies.Figure 7:Fan efficiency distribution of different control stategyWith known fan working points and the fan performance curve, Using simulation method, we can also get the fan rotation speed. Figure 8 shows the whole years fan rotation speed with different c
27、ontrol strategies.Figure 8:Fan rotation speed with different control stratergyFrom Figure 8,we can see in winter and summer, the supply air fan controlled with three different methods all runs in high speed, it just because the supply air volumes are large in these two seasons. In spring and autumn,
28、 the situation is different.Fan working with the static pressure setting at its export has the highest rotation, next is the fan working with the static pressure setting at two-part of the whole air duct, the speed of the fan controlled with the float pressure runs in the lowest speed.Knowing the fa
29、n supply air volume, pressure head, efficiency and rotation speed, then we can use simulation to get the fan running energy of the whole year.How much difference between these three different control strategies? Figure 9 told us the answer. In Figure 9,the fan operation energy is only for the outer
30、space one floor of the building refers in above paragraphs.Figure 9 Fan energy with different control strategyThe float pressure control method consumes only 29.6%fan operation energy of the static pressure control method.This building have 30 floors altogether, so the float pressure could save 3500
31、00(kWh)fan energy comparing with the static pressure control method which sets static pressure point at fan export.FAN CONTROL STRATEGY OFLOOPING DUCTFigure 10 shows the other type supply air duct layout of the building refers in above paragraphs.The simulation results of the looping duct layout are
32、 similar with the tree duct layout.Figure 11 shows the fan working point of three different control strategies for looping duct layout.The fan efficiency of this looping duct is similar with the tree duct. In Figure 12,the static control method with the static pressure point setting at fan export an
33、d the float pressure control method have the large high efficiency percentage than the method setting static point at the two-part of the whole duct.Are there some difference between with the tree and looping duct layout? Figure 13 give us the answer. Using the float and part-static pressure control
34、 method ,fan energy of the looping duct layout is little than the tree duct, but using the static pressure control with the static pressure point setting at fan export, these two kind methods have the same energy consumption.Although the fan energy of tree or looping duct with the static pressure po
35、int settign at fan export is same, they have some difference. We research the fan energy using efficiency of these two duct layouts.The efficiency is defined in the following formula.Where E is the fan energy consumption of the whole year.Table 2 shows the fan energy using efficiency of tree and loo
36、ping duct layout. With the building refers in above paragraphs, the looping duct layout has the low efficiency than the tree duct layout. That is to say most of the fan energy was consumes at the terminal VAV box, so in this building, if the designer chooses the static control method, he should choo
37、ses the tree duct layout. This result is not always right ,it is related with the different project.Table 2: Fan energy using efficiency of looping or tree duct layout for static pressure control methodCONCLUSIONS1. Using simulation method can solve many problems for VAV system analysis.2. Three kin
38、ds of fan speed control strategy are different in fan pressure head, fan rotation speed, fan running efficiency and fan operation energy.3.The static pressure control method with static pressure point setting at the fan export implement easily, but when the supply air volume decrease, the fan pressu
39、re head will much larger than the VAV system needs, this part surplus energy becomes the terminal noise. This kind of method isnt a good method. When the static pressure point move from the fan export to the two-part of the whole supply air duct, the situation become better, but there are also surpl
40、us fan energy.4.The most energy-saving fan speed control strategy is the float pressure control method. It only consumes 30%fan operation energy of the static pressure control method.5.With the same control method, the different air duct layout may influence the fan energy consumption and the fan en
41、ergy using efficiency.6.VAV systems researcher should find some manners to help the float pressure control method step into the practical application.REFERENCES1. Jiang Yi, Computer aided monitoring and control slystem in HVAC(Part 2):Monitoring and control of air conditioning systems. Heating, vent
42、ilating& Air Conditioning. June 1997,Vol.27,No.115.2. Sun Ning, Li Jisheng and Yan Qisen, Some issues in design of variable air volume systemes. Heating, ventilating&Air Conditioning. October 1997, Vol.27,No.118.3.Goswami Dave.VAV Fan Static Pressure Control with DDC. Heating/Piping/Air Conditioning
43、, Dec 1986.4.I.Khoo,BEng(Hons),G.J.Levermore, Duct Loops and VAV Modelling and Control. CLIMA 2000, conference proceedings,1997,Brussals.5.Y.Jiang, State space method for the calculation of air-conditioning and the simulation of thermal behavior of the room .ASHRAE Transaction 1991,88(2);122-132.6.C
44、hen Feng, Jiang Yi. Introduction of Designers Simulation Toolkit(DeST).BS99,1999,Kyoto.2、外文资料翻译译文变风量空调系统分析薛志峰，陈峰和江亿清华大学中国北京 100084xuezhf摘要 有两种送风机控制方法,一是定静压控制法,另一个是变静压法。仿真研究结果表明,在一年中他们有不同的工作点。变静压控制法仅需要很低的转速即能达到较高的工作效率,所以变静压控制法下风机运行所消耗的能量只是定静压控制法下运行所耗的30%。空调风管的布局可能影响风机控制方法。简介随着变风量空调系统在中国变得越来越流行,其设计，生产
45、操作和控制方面也开始出现许多问题（江1997）。根据对北京的几个变风量系统的调查研究发现，由于设计和控制的不同，能源的消耗在1到1.5倍的大范围内波动。送风机控制的方法是影响变风量空调系统能耗的重要因素之一。有两种类型的控制方法,一是定静压控制法,它是在风机出口或在送风风管的一个点上设定一个静压。另一个是变静压控制法,使用这种方法时,电源风机压头只是等同于风管送风的阻力。变静压控制法需要变风量空调箱的耦合,所以很难实现。北京的商业建筑物中大部分的变风量空调系统正在使用定静压控制法。但是一些研究工作认为变静压控制法应该被推广应用 (孙,1997)。有两种送风管道布局方式，一种是树类型，另一种是循
46、环式（哥斯瓦米1986年和邱一1997年）。不同的管道布局会影响定静压控制法和变静压控制法的运行效果。这些以往对变风量系统控制方法和通风管道的布局的研究均与控制器（例如PID）相结合，他们只得出了一些定性的结果。 为了引导变风量系统的运作，本文依据仿真模拟比较了不同送风机控制模式下风机压头，旋转速度，效率还有运行耗能。也对树类型和循环式管道的仿真模拟的结果进行了比较。表1：标准层信息时间段空调系统运行的空调系统运行的时间段系统设置预设工作点所需新风量设备单人所占空间照明空调区域图1：标准层图1是一个在中国的天津的商业大厦的建筑图纸，中间是放置机械装置的空间,周围是办公的空间。各标准层包括外层空
47、间及内层空间.办公空间深度约为15 米.这栋大楼一共30层.表1显示了建筑物（标准层）的信息。整个建筑外墙是玻璃幕墙。送风量和送风温度运用数值仿真软件DeST(陈、1999和江1991年),基于全年天气数据,我们可以计算出建筑物整整一年的制冷和加热负荷。变风量空调系统的送风量可变，送风温度也可变.最佳送风温度可最节省能量.知道了空调的冷负荷和送风温度，我们就可以得到全年送风量。图2显示了外层空间全年的送风量，最大值，最小值，还有同一天内从早晨8:00到下午17:00的最大、最小和平均送风量的代表曲线。日期送风量图2：全年送风量在冬季和夏季,建筑物内的一些房间（例如夏季朝向为南的房间和冬季朝向为
48、北的房间），这些房间都有大量的冷负荷或热负荷，但是其他房间的负荷都很小。为了满足各个朝向的房间，送风温度在冬季不能太高且在夏季不能太低。图3显示了全年的送风温度，最高的温度是32摄氏度，最低的是16摄氏度。在冬季和夏季,送风温度和室内温度之间的差异不能太大。因此建筑物内最冷的房间将需要非常大量的送风量。在春季和秋季,情况则不同,所有房间的冷负荷差异非常小,因此送风量在最大值和最小值之间。在春秋两季的时候,室外温度介于夏季和冬季的室外温度之间,所以送风量小于冬季和夏季的。因此在冬季和夏季整个建筑物的送风量得到了最充分的应用。在春季和秋季送风量介于冬季和夏季之间。日期 温度 图3：全年送风温度图4显示了南方和东方朝向的房间的送风量。最大的送风量出现在不同的日期。日期送风量
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