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摘要：通过5个工程实例，探讨在供热空调系统中利用变速风机和变速泵代替调节用风阀水阀实现风和水系统的调节的可能性。分析表明，这样做可以节省运行能耗，同时改善系统的调节品质，系统的初投资一般也不会增加。水泵和风机能耗约占供热空调系统总能耗的40？这些能耗中的1/3左右被各种调节阀门所消耗，但这样大的代价并没有换来好的调节效果，反而导致系统中许多问题发生。采用变速风机和变速泵充当调节手段，可节省这部分能耗，并可解决许多调节中的困难。 关键词：变频调节 水系统 风系统 变速水泵 变速风机 1、引言 在暖通空调工程中，使用大量的风阀水阀对系统中的风量水量进行调整，使其满足所要求的工况。它们的调节原理是增加系统的阻力，以消耗泵或风机提供的多余的压头，达到减少流量的目的。因此这些调节阀的调节作用是以消耗风机或水泵运行能耗为代价的。目前暖通空调工程中愈来愈多地使用自动控制系统。为实现自控，许多风阀水阀还要使用电动执行机构。目前质量好的电动水阀价格为几千甚至上万元。电动风阀亦需要几千元。电动风阀水阀的费用常常占到自控系统总费用的40％以上。能否改变系统的构成方式，减少使用这些既耗能、又昂贵的阀门，用其它方式实现对流量的调节？风机水泵与风阀水阀是一一对应的两类调节流量的设备。风机水泵为流体提供动力，而风阀水阀则消耗流体多余的动力。因此，若用风机水泵代替风阀水阀，不是在能量多余处加装阀门，而是在能量不足处增装水泵或风机，通过调节风机水泵的转速，同样可以实现对系统的流量调节。此时由于减少了调节阀，也就减少了阀门所消耗的能量，因此会减小运行能耗。同时，目前可变转速的风机、水泵价格与相同流量的电动风阀、水阀价格接近，甚至更低，因此初投资也不会提高。从这一思路出发，本文先给出几个用泵代阀的例子，然后进一步讨论这一方案对暖能空调工程的意义及要注意的问题，以期引起大家的讨论。 2、实例分析 2.1 简单系统的流量控制 图1为一个简单的控制循环流量的系统，泵P提供动力以实现水通过阀V、管道及用户U间的循环。图2给出当阀全开、泵的转速n=n0时系统的工作点。此时，流量为G0，水泵工作效率为η0，即效率{zg}点。要使流量减小一半，一种方式是将阀门关小，使管网等效阻力特性曲线向左偏移，见图2。此时泵的效率降低至η1，压力升至p1。由于压力升高，效率降低，因此尽管流量减少至一半，泵耗仅减少20％～30％，此时除阀门以外的管网部分由于其阻力特性不变，因此仅消耗压降p0/4，剩余部分3(p0+(p1-p0))/4均消耗在阀门上，它消耗了此时泵耗的80％，这就是为什么说调节阀消耗了大部分水泵能耗的依据。此外，水泵工作点偏移造成的不稳定、阀关小后大的节流和压降引起的噪声，都对系统有不良影响。 若保持不变，但将泵的转速降至50％，图2同时给出此时的工作状况，这时管网的阻力特性曲线不变，泵的工作曲线下移，泵的工作效率仍将为η0，压力p2为p0/4。这样，减少流量后泵耗仅为原来的1/8，具有极显著的节能效果。同时，由于泵的工作点及阀的位置均未变，因此系统工作稳定，且不会有节流噪声。 此简单例子说明： (1) 当调节阀产生调节作用时，将消耗其所在支路的大部分流体动力。并且由于改变了管网阻力特性，使管网中的动力机械工作点偏移，在多数情况下这将导致效率下降。 (2) 当采用变速方式调节流量时，泵或风机能耗可与流量变化的三次方成正比。并且由于系统阻力特性不变，泵或风机的工作点不变，因此效率不变，泵、风机及系统均可稳定地工作。 (3) 以调整泵或风机的转速来调整流量应该是流量调节的{zh0}手段。 2.2 供热水网 图3为一简单的供热水系统。当各用户要求的资用压头相同时其水压图见图4中实线。 图中虚线以下部分为用户所消耗的资用压头，而虚线以上部分则为阀门所消耗。若系统设计合理，泵选择适当，则最远端用户处的余压恰好为它所需要的压头，阀V5全开，不多消耗能量。此时，若各用户流量相等，彼此距离相等，主干管上比摩阻相同且忽略阀门全开时的阻力，对于n个用户，阀门V1消耗的能量与用户外管网所消耗的总能量的百分比EV1为： EV1＝(1/n)×((n-1)/n) 第k个阀门所消耗能量与用户外管网总能耗的百分比EVk EV1＝(1/n)×((n-1)/n) 前n-1个阀门共消耗的能量为： 当热用户个数足够多时，（n－1）／(2n)约等于50％，也就是消耗在外网的能耗约有一半被各支路的调节阀所消耗。一般用户侧真正需要的扬程仅为循环泵扬程的20％～30％，即外网消耗70％～80％。因此，总泵耗的35％～40％的能量被调节阀消耗掉。有时为安全起见，循环泵的扬程还要选大些，然后再通过图3中的阀门V0将多余部分消耗掉。由此使一般供暖用热水网中调节阀消耗一半以上的泵耗。 若改用图5方式连接热水管网，在各用户处安装用户回水加压泵，代替调节阀，减小主循环泵的扬程，使其只承担热源及一部分干管的压降，用户的压降及另一部分干管压降由各用户内的回水加压泵提供，则其水压图见图6。 此时无调节阀，因此也无调节阀损失的泵耗，用户处各个回水加压泵的扬程应仔细选择。若选择过大，再用阀门降低同样会消耗能量。但如果安装变速泵则可以通过调整转速来实现各个用户所要求的流量，因此不再靠调节阀消耗泵耗，这样，尽管多装了许多泵，但运行电耗将降低50％以上。 在这种情况下，若各用户要求的流量变化频繁，整个系统的总流量亦在较大范围内变化，总循环泵也可用变频泵，并根据干管中部供回水压差（见图5、6中点A）来控制其转速，使该点压差维持为零，则系统具有非常好的调节性能与节能效果。分析表明，当采用如图3常规的管网方式时，若由于某种原因，一半用户关闭，不需要供水时，未关的用户水量会增加，{zd0}的流量可增加50％以上，而同样的管网采用图5的方式，并且对主循环泵的转速进行上述方式的控制，则同样情况下未关闭的用户的水量增加{zd0}的不超8％，系统的水力稳定性大为改善。此方面的进一步详细分析见文献[1]，这一方案准备在已开始施工的杭州热电厂冷热联供热网中使用，各用户为吸收式制冷机、生活热水用换热器，冬季则为建筑供暖及生活热水。分析表明，对于这种负荷大范围变化的系统，采用这种方式，比常规方式节省泵的电耗62％，并改善了系统的水力稳定性。同时还使整个系统压力变化范围减小，从而可降低管网承压要求，处长管网寿命。在各用户处安装调速泵所增加的费用基本上可以从各用户省掉的电动调节阀及节省的用电增容费中补齐，因此总投资可以不增加甚至有所降低。 2.3 空调水系统 为减少水泵电耗，便于系统调节，许多系统采用两级泵方式，如图7。泵组P1可根据要求的制冷机的运行台数而启停，其扬程仅克服蒸发器阻力及冷冻站内部分管路的压降，泵组P2则克服干管及冷水用户的压降。为了节能，P2有时还采用变速泵，根据用户要求的流量调节泵的转速，调节规则是维持最远端用户处的供回水压差为额定的资用压头。文献[2]中指出，P2采用变速泵后，其能耗并非如厂商所宣传的那样“与流量的三次方成正比”。假设冷水用户所要求的{zd0}压降与干管{zd0}流量下的压降各占50％，例如均为5m，则泵组P2的转速就要按照使最末端压差恒定为5m来控制。假设各用户要求的流量均为{zd0}流量的50％，则各用户本身的调节阀都纷纷关小，此时末端压差仍为5m，干管流量降低一斗，故压降变为1.25m，泵组P2所要求的压降从原来的10m降至6.25m，流量虽降至一半，但泵的工作点左偏，效率降低，因此泵耗约为{zd0}流量时的45％左右，而并非按照三次方规律所预测的12.5％。造成这种现象是由于现象是由于各用户调节阀关小，消耗了多余的这部分能量。见图8。 此外，如果干管压降占P2扬程的一半，则如同上一例所分析，由于各用户远近不同，这部分泵耗的一半也被各用户的调节阀所消耗。并且空调系统为了改善其调节性能，还希望调节阀两侧压差占所在支路资用压头的一半以上。这样，平均估计，即使采用变速泵，泵组P2的能量中也有60％以上被各个调节阀消耗掉。 图9 为按照前一例的思路，将各调节阀改为变频泵，取消泵P2的新方案。图10a为按照这个方案运行，当制冷机要求的水量大于用户需要的水量时的水压图；图10b为用户要求的水量大于制冷机侧水量时的水压图。采用这种方式将不再需要调节阀，由图10可看出，对于大多数支路来说，供回水干管间是负压差，当某台空调机的水泵停止时，流量会自动成为零。改变用户处水泵的转速，可以很好地实现流量调节。由于不再安装任何调节阀，因此再没有调节阀所造成的损失。当流量减少一半时，用户水泵的工作点将略有偏移，但能耗仍可降低80％以上。当系统平均运行流量为{zd0}流量的70％时，可以计算出与采用变速泵P2的方式相比，各用户泵电耗的总工程和不足泵P2电耗的35％。 再分析这种系统的稳定性。当由于某种原因，一些用户关闭，一些用户调小，总流量降低50％时，干管压降减少，泵的转速未变化的用户的流量{zd0}增加幅度约为10％～20％，与泵的性能曲线形状有关。这时只要将转速相应地减少，即可维持原流量。采用这种方式，用各个小变频泵代替一组大变频泵，由于总功率降低20％～30％，因此价格不会增加。采用新方案后，还省掉各个空调机的电动调节阀，因此初投资将降低。 2.4 空气处理室 图11为常见的可变新风量的空气处理室。为了充分利用新风，希望能够通过调整3个风阀来改变新回风比，实现要求的送风参数。由于空气被排风机从房间抽回后，要经风阀A排至大气，因此点a处必须为正压，而外界新风又要经过风阀B进入空气处理室，因此点b处必须是负压。a、b两点间的压差将等于新风阀B和新风风道的压降与排风阀A和排风风道压降之和。若新风道新风阀和排风道排风阀的压降分别为100Pa则a、b间的压降为200Pa。这样大的压差仅依靠一个风阀C来调节很困难。因此，这样的系统实际上很难真正实现新回风比连续可调。由于3个风阀的位置不协调，使a、b两点间的压降很难保持不变，这样还导致实际的总风量随3个风阀的调整而变化，当全新风运行时，总风量有时可比最小新风时小10％以上。 根据风机代替风阀的思路，可以按图12的方式设计空气处理室。将原来的回风机改为可以变速的排风机。送风机F1克服空气处理室设备及送、回风道的阻力。点a处为负压，其数值为回风道的压降。单独调整新风阀B或排风机F2的转速，可改变a点的压力，从而改变室内正压度；同时调整F2的转速和阀A的开度，则可以准确地调整新回风比，而不影响总风量。图中的单向导流叶片用来防止新风进入后与回风混和，一部分由排风机排走，保证a处空气向b处流动，而无气流倒流的现象。当空调室的新风和排风道较长或断面较小、阻力较大时，采用这种方式还可以彻底解决图11方式的新风量难以增大的问题。只要新风风道的压降小于回风风道的压降，就可以实现从最小新风至全新风的连续有效的调节。 这一方式的缺点是：当回风风道阻力较大时点a负压降大，于是要求排风机F2即使在小风量时（如最小新风时）也要有较大的压头以克服点a处的负压。这与变转速风机的特性不一致。出于这一点，还可以采用图13的方式，用4台风机分别担当送风、回风、排风和送新风的任务。这时，图中的点a处压力与大气压相同，送风机克服送风风道及空气处理室设备的阻力，回风机F2克服回风道的阻力，排风机F3和新风机F4可以为一台电机连接同步运转的变速风机。改变其转速即可改变新风与回风比。此时的新回风比严格与F3、F4的转速成正比。房间正压度可用设在回风风道或送风风道上的风阀来调节，调好后总送量量将维持不变。新回风比则xx由F3、F4的转速决定，它们的改变对总风量及房间内压力无任何影响。 图13方式虽然安装了4台风机，但实际的运行能耗反而小于图11的常规系统及图12的双风机系统。这是由于它不再有常规系统中混风阀C和图12系统中的新风阀节流能耗。与常规系统相比，在全新风时，图13中风机F4与F1的压力之和与常规系统的送风机压力相同。这样，图13中4台风机的电机功率应与同样风量常规系统两台风机的电机功耗不变，而图13系统的F3、F4低转速运行，功耗降低。对图12所示系统而言，如果新风风道及排风风道阻力与图13相同，则{zd0}新风时，二者能耗相同，而当最小新风时，图12的排风机为了将空气从a点附近的负压区排至室外，仍需用提供较高压头，使得工作点偏移，效率下降，而图13中点a永远为零压，F3、F4工作点不变，最小新风时能耗要低些。 2.5 变风量空调系统（VAV） 采用变风量空调系统，在每个房间送风口装VAV末端装置，根据房间温度调整末端装置内风阀的开度以改变房间的送风量，从而满足各房间不同的环境要求，适应各房间的热负荷变化。图14为这种变风量系统的原理图。 为了使总风量也能相应变化，总的送排风机亦采用变频风机，并根据最末端风道内的压力调整转速，保证各VAV装置有足够的资用压头。一些工程人员及研究者认为[3]，这样做当最末端仅需要一部分风量时，VAV装置需要关小，而风机转速不会随之降低，导致各VAV装置都关小，而风机转速不会随之降低，导致各VAV装置都关小，风机能量很大一部分都消耗在风阀上，建议将参考测压点前移至距末端1/3总长度处。这样做有时在各房间均希望大风量送风时，末端又不能保证足够的压头。并且，如同前面讨论的那样，风阀的目的是调节风量，要使其具有良好的调节特性，就需要使它的压降占支管总压降的较大比例。而这就必然增加风阀所消耗的能量，同时还增加了由于风阀两侧压降形成的噪声。此点再怎样通过改变控制方式也难以彻底改善。按照风机代替风阀的思路，在末端装置中用风机代替风阀，调节风机转速以调整风量，就可以彻底解决这一问题。 图15为这种方式的系统原理图，其中为便于分析画为双风机系统，实际上，空气处理可采用上例中的多风机方式。主送风机仍采用变速风机，但它仅承担空气处理室及一部分风道的压降，其转速可以根据主送风道内接近{dy}个送风口处（点Q）的静压来控制，维持该点压力为大气压，从该点至各房间的压降由末端装置内的风机来承担。某个房间送风口内风机停止时，由于送风道内为负压，因此逆止阀自动关闭。风机开启后，房间送风量随风机转速增加而增加，并以接近于线性的规律变化。由于xx了各VAV装置中调节风阀的能耗，因此可以计算出各风机总能耗比原来的送风机降低10％以上。此种小功率变频器和风机的价格与电动风阀基本相同，而系统的调节性能则大为改观。 3、结论 本文通过暖通空调工程中的5个例子说明采用变速风机、水泵替代部分调节用风阀、水阀的方法及其优点。从上述的简单分析中可以看出，采用这一方式既可获得较大的省能效果，又可以改善控制调节效果，增加的初投资也不会太大。因此应该是一种值得注意和考虑的新方式。 调节阀的作用是增加阻力，以消耗多余部分压头，实现调节流量的作用，调节阀所消耗的压力占总的压力损失比例愈大，调节性能愈好。这样，要获得调节性能与能耗成为一对不可兼顾的矛盾。采用变速风机或变速泵充当调节装置，是通过减少向系统投入的能量来减少能量，这就有可能通过合理的系统结构设计来达到好的调节品质，而不增加能耗，同时获得节能和调节性能好的效果。 工程设计必须考虑富余量，以保证在实际情况发生各种变化时系统仍可达到要求的参数。在实际运行时，为了xx这些富余量，又要靠阀去调整，由此造成浪费。采用变速泵或变速风机设计时也留有富余量，但在运行时不是靠阀而是靠降低转速来xx这些富余量。转速降低后电耗减小，因而这些富余量并未消耗掉，避免了浪费。 常规方式下选择风机或水泵时，扬程必须按照最不利支路选择，由最远支路或用户要求资用压头{zd0}的支路来确定。这一支路的流量可能仅为系统总流量的很小一部分。为了这一小部分流量选用大扬程，其它流量也只好通过泵或风机来达到同样的扬程，再由阀门消耗，既造成调节的困难，又浪费能量。用变速风机或水泵代替调节阀，每个支路所要求的扬程由该支路的风机和水泵单独解决，不是统一加大后再分别消耗掉，而是哪里需要多少哪里局部加多少。这样自然就获得了好的调节效果和节能效果。 泵和风机所耗能源在暖通空调消耗的能源中占很大部份，供暖运行能耗的15％～25％为水泵电耗（按价格计算），空调运行能耗35％～45％为风机水泵能耗。在这部分风机水泵能耗中，40％以上又被各种调节阀门所消耗，采用本文讨论的方式，有可能将调节阀所消耗能量的很大一部分节省下来，因此这一方式有重要的节能意义。 采用这一方式，由于所要求的系统流动状况、流量分配方式等都不变，因此风道、水管的设计可以不变，但系统的压力分布有很大变化，在选择这些局部支路的变速风机、变速泵时，要仔细计算，使其压力{yl}量曲线与系统的要求相匹配。从而保证在不同的运行工况下，这些泵或风机的工作点仅在允许使用的范围内变化。 在用户支路上增加了这么多的动力设备，是否会降低系统的可靠性，增加维修工作量？目前较容易找到高质量的风机水泵，可以长期无故障运行。还有些分档变速的水泵，通过改变绕阻来改变转速，价格低，可靠性高。相反，目前电动风阀、水阀的可靠性低于风机、水泵，是暖通空调系统中故障率{zg}的设备之一。因此，将阀改为泵或风机后，可靠性应有所增加。在一些关键部位，还可加装备用风机和备用泵，故障时可及时转换。

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原文：
Abstract: The five engineering examples to explore the use of heating and air conditioning system, variable speed fans and variable-speed pumps to replace air conditioning with air valve and water valve to achieve the possibility of regulating the system. Analysis shows that doing so can save energy consumption, while improving the quality of the system regulating the system generally does not increase the initial investment. Water pump and fan energy consumption, heating and air conditioning system's total energy consumption accounts for about 40? The energy consumption in the 1 / 3 has been consumed by a variety of adjustable valves, but such a high price, and there is no regulation in exchange for good results, but cause the system to many problems. Using variable-speed fans and variable-speed pumps to serve as means of regulation can save this part of the energy consumption, and can solve many difficulties in the regulation. Key words: frequency-conditioning water system, air system variable speed fan pump 1 Introduction In the HVAC engineering, the use of a large number of air valve in the air valve on the system to adjust the amount of water to meet the required conditions. Their principle is to increase the system regulating the resistance to drain the pump or fan to provide extra pressure head, to reduce the flow of goals. Therefore, the regulating role of the regulating valve or pump operation is based on consumption of fan energy consumption for the price. HVAC engineering is currently more and more use of automatic control system. To achieve self-control, and many would also like to use the wind valve valve actuator. The current price of good quality electric valves for the several thousand or even million. Electric air valve also need a few thousand dollars. The cost of electric air valve water valve automatic control system is often accounted for over 40% of the total cost. If they change the composition of the system approach to reduce the use of these both energy-consuming and expensive valves, using other means to achieve the regulation of traffic? Fan pump-one correspondence with the air valve is a valve regulating flow of two types of equipment. Fan powered water pump for the fluid, while the air valve excess flow valves are power consumption. Therefore, if the water pump with the fan instead of air valve valve, not in excess of energy at the valve installed, but installed by the energy deficiencies in the pump or fan, water pump by adjusting the fan speed, the same can be achieved on the system of traffic regulation. At this time due to a decrease of regulating valve, thus reducing the energy consumed by the valve, thereby reducing energy consumption. The same time, variable-speed fans, pumps the price with the same flow of electric air valve, valve prices close to or even lower, it would not raise the initial investment. Proceeding from this idea, this paper first gives a few examples of pumps on behalf of the valve, and then to further discuss this program works on the warm air can be the meaning and pay attention to the issue in order to raise the discussion. 2, Case Study 2.1 The simple system of traffic control Figure 1 shows a simple control loop flow system, pump P to provide power in order to achieve the water through the valve V, pipelines and user inter-U cycle. Figure 2 shows when the valve fully open, the pump rotational speed n = n0 the system operating point. At this point, flow G0, pump efficiency for η0, that is the highest point of efficiency. Make the flow reduced by half, one way is to valve off small, so that the equivalent resistance of pipe network characteristic curve to the left offset, shown in Figure 2. At this point the pump efficiency is reduced to η1, the pressure rose to p1. As the pressure increases, less efficient, so despite the flow reduced to half of the pump consumption is only reduced by 20% to 30%, except at this time other than the pipeline network part of the valve because of its resistance characteristics remain unchanged, so only the consumption drop p0 / 4 and the rest 3 (p0 + (p1-p0)) / 4 are all consumed by the valve on the pump at this time that it consumes 80% of consumption, which is why most of the pump control valve consumes energy basis. In addition, the pump operating point offset the instability caused by the valve off small and then big government spending and pressure drop caused by the noise, all have an adverse effect on the system. If it remains unchanged, but will pump speed reduced to 50%, Figure 2 also shows the status of work at this time, when the resistance of pipe network characteristic curve of the same, the pump working curve down, the pump efficiency will continue to To η0, the pressure p2 to p0 / 4. In this way, reduce the flow of consumption after the pump is only the original 1 / 8, with a very significant energy-saving effect. At the same time, due to the pump operating point and the location of valves were not changed, so the system work stable, and do not have throttling noise. This simple example shows: (1) When a regulatory role of the regulating valve, it will consume most of their fluid dynamics in the slip. And because of changes in resistance characteristics of the pipe network, so that pipe network in the power machinery operating point offset, in most cases this will lead to reduced efficiency. (2) When using variable-speed mode adjust flow, pump or fan flow of energy can change is proportional to the cube. Resistance characteristics and because the system remains unchanged, pump or fan operating point remains unchanged, so the efficiency of the same, pumps, fans and systems can work steadily. (3) to adjust the pump or fan speed to adjust the flow rate should be the best means of regulating traffic. 2.2 Heating water network Figure 3 is a simple heating water systems. When the user requirements of the capital with its hydraulic pressure head relative to the same time, shown in Figure 4, solid line. The following sections map dotted line of the capital consumed by the user to use pressure head, while the dotted line above the valve element is consumed. If the system design is reasonable, select the appropriate pump, the most remote users at the residual pressure just as it needs pressure head, valve V5 fully open, no less consumption of energy. At this point, if the flow of each user equal to the distance to each other equal to the same trunk pipe and neglect than the friction resistance when the valve fully open, for n users, the valve V1 and the users who consume the energy consumed by the total pipe network The percentage of energy EV1 as follows: EV1 = (1 / n) × ((n-1) / n) K-valve first amount of energy consumed outside the pipe network with the user a percentage of total energy consumption EVk EV1 = (1 / n) × ((n-1) / n) N-1 before the valves of the energy consumed is: When the number of heat users enough for a long time, (n-1) / (2n) approximately equal to 50%, that is, outside the network, power consumption of about half of each branch of the control valve consumed. The average user really need to lift side circulation pump head is only 20% to 30%, which is outside the network consumes 70% ~ 80%. Therefore, the master cylinder consumption of 35% ~ 40% of the energy consumed by control valve. Sometimes, for security reasons, circulation pump head even bigger selection, and then by Figure 3, the excess part of the valve V0 consumed. Thus the general heating networks with hot water control valve of the pump consumes more than half of consumption. If the switch to Figure 5 connected hot water pipe network, in all the user to install the user backwater pressure pump, replace the valve, reducing the main circulating pump of the head, so that they bear only part of the heat source and dry pipe pressure drop, the user The pressure drop and another part of the trunk mains pressure drop within a backwater by the user to provide pressurized pump, its pressure diagram shown in Figure 6. At this point no control valve, and therefore no loss of control valve pump consumption, the user at every backwater pressure pump head should be carefully selected. If you choose too large, then the valve will reduce the same amount of energy consumed. However, if the installation of variable speed pumps can be achieved by adjusting the speed required by each user traffic, it is no longer rely on consumption of pump control valve consumption, so that despite the many has a lot to pump, but it will reduce power consumption to run more than 50%. In this case, if the flow of the user requirements change frequently, the total flow of the entire system is also in the larger context of change, with a total circulation pump can also be used pump-and, based on supply and return water pipe for the central pressure (see Figure 5 , 6 mid-point A) to control its speed, so that the point of pressure to maintain zero, then the system has a very good regulating performance and energy-saving effect. Analysis shows that when using the conventional pipe network in Figure 3 way, if for some reason, half of the users off, no water supply, no water will increase the user off, the largest increase the flow of more than 50%, while the same pipe network approach using Figure 5, and the speed of the main circulating pump to control the manner described above, then under the same conditions did not increase the amount of water off the user's largest does not exceed 8%, the system's hydraulic stability greatly improved. In this regard and further detailed analysis, see [1], this program has begun preparing hot and cold thermal power plant construction in Hangzhou, the use of associated heating network, the user-absorption chiller, hot water with heat exchanger, in winter for building heating and hot water. Analysis shows that this kind of load changes in large-scale systems, using this approach than the conventional methods to save the pump power consumption 62% and improve the hydraulic stability of the system. It also changes the scope of the entire system pressure decreases, thereby reducing pressure pipeline network requirements, Director of pipe network lifetime. In each user to install speed pump is basically the cost of the additional users can be saved from the electric control valve and the savings in electricity capacity increase fees padded, so the total investment may not increase or even decreased. 2.3 The air conditioning water system In order to reduce pump power consumption, easy system adjustment, many systems use two pumps manner shown in Figure 7. Pump group P1 in accordance with requirements of the operation of chiller units and the number of start and stop, its head only to overcome the resistance and refrigeration evaporator station in charge of the road within the pressure drop, pump group P2 is to overcome the dry pipe and cold water pressure drop users. For energy-saving, P2 and sometimes also uses variable speed pumps, according to user requirements regulating the flow of pump speed to regulate the rules is to maintain the most remote users to office supply and return water pressure as the nominal capital with the pressure head. [2] pointed out, P2 with variable speed pump, its power is not, as promoted by vendors as "and the flow rate is proportional to the cube." Assume that users demand, the largest cold-water pressure drop and dry pipe under the maximum flow pressure drop 50 percent each, for example, are 5m, then the pump group P2 so that the most speed we must follow the end of the constant pressure to control for 5m. Assumed the flow of user requirements are 50% of maximum flow, then each user have their own control valve is closed is small, the end of this time pressure is still 5m, dry pipe flow to reduce a bucket, so drop into 1.25m, P2 pump group required pressure drop from the original 10m down to 6.25m, although traffic fell by half, but the pump's operating point the left side, efficiency, and so the maximum flow when the pump consumption is about 45%, while not in accordance with cubic law predicted 12.5%. This phenomenon is due to the phenomenon is due to the user to adjust the valve closed small, consume excess energy of this part. Figure 8. In addition, if the dry pipe pressure drop accounts for half of P2 head, then, as the case of the analysis, due to various users near and far, this part of the consumption of half of the pump was all consumed by the user's control valve. And air-conditioning system in order to improve its regulatory functions and, we hope both sides of the differential pressure regulating valve where the slip-funded account for more than half with the pressure head. In this way, the average estimate, even with variable speed pump, pump group P2 also has the energy of more than 60% was consumed by the various regulating valve. Figure 9 is an example of the former idea, would be replaced by the pump-control valve to remove pump P2 of the new program. Figure 10a in accordance with the program running, when the refrigerator is greater than the amount of water required amount of water when the user needs to pressure diagram; Figure 10b is greater than the amount of water required for the user-side refrigerator water when the pressure diagram. Such an approach will no longer be necessary to readjust the valve, can be seen from Figure 10, for most of the slip road, the supply and return water is a negative pressure difference between the dry tube, air conditioning units when a pump stops, traffic will automatically become a zero. To change the user at the pump speed, flow control can be achieved well. No longer install any control valve, control valve, therefore there is no damage caused. When the flow rate reduced by half, the user water pump working point slightly offset, however, can reduce the energy consumption over 80%. When the system is running an average flow of 70% of maximum flow can be calculated with the use of variable speed pump P2, as compared to all users pump power consumption less than the total project and the pump P2 power consumption of 35%. And then analyze the stability of the system. When for some reason, some users off, some users transfer is small, the total flow decreased by 50%, the dry pipe pressure drop reduction in pump speed did not change in the user's largest ever increase in traffic by about 10% to 20%, and pump The shape of the performance curve. Just then a corresponding reduction in speed, you can maintain the original flow. In this way, using various small pump-pump-instead of a group of large, because the total power reduced by 20% to 30%, so the price will not increase. After the introduction of new programs, but also dispense with the various air-conditioning electric control valve, so the initial investment will be reduced. 2.4 Air Handling Room Figure 11 is a common variable volume of outdoor air-handling room. In order to take full advantage of new wind, hoping to by adjusting the three new air return air valve to change the ratio of parameters to achieve required air supply. As the air is exhaust machine, after withdrawing it from the room, it is necessary to the atmosphere through the air valve A row, it must be a pressure point of a Department, while the outside fresh air but also through the air valve B into the air handling room, so point b Department must be negative pressure. a, b of the pressure difference between two points will be equal to the new air valve B and the new air damper Road A pressure drop and exhaust valves and the exhaust duct pressure drop combined. If the new new air valve and the exhaust duct Road exhaust valve pressure drop 100Pa respectively, while a, b between the pressure drop of 200Pa. Such a large differential pressure is only on an air valve C is difficult to regulate. Therefore, such a system was actually very difficult to really achieve the new air return than continuous variable. Because the location of three air valve uncoordinated, so that a, b the voltage drop between two points is difficult to remain unchanged, this has also led to the actual total air volume adjustment with three air valve change, when new wind run, the total Airflow is sometimes smaller than the minimum fresh air when more than 10%. According to the idea of fans instead of air valve can be designed in a manner according to Figure 12 air-handling room. Back to the original speed of the exhaust fan can be replaced by machines. F1 blower to overcome the air-handling room, and send, return duct resistance. Point of a Department to negative pressure, its value as a return air duct pressure drop. Individually adjust to the new air valve B or F2 Exhaust Fan speed can change a point of pressure, thus changing the interior pressure degrees; simultaneously F2 speed and valve A of the opening, you can accurately adjust to the new return air ratio, rather than affect the total air volume. Figure in the one-way diversion is used to prevent new air into the leaves after the return air mixed, in part to drain away from the exhaust fan to ensure that a Department of air flow to the b Department, without air back phenomenon. When the air-conditioned room fresh air and exhaust Tao longer or a smaller cross-section, the resistance is large, this approach can also solve the mode of Figure 11 increase the volume of outdoor air is difficult problem. Long as the new air damper pressure drop is less than the return air damper Tao Tao pressure drop can be achieved from a minimum fresh air to the fresh air of the continuous and effective regulation. The disadvantage of this approach: When the return air damper airway resistance point in a negative pressure drop greater large, was required to exhaust plane F2, even in a small air volume (for example, the minimum fresh air time) must also have a greater pressure head to overcome the point of a Department of the negative pressure. This is inconsistent with the characteristics of variable speed fan. For this point, you can also use Figure 13 ways to play with 4 Typhoon aircraft were air supply, return air, exhaust air and sending a new task. At this time, the figure of the point of a pressure and atmospheric pressure at the same blower to overcome the air supply duct and air handling room equipment, resistance, back to F2 blower to overcome the resistance return air duct, ventilation machines F3 and F4 of new fans for a motor variable-speed fans to connect in synchrony. To change its speed can change the new wind and return air ratio. This time a new return air than strictly with the F3, F4 is proportional to the speed. Degree of available rooms located in the back pressure air damper Road or the blast of the air valve to regulate air paths, after a good tune to send the amount of the total volume will remain unchanged. The new return air than is entirely up to F3, F4 speed decisions, and their change of the total air volume and pressure of the room without any impact. Figure 13 means that even properly installed four Typhoon aircraft, but the actual energy consumption rather than the conventional system and Figure 11 Figure 12 dual-fan system. This is because it is no longer a conventional system, mixed with air valve C and Figure 12 the system of the new air valve throttle energy. Compared with conventional systems, in the fresh air, the graph 13 in the F4 and F1 fan and with the pressure of the blower pressure on conventional systems the same. In this way, Figure 13 in the four Typhoon aircraft electrical power should be with the same volume of conventional systems of two air fan motor power consumption remains unchanged, while the Figure 13 system, F3, F4 low-speed operation, lower power consumption. On the system as shown in Figure 12, if the new air damper Road and exhaust air duct resistance and Figure 13 the same as the maximum fresh air, the two power consumption the same, and when the minimum fresh air, the Figure 12 machine in order to exhaust the air from the a negative pressure near the area to the outdoors, still need to use a higher pressure head, making the working point offset, reduced efficiency, while Figure 13 is always the midpoint of a zero pressure, F3, F4 operating point remains unchanged, the minimum fresh air when the energy consumption should be lower. 2.5 Variable Air Volume System (VAV) Use of variable air volume air-conditioning systems installed in each room outlet VAV terminal unit, terminal unit according to room temperature within the air valve to adjust the opening degree to change the room's air supply to meet the environmental requirements of all the different rooms, adapted to the room heat load changes. Figure 14 for this variable air volume system schematic. In order to allow air flow can also be a corresponding change in the overall machine is also used to send exhaust fan inverter, and based on the most end of the pressure inside the air duct to adjust speed, ensure that all VAV device has sufficient funds to use pressure head. Some engineers and researchers believe that [3], this requires only a part of the end when the most amount of wind, when, VAV devices in need of small, but fan speed is not decreased, leading to the VAV devices are off small, but fan speed is not decreases, leading to the VAV devices are off small, fans are a large part of the energy consumed by air valve on the proposed move away from the reference pressure measurement point before the end of the 1 / 3 the total length of the office. This is sometimes in all rooms all hope that the amount of wind blowing, the terminal can not guarantee sufficient pressure head. And, as earlier discussed, the air valve is intended to regulate air flow, it is necessary to have good conditioning properties, it is necessary to drop it accounts for branch pipe of a large proportion of the total pressure drop. And this will increase the energy consumed by air valve, but also increase the pressure drop due to air valve on both sides of the formation of noise. This point no matter how difficult by changing the control mode overhaul. Fans instead of air valve in accordance with the idea, at the end using fans instead of air valve installed to regulate the fan speed to adjust the air volume, we can solve this problem. Figure 15 is a schematic diagram of this approach, which for ease of analysis painting a dual fan system, in fact, can be used on air handling cases in the multi-fan way. The main blower still use variable speed fans, but it is only a commitment to air-handling room and part of the air duct of the pressure drop, its speed according to the main air supply Road, close to the first outlet within the Department (point Q) of the static pressure to control and maintain pressure on the point for the atmospheric pressure, from that point to various rooms within the voltage drop from the terminal unit fan to bear. An outlet in the room when the fan stops, due to negative pressure within the blast Road, so check valve automatically closes. Fan is turned on, the room air supply with the wind machine speed increases and to close to a linear change in the law. Since the elimination of the VAV device adjustable air-valve power consumption, so you can calculate the total energy consumption of fan blower lower than the original 10%. Such low-power inverter and the fan is basically the same price and electric air valve, and adjust the system performance is significantly improved. 3, the conclusion In this paper, HVAC engineering five examples of using variable speed fan and water pump replaced part of the regulator with air valve, valve method and its advantages. From the above simple analysis can be seen, using this approach can achieve greater energy-saving effect, and also control and regulation can improve the effect of increasing the initial investment will not be too much. Should therefore be a noteworthy and consider new ways. The role of regulating valve is to increase the resistance to drain the excess part of the pressure head and realize the role of regulating flow, pressure regulating valve of the total consumed by the pressure loss ratio of the larger, better conditioning properties. In this way, adjust performance and power consumption to get a balance between a pair of non-contradiction. Using variable-speed fan or variable speed pump to act as conditioning, is by reducing the energy inputs to the system to reduce energy, which may be through a rational system architecture designed to achieve good regulation quality, without increasing power consumption, while access to energy conservation and regulation of performance, good results. Engineering design must take into account the amount of surplus to ensure that the changes that occur in real-time system can meet the required parameters. In actual operation, in order to eliminate these redundant capacity, but also rely on valves to adjust, thus resulting in waste. Use of variable speed pump or variable speed fan design also leave the surplus volume, but at run time does not depend on valve but by reducing the amount of speed to eliminate the surplus. After the speed to reduce power consumption decreases, and thus the amount of such excess is not consumed, avoiding waste. Conventional way, select fan or pump, the head must follow the slip road to choose the most disadvantaged, from the farthest branch or user requested it with the largest slip indenter to determine. The slip flow may be only a small fraction of the total system traffic. In order to use this small part of the flow of large head, the other flows have no choice but through a pump or fan to achieve the same head, and then consumed by the valve, both caused by the difficulties of adjustment, but also a waste of energy. Replaced with variable-speed fan or pump control valve, required by the head of each branch by the branch of the fans and pumps alone is not a uniform increase and then were consumed, but where they need to increase the number of where the number of local. This naturally was a good conditioning effect and energy saving effect. Pumps and fans of the consumption of energy in HVAC energy consumption account for a large part of the heating energy consumption of 15% to 25% of the pump power consumption (in prices), air-conditioning energy consumption of 35% ~ 45% energy consumption for the fan pump. In this part of the fan pump energy consumption, 40% or more was again consumed by a variety of adjustable valves, using methods discussed in this article, it is possible to control valve consumes a large part of the energy savings, so this approach has important Energy-saving significance. Using this approach, since the required system flow conditions, flow distribution are all the same, so air duct, water pipes designed the same, but the pressure distribution system, there are significant changes, the choice of these partial slip variable-speed fans, variable speed pumps, we should carefully calculated so that the pressure-flow curve and the system requirements to match. So as to ensure the different operating conditions, these pump or fan working point is only allowed to use the range. An increase in the user support on the road so much power equipment, would reduce the reliability of the system, increase the maintenance workload? At present, more easy to find high-quality fan pump of long-term trouble-free operation. Also some sub-file speed of the pump around the resistance to change by changing the speed, low price and high reliability. On the contrary, the current electric air valve, valve lower than the reliability of fans, pumps, HVAC systems is the highest failure rate in one of the devices. Therefore, valves changed to pump or fan, the reliability should be increased. In some key parts, can also be fitted back fans and spare pumps, failure timely conversion.

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