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动态平衡阀门在暖通空调工程中的应用

(2009-03-14 08:39:44)
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杂谈

      随着我国国民经济的高速发展,城市的建筑建设规模越来越大,人们对室内环境的要求也越来越高。尤其是建设在黄金地带的商业建筑,如何能提高有效的商用面积率:保证空调系统的使用和运行并不由此而增加能耗?是暖通专业及建筑开发商共同关注的问题。
  一、暖通空调设计中水力系统的现状
  无论是空调或采暖工程中,由于条件的制约及不可能完全采用同程系统。而异程系统在实际的设计中,为了保证系统最不利环路末端的资用压头,所有其他空调采暖设备末端的资用压头往往大于设计工况的需要值,特别是在规模大建筑功能复杂的工程中,异程管线长,末端设备的阻力差异大及空调末端启停差异大的系统,在靠近冷热源位置的资用压头余量过大,往往出现流量分配偏离设计状态,导致其系统水力失调。流量的偏差会产生冷热源近端的空调太凉或采暖不热的现象。不但不能保证使用的功能,还造成了能源上的浪费。
  二、解决水利失调的办法
  1、加节流孔板
  在热力入口或空调靠近冷源环路的部分管段上增加节流孔板。采用这种办法解决水力失调的前提是:水系统阻力计算准确、热力或空调末端流量不能发生变化。因此在末端流量变化时仍会造成水力失调及能源上的浪费。
  2、安装手动调节阀
  对大型空调系统而言,采用手动调节阀调节过程复杂,手动调节前端阀门,后端流量会受影响。后端调整流量,前端流量又会变化。因此调节费时费力;对于复杂系统,要求调节阀门的工程师经验丰富。并且一旦系统压力或负荷发生变化仍需要重新调整水力系统。
  3、安装动态流量平衡阀
  热力入口或空调设备末端的设计流量确定后,根据流量及阀门处的压力变化范围选定动态平衡阀,安上设置好的阀门既可使用。只要阀门处的压差变化在阀门的设计压力范围内,无需任何人为的调节。
  三、动态平衡阀的特点
  1、动态平衡阀的工作原理:
  通过改变平衡阀的阀芯的过流面积来适应阀门前后的变化,从而达到控制流量的目的。动态平衡阀是一个局部阻力可以变化的节流元件,对于不可压缩的流体其简化流量的方程为:
  Q=KA(△P)
  式中:Q——通过平衡阀的流量;
  K——阀门开度的流量系数;
  A——阀芯的过流面积
  △P——阀门进出口压差
  由于在阀门的开度不变的前提下,K值的变化可忽略,因此阀门的流量要保持恒定应控制A(△P)不变。
而平衡阀由可变过流面积的阀胆和高精度(±5%)的弹簧及支撑装置构成。弹簧受压差的作用自动控制阀胆上过流面积的大小,从而使通过阀门的流量恒定。
  2、阀门的工作过程:
  当平衡阀前后压差小于最小启动压差是弹簧未被压缩,流通面积最大。当阀门前后压差在工作范围时阀胆压缩弹簧,进入工作状态,水流通过阀胆两边的圆孔和几何型的通道流过;由于阀胆在运动,两边几何流型的通道也因此变化—阀体的流通面积不断变化,在这一压差范围内水流流量基本保持恒定。当平衡阀前后压差超越工作范围是,阀胆完全压缩弹簧,水流只从阀胆两边的圆孔流过,此时阀胆变成了固定的调节器,流量与压差成正比,随压差的增大而增大。 

With the rapid development of China's national economy, the city more and more large scale building construction, the interior environment of increasingly high. In particular, are building at Golden Strip commercial building, how can we improve the effective rate of the business areas: air-conditioning system to guarantee the use and operation is not the resulting increase in energy consumption? HVAC professional and are building developer issues of mutual concern.

First, the design of hydraulic HVAC system status quo

Whether it is air-conditioning or heating project, because of conditions and can not be completely the same way system. Vary-way system in the actual design, in order to ensure the most disadvantaged end of the funding loop with pressure head, all other air-conditioning heating equipment owned by the end of pressure head is often greater than the design value of the status of required, especially in large scale function of the complexity of building projects, the different long-range pipeline, terminal equipment, large differences in resistance and air-conditioning big difference between the end of start and stop system, in close proximity to the location of cold and heat source funding over excessive use of pressure head, often deviated from the design of flow distribution status , resulting in its hydraulic system disorders. Flow deviation will produce proximal air-conditioning cold and heat source or heating not hot太凉phenomenon. Not only can not guarantee that the use of the function, but also resulted in a waste of energy on.

Two, to resolve the imbalance of water approach

1, add savings Orifice

   Heat or air conditioning at the entrance near the cold source loop on part of tube sections to increase savings Orifice. Use this solution to the premise of the hydraulic imbalance is: accurate calculation of water system resistance, heat or air-conditioned terminal flow should not change. So at the end of the flow change will cause an imbalance and energy on water waste.
2, installation manual control valve
Of large air-conditioning system, using the manual control valve regulating the complex process of manually adjusting the front-end valves, back-flow will be affected. Adjust the back-end traffic flow will change the front end. Therefore time-consuming and laborious adjustment; for complex systems, the requirements regulating valve experienced engineers. And once the system pressure or load changes still need to re-adjust the hydraulic system.
3, installation of dynamic flow balance valve
Thermal entrance or air-conditioning equipment to determine the end of the design flow, based on flow and pressure valves Department Change the scope of the selected dynamic balance valve, the valve can be installed using the best settings. Department as long as the valves at the valve of the pressure changes in the design pressure range, without any artificial adjustment.
Third, the characteristics of dynamic balance valve
1, dynamic balance valve working principle:
By changing the balance valve spool of the flow area to adapt to the changes before and after the valve, so as to achieve the purpose of flow control. Dynamic balance valve is a local resistance to changes in expenditure components, for incompressible fluid flow equation is simplified as follows:
Q =KA (△ P)
Where: Q - flow through the balance valve;
K - valve opening the flow coefficient;
A - cross-flow area of spool
△ P - pressure valves Import and Export
Because at the opening of the valve remain unchanged under the premise, K value changes can be neglected, so the flow valve should be controlled to maintain a constant A (△ P) unchanged.
The alance valve by the variable flow area valve bulbs and high-precision (± 5%) of the spring and support installations pose. The role of compression springs bad gall on automatic control valve flow area of the size, so that a constant flow through the valve.
2, valve job process:
When the pressure balance valve before and after the start smaller than the smallest pressure spring are not compressed, the largest circulation. When the valve before and after the differential pressure valve at the scope of work when the compression spring bulbs into the job status, bile flow through the valve on both sides of the hole and geometry-based channel flow; at sports because of gall bladder valve on both sides of the channel geometry flow pattern also changes - Valve flow area are constantly changing, in this pressure range of water flow remained constant. When the pressure balance valve before and after are beyond the scope of work, valves fully compressed spring bulbs, bile flow only from the valve hole on both sides of the flow, when the valve into a fixed gall regulator, flow and pressure differential is proportional to, with the pressure bad increases.

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