闪蒸现象的原理
闪蒸
现象:
闪蒸就是高压的饱和水进入比较低压的容器中后由于压力的突然降低使这些饱和水变成一部分的容器压力下的饱和水蒸气和饱和水。
形成原因:
当水在大气压力下被加热时，100?是该压力下液体水所能允许的最高温度。再加热也不能提高水的温度，而只能将水转化成蒸汽。水在升温至沸点前的过程中吸收的热叫“显热”，或者叫饱和水显热。在同样大气压力下将饱和水转化成蒸汽所需要的热叫“潜热”。然而，如果在一定压力下加热水，那么水的沸点就要比100?高，所以就要求有更多的显热。压力越高，水的沸点就高，热含量亦越高。压力降低，部分显热释放出来，这部分超量热就会以潜热的形式被吸收，引起部分水被“闪蒸”成蒸汽。
实际情况:
闪蒸在管道系统中出现，容易对阀门产生汽蚀损坏，可以选择反气蚀高压阀，其特点是多次节流分摊压差，也可以选用耐气蚀冲刷材料。
闪蒸也可以作为能源，被利用在热力发电厂中锅炉排水的回收和地热发电中。
调节阀气蚀与闪蒸控制
n the main terminal, and the telephone Office is responsible for providing the appropriate size adapter patch panels and electrical protection unit. (Shuttle bus) wiring (IDF) t up in the workshop on the cond floor of the building, located in the District of weak electrical cabinets (well). Engine room placed inside the Cabinet, IDF placed a standard 40U cabinets for installation of network and wiring devices, management computer and telephone information. Cabinet distribution frame are made of Super five RJ45 patch panel horizontal twisted pair connections. Computer information management, admin area using the jumpers, which us private RJ45-RJ45 soft jumpers for network devices with jumpers hopping between all switches, changes, expansion and maintenance were done quickly in the wiring clot. Twisted length Centre room is located on the cond flo
or, outward radiation of each line (except some points may exceed) does not exceed 100 metres in length, all information for the various floors all rooms (distribution Cabinet) unified management. District workshop building distribution lines (IDF) via fiber optic cables connected to the total room cabinets. Fiber length were: workshops two IDF: total more than 1200 square meters, double the number of strands can be calculated by multiplying the average length of the number of information points are. Average level of each length of cable: L=[(S1+S2)/2]+L1+L2 l: average length of cable; L1: MDF cable allowance; L2: other allowances S1: minimum horizontal cable length; S2: maximum horizontal length of cable; Office building of information: a minimum of 26 meters, the longest was 92 meters, L=[(28+92)/2]+2.5+1=62.5 m; Total length of 62.5 m x792 = 49500-meter in each box (KFT) by 300 meters per carton; The twisted-pair cable box you want = 49500 ? 300=165 (KFT); loss not included, each about 15 meters. Metal line slot, and metal line tube of
作 者:李庞伟
摘 要:分析了气蚀和闪蒸给调节阀带来的影响和危害，介绍了有效防止气蚀与闪蒸破坏的阀门结构。
关键字:气蚀 闪蒸 饱和压力 气蚀系数 压力恢复系数
1 概述
气蚀和闪蒸是一种水力流动现象，这种现象既能引起调节阀流通能力Kv减小，又能产生噪声、振动及对材料的损害。因此控制和降低调节阀受气蚀和闪蒸的影响是阀门设计时要考虑的问题之一。
2 气蚀和闪蒸
气蚀和闪蒸产生的条件不同。闪蒸是一种非常快速的转变过程，当流动液体的下游压力低于它的饱和压力时就会出现闪蒸，因此它是一种系统现象。调节阀能够避免闪蒸的产生，除非系统条件改变。而当阀门中液体的下游压力又升回来，且高于饱和压力时，就会产生气蚀现象。在气蚀过程中饱和气泡不再存在，而是迅速爆破变回液态。由于气泡的体积大多比相同形式的液体大。所以说，气泡的爆破是从大体积向小体积的转变。气蚀是一种从
液态?饱和?液态的转变过程，它不同于闪蒸现象。正确合理地设计调节阀能够避免气蚀的产生。
3 防止闪蒸的阀门设计
在调节阀里闪蒸是不能预防的，所能做到的就是防止闪蒸的破坏。在调节阀设计中影响着闪蒸破坏的因素主要有阀门结构、材料性能和系统设计。
闪蒸破坏是高速度的饱和气泡冲击阀体表面，并腐蚀阀体表面造成的。由于角形阀中的介质直接流向阀体内部下游管道的中心，而不是象球形阀一样直接冲击体壁，所以大大减少了冲击阀体体壁的饱和气泡数量。从而减弱了闪蒸的破坏力。因此在闪蒸破坏出现的情况下，角n the main terminal, and the telephone Office is responsible for providing the appropriate size adapter patch panels and electrical protection unit. (Shuttle bus) wiring (IDF) t up in the workshop on the cond floor of the building, located in the District of weak electrical cabinets (well). Engine room placed inside the Cabinet, IDF placed a standard 40U cabinets for installation of network and wiring devices, management computer and telephone information. Cabinet distribution frame are made of Super five RJ45 patch panel horizontal twisted pair connections. Computer information management, admin area using the jumpers, which us private RJ45-RJ45 soft jumpers for network devices with jumpers hopping between all switches, changes, expansion and maintenance were done quickly in the wiring clot. Twisted length Centre room is located on the cond floor, outward radiation of each line (except some points may exceed) does not exceed 100 metres in length, all information for the various floors all ro
oms (distribution Cabinet) unified management. District workshop building distribution lines (IDF) via fiber optic cables connected to the total room cabinets. Fiber length were: workshops two IDF: total more than 1200 square meters, double the number of strands can be calculated by multiplying the average length of the number of information points are. Average level of each length of cable: L=[(S1+S2)/2]+L1+L2 l: average length of cable; L1: MDF cable allowance; L2: other allowances S1: minimum horizontal cable length; S2: maximum horizontal length of cable; Office building of information: a minimum of 26 meters, the longest was 92 meters, L=[(28+92)/2]+2.5+1=62.5 m; Total length of 62.5 m x792 = 49500-meter in each box (KFT) by 300 meters per carton; The twisted-pair cable box you want = 49500 ? 300=165 (KFT); loss not included, each about 15 meters. Metal line slot, and metal line tube of
