阀门流量计算方法发表于： 2010-1-29 9:39:55如何使用流量系数How to use Cv阀门流量系数(Cv)是表示阀门通过流体能力的数值。

Cv越大，在给定压降下阀门能够通过的流体就越多。

Cv值1表示当通过压降为1 PSI时，阀门每分钟流过1加仑15o C 的水。

Cv值350表示当通过压降为1 PSI时，阀门每分钟流过350加仑15o C的水。

Valve coefficient (Cv) is a number which represents a valve's ability to pass flow. The bigger the Cv, the more flow a valve can pass with a given pressure drop. A Cv of 1 means a valve will pass 1 gallon per minute (gpm) of 60o F water with a pressure drop (dp) of 1 PSI across the valve. A Cv of 350 means a valve will pass 350 gpm of 60o F water with a dp of 1 PSI.公式1FORMULA 12.DN350 x DN300 x DN350，压力等级Class 900缩喉管压力密封闸阀，其它条件与例1相同，求压降。

What is the pressure drop through a 14"x12"x14"Class 900 Venturi pressure seal gate valve with the same conditions as example 1.解：采用公式1Solution: Use formula 1.Cv = 6285 (来自本页)Cv = 6285 (from page 26)3.温度900o F, 压力1200 PSI，流速500,000磅/小时的蒸汽应用中压降小于5 PSI的压力等级Class 2500闸阀的最小通径是多少？What is the smallest Class 2500 gate valve that will have less than a 5 PSI pressure drop in 900o F, 1200 PSI steam service at a flow rate of 500,000 lbs/hr?解：采用公式1Solution: Use formula 1.F = 500,000= 0.785 (来自900o F, 1200 PSIG蒸汽表)流速：磅/小时(蒸汽或水)FLOW RATE LBS/HR (Steam or Water)在此：Where:dp = 压降，单位：PSIdp = pressure drop in PSIF = 流速，单位：磅/小时F = flow rate in lbs./hr.= 比容积的平方根，单位：立方英尺/磅(阀门下游)= square root of a specific volume inft3/lb.(downstream of valve)公式2FORMULA 2流速：加伦/分钟(水或其它液体)FLOW RATE GPM (Water or other liquids)= 0.785 (from chart for steam at 900o F, 1200 PSIG)= = 2.24最接近的、较大的Cv是DN250压力等级Class 2500闸阀，其Cv是3130。

这里是压降小于5 PSIG的最小的阀门。

The closest higher Cv is a 10" Class 2500 gate with a Cv of 3130. This is the smallest valve with a pressure drop less than 5 PSIG.水和蒸汽的备选特性Selected Properties of Water and Steam水的(下游)For Water (Downstream)蒸汽的(下游)For Steam (Downstream)在此：Where:dp = 压降，单位：PSIdp = pressure drop in PSISg = 比重Sg = specific gravityQ = 流速，单位：加伦/分钟Q = flow rate in GPM局限性LIMITATIONS上列公式在下列条件下无效：Above formulas are not valid under the following conditions:a.对于可压缩性流体，如果压降超过进口压力的一半。

For compressible fluids, wherepressure drop exceeds half theinlet pressure.b.对于不可压缩性流体，如果压降产生空穴或闪蒸。

For non-compressible fluids, where pressure drop causes cavitation or flashing.c.对于双相流体，如蒸汽-水混合流体。

For dual-phase flow such assteam-water mixtures.例子EXAMPLE1.通过DN350, 压力等级Class 900的压力密封闸阀，水温400o F，压力为1500 PSIG，流速为5,000,000磅/小时的压降是多少？What is the pressure drop througha 14" Class 900 pressure seal gatevalve with 400o F water, 1500 PSIG, and 5,000,000 lbs/hr flow rate?解：采用公式1Solution: Use formula 1.F = 5,000,000= 0.137 (从水温为400o F的表中得到)= 0.137 (from chart for water at400o F)Cv = 9150 (来自本页)Cv = 9150 (from page 26)阀座端口流速计算Calculating Seat Port Velocity下列公式可以用来计算任何阀门的阀座流速： The following formulas can be used to calculate seat port velocity in any valve:流量(磅/小时): 流速:(英尺/秒)= F()225AFlow (lbs/hr): vel:(fps) = F()225A流量(加仑/分钟): 流速: (英尺/秒)= 0.32QAFlow (GPM): vel: (fps) = 0.32Q阀座端口面积“A ”(英寸2) 适用于螺栓阀帽阀门SEAT PORT AREA "A" FOR BOLTEDBONNET VALVES (in 2)A在此：Where:F = 流量(磅/小时)F = flow (lbs/hr)= 比容积的平方根= square root of specific volumeA = 阀座端口面积 (英寸2)A = seat port area (in2)Q = 流量 (加仑/分钟)Q = flow (gpm)例：DN300型号58809 (压力等级Class 900)止回阀，流体介质为温度500 o F，压力200 PSIG的蒸汽，流速为90,000磅/小时，求阀座端口的流速？Example:What is the seat port velocity in a 12" Figure 58809 (Class 900) check valve with a flow rate of 90,000 lbs/hr of steam at 500 o F and 200 PSIG?阀座端口面积(英寸2)适用于压力密封闸阀，截止阀，提升式阀瓣止回阀SEAT PORT AREA FOR PRESSURE SEAL GATE,GLOBE, TILT DISC CHECK VALVES (in2)解：从蒸汽表得为1.61，从阀座端口面积表A 得阀座端口面积为78.5英寸2。

Answer:From the steam tables is 1.61, and from the seat port area table A is 78.5 in 2.流速: (英尺/秒)= F()225A=90,000 (1.61)2 25 (78.5) = 118.8 英尺/秒Vel (fps) = F()225A=90,000 (1.61)2 25 (78.5)= 118.8 fps例：DN300型号180 (压力等级150)旋启式止回阀，流体介质为温度500o F ，压力200 PSIG 的蒸汽，流速为90,000磅/小时，求阀座端口流速？ Example:What is the seat port velocity in a 12" Figure 180 (Class 150) Swing Check Valve with a flow rate of 90,000 lbs/hr of steam at 500o F and 200 PSIG?阀座端口面积(英寸2) 适用于压力密封Y 形截止阀SEAT PORT AREA FOR PRESSURE SEAL Y-GLOBE2解：查表得为1.61，A 为 113.1英寸3. Answer:From the tables is 1.61 and A is 113.1 in 3.流速: (英尺/秒)= F()225A=90,000 (1.61)2 25 (113.1) = 82.5英尺/秒Vel (fps) = F()225A=90,000 (1.61)2 25 (113.1)= 82.5 fps局限性 LIMITATIONS流速公式在下列条件下无效：Velocity formulas are not valid under the following conditions:a. 对于可压缩性流体，如果压降超过进口压力的一半。

For compressible fluids, where pressure drop exceeds half the inlet pressure.b.对于不可压缩性流体，如果压降产生空穴或闪蒸。