文档介绍：: .
阀门流量计算方法
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15oC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15oC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 60 oF water with a pressure drop (dp) of 1 PSI across the valve. A Cv of 350 means a valve will pass 350 gpm of 60 oF water with a dp of 1 PSI.
公式 1
FORMULA 1
流速：磅 /小时 (蒸汽或水 )
FLOW RATE LBS/HR (Steam or Water)
在此：
Where:
dp =压降，单位：PSI
dp = pressure drop in PSI
F =流速，单位：磅/小时
F = flow rate in lbs./hr.
Fh =
比容积的平方根，单位：立方英尺
（阀门下游）
= square root of a specific volume in ft 3/lb.
(downstream of valve)
公式2
FORMULA 2
流速：加伦/分钟（水或其它液体）
FLOW RATE GPM （Water or other liquids）
在此：
Where:
dp =压降，单位：PSI
dp = pressure drop in PSI
Sg =比重
Sg = specific gravity
Q =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, 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。
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 as steam-water mixtures.
例子
EXAMPLE
1. 通过DN350,压力等级Class 900的压力密封闸阀，水温 400°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 through a 14" Class 900 pressure seal gate valve with 400 oF water,
1500 PSIG, and 5,000,000 lbs/hr flow rate?
解：采用公式1
Solution: Use formula 1.
F = 5,000,000
丽= (从水温为400 oF的表中得到)
<'7 = (from chart for water at 400 o F)
Cv = 9150 (来自本页)
Cv = 9150 (from page 26)
d = i F刃 ?二 / >: J 37?
P _ I Cv 丿 _ X 91 59 '
=(1 18)= = 14 PSI
2. DN350 x DN300 x DN350 ，压力等级Class 900缩喉管压力密封闸