阀门流量计算方法.docVIP

阀门流量计算方法 发布时间：2010-1-29 ??来源地：shhbqfm 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 valves 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 60oF water with a pressure drop (dp) of 1 PSI across the valve. A Cv of 350 means a valve will pass 350 gpm of 60oF water with a dp of 1 PSI. 公式1FORMULA 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. = 比容积的平方根，单位：立方英尺/磅(阀门下游) = square root of a specific volume in ft3/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) 　　 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: 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. 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. 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 通过DN350, 压力等级Class 900的压力密封闸阀，水温400oF，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 400oF 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400oF的表中得到) = 0.137 (from chart for water at 400oF) Cv = 9150 (来自本页) Cv = 9150 (from page 26) ? 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 14x12x14 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)C