• 流量计算

    发布者:旭达流体 添加时间:2008/10/12

    如何使用流量系数
    How to use Cv

      法门流量系数(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 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.
    =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:

    1. 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.
    2. 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.
    3. 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1
      Solution: 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)

     
    1. 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1
      Solution: Use formula 1.
      Cv = 6285 (来自本页)
      Cv = 6285 (from page 26)
    2. 温度900oF, 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 900oF, 1200 PSI steam service at a flow rate of 500,000 lbs/hr?
      解:采用公式1
      Solution: Use formula 1.
    F=500,000
    =0.785 (来自900oF, 1200 PSIG蒸汽表)
    =0.785 (from chart for steam at 900oF, 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)
    所有压力等级
    All
    Pressures
    温度(oF)
    Temperature (oF)
    100200300400500600
    0.1270.1290.1320.1370.1430.154
     
    蒸汽的(下游)
    For Steam (Downstream)
    压力
    PSIG
    Pressure
    PSIG
    温度(oF)
    Temperature (oF)
    Sat50060070080090010001100
    100
    200
    300
    400
    500
    600
    700
    800
    900
    1000
    1100
    1200
    1300
    1400
    1600
    1800
    2000
    2500
    3000
    4000
    5000
    6000
    1.97
    1.46
    1.21
    1.06
    0.950
    0.865
    0.801
    0.747
    0.701
    0.662
    0.628
    0.598
    0.570
    0.545
    2.20
    1.61
    1.30
    1.11
    0.979
    0.895
    2.32
    1.68
    1.38
    1.19
    1.06
    0.960
    0.880
    0.815
    0.759
    0.710
    0.670
    0.629
    0.590
    0.559
    2.44
    1.77
    1.46
    1.26
    1.12
    1.02
    0.941
    0.875
    0.821
    0.773
    0.732
    0.695
    0.662
    0.633
    0.58
    0.54
    0.50
    0.41
    0.31
    0.17
    0.16
    0.16
    2.54
    1.85
    1.52
    1.32
    1.18
    1.08
    0.994
    0.926
    0.870
    0.816
    0.781
    0.745
    0.710
    0.683
    0.63
    0.59
    0.55
    0.48
    0.42
    0.32
    0.24
    0.19
    2.64
    1.95
    1.60
    1.38
    1.23
    1.13
    1.04
    0.972
    0.914
    0.865
    0.823
    0.785
    0.752
    0.723
    0.67
    0.63
    0.59
    0.52
    0.46
    0.38
    0.32
    0.28
    2.74
    2.00
    1.65
    1.43
    1.28
    1.17
    1.08
    1.01
    0.955
    0.917
    0.872
    0.813
    0.789
    0.752
    0.70
    0.66
    0.62
    0.55
    0.49
    0.42
    0.36
    0.32
    2.84
    2.07
    1.71
    1.47
    1.33
    1.22
    1.12
    1.05
    0.99
    0.94
    0.90
    0.86
    0.83
    0.79
    0.74
    0.69
    0.65
    0.58
    0.52
    0.44
    0.39
    0.35

    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()2
    25A
    Flow (lbs/hr): vel: (fps) =
    F()2
    25A
    流量(加仑/分钟): 流速: (英尺/秒)=
    0.32Q
    A
    Flow (GPM): vel: (fps) =
    0.32Q
    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 volume
    A=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 oF,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 oF and 200 PSIG?

    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 in2.

    流速: (英尺/秒)=
    F()2
    25A
    =
    90,000 (1.61)2
    25 (78.5)
    = 118.8 英尺/秒
    Vel (fps) =
    F()2
    25A
    =
    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500oF,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 500oF and 200 PSIG?

    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 in3.

    流速: (英尺/秒)=
    F()2
    25A
    =
    90,000 (1.61)2
    25 (113.1)
    = 82.5英尺/秒
    Vel (fps) =
    F()2
    25A
    =
    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:

    1. 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.
    2. 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.
    3. 对于双相流体,如蒸汽-水混合流体。
      For dual-phase flow such as steam-water mixtures.

    注意
    NOTE

      在确定止回阀通径时,最适宜的工作流速应该位于这些范围内:
      When determining sizing for check valves, the optimum operating velocities should fall within these ranges:

    BB旋启式止回阀:55 至115或135至240
    BB截止止回阀:40 至120
    PS提升式阀瓣止回阀:55至200
    PSY形止回阀:148 至200
    BB Swing Check Valves - 55 to 115 or 135 to 240
    BB Stop Check Valves - 40 to 120
    PS Tilt Disc Check Valves - 55 to 200
    PS Stop Check Valves - 40 to 180
    PS Y- Stop Check Valves - 148 to 200

     
    阀座端口面积“A”(英寸2)
    适用于螺栓阀帽阀门
    SEAT PORT AREA "A" FOR BOLTED
    BONNET VALVES (in2)
    阀门通径
    Valve Size
    压力等级
    Pressure Class
    1503006009001500
    11/2
    2
    21/2
    3
    4
    6
    8
    10
    12
    14
    16
    18
    20
    24
    30
    36
    1.8
    3.1
    4.9
    7.1
    12.6
    28.3
    50.3
    78.5
    113.1
    137.9
    182.7
    233.7
    291.0
    424.5
    671.9
    969.0
    1.8
    3.1
    4.9
    7.1
    12.6
    28.3
    50.3
    78.5
    113.1
    137.9
    182.7
    227.0
    283.5
    424.5
    672.0
    942.0
    1.8
    3.1

    7.1
    12.6
    28.3
    48.7
    74.7
    108.4
    130.2
    170.9
    213.8
    261.6
    380.1
    590.9
    851.2
    1.8
    3.1
    4.9
    6.5
    11.8
    26.0
    44.2
    71.0
    100.0
    117.9





    1.5
    2.8
    4.0
    6.0
    10.3
    22.7
    38.5
    60.0
    84.5
    101.6





     

    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)

    阀门通径
    Valve Size
    压力等级
    Pressure Class
    60090015002500
    21/2
    3
    4
    6
    8
    10
    12
    14
    16
    18
    20
    24
    5.4
    5.4
    9.6
    23.2
    39.9
    61.0
    88.7


    173.8

    310.25
    5.9
    5.9
    10.3
    21.7
    37.7
    58.4
    80.5
    97.2
    125.2
    156.7
    198.0
    287.3
    3.3
    4.9
    8.3
    18.9
    31.9
    48.7
    69.0
    82.5
    108.4
    137.9
    170.9
    247.5
    2.4
    3.6
    5.9
    12.6
    21.7
    34.5
    47.2
    58.2
    76.6
    97.2
    117.9
    170.9

     

    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-GLOBE
    VALVES (in2)

    阀门通径
    Valve Size
    压力等级
    Pressure Class
    90015002500
    8
    10
    12
    14
    16
    18
    20
    24
    39.9
    61.9
    86.6
    86.6
    135.4
    135.4
    198.1
    302.6
    39.9
    61.9
    86.6
    86.6
    135.4
    135.4
    198.1
    302.6
    27.2
    42.8
    60.1
    86.6
    86.6
    135.4
    135.4
    198.1
    螺栓阀帽闸阀全开状态下的流量系数Cv
    Bolted Bonnet
    Gate Valves FULL OPEN Cv
    阀门通径
    Valve Size
    压力等级
    Pressure Class
    1503006009001500
    11/2
    2
    21/2
    3
    4
    5
    6
    8
    10
    12
    14
    16
    18
    20
    24
    30
    36
    165
    307
    490
    710
    1300
    2090
    3110
    5720
    8935
    13350
    16275
    21560
    28720
    35760
    52165
    86235
    129500
    165
    307
    490
    710
    1300

    3110
    5720
    8935
    13350
    16275
    21560
    27890
    34840
    51050
    84765
    125825
    165
    307
    490
    710
    1300

    3110
    5540
    8495
    12800
    15370
    29170
    26270
    32140
    46710
    75530
    114250



    650
    1220

    2850
    5025
    7850
    11475
    13910





    138
    270
    400
    600
    1070
    1600
    2500
    4375
    6840
    9980
    12000





     
    图1
    螺栓阀帽截止阀
    Figure 1
    Bolted Bonnet
    Globe Valves

    (1)当开启度小于
    10%时,不建议
    用于节流应用。
    (1) not recommended for
    throttling at less
    than 10% Open.

     

    压力密封闸阀全开状态下的流量系数Cv
    Pressure Seal
    Gate Valves FULL OPEN Cv

    阀门通径
    Valve Size
    压力等级
    Pressure Class
    60090015002500
    21/2
    3
    4
    6
    8
    10
    12
    14
    16
    18
    20
    24
    350
    525
    925
    2150
    3775
    5750
    8600
    10275
    13425
    17200
    20950
    30850
    350
    450
    850
    1925
    3575
    5250
    7550
    9150
    11950
    15575
    19200
    27675
    275
    415
    730
    1675
    2925
    4550
    6570
    7890
    10325
    13425
    16825
    24150
    190
    275
    460
    1100
    1970
    3130
    4535
    5500
    7210
    9215
    11450
    16575

     

    压力密封缩喉管闸阀全开状态下的流量系数Cv
    Pressure Seal
    Venturi Gate Valves FULL OPEN Cv

    阀门通径
    Valve Size
    压力等级
    Pressure Class
    60090015002500
    8 x 6 x 8
    10 x 8 x 10
    12 x 10 x 12
    14 x 12 x 14
    16 x 14 x 16
    18 x 16 x 18
    20 x 18 x 20
    22 x 20 x 22
    26 x 24 x 26
    1570
    2795
    4485
    7310
    9000
    11000
    14200
    16800
    25000
    1385
    2385
    4065
    6285
    7200
    9760
    12185
    16005
    23000
    1185
    2155
    3450
    5640
    6270
    8465
    11120
    14130
    815
    1430
    2515
    3855
    4415
    6165
    7960
    9645
     
    螺栓阀盖旋启式止回阀全开状态下的流量系数Cv
    Bolted Cap
    Swing Check Valves FULL OPEN Cv
    阀门通径
    Valve Size
    压力等级
    Pressure Class
    1503006009001500
    11/2
    2
    21/2
    3
    4
    6
    8
    10
    12
    14
    16
    18
    20
    24
    30
    63
    142
    217
    356
    716
    1414
    2961
    5720
    7860
    10416
    13800
    13420
    16708
    33384
    54556
    63
    168
    275
    392
    740
    1992
    2340
    5720
    8544
    19464
    13800
    13029
    16276
    36672
    54652
    97
    139
    227
    246
    499
    1334
    3359
    5440
    7045
    9840
    12912

    19540




    358
    605
    1623
    2508
    4069
    6316






    111

    315
    564
    1520








     

    螺栓阀帽截止阀全开状态下的流量系数Cv
    Bolted Bonnet
    Globe Valves FULL OPEN Cv

    阀门
    通径
    Valve Size
    压力等级
    Pressure Class
    150300600900
    塞形

    球形
    阀瓣
    Plug or
    Ball
    Disc
    V形
    端口
    阀瓣
    V-Port
    Disc
    塞形

    球形
    阀瓣
    Plug or
    Ball
    Disc
    V形
    端口
    阀瓣
    V-Port
    Disc
    塞形

    球形
    阀瓣
    Plug or
    Ball
    Disc
    V形
    端口
    阀瓣
    V-Port
    Disc
    塞形

    球形
    阀瓣
    Plug or
    Ball
    Disc
    11/2
    2
    21/2
    3
    4
    5
    6
    8
    10
    12
    23
    43
    70
    100
    185
    297
    440
    810
    1260
    1890

    40

    92
    170
    273
    405
    745
    1150
    23
    43
    70
    100
    185

    440
    810
    1260
    1890
    21
    40

    92
    170

    405
    745

    23
    43
    70
    100
    185

    440
    780

    1810

    40

    92
    170

    405





    90
    170




     

    压力密封提升式阀瓣止回阀全开状态下的流量系数Cv
    Pressure Seal
    Tilting Disc Check Valves FULL OPEN Cv

    阀门通径
    Valve Size
    压力等级
    Pressure Class
    90015002500
    21/2
    3
    4
    6
    8
    10
    12
    14
    16
    18
    20
    24
    95
    146
    268
    627
    1062
    1722
    2420
    2955
    3945
    4900
    6275
    9295
    80
    132
    230
    536
    940
    1465
    2110
    2550
    3395
    4365
    5465
    8060
    60
    94
    146
    355
    627
    1020
    1420
    1775
    2355
    3025
    3705
    5465

     

    压力密封缩喉管提升式阀瓣止回阀全开状态下的流量系数Cv
    Pressure Seal
    Venturi Tilting Disc Check Valves FULL OPEN Cv

    阀门通径
    Valve Size
    压力等级
    Pressure Class
    150300600
    8 x 6 x 8
    10 x 8 x 10
    12 x 10 x 12
    14 x 12 x 14
    16 x 14 x 16
    18 x 16 x 18
    20 x 18 x 20
    22 x 20 x 22
    565
    955
    1550
    2175
    2660
    3550
    4410
    5650
    480
    845
    1320
    1900
    2295
    3055
    3930
    4920
    320
    565
    920
    1275
    1598
    2120
    2725
    3335

    球形止回阀,截止止回阀,提升式止回阀的流量特性曲线
    Characteristic Flow Curves for Globe Stop, Stop-Check, Lift-Check Valves

    小于全开状态的估计流量系数Cv
    Estimating Cv For Less Than Fully Open Valves


    图2
    球形止回阀,截止止回阀和提升式止回阀
    Figure 2
    Globe Stop, Stop-Check and
    Lift-Check Valves

    压力密封T形球形止回阀,截止止回阀和提升式止回阀
    阀全开状态下的流量系数Cv
    Pressure Seal T-Globe Stop,
    Stop-Check and Lift-Check Valves FULL OPEN Cv
    阀门通径
    Valve Size
    压力等级
    Pressure Class
    90015002500
    21/2
    3
    4
    6
    8
    10
    12
    14
    90
    105
    195
    455
    800
    1250
    1820
    2205
    65
    95
    170
    395
    695
    1085
    1580
    45
    65
    105
    265
    470
    750
    1100

     

    压力密封Y球形止回阀,截止止回阀和提升式止回阀
    阀全开状态下的流量系数Cv
    Pressure Seal Y-Globe Stop,
    Stop-Check and Lift-Check Valves FULL OPEN Cv

    阀门通径
    Valve Size
    压力等级
    Pressure Class
    60090015002500
    8
    10
    12
    14
    16
    18
    20
    24
    2025
    3025
    4600
    4300
    7650
    7325
    11800
    16450
    1750
    2725
    3825
    3650
    6000
    5825
    9125
    13500
    1750
    2725
    3825
    3650
    6000
    5825
    9125
    13500
    1175
    1875
    2650
    4075
    3775
    6625
    6225
    9050

      表中所列流量系数仅适用于全开状态下的阀门。不是全开状态的流量系数可以采用适用于提升式阀瓣止回阀和截止阀的流量特性曲线进行估算。不建议将闸阀用在节流应用中。
      The flow coefficient (Cv) listed in the tables apply to fully open valves only. Flow coefficients at other than fully open may be approximated by use of the characteristic flow curves for tilting disc check and globe valves. Gate valves are not recommended for throttling service.

    例:
      DN300,压力等级Class 900的美国太平洋压力密封截止阀在开气度为1/4时的流量系数是多少?
    EXAMPLE:
     

     


    图3
    Y形球形止回阀,截止止回阀和提升式止回阀
    Figure 3
    Y-Globe Stop, Stop-Check and
    Lift-Check Valves

    压力密封缩喉管球形止回阀,截止止回阀和提升式止回阀
    阀全开状态下的流量系数Cv
    Pressure Seal Venturi Globe Stop,
    Stop-Check and Lift-Check Valves FULL OPEN Cv
    阀门通径
    Valve Size
    压力等级
    Pressure Class
    90015002500
    8 x 6 x 8
    10 x 8 x 10
    12 x 10 x 12
    14 x 12 x 14
    16 x 14 x 16
    450
    770
    1215
    1775
    2125
    390
    690
    1055
    1550
    260
    465
    745
    1070

     

    压力密封缩喉管Y球形止回阀,截止止回阀和提升式止回阀
    阀全开状态下的流量系数Cv
    Pressure Seal Venturi Y-Globe Stop,
    Stop-Check and Lift-Check Valves FULL OPEN Cv

    阀门通径
    Valve Size
    压力等级
    Pressure Class
    60090015002500
    8 x 6 x 8
    10 x 8 x 10
    12 x 10 x 12
    14 x 12 x 14
    16 x 14 x 16
    18 x 16 x 18
    20 x 18 x 20
    22 x 20 x 22
    16 x 24 x 26
    1100
    1925
    2875
    4375
    4075
    7250
    6950
    11200
    15850
    1000
    1675
    2600
    3650
    3450
    5700
    5525
    8675
    12825
    1000
    1675
    2600
    3650
    3450
    5700
    5525
    8675
    12825
    650
    1125
    1775
    2525
    3875
    3575
    6300
    5925
    8600

    解:
      从上列流量系数表中得到,DN300,压力等级Class 900截止阀在全开状态下的Cv是1820。
    SOLUTION:
      From the flow coefficient table above, the fully open Cv for a 12 inch, Class 900 globe valve is 1820.

      查询图2,全开状态的1/4时阀门的比率是52%.
      Consulting Figure 2, the percent of fully open Cv at 1/4 valve open is 52%.

      因此计算1/4全开的流量系数Cv为:
      0.52 x 1820 = 946.
      The Cv at 1/4 open is then computed as:
      0.52 x 1820 = 946.

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