Gas Flow Calculations



The following formulae should be used for converting Actual flow rates at operating Pr. & Temp. conditions to Standard / Normal flow rates at STP / NTP conditions.


SCFM = ACFM * P/14.69 * 519/(459+T)

Where
P = Absolute Operating Pressure in psiA. = Operating Gauge Pressure psiG + 14.69
T = Operating Temperature in degree Fahrenheit.
SCFM : Standard Cubic Feet per Minute, at STP conditions.
ACFM : Actual Cubic Feet per Minute, at Operating Conditions.
STP CONDITIONS
Pressure = 14.69 psiA.
Temperature = 60 deg. F.

Nm3/h = Am3/h * P/101.32 * 273/(273+T)

Where
P = Absolute Operating Pressure in kPa(Kilo pascal)= Operating Gauge PressurekPa+101.32
T = Operating Temperature in degree Centigrade.
Nm3/h : Normal Cubic Meter per Hour, at NTP Conditions.
Am3/h : Actual Cubic Meter per hour, at Operating Conditions.
NTP CONDITIONS
Pressure = 101.325kPa
Temperature = Zero deg. C.


PERMANENT PRESSURE LOSS

  • For Insertion flowmeter Sizes 10 Inch to 118 Inch pressure loss is Negligible.

  • For Inline Flowmeters

    • DP=1.2 * 10-5 * r * V2


    Where
    DP = Total Pressure Drop in kg/cm2
    r = Operating Density in kg/m3
    V = Velocity in m/s.
    FOR INLINE FLOWMETER SIZES 2 INCH TO 8 INCH
    Typical Example           For Water at 15 deg.C. r = 999.110 kg/m 3
    Flow Velocity m/s 0.5 1.0 1.5 2.0 3.0 4.0 5.0
    DP kg/cm2 0.003 0.012 0.027 0.048 0.107 0.192 0.299
    Typical Example           For Air at 15 deg.C., Pr.=1kg/cm2 G,r =2.41 kg/m3
    Flow Velocity m/s 5 10 15 20 30 35 40 50
    DP kg/cm2 7.2*10-4 2.9*10-3 6.5*10-3 0.012 0.026 0.035 0.046 0.072




    Useful Conversion Units

    1 cubic meter = 35.31 cubic ft = 264.20 U.S Gallons.
    3.785 litres = 1 U.S Gallon.
    4.546 litres = 1 Imp. Gallon.
    1 kg/square cm = 100 kPa = 14.503 psi
    absolute pressure = gauge pressure + atmospheric pressure

    Profile - Flow Meter - Users Info - Contact Us - Feedback