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Thread: Steam Energy Flow

  1. #1
    Associate Engineer
    Join Date
    Feb 2017
    Posts
    2

    Steam Energy Flow

    Hi,
    I need to calculate the energy flow down a steam line. I have the mass flow, gauge pressure and temperature of the steam and would like an equation/formula to put into the SCADA/DCS to work out the Energy flow in the line. There is a variable amount of superheat in the steam so I need to compensate with the temperature. Has anyone got a simple formula to calculate it dynamically?
    The gauge pressure ranges from between 3 and 5 barg and the temperature between 180 and 220C, normal operation conditions 3.5 barg and 205C.
    Thanks in advance

  2. #2
    Senior Engineer
    Join Date
    May 2015
    Posts
    51
    Find something called a Mollier chart for steam.

  3. #3
    Associate Engineer
    Join Date
    Feb 2017
    Posts
    2
    Thanks Hudson. Unfortunately I haven't got the facility to look up a value in a table or chart. I was after the equation that would produce the curve on the chart to enter in the scada for the calculation. I thought there might be a rough mathematical relationship between the variables to enable a viable energy figure to be worked out, especially since I'm only looking at a narrow operation band, but it is looking like it is too complex to work out

  4. #4
    Lead Engineer Cake of Doom's Avatar
    Join Date
    Aug 2012
    Location
    UK
    Posts
    367
    The "simple" equation is h=u+Pv.

    h=Enthalpy (kJ/kg)

    u=internal energy

    P=pressure

    v= Volume

    You'll be screaming out for chart or a big old MathCAD lesson after you're done trying to have fun with this.

    PS

    I hated Thermodynamics. Still do, to a degree.

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