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Thread: Flow calculation through a valve

  1. #1
    Associate Engineer
    Join Date
    Nov 2021

    Flow calculation through a valve

    Hello all. I'm looking solve a problem with a pressure reducing valve where I'm trying to find the outlet flow from a pressure drop. My medium is diesel at 20 deg C, which I've read needs to be factored in from the Kv which is a value given for water between 5 and 40 deg C.

    40 bar

    1 bar

    The valve has a Kv value of 3 or another one has a Kv of 15 for example. Which one do I choose and why? From what I've gathered so far, the Kv of 3 means 3m^3/h can pass per 1 bar pressure drop. So 39 bar pressure drop is 3 * 39 = 117m^3/h flow rate?

  2. #2
    Technical Fellow Kelly_Bramble's Avatar
    Join Date
    Feb 2011
    Bold Springs, GA
    I believe that the formulas is:

    GPM = Cv [ (p1 - p2) / G ]1/2


    Cv = GPM that will pass through valve with pressure drop = 1 psi
    G = specific gravity of the fluid,
    p1 = start pressure
    p2 = end pressure
    Tell me and I forget. Teach me and I remember. Involve me and I learn.

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