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Orifice Pressure and Flow drop

  1. Sep 25, 2014 #1
    0http://math.stackexchange.com/questions/946493/solve-for-pressure-drop-across-and-orifice# [Broken]
    I'm running 1/2" pipe but the only way to connect a 9/16" flow switch is with a 1/4" adapter. I'd have to go from 1/2" down to 1/4" to the 9/16" flow switch down to 1/4" back to 1/2".

    I was wondering if this would cause a large pressure drop but I used this online calculator and was wondering if anyone could verify these numbers:

    Calculation output

    Flow medium: Water 20 °C / liquid

    Volume flow: 2 l/min

    Weight density: 998.206 kg/m³

    Dynamic Viscosity: 1001.61 10-6 kg/ms

    Element of pipe: Orifice sharp-edged

    Dimensions of element: Diameter of pipe D1: .5 in.

    Diameter of pipe D2: .25 in.

    Velocity of flow: 0.86 ft./s

    Reynolds number: 3330

    Velocity of flow 2: 3.45 ft./s

    Reynolds number 2: 6661

    Flow: turbulent

    Absolute roughness:

    Pipe friction number:

    Resistance coefficient: 30.68

    Resist.coeff.branching pipe: -

    Press.drop branch.pipe: -

    Pressure drop: 22.14 lbw./sq.ft.

    0.15 psi

    I've also looked at a flow rate calculator and was wondering if the down size in the piping would affect the flow rate substantially? I'm really trying to stay at 2L/min.
    Last edited by a moderator: May 7, 2017
  2. jcsd
  3. Aug 8, 2016 #2
    Head Loss due to sudden contraction or sudden expansion in area of flow is given by the formula,
    hL = (Vs2/2g)×{1-(As/Al)}2
    where the subscripts 's' and 'l' denote the flow properties at the smaller area region and the larger area region respectively.
    Substitute the values in this equation and you can determine how much extra pressure difference needs to be created to maintain the same flow as the case when there was no variation in area of flow.
    Last edited by a moderator: May 8, 2017
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