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Horizontal ring water main pressure drop

  1. Feb 10, 2015 #1
    1. The problem statement, all variables and given/known data
    The accompanying figure shows a horizontal ring main consisting of a single loop of pipe, as might be used for supplying water to various points on one floor of a building. Water enters the main at A at 50 psig and is discharged at B and C at rates of 20 gpm and 60 gpm, respectively. Tests on the particular pipe forming the main show that the frictional pressure drop
    (psi) is given by –Δp = 0.0002Q2L, where L is the pipe length in feet and Q is the flow rate in gpm. Estimate the flow rates in the individual sections AB, BC and AC, and the pressures at B and C. The distances are AB = 100 ft, BC = 50 ft and AC = 200 ft

    7b896101a01606b79ad595086f6349b2.jpg

    3. The attempt at a solution
    I used the mechanical energy balance.
    I'm left with P1/rho=(P2/rho)+hf
    hf= Pipeline + Minor Losses
    hf= Pipeline + 0
    Pipeline= ((4fL)/D)*(Velocity^2)/2
    mass flow= 80 gpm
     
  2. jcsd
  3. Feb 11, 2015 #2

    BvU

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    As far as I can oversee this, the place of your ((4fL)/D)*(Velocity^2)/2 is taken by the given –Δp = 0.0002Q2L, right ?

    Now try and approach this a bit more systematically: you have some givens, you have some equations (you do, I suppose, even though part 2 from the template has mysteriously disappeared ?) and you have some unknowns. Work towards setting up N equations with N unknowns, then solve them.

    And make (also for yourself) a list of symbols you use. P1 ? P2 ?
     
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