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Homework Help: Orifice problem

  1. Mar 7, 2012 #1
    Orifice problem ive been given a list of quantities

    Pipe before orifice head = 255mm
    Diameter = 31.75mm

    Pipe after orifice head = 230mm
    Diameter= 20mm

    Time for 10litres to fill in collection tank 67.09seconds
    Assuming g= 9.81 and density = 1000

    from the experiment difference in pressure head = 25mm
    They wanted to know the theorectical.

    Calling everything before head 1 and after head 2

    u1= Q/ A where Q= 0.149 x 10^-3 m^3/s and A = 0.791x10^-3 m^2

    u1 = 0.188

    u2= Q/ A where Q= 0.149 x 10^-3 m^3/s and A =0.314x 10^-3 m^2

    u2= 0.475

    putting into equaton

    P1-P2/p x g = u2^2/2g - u1^2/2g where p=density

    gives the difference in theoretical head = 9.7mm

    Im not sure if that is right as its a third of the experiment, if it is right how can it be because surely the theory should be higher as you dont take into account the local or frictional losses.

    Hope someone can help.
  2. jcsd
  3. Mar 7, 2012 #2

    rude man

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    Homework Helper
    Gold Member

    Diagram or complete staement of the problem?
  4. Mar 8, 2012 #3
    The problem was find the theoretical difference in head pressure before and after orifice. Then compare with experimental difference in head pressure. No diagram wasnt given one to begin with. sorry
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