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Venturi tube help needed in determining pressure difference

  1. May 20, 2011 #1
    1. The problem statement, all variables and given/known data

    Water flows through venturi tube at 0.3 litres/s. Diameter of venturi tube is 32mm to 20mm to 32mm and the water density is 1000kg/m^3.


    2. Relevant equations

    a) Assuming head loss is neglible, what is pressure difference between 1 and 2.

    b) If pressure head difference between these is 45mm what is head loss.


    3. The attempt at a solution


    So far I have V2 = P1A1V1/P2A2 = 0.9548 and V1 (Q/A) = 0.3731

    delta H 1/2 = H1 - H2 = 1/2g (V2^2-V1^2))
    delta H 1/2 = 39.3mm

    Where do I go from here, if this is even correct ?

    Thanks a lot for your help.
     
  2. jcsd
  3. May 20, 2011 #2

    tiny-tim

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    welcome to pf!

    hi timothy1875! welcome to pf! :smile:

    (try using the X2 and X2 icons just above the Reply box :wink:)

    i don't follow you :confused:

    use the fact that the volume per time is constant, and Bernoulli's equation :wink:
     
  4. May 20, 2011 #3
    Hi Tim,

    Thanks for getting back to me.I am trying to answer the question but think I may be going about it the wrong way.

    Using the Bernoulli equation do I need to transpose to find P ?
     
  5. May 20, 2011 #4

    tiny-tim

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    show us what you have so far :smile:
     
  6. May 20, 2011 #5
    V2 = P1A1V1/P2A2 = 0.9548 and V1 (Q/A) = 0.3731

    delta H 1/2 = H1 - H2 = 1/2g (V22-V12)
    delta H 1/2 = 39.3mm

    This where I have got to so far, :(
     
  7. May 20, 2011 #6

    tiny-tim

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    what does this mean? :confused:

    where does it come from?
     
  8. May 20, 2011 #7
    Basically we have been set this question and there are numerous equations on the back that we have to pick from. I take it from your response I have selected the wrong equation initially. Should it be 1/2g (V22 - V1 2) ??
     
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