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P.S.I. in a pipe

  1. Jun 1, 2010 #1
    To keep it simple: I have a vertical 60 foot drop. I want to create the maximum P.S.I. at the bottom of the pipe possible to run a water wheel or a turbine. If the bottom hole (say 2") and the vertical drop of two pipes is the same will there be a difference in a 4" or a 2" pipe? Note: there would be a small dam at the top to fill the pipe to maximum capacity. Also, is there a formula to easily figure out P.S.I. using drop height, water area and weight including the limiting factor of the bottom hole? Thanks!
    (I am only a Physics 12 grad so keep it simple) :smile:
  2. jcsd
  3. Jun 2, 2010 #2


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    Staff: Mentor

    Welcome to PF.

    The larger the pipe, the lower the resistance to flow (and loss of energy) once the water starts moving, but otherwise, no: the pressure at the bottom of the pipe is dictated by the vertical drop alone. So you'll want to figure out how much flow rate you have available and make sure the pipe can handle it without too much loss (keep it below about 5 fps velocity), but otherwise pipe size doesn't matter much. The formula is p=.433h (h is height in feet, p is pressure in psi).
  4. Jun 2, 2010 #3
    Thank you very much, that's exactly what I needed!
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