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Fluids - Multiple outlets

  1. Aug 23, 2012 #1
    Hey, so my situation is a positive displacement pump churning out 30gpm. Theres a bunch of pipe losses that I can deal with, and then a long 1.5" pipe with 8 possible outlets (you can screw on a hose). When one hose is attached the pressure is a we will say P1 (read from a gauge on the 1.5" pipe). When two hoses are attached P2 < P1. So the pressure in the pipe goes down. This makes sense when you think about it, less pressure required to push all that liquid out since you have twice the area.

    My problem is trying to explain this with the bernoulli equation. Shouldnt the energy (head or stagnation pressure if you want) in the pipe stay constant in these two situations? But since I am sure there is 30gpm going through either one hose, or 15gpm each going through 2, there is always 30gpm going through the 1.5" pipe. That means the pressure has to stay constant for the total energy to stay constant right?

    Whats happening here?!?!

    Update: At this point im of the thought the pump just pushes harder. Now im at the stage of trying to get the pipe losses in a 6mm diameter steel tube with water going through at 33m/s. This goes past my moodly chart, and therefore the answers seem to give giant pressure drops...
     
    Last edited: Aug 23, 2012
  2. jcsd
  3. Aug 23, 2012 #2
    Update: At this point im of the thought the pump just pushes harder. Now im at the stage of trying to get the pipe losses in a 6mm diameter steel tube with water going through at 33m/s. This goes past my moodly chart, and therefore the answers seem to give giant pressure drops...
     
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