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Will this flow the same?

  1. Apr 26, 2010 #1

    ISX

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    So basically we have 2 pipes, one is straight, one has 90* bends in it and a concave surface to hit and stir things up even more. X shows that all the widths are the same everywhere, so it's not like the pipe is getting bigger or smaller in diameter. We have 20psi of pressure, will the CFM out of both pipes be the same?

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  2. jcsd
  3. Apr 26, 2010 #2

    Q_Goest

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    If the actual lengths of the two are the same, and the dP across them is the same, then the straight pipe will have a higher flow. There is something called an "equivalent length" for any pipe or tube with bends and other restrictions. It is this equivalent length that has to be the same in order for the two pipes to flow the same. Bends and other restrictions increase the equivalent length.
     
  4. Apr 26, 2010 #3

    ISX

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    Alright so lets say they are the same length and everything and therefore have the same flow, why is it that they do have the same flow when the bent and screwed up one has to fight the 90* corners? Wouldn't the turbulence cause a reduction in flow rate?
     
  5. Apr 26, 2010 #4
    Of course. There might be an increase in velocity, but the flow-rate itself, during restriction, is lower.
     
  6. Apr 26, 2010 #5

    ISX

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    Hmmmm, so lets say I turn the pressure on to both pipes and hook it to a tank and 10 seconds goes by and I turn it off, would there be the same amount of air in both tanks?

    The reason I ask is because you say flow rate goes down but velocity increases.. Are those 2 variables just like volts and amps? As in, if one goes down the other increases and you still have the same amount of watts. Or in this case, velocity goes up flow goes down but you still end up with the same volume..? Or is this wrong?
     
  7. Apr 26, 2010 #6

    Q_Goest

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    I'm afraid you read me wrong. If they have the same length and the same pressure drop (ex: they are both connected to the same tank and discharge to atmosphere so the pressure drop is the same) then the STRAIGHT pipe flow rate will be HIGHER. So yes, the additional restrictions in the line will cause a reduction in flow rate.
     
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