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Friction loss to vertical pipes in a closed system?

  1. Apr 23, 2015 #1
    So in designing closed systems, mostly heating systems, I realized today that I've probably been doing one thing wrong all these years. In such a system one doesn't take elevation loss due to gravity into account since you "get it back" on the way down. This I've always been aware of, but what I've still been doing is treating the vertical lengths of pipe as if they were horizontal, that is applying to them a friction loss per meter. Can someone just confirm that I can stop doing this? I'll just go back to my corner and be ashamed...
     
  2. jcsd
  3. Apr 23, 2015 #2
    Have you estimated how much of a pressure difference is involved as a result of the elevation differences, as compared with the frictional losses?

    Chet
     
  4. Apr 23, 2015 #3
    Pressure loss due to elevation would be much higher than the major head loss per meter. Elevation loss is just a result of gravity, 9,8 kPa/m in addition to the friction loss, compared to about 0,15 kPa/m in the horizontal piping. But I believe the elevation loss doesn't need to be considered at all in a closed circulating system.
     
  5. Apr 23, 2015 #4
    What about when you select the fan? Doesn't it need to have enough ooomph to get significant air flow to the upper floor(s)?

    Chet
     
  6. Apr 23, 2015 #5
    It's a central heating system, so there is a water circulation pump, not a fan.
     
  7. Apr 23, 2015 #6

    stewartcs

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    Technically you should consider the elevation changes so you can size your pump correctly. I imagine that since it's a closed loop system that is being constantly recirculated that you'll end up with the same answer. Why not just run a couple of hand calcs and do one like you've been doing it and then one that includes the elevations and see what the results tell you?

    CS
     
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