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Will the air in the shaft condense?

  1. Oct 29, 2015 #1
    Consider a small enclosed vertical shaft (say 50x50 cm) inside an aparment building with an Ø160 mm uninsulated steel exhaust duct moving air at anything from +20°C to -10°C depending on time of year. Surrounding areas are at room temperature, 21°C.

    The air surrounding the duct inside the shaft will practically be stagnant, and I'm wondering how probable it is that this air will condensate. I'm under the impression that the air needs to have some flow in order to condensate, but I'm not sure if that's at all true. Also, what if the shaft is completely filled with insulation (mineral wool). Will that make a differance?
  2. jcsd
  3. Oct 31, 2015 #2


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    The air itself won't condense, but water vapour in it certainly will at -10°C at the surface of the steel pipe, unless there is some reason to expect very dry air in the shaft.
    There is still some remaining water vapour close to the steel pipe, but the effect might be negligible. Insulating the pipe only could be better.
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