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Homework Help: Air Volume Speed to Air Speed

  1. Sep 28, 2008 #1
    I was doing some research for my senior design project and came across a problem.

    We are working with the PacWind Detla I wind generator and need to mimic high wind conditions. You see, we don't want to have to rely on just the natural wind for generation, we would like to create a high wind environment so that we can get the most out of our generator. Higher wind speed = more output power.

    My problem is that most industrial fans are rated in CFM, which is air volume speed, not air speed.

    I need to figure out how to convert from CFM to mph (or m/s) or any form of air speed.

    Is there anybody in here that can help me?

  2. jcsd
  3. Sep 28, 2008 #2


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    Welcome to PF.

    As a gross estimate, how would you expect to get from volume/min to linear speed?

    Volume/minute is Distance3/time and Speed is distance/time?
  4. Sep 28, 2008 #3
    LowlyPion, that is exactly my point. Mathematically it seems impossible, however, I know there is some kind of way to relate the two quantities.

    Also, I know that air speed will depend on the diameter of the fan/tube. For example, air will flow faster through a tube w/ a smaller diameter than with a larger one.. And I'm assuming that if it is just a simple fan, the speed will be even lower.

    I was just seeing if anyone knew how to get a fairy accurate estimate based on CFM alone.
  5. Sep 29, 2008 #4


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    You weren't paying close attention to what I was saying. Volume/min is roughly speaking in air flow terms equal to the cross section of the wind channel times the air speed. Now of course the reason I say "roughly" is because it's a pretty lossy system because of air leaking and non-uniformity between circular fans and rectangular channels, and the air pressure differentials that a fan can support and such. But it's not a bad place to start.
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