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  1. #1

    Hmm Air duct calculation. HELP!!

    By design, which of the following air ducts will allow 250 cfm to flow with a velocity of 500 ft/min?

    A. 9" x 8"
    B. 16" x 9"
    C. 10" x 9"
    D. none of the above

  2. #2
    Join Date
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    a.
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  3. #3
    How did you come up with that answer?

  4. #4
    Join Date
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    Louisville, KY
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    9*8/144 = 0.5 sf

    250 cfm / 500 fpm = 0.5 sf


    Volumetric Flow = Velocity * Area

    So, Area = Volumetric Flow / Velocity
    Perhaps you should have read the instructions before calling.

  5. #5
    Join Date
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    CFM/velocity=duct area in sq ft.
    250CFM/500FPM=.5sqft, 144 sq in to a sq ft, so .5 times 144 =72 sq in. So 9 x 8 duct.
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  6. #6
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    I type too slow.
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    How many times must one fix something before it is fixed?

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