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Need Help with an Air Flow Problem?

  1. Nov 16, 2006 #1
    We are having trouble calculating a required ft^3 per minute air flow for a particular vessel which was constructed to measure the accuracy of a vacuum machine.
    Our vessel is a steel cylindrical drum 1mm thick with a diameter of 22.5" and a height of 34.5". It has 50 holes around the lower perimeter measuring 13 mm in diameter. What is the air flow rate if we pull a vacuum of 1" of H20 at a temp of 70 deg. F and Relative Humidity of 26%. Can anyone help us out?
  2. jcsd
  3. Nov 16, 2006 #2


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    Hi naboulsi,
    This probably belongs in the mechanical engineering forum. Anyway, assuming your system is maintaining 1" water vacuum, steady state, and assuming a discharge coefficient for your drilled holes of roughly 0.7 (from experience) I'd estimate your flow rate to be 280 SCFM.
  4. Nov 16, 2006 #3


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    The way to calculate it is to use Bernoulli's equation: assuming perfect nozzles, that 1" of static pressure becomes your velocity pressure.
  5. Nov 16, 2006 #4


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    That is a pretty poor sounding calibration standard.
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