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Air flow between two different pressures

  1. Jun 1, 2005 #1
    I have a problem for a project i'm doing:
    I have one chamber that is 120 mm Hg higher than another chamber(which is at atmospheric pressure) and is slowly being deflated. Force being applied causes this 120 pressure difference, and is constantly being applied. The 2nd chamber will always be atmospheric, as the added air will not make a difference. I have a starting volume of the higher pressure chamber, but as the chamber is deflating, the volume will change. I want the volume to completely deflate in 5 min, and i will be solving for the diameter hole i need for this to happen. The volume is small, and the hole will be extremely small. How would I do this? Thank you for the help
  2. jcsd
  3. Jun 1, 2005 #2


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    Staff: Mentor

    Assuming no other losses, apply Bernoulli's equation to all of that static pressure difference to dynamic pressure and calculate the associated velocity of the air. Then its just volume divided by flow rate divided by velocity to get area.
  4. Jun 3, 2005 #3
    So if you have a volume of .10508 in^3 that you want to deflate in 300 s, that is 3.502666 X 10^-4 in^3/s for a flow rate. The pressure difference starts at 120 mm Hg, the air density is about 1.2 kg/m^3. What would you get for the hole diameter? or what exactly will the equation look like, i am not very familiar with Bernoulli's equation. I just want to make sure I do this right, thanks a lot.
    Last edited: Jun 3, 2005
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