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I How Does a Pressurized Tank Empty Over Time Through a Hole?

  1. May 29, 2018 #1
    I having difficulty wrapping my head around a concept that I wish to solve. I have a 10L tank of compressed air at 100psi. When an outlet hole of cross-sectional area of 0.115 in^2 is opened, I wish to develop a curve of pressure vs. time from t=0 until pressure drops to atmospheric. Many things can be neglected in this situation, such as friction etc., since I would like a general curve to compare with experimental data. I am unsure of how to apply fluid dynamics to a vessel that empties simply due to its own pressure difference through an area.

    Temperature can be assumed to be constant at 25C as well.
     
  2. jcsd
  3. May 29, 2018 #2

    Henryk

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    You can find engineering formula in places such as valve manufacturers, pneumatic handbooks, etc. Here is an example http://www.theleeco.com/engineering/engineering.cfm#lohm-laws-working-with-gases

    You have to be aware that you will need two regimes for your problem: initially the inside pressure is greater than 1.9 x atmospheric and you need a sonic formula. At lower pressures subsonic equations will do.
     
  4. May 30, 2018 #3
    Doesn't
    100psi relative is 114psi absolute, which is nearly eight times greater than atmospheric. Are you aware of any ways that this could be done to give a rugh estimate? After all I will be testing this and ultimately have the real data to compare this to.
     
  5. Jun 1, 2018 #4

    Henryk

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    Follow the link. You will find a number of pages with relevant information. Lee valve company uses LOHMS concept. Find how to calculate LOHM for a give size orifice and then the flow rate as a function of pressure.
     
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