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Vacuum Problem (pumping speed and pressure as a functino of time)

  1. Sep 14, 2008 #1

    I am in experimental physics and having some problems with a question about vacuum technology. They want you to calculate and plot the pressure and pumping speed at the vessel as a function of time. They give you vessel volume, the cylindrical pipe dimensions, and the initial pump speed. I started using this equation; Pt=Ps + (Po-Ps)e^-st/v and conductance which is 1/s=1/so-1/c. If you can get effective pumping speed from this wouldn't it be constant and not changing with time? Thank you.
  2. jcsd
  3. Sep 23, 2008 #2
    the equataion to start is p.V = m R T

    p is the pressure (vacuum) in the chamber (of volume V),

    looking for dp and dT, m becomes the suction flow of your pump,

    => t = (V/CAP).Ln (p1/p2), CAP is the volumic flow of the vacuum pump

    pls refer to: http://vacuum-guide.com/english/equipment/technikfaq.htm
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