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

[minna233]

Hi,

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.

 

[Torricelli]

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