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

 

[astrokreng]

Hello,

Thank you for your question. In vacuum technology, the pumping speed and pressure are indeed related to each other through the conductance of the system. However, the pumping speed is not necessarily constant and can change over time as the system reaches equilibrium. This is because the conductance is not a constant value and can vary depending on factors such as the type of pump used, the size and geometry of the piping, and any potential leaks in the system.

To accurately calculate the pressure and pumping speed as a function of time, you will need to consider the initial pump speed, the conductance of the system, and any changes in these parameters over time. This can be a complex calculation, and it may be helpful to consult with a vacuum technology expert or use specialized software to accurately predict the behavior of your system.

Additionally, it is important to note that the equation you mentioned, Pt=Ps + (Po-Ps)e^-st/v, is a simplified version of the more complex equations used in vacuum technology and may not provide accurate results in all cases. It is always best to consult with experts and use specialized tools when dealing with vacuum systems.

I hope this helps and wish you success in your research.