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Initial Conditions in a vessel: P~my unknown, but ~100torr, V=5000cc, T=35C, gas is 50/50 N2/He

Laser drill a hole in the initial volume of diameter=10mils through a chamber wall thickness of 0.75mm.

Expand gas into sampling chamber (where pressure gauge is) of V=100cc, P before expansion=vacuum 10E-6 at highest, T=20C. I've previously been assuming the T was constant and only using P1V1=P2V2 to back calculate pressure in the original vessel, but now I'm questioning, how fast does the gas temperature equilibrate with the sampling chamber where my pressure gauge is. It takes minutes for the gas pressure to equilibrate (~3-5min) through the orifice. Do I need to be taking the temperature of the sample chamber into account? How can I calculate the rate of temperature decrease? Is it gas species dependent?

Thank you!

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  • $\begingroup$ It definitely depends on the chamber material, right? $\endgroup$ – Chet Miller Mar 22 at 21:10
  • $\begingroup$ Both chamber materials are mostly stainless steel. @ChetMiller $\endgroup$ – Kelvin Mar 22 at 21:14
  • $\begingroup$ And if it matters, the original vessel is the a gas bottle and the sample chamber is 40cc of 1/4 tubing and two sample bottles of 50 and 10ccs. $\endgroup$ – Kelvin Mar 22 at 21:32
  • $\begingroup$ If the temperature can be assumed to be constant for the 5 min it takes for the pressure to equilibrate (for me to take my pressure measurement), then I'll happily continue to assume T is constant, but I'm looking for guidance on the dT/dt rate, so I can determine if I need to take it into account. $\endgroup$ – Kelvin Mar 22 at 21:42
  • $\begingroup$ You are introducing gas initially at 100 torr through an orifice into a chamber that originally contains vacuum? Even if the gas exchanged no heat whatsoever with the chamber, it would still heat up. $\endgroup$ – Chet Miller Mar 25 at 11:53

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