Thermal Vac chamber pressure gain question

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Discussion Overview

The discussion revolves around a thermal vacuum chamber incident where a gas release caused a pressure increase. Participants are exploring how to calculate the volume of gas released based on the initial and final pressures in the chamber, using principles of gas laws and calculations related to vacuum systems.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant describes the incident involving a pressure rise from 3.7E-7 to 5.0E-7 and seeks to calculate the volume of gas released.
  • Another participant suggests considering the number of atoms involved due to the low pressures and mentions potential contamination issues with the vacuum system.
  • A third participant proposes using the ideal gas law (PV=nRT) to estimate the gas volume released, suggesting a specific pressure for calculations.
  • Further, a participant outlines a method to calculate the volume of the chamber in liters and how to derive the moles of gas before and after the incident using standard molar volume.
  • One participant questions whether the pressure rise occurred during the evacuation process, implying a potential link to the incident's timing.

Areas of Agreement / Disagreement

Participants are exploring various methods to calculate the gas release, but there is no consensus on the exact approach or the implications of the incident, indicating multiple competing views and unresolved questions.

Contextual Notes

Participants have not fully resolved the assumptions related to the ideal gas law application, the specific conditions of the chamber, or the timing of the incident in relation to the evacuation process.

Who May Find This Useful

Individuals interested in vacuum technology, gas dynamics, and those involved in experimental physics or engineering may find this discussion relevant.

loctwo
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Hi group, I work at Thermal Vacuum Chamber, and we had an incident last night where our chamber, Which is 70' H x 30' D, was pumped down to a pressure of 3.7E-7. There was a release of gas into the chamber abruptly last night that caused the pressure in the chamber to rise to 5.0E-7, before it recovered back to it's original pressure. My question is How can I tell in liters how much gas was released into the chamber to cause this amount of rise in chamber pressure, based on the starting pressure and the ending pressure?
 
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Wow! both # are so far below viscus flow, it might be worth thinking about how many atoms we are talking about. (it's been over 30 years since I did vacuum stuff.)
From the interweb, http://en.wikipedia.org/wiki/Mean_free_path
In a chamber that size, I am thinking some type of contamination, even roughing pump oil out gases at 10 -7. I have seen a case where diffusion pump could not get to a high vacuum. It turned out that the diffusion pump oil was contaminated with another oil.
 
loctwo said:
Hi group, I work at Thermal Vacuum Chamber, and we had an incident last night where our chamber, Which is 70' H x 30' D, was pumped down to a pressure of 3.7E-7. There was a release of gas into the chamber abruptly last night that caused the pressure in the chamber to rise to 5.0E-7, before it recovered back to it's original pressure. My question is How can I tell in liters how much gas was released into the chamber to cause this amount of rise in chamber pressure, based on the starting pressure and the ending pressure?

Use the ideal gas law (PV=nRT) with a pressure of 1.3E-7.
 
Calculate the volume of the chamber in liters.
Divide by the standard molar volume of a gas at STP (22.41 liters)
Multiply this volume by 3.0E-7/760 and 5.0E-7/760 to get moles of gas before and after.
Subtract and get gas released into chamber, in moles (e.g., 29 grams per mole of air).
 
Did the incident occur while the evacuation was going on?
 

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