Vacuum Chamber: How Long Will It Maintain Pressure?

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SUMMARY

The discussion centers on the behavior of a syringe plunger in a vacuum chamber with an initial pressure of 29.9 Hg. It concludes that the plunger will indeed move forward on the first run due to the pressure differential created by the vacuum. Subsequent runs will continue to draw the plunger forward, assuming minimal friction and that the vacuum chamber is not emptied. The pressure differential will decrease with each run as air is introduced, with calculations indicating that after five runs, the pressure will be 0.5 atm based on the volume of air added.

PREREQUISITES
  • Understanding of vacuum pressure measurement (Hg)
  • Basic principles of pressure differentials
  • Knowledge of syringe mechanics and operation
  • Familiarity with gas laws and volume calculations
NEXT STEPS
  • Research the effects of pressure differentials on fluid dynamics
  • Learn about vacuum chamber maintenance and performance optimization
  • Explore gas laws, particularly Boyle's Law and its applications
  • Investigate the impact of temperature on gas pressure and volume
USEFUL FOR

This discussion is beneficial for engineers, physicists, and anyone involved in vacuum technology or fluid mechanics, particularly those working with syringes and vacuum chambers.

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The syringe' plunger is in a fully retracted position (non-vacuum state) and is then connected to the tube forming an airtight seal. Then the valve to the vacuum chamber, having 29.9 Hg of vacuum, is opened.

I am fairly, certain that the plunger in the syringe will move to its forward most stop, on the first run. What will happen with the 2nd, 3rd, 4th, and subsequent runs, provided the vacuum chamber is not emptied after each run?

 Will the plunger be drawn forward on its tenth run?
 How will the pressure differential be affected after the first run, then the following runs?
 

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Assuming minimal friction, the plunger will be drawn forward on its 10th run.

Assuming you allow the air to return to equilibrium temperature after each "run", you can simply ratio the volume added to the total volume to find the pressure. Ie, after 5 runs, you've added 500 cc of 1atm air for a pressure of 500/1000=.5atm.
 

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