Measure the volume of a lighter than air balloon

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SUMMARY

The discussion focuses on calculating the volume of a helium-filled balloon without fully inflating it. The user has access to the volume of helium storage tanks, initial and final pressures in the tanks, and seeks to inflate the balloon to a specific percentage of its maximum volume. Two methods are proposed: weighing the helium cylinders before and after filling the balloon to determine the moles of helium transferred, and using the ideal gas law (PV=nRT) to relate pressure changes in the cylinders to the volume of helium in the balloon, adjusted for temperature and pressure conditions.

PREREQUISITES
  • Understanding of the ideal gas law (PV=nRT)
  • Knowledge of pressure measurement (absolute vs. gauge pressure)
  • Familiarity with basic thermodynamics (effects of temperature on gas volume)
  • Experience with weighing techniques for gas volume calculations
NEXT STEPS
  • Research the ideal gas law applications in real-world scenarios
  • Learn about pressure measurement techniques and their implications in gas calculations
  • Explore methods for accurately weighing gas cylinders before and after use
  • Investigate the effects of temperature on gas behavior during transfer processes
USEFUL FOR

This discussion is beneficial for physicists, engineers, and hobbyists involved in gas dynamics, balloon design, or any applications requiring precise volume measurements of gases under varying pressure and temperature conditions.

psuedoben
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hello, i am trying to calculate the volume of a balloon (which is quite large). It has been filled with helium via a valve connecting helium storage tanks to the balloon. The knowns I have are the volume of the storage tanks, the intital pressure in the tanks, and the final pressure in the tanks after filling the balloon. I am confident there are enough knowns here to solve this problem and my gut feeling is that its a pretty straightforward solution too. despite this, i cannot seem to solve it.
 
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Measure the balloon ?
 
I'm sorry Nidum, I suppose I left out a key detail. I don't want to fully inflate the balloon. I want to inflate it to a percentage of its maximum volume and then confirm that I've achieved that percentage by doing this calculation
 
What is the pressure in balloon? Is the balloon envelope elastic and under tension with greater than atmospheric pressure, or is the balloon a bag with a slack surface at 1 atm?
What is the balloon temperature? As He is transferred it will cool, so volume will be less until it equilibrates.
Is the pressure in the cylinder measured absolute or gauge, above atmospheric?

Method 1.
You could weigh the cylinders, fill the balloon, then weigh the cylinders again. The weight reduction will give the moles of He transferred. Convert moles to volume at balloon temperature and pressure.

Method 2.
Absolute pressure in cylinders will be proportional to helium content. PV=nRT.
Pressure reduction will give moles of He transferred = volume of balloon, adjusted for pressure and temp.
 
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