Flow rate of air in discharging reservoir

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SUMMARY

The discussion centers on calculating the volume flow rate of air discharging from a tank using Boyle's Law and flow measurement techniques. The user proposes using the formula Vc = Va*(Pc/Pa) to determine the compressed volume of air, followed by calculating the average flow rate Q = (Va,2 - Va,1) / (t2 - t1) based on pressure measurements over time. The conversation suggests exploring compressible flow theory and flow through an orifice, specifically choked flow, for more accurate results.

PREREQUISITES
  • Understanding of Boyle's Law and its application in gas behavior
  • Familiarity with flow rate calculations and measurement techniques
  • Knowledge of compressible flow theory
  • Basic principles of fluid dynamics, particularly regarding orifices and nozzles
NEXT STEPS
  • Research compressible flow theory and its applications in fluid dynamics
  • Learn about flow measurement techniques for gases, including orifice flow calculations
  • Study the principles of choked flow and its significance in high-speed gas discharge
  • Explore practical applications of Boyle's Law in engineering scenarios
USEFUL FOR

Engineers, physicists, and anyone involved in fluid dynamics or gas discharge systems will benefit from this discussion, particularly those focusing on air flow measurement and analysis.

rcummings89
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If I have a tank of volume V, pressure P, and temperature T, what is the most effective way to determine the volume flow rate if I were to suddenly allow the air to discharge through a hose?

My first thought was that I could use Boyle's Law to determine the compressed volume of air in the tank:

Vc = Va*(Pc/Pa)

Where Va is the volume of the non-pressurized vessel, and Pa is atmospheric pressure. Then I could measure the pressure at certain time intervals (say, once every 5 seconds) and calculate a new compressed volume. From there I could calculate the average flow rate during that period as

Q = (Va,2 - Va,1) / (t2 - t1)

And if I take the measurements at even shorter time intervals I believe the result should tend toward the instantaneous flow rate.

Am I on the right track with this? Should I be looking at compressible flow theory for a crude converging nozzle instead? Any help or feedback is greatly appreciated in advance!
 
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I had a similar question regarding air flow through a nozzle. The best bet is to look into flow through an orifice, also choked flow.
 

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