How Do You Calculate the Flow Rate of Oxygen in a Pressurized System?

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Discussion Overview

The discussion revolves around calculating the flow rate of oxygen (O2) from a pressurized tank into a known volume of 25 in³. Participants explore various factors affecting the flow rate, including pressure, tubing dimensions, and the time taken to fill the cylinder.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant seeks assistance in calculating the flow rate of O2, questioning whether the Bernoulli equation is applicable.
  • Another participant emphasizes the need to specify the dimensions of the path through which O2 flows.
  • Details about the tubing length (35 ft) and inner diameter (1/16”) are provided, along with the pressure source (150 psi) and the filling pressure (140 psi).
  • Concerns are raised about the pressure drop (10 psi) across the tubing and whether a booster pump is involved.
  • Further clarification is sought regarding the flow rate specification, including whether it should be expressed in volume per second at standard atmospheric pressure.
  • Participants discuss the volume of the piping compared to the volume being filled, questioning its significance in the calculations.
  • Some participants suggest that the average flow rate can be calculated using the known volume, initial and final pressures, and filling time.
  • There is a proposal to apply Bernoulli principles and consider Reynolds equation under the assumption of turbulent flow.
  • One participant notes that simply dividing the volume by the filling time yields the average volumetric flow rate but does not account for the mass of O2 unless certain assumptions about temperature and process type are made.

Areas of Agreement / Disagreement

Participants express differing views on the methods for calculating flow rate and the assumptions necessary for accurate results. There is no consensus on the best approach or the applicability of specific equations.

Contextual Notes

Participants highlight the importance of initial conditions, such as pressure in the piping and the presence of valves, which may affect flow calculations. The discussion also touches on the potential impact of temperature on gas behavior during the filling process.

Nando
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TL;DR
Fluid dynamics and flow rate calculation from outside tank to inside tank!
I am trying to calculate the flow rate of O2 from a known volume 25 in^3. The cylinder will fill up to a maximum pressure of 140 psi in 11.26 seconds. Any help to determine the flow rate will be appreciated. Do I use Bernoulli equation to find the flow rate?
 
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Welcome to PF.
I think you must specify the dimensions of the path the O2 will flow to escape from the volume.
 
The tubing length is about 35 ft with an ID of 1/16”
 
Nando said:
Summary:: Flow rate calculation from a known volume. Time to fill the cylinder of 25 in^3 and max pressure

I am trying to calculate the flow rate of O2 from a known volume 25 in^3. The cylinder will fill up to a maximum pressure of 140 psi in 11.26 seconds. Any help to determine the flow rate will be appreciated. Do I use Bernoulli equation to find the flow rate?
The O2 is flowing from where to where? Into or out of the ##25 in^3## volume? If into, what is the pressure available from the source?
 
berkeman said:
The O2 is flowing from where to where? Into or out of the ##25 in^3## volume? If into, what is the pressure available from the source?

Pressure source is from a tank outside the building. Pressure on that tank is 150 psi. So o2 flows from that tank and into 25 in^3 volume. Tubing ID is 1/16”
 
Nando said:
The cylinder will fill up to a maximum pressure of 140 psi in 11.26 seconds.
Nando said:
Pressure source is from a tank outside the building. Pressure on that tank is 150 psi.
Nando said:
The tubing length is about 35 ft with an ID of 1/16”

So there is only a 10psi drop in flowing from the outside tank through all that tiny tubing and the final valve into the smaller tank? Or is there a booster pump involved? Have you tried this yet?
 
berkeman said:
So there is only a 10psi drop in flowing from the outside tank through all that tiny tubing and the final valve into the smaller tank? Or is there a booster pump involved? Have you tried this yet?
Ok. Just found out that part of that line will be 1/4" ID on 20' length.
 
I am trying to calculate the flow rate of O2 that flows from a tank outside a building to a known volume 25 in^3 inside the building. The pipe length from outside source to inside source is 70 ft at .25” ID and 1 ft at 1/16” ID. Outside source is at 150 psi. The cylinder inside will fill up to a maximum pressure of 140 psi in 11.26 seconds. Any help in determining the flow rate will be appreciated. Do I use Bernoulli equation to find the flow rate?

[Mentor Note -- two threads on the same question merged]
 
Last edited by a moderator:
This appears to be a duplication of a previous thread.

The flow rate will change as the gas flows between the two volumes.
Why specify the flow ?
How do you want to specify the flow ?
Will it be by volume/second if the gas was at a standard atmospheric pressure ?
 
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  • #10
What is in the piping and receiver before filling begins (pressure?)?

Is there a valve between the source and the inlet piping? If so, how restrictive is this valve?

You realize that the volume of the piping is much greater than the volume you are filling, right?
 
  • #11
You know the volume of the inside cylinder. You know the initial and final pressures in the inside cylinder. You know the filling time to four decimal places. That is sufficient information to calculate the average flow rate.
 
  • #12
jrmichler said:
You know the volume of the inside cylinder. You know the initial and final pressures in the inside cylinder. You know the filling time to four decimal places. That is sufficient information to calculate the average flow rate.
Yes. So is it as simple as applying Bernoulli principles? Can I also use Reynolds equation assuming the flow is turbulent?
 
  • #13
Is this not done simply by dividing the volume of the 25 inch3 by 11.26 seconds?
 
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  • #14
inkblotch said:
Is this not done simply by dividing the volume of the 25 inch3 by 11.26 seconds?
It will give you the average volumetric flow rate, but not the amount of mass of o2 in the second tank.
Unless we assume that the temperature of the gas in the 25 inch3 volume does not rise and it is an isothermal process with heat flow out of that small tank.
Or we could wait until the temperature stabilizes, re-measure the pressure, and use the ideal gas law to determine the mass of O2 in the small container.
See http://web.mit.edu/16.unified/www/FALL/thermodynamics/notes/node17.html section 2.3.3
 

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