- #1
Compressed air flowrate calculation
- Thread starter Durgaprasad123
- Start date
Click For Summary
Discussion Overview
The discussion revolves around calculating the flow rate of compressed air from a pressure-reducing valve connected to an air bottle. Participants explore various factors affecting flow rate, including pipe dimensions, pressure settings, and system configuration.
Discussion Character
- Technical explanation
- Debate/contested
- Mathematical reasoning
Main Points Raised
- One participant requests assistance in calculating the flow rate from a 30 bar air bottle through a 25 nb pipe with a pressure-reducing valve set to 5 bar.
- Another participant clarifies the terminology used, suggesting that 'nB' should refer to inner diameter in mm rather than a different unit, and questions the length of the pipe, indicating it could affect calculations.
- A participant notes that the characteristics of the valve are important but emphasizes that the primary function of the pressure-reducing valve is to maintain constant pressure as flow varies.
- Further details are requested regarding the pipe length and internal diameter surface finish, with an online estimator providing flow rate estimates for different lengths of pipe under specific conditions.
- One participant expresses frustration over a lack of relevant dimensions and notes that the situation described has changed, indicating a need for clearer information.
Areas of Agreement / Disagreement
Participants do not reach a consensus on the flow rate calculation, as multiple factors remain unclear and different views on the system setup are presented.
Contextual Notes
Limitations include missing assumptions about the system configuration, dependence on specific definitions (e.g., nB), and unresolved details regarding pipe dimensions and characteristics that could significantly affect flow rate calculations.
- #2
BvU
Science Advisor
Homework Helper
- 16,219
- 4,934
Hello Durgaprasad, 
To physicists you have to explain that you mean 'inner diameter in mm' when you use the term nB (nominal bore). A lot of us would think 25 nanobarn (i.e. an area ##25 \times 10^{-28} ## m2
)
How many km long is this 25 nB pipe ? makes a difference!
You can do a lot yourself with pressure drop calculations. I would concentrate on the lower pressure part of the pipe
unless the valve is close to the exhaust point.
To physicists you have to explain that you mean 'inner diameter in mm' when you use the term nB (nominal bore). A lot of us would think 25 nanobarn (i.e. an area ##25 \times 10^{-28} ## m2
)How many km long is this 25 nB pipe ? makes a difference!
You can do a lot yourself with pressure drop calculations. I would concentrate on the lower pressure part of the pipe
unless the valve is close to the exhaust point.- #3
russ_watters
Mentor
- 23,873
- 11,325
The valve characteristics also matter, but the the point of a prv is to keep pressure constant as flow varies. So if what you have shown is sized properly, none of it is relevant to the question!
What we would need is what the rest of the system looks like.
What we would need is what the rest of the system looks like.
- #4
- #5
Asymptotic
- 781
- 529
Pipe length from regulator outlet to exit?
Pipe ID surface finish? It makes a difference.
If ID is smooth, for 5 bar regulator setting with air exhausting to atmosphere an online estimator calculates about 0.47 m3/minute for 1 kilometer, and 10.1 m3/minute for 3 meters of pipe. This estimator doesn't capture all of the nuances, nor does it address at all this new aspect to your question, namely, flow rate as the second vessel is filled. Air flow will be at nearly the 'exhausting to atmosphere' rate at first, and drop to zero as vessel #2 pressurizes to the 5 bar source.
Pipe ID surface finish? It makes a difference.
If ID is smooth, for 5 bar regulator setting with air exhausting to atmosphere an online estimator calculates about 0.47 m3/minute for 1 kilometer, and 10.1 m3/minute for 3 meters of pipe. This estimator doesn't capture all of the nuances, nor does it address at all this new aspect to your question, namely, flow rate as the second vessel is filled. Air flow will be at nearly the 'exhausting to atmosphere' rate at first, and drop to zero as vessel #2 pressurizes to the 5 bar source.
- #6
BvU
Science Advisor
Homework Helper
- 16,219
- 4,934
My neck hurts from the leaning 90 degrees sideways.
You now describe a completely different situation. And still haven't given the relevant dimensions.
You now describe a completely different situation. And still haven't given the relevant dimensions.
Similar threads
- · Replies 3 ·
- · Replies 22 ·
- · Replies 8 ·
- · Replies 45 ·
- · Replies 11 ·
- · Replies 14 ·
- · Replies 2 ·
- · Replies 2 ·