Durgaprasad123
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Compressed air flowrate calculation
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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.
Mentor
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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.
Durgaprasad123
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Asymptotic
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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.