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Flow between the Vessels

Posted: Thu Mar 30, 2017 9:10 am
by moin
Respected Members!
I'll be grateful if you please help me out in calculating the time to achieve 12 bar pressure in a 5000m3 AIR storage vessel by filling it through given pipe and flow coming from a 250m3, 40 bar AIR storage vessel.
Thank you in advance
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Re: Flow between the Vessels

Posted: Sat Apr 01, 2017 8:06 am
by admin
This type of calculation requires differential equation solution, meaning it is not an easy task, because the pressure on the exit of the pipe line is changing from 6 bar to 12 bar, and flow through connecting pipeline slows every moment.

As you want to fell 5000 m3 tank through 1" pipe - I can tell you that it is going to take a long time.
I have calculated that for 12 bar to 6 bar situation, flow through the the 1" pipe is 60 m3/h on 12 bar, and it is 720m3/h on atm pressure.
So it will take 5000/720 = 7 hours for 1 bar at that condition (this is just approximation without taking care about that the pressure is changing from 6 to 7 bar during that time).

As a total I get about 75 hours, but again it is just my very rough approximation.
It would be great if you can confirm it after the process is done.

On the other hand, as you have PRV on the line it might also limit the maximum flow rate on the system. You should know its Kg value.

One more data is needed, which fluid is flowing as density and gas constant is used in calculation? I have used data for propane. Just my assumption.

Re: Flow between the Vessels

Posted: Sat Apr 01, 2017 10:32 am
by moin
Dear Respondent..

Thank you a lot for your time. I'm sorry for not mentioning the fluid; it is AIR and I have updated the post also.
Can you please give me the calculation steps..? It may help me reaching a concluding solution by incorporating all the required parameters in Standard Equations.
Reason to do this uncommon procedure is that my Compressing Units for 5000m3 Vessel are under maintenance & I got an urgent requirement of 12 bar from these vessels :(

Re: Flow between the Vessels

Posted: Tue Apr 04, 2017 6:52 pm
by admin
I have used my calculator for gas flow on
As you say the fluid is air than one can use air pressure drop calculator available on the same web site.

I have divided the process into segments:
A. What I have done is calculate flow rate for 12 bar inlet and 6 bar outlet.
B. After that calculate flow rate for 12 bar inlet and 7 bar outlet.
X. And at the end for 12 bar inlet and 11 bar outlet.

All flow rates in segments of time A, B, .... X are calculated as m3/h flow at atm pressure using calculator. So to add 1 bar in sphere, you need 5000 m3 of air. If you have flow rate of 1000 m3/h in segment A than 5 hours are needed for that 1 bar pressure increase. This is very rough but I think close to reality. This calculation is done for every of segments A,B,C, ... X and the total time is the sum of them all.

Instead of the calculator you can use formula for pressure drop in the pipe at t=const. for the compressible fluid.

This is also with assumption that PRV has the capacity as the pipe which I think is not true - have to check Kg of PRV.
Also, I think that 1" 100 ft pipe line is the limitation of the system and no other component will reduce capacity more.

Flow between the Vessels

Posted: Tue Dec 11, 2018 10:05 am
by KennethBib
Do I have to optimize it even if I am going to use the flow to detect the fluorescence only not the size of the cell ?Does it has effect on the surface receptor fluorescence detection ?