Flow between the Vessels

Forum about flow calculators available on pipeflowcalculations.com and how to find solution for your fluid flow problem.
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moin
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Joined: Thu Mar 30, 2017 8:31 am

Flow between the Vessels

Post by moin » Thu Mar 30, 2017 9:10 am

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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Last edited by moin on Sat Apr 01, 2017 10:26 am, edited 1 time in total.

admin
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Joined: Mon Feb 08, 2010 7:47 pm

Re: Flow between the Vessels

Post by admin » Sat Apr 01, 2017 8:06 am

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.
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moin
Posts: 3
Joined: Thu Mar 30, 2017 8:31 am

Re: Flow between the Vessels

Post by moin » Sat Apr 01, 2017 10:32 am

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 :(
Regards

admin
Site Admin
Posts: 358
Joined: Mon Feb 08, 2010 7:47 pm

Re: Flow between the Vessels

Post by admin » Tue Apr 04, 2017 6:52 pm

I have used my calculator for gas flow on pipeflowcalculations.com.
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.
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