how to calculate the volume of PRESSURIZED Natural gas in a pipe

[Gasdealer]

Hello,
i need to know exactly how to calculate volume (to know the the time it will take till the pipe line will be empty)
for PRESSURIZED natural gas.
i was using Volume X pressure ( gauge pressure )
and then i have been told that i must use the absolute pressure.
please advice.
Thanks

 

[MortenA]

It seems to me that you have a very basic understanding of thermodynamics.

Maybe you should seek help either within you company or external consultant?

A blowdown calculation is much more than just the inventory.

BTW: The VOMUME is just the volume of the pipeline - but the STANDARD volume is actually just the no. of mol gas in the pipeline - but thats not "jus" the volume.

Best regards

Morten

 

[Gasdealer]

yes you are right. i need the standard volume

 

[dcasto]

To convert from the volume at actual conditions start with PV=znRT rearrange to PV/zRT = n. Since we want the n (number moles) at each condition to be equal (PV/zRT) at standard = (PV/zRT) at start 1=starting 2=standard

P2 * V2 /z2 /T2 = P1 * V1 / z1 / T1

V1 = P1/P2 * T2/T1 * z2/z1 * V1

 

[dcasto]

V2 = P1/P2 * T2/T1 * z2/z1 * V1

 

[Gasdealer]

thank you dcasto, the question is the pressure is absolute right?

 

[dcasto]

use absolute pressures.

 

[tgmcg]

Flowrate through a fixed orifice varies with inlet pressure (and temperature). For an adiabatic system, temperature also varies with pressure.

There's more to consider than just volume.