Pipeline De-Isolation & Gas Expansion

[Alph]

I have been asked the following question :

Two subsea gas pipelines, both shut-in, connected via a manifold with 6” gate valve as the barrier between the two pipelines.

Pipeline 1 : Volume =500m³, Pressure = 50 Bara, Temperature = 8°C
Pipeline 2 : Volume = 60m³, Pressure = 200 Bara, Temperature = 8°C

When the gate valve is opened, the two systems will equalise in pressure, Pipeline 2 pressure will drop. What is the resulting gas temperature drop in pipeline 2?

Regards
Alph

 

[BigInch]

I think your final temperature will obviously stabilize at 8C, so I'll place the final pressure at 54.4 bara.

**********************
"Being GREEN isn't easy" ..Kermit

http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.live.com/

 

[zdas04]

And the reason the temperature doesn't drop through some mechinism like J-T cooling is that you don't get J-T cooling unless you are sustaining a dP through a choke or throttled valve. You might think that this is a violation of the ideal gas laws, but you'd be wrong. PV=ZnRT, but the whole right side of the equation can remain constant (or nearly so, the change in compressibility is probably close enough to zero to be ignored, even if not then P1V1/Z1=P2V2/Z2) while the volume changes in one direction and the pressure changes in the other direction.

David

 

[Alph]

Thanks Guys,

I did get temperature close to 8°C, did not seem to make sense. Thanks for the explanation david.

Regards
Al

 

[dcasto]

you shuld get exactly 8C because that huge heat sink (either way) called the ocean will always over shadow and JT effect.