Gas Temperature Rise Due to Compression
Gas Temperature Rise Due to Compression
(OP)
I understand that compression of a fixed volume of gas will result in a temperature rise in a gas e.g. in a gas compresssor. However, would the following result in a temperature rise to gas:
3 km sub sea pipeline initially filled with hydrocarbon gas at 4oC and 15 barg pressure. Pipeline then compressed to 300 barg by supplying more hydrocarbon gas (assuming gas supplied at a constant 4oC irrespective of pressure).
My thought is that the upstream end of the pipe, from where gas is supplied, will remain at 4oC. However, will the downstream end of the pipe rise in temperature due to the heat of compression (from the incoming gas)?
3 km sub sea pipeline initially filled with hydrocarbon gas at 4oC and 15 barg pressure. Pipeline then compressed to 300 barg by supplying more hydrocarbon gas (assuming gas supplied at a constant 4oC irrespective of pressure).
My thought is that the upstream end of the pipe, from where gas is supplied, will remain at 4oC. However, will the downstream end of the pipe rise in temperature due to the heat of compression (from the incoming gas)?





RE: Gas Temperature Rise Due to Compression
Your 300 barg into 15 barg is certainly a condition that is ripe for choked flow, and I think that you will have choked flow until the pipe pressure is around 150 barg which is 9 compression ratios. If the gas is methane (call it k=1.31), then I get a temperature for mixing to begin of 200C. From that point on, mixing temperature and J-T cooling would dominate. It would make since for the final system to be around 30-60C at 300 barg (but I didn't calculate it).
On the other hand, if you are careful to strictly control the inlet velocity to under 0.6 Mach then J-T cooling will dominate and your final temp could easily be 10-20C cooler than you started with.
David Simpson, PE
MuleShoe Engineering
www.muleshoe-eng.com
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RE: Gas Temperature Rise Due to Compression
I happend to have HYSYS open and with a gas case and just tapped in 15 barg 5ºC->300 barg - just using 100% adiabatic compression you get a final temperature of 450 deg C. This is of course only valid for the far end of the pipeline where no "new gas" arrives! Now this will not happen since the heat will leak into the surrounds. IMO you have a choise to make:
- Ignore this and assume it will cool
- Make a detailed calculation using transient calculations etc. this could also tell you someting about the problems david mentions and how long it will take.
I think i would lean towards the first even though i make a living out of the latter solution
Best regards
Morten
RE: Gas Temperature Rise Due to Compression
I've seen this with HYSYS before, it seems to see the problem as black and white--the incoming gas is either a piston (adiabatic, and no heat transfer from the incoming gas to the static gas) or as a straight mixing problem. I don't think that it is purely either one. I see it as an adiabatic compression problem until somewhere past the critical downstream pressure, then it is a mixing problem. I would be really shocked if the final temperature is much above 30C.
David
RE: Gas Temperature Rise Due to Compression
But my point was: Its either very complicated or very simple
Best regards
Morten
RE: Gas Temperature Rise Due to Compression
RE: Gas Temperature Rise Due to Compression
Yes, pipeline is an existing pipeline. It is 100 m sub sea ans is fully rated for sub hydrostatic pressure.