Enthalpy of Methane?? 1

[MonkeyNuts2479]

Hi all,

I am trying to calculate the temperature I need to raise methane so that it doesn't begin to freeze once its pressure has been droped through a regulator via the Joule Thompson affect. I know the following conditions - upstream pressure, downstream pressure, downstream temperature to prevent freezing, say about 3 deg. C or so.

It is my understanding that the enthalpy of methane remains the same during the J-T affect.

Therefore my question is, where can I find values of enthalpy for methane for a given pressure & temperature so I can find the temperature the methane needs to be at before its pressure is reduced.

Many thanks

 

[zekeman]

Have you googled Mollier chart for methane?

 

[zdas04]

Oh yeah, the boiling point of methane is -160C, the freezing point is -182C, that is REALLY a lot of J-T cooling to be worried about. Maybe your concern is that the cold methane will freeze water vapor in the gas stream and/or humidity in the surrounding air? If it really is a concern about freezing methane I think you can put those concerns to rest.

David

 

[25362]

http://webbook.nist.gov/cgi/fluid.cgi?ID=C74828&Action=Page

 

[PaoloPemi]

Joule-Thomson gives dT/dP for a specific point, you can use this parameter to estimate the final temperature however for real gases cp, cv are not constant and you need some sort of iterative solution to find accurate final temperatures (and the related saturation pressures for a pure fluid), tools as REFPROP (nist.gov) or Prode Properties (prode.com) can provide the tables which you need.

 

[zekeman]

"MonkeyNuts2479
............I know the following conditions - upstream pressure, downstream pressure, downstream temperature to prevent freezing, say about 3 deg. C or so.........."

Well, what are the upstream and downstream conditions, since the J-T coefficient varies with T and P?