Nitrogen: Any EOS that works well in DWSIM at cryogenic temperatures?
Simulate chemical processes using advanced thermodynamic models
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I've downloaded DWSIM today and have spend a couple of hours going through the options. So far looking very nice. The only problem is that I'm basicly working in the cryogenic field and I'm trying to build a simulation similar to one I already have in Promax, to check if I get similar outcome. The problem is, I can't get it to work right. A very simple case:
- Pure nitrogen (I've tried this with the DWSIM component, with Coolprop and with ChemSep)
- PR EOS
-stream pressure 3 barg
- stream temperature -190ºC (should be 0 vapor phase fraction at this point
- then add a valve with a pressure drop of 2,9 bar
- outlet stream will not calculate what it should be: a 2 phase flow at approx -195ºC of liquid and vapor nitrogen at 0,1 barg
Now I've somewhere that in the past it did not work well with temperatures below 150K. Has this part been improved and can I work at these temperatures in one of the EOS packages? Or better to stop trying because this part has not been solved yet?
Thanks in advance!
Last edit: gsalomons 2015-11-10
Hi,
The problem is that it calculates a value for the saturation temperature at 0.1 bar that is lower than the temperature of fusion, so the outlet of the valve is... pure solid.
Are you sure that it will not cool this much when lowering the pressure to 0,1 bar through a valve? If it doesn't, then there is a problem with the vapor pressure curve for nitrogen in the ChemSep database.
Regards
Daniel
Ops, sorry. Pressure is in barG, not barA...
Fixed! It will be working on the next release in a few days.
Hi Daniel, thanks for the update! Yep, it was in barG :-)
What was the problem that prevented from simulating? Some temperature limit?
When searching for DWSIM in google and the term cryogenic, I saw some messages between you and Bodhisatya. He said that he was planning on designing a Cryogenic Air Separation Unit using DWSIM. Did you hear if he succeeded? Because he must have run into the same problem at some point (those kind of plants run on very low temperatures).
Even when not indicating any pressure drop for the valve, it seems to have this problem (see image):