DanWBR
[Bug] PVF / dew point calculation error
Describe the bug Dewpoint calculation fails for the PVF flash for PR, SRK, GERG etc
Expected behavior Identify dew point temperature of -11 / -12 C'ish at 40 barg
Desktop (please complete the following information):
- OS: [e.g. Windows]
- Version [e.g. v8.0.0]
Additional context See attached file dewpoint_error.zip
@andr1976 does it fails due to an error or wrong temperature value? just to be sure
@andr1976 initial estimates are close to the trivial solution. the algorithm conditions are satisfied in the end, even with the wrong temperature. do you have any suggestion?
The calculation runs but returns a temperature which is not the dew point at the specified pressure. Far from. Things start to go sideways above 30'something bar.
Ok one is with SRK but the same applies with PR. There is apparently a regression in the stability of the PVF/TVF algorithm
Sorry, no haven’t had time yet
tir. 28. jun. 2022 kl. 20.34 skrev Daniel Wagner @.***>:
@andr1976 https://github.com/andr1976 did you check this with latest code?
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@DanWBR , yes dew point is fine now, but the bubl-point is messed up now above 44-46 bar depending on EOS. I also think the critical point is way off. Above this pressure bubl point temperature suddenly jumps from -76 C to -10 C
@andr1976 the critical point is the reference to stop calculating dew and bubble points... it is very far from the correct one in this specific case
Yes, I see. Thing is, this is natural gas (although a little to the heavy side), so this is something that could potentially be encountered quite often
This looks better (PR). SRK still fails to calculate the correct critical point. GERG will need a new algorithm as I don't have a general procedure to calculate critical points - only PR and SRK for now.
Looks way better now - I think PP is somehow defaulting to the last PP available, for the title, not for the calcs
Could be nice to have Ian Bell on-board to do the critical point calculation method :-)
https://www.nist.gov/publications/calculation-critical-points-helmholtz-energy-explicit-mixture-models
@andr1976 I have an implementation of this method for quite some time already, but I've let it aside as it is slow and was not working. I'm revisiting it to see if I can get it working.
