Bug in pipe (outlet temperature)?

[Hans Eisenstein]

Dear Daniel,
Dear Greg,

First, thanks a lot for all your efforts in creating and maintaining this wonderful piece of software.

Using the latest version of DWSIM (3.4 build 5608), pipe outlet stream temperatures do not match the temperature drop in the pipe, with and without applying the Joule-Thomson effect in the calculation. May be I am using a very special setup (vertical pipe of 550 m length representing a well), so that it was not noticed before by any other user. Please let me know, if I am misunderstanding the general pipe implementation concept (or misusing it) or if this is an unwanted behavior of the pipe module implementation.

Thanks a lot and best regards,

Hans

[Daniel Medeiros]

Hi Hans,

Are you injecting or producing CO2?

[Hans Eisenstein]

Dear Daniel,

Wow, that is a really fast reply.

Yes (injecting it as a ChemSep component), but I also experience this behavior with methane or water.

Thanks, Hans

[Daniel Medeiros]

Ok. It seems to be something related to the equilibrium calculation at the outlet stream, because the pipe property profiles are ok. Taking a look right now.

[Hans Eisenstein]

I agree that the pipe property profiles look reasonable, too. It is just the outlet stream exposing wrong temperatures, and thus wrong properties.

Thanks for your prompt reply, Hans

[Daniel Medeiros]

Hi Hans,

I found a quick workaround: try adding a small amount of air, for instance, to the inlet stream (0.01 is ok). This will force DWSIM to calculate equilibrium as a mixture and not as a single compound, which is what is causing the error in the outlet temperature.

I'll have to modify the pipe model to correctly calculate the outlet enthalpy for single compound cases.

Regards,
Daniel

[Hans Eisenstein]

Many thanks for this workaround, Daniel!

Adding, e.g., 0.0001 of N2 to the CO2 (to comply with FPROPS calculations) works very well.

Best regards,

Hans