[Avksent]

Good afternoon, dear forum users!

Please help in solving the following problem (test problem, which means conditional): suppose that there is a choke (inner diameter of the main pipe is 100 mm, inner diameter of the choke is 10 mm).



The working medium is gas (Redlich-Kwong model from the CFX library).



Border conditions:
- input - mass flow (0.01 kg / s), total temperature (623 K)
- outlet - average static pressure (1 MPa)
- walls and symmetry
- domain: pressure 1 atm .; Heat Transfer - Total Energy

After solving, the following is obtained:
Pressure (meets expectations):


Speed (let's close our eyes to the huge speeds for now):


Temperature (...):


The result of the solution seems strange to me - I expected to see a temperature drop not only in the choke, but also behind it (compared to the gas temperature at the inlet), as it happens in real throttling devices behind which sections of the pipeline can be covered with frost.

The temperature pattern along the central axis - behind the throttle was restored:


Please point me to my mistakes in assumption / modeling.

[ghorrocks]

Please post images directly on the forum and do not use third party download sites.

To answer your question: Accuracy is an FAQ: https://www.cfd-online.com/Wiki/Ansy..._inaccurate.3F

Have you calculated what temperature loss you expect? Have you looked at your results carefully to get the exact temperature loss predicted by your model?

[Stel]

Did you get any warning message during solution regarding the enthalpy calculation bounds? (I see that you are not generating table interpolation in the EOS)