[DevilX]

Hey Foamers!


I have a huge problem with my steady rhoSimpleFoam simulation case.

Let me descirbe the case a bit, please consider also the images below.

I am investigating the massflow and forces on/through a valve in a compressor. As you may know, the compressor compresses the fluid to high pressure and then it will flow over a valve through the rest of the cooling system.
In my simulation, there is the cylinder room, where the pressure rises. It then is driven by pressure though a valve (thin metallic plate), flows through a cylindrical domain until it reaches the outlet on top.


With CO2 (R744) it worked fine with my BC, Solver Settings with Pin=142bar, Pout=125 bar, with Peng-Robinson-EOS and polynomial mu,Cp and kappa. Also transient worked out really well with lowering the residuals and timeStepErrors .


If i take the exact same Mesh from Co2 Case and try to simulate it with R1234yf (2,3,3,3-Tetrafluorpropene) with also same EOS and polynomial approach, it chrashes after 400 Iterations.


I am completely lost actually!


Things i tried:


- transient with rhoPimple (crashes)
- nOrtho up, SIMPLEC, relax.Factor lowered, Tolerances tightend/lowered
- buoyantSimpleFoam
- Mesh refined
- very small timesteps (IterationSteps)
- Turbulence off
- constant thermo-Properties



All in all, its the "fault" of R1234yf with their special properties, but i need the Peng-Robinson-EOS for accurate Density.


Can anyone please help me?

[DevilX]

So, nobody has an idea?


I tried some testing again and also applied the CO2 thermophysical Properties to the case of R1234yf. In Short:


- same Mesh
- same fvSchemes/fvSolution
- different Pressure (20 bar internal and up to 32 bar inlet instead of the Co2 Case with 125 bar internal and inlet up to 142 bar Inlet pressure)
- different Temperature (370K bar internal and 380K inlet instead of the Co2 Case with 445K internal and inlet with 450K Inlet pressure)


So it still crashes after 400 Iterations. If i use the thermodyanmic Properties in CO2 Case with 125 bar and 450 K, it works fine.



So, how ist this possible? I am truly confused.