July 4, 2019 at 3:23 pmefremsurbaktiSubscriber
Hello. I tried to calculate the temperature in the outlet of Sudden Expansion. My working fluid is R-134a. I turn on the energy equation and i use k epsilon. I used couple with second order in solution. for the boundary condition i used flow rate at inlet and pressure outlet. In theory the fluid should decrease if the pressure decrease but in my case only the pressure is decreasing. Any answer would be appreciated.
July 5, 2019 at 4:31 amDrAmineAnsys EmployeeAre both regions somehow connected? Please where are the bcs located in your images? I hope the working fluid is modeled as compressible fluid.
July 5, 2019 at 7:54 am
July 5, 2019 at 8:10 amDrAmineAnsys Employee
Yes, NIST is compressible. Temperature is decreasing towards the outlet. Are you above or below the inversion temperature? Is your case converged?
July 5, 2019 at 8:21 amefremsurbaktiSubscriber
Based on theory, the Temperature should starting to decrease from point A, but as you can see in my case the temperature starting to decrease in point B. The temperature inlet is 311 K and the temperature at outlet should be around 288 K and in my simulation the temperature only decrease to 300 K.
Pordon me, can you explain what do you mean about my case is converged or not?
July 5, 2019 at 9:58 amDrAmineAnsys Employee
Is your case converged or not? You know: convergence. Screenshot of residuals, Fluxt reports for mass and energy and monitors of temperature are of great benefit here.
July 5, 2019 at 9:59 amDrAmineAnsys Employee
What about reversal flow? Is it occuring at the outlet? Again a screenshot of the velocity vectors plotted on the same plane is helpful.
July 5, 2019 at 10:40 am
July 5, 2019 at 10:45 amDrAmineAnsys Employee
You should run for more iterations (much much more..) and check all other stuff I was mentioning. If the reversal flow is occuring, this might be due to numerical reasons and could disappear or even physical. What you can do is to elongate the outflow region and use realistic backflow quantities at the outlet. Other way (not like it) is to switch on "prevent backflow".
July 5, 2019 at 10:50 amefremsurbaktiSubscriber
Thank you for your advice, I shall try your suggestion.
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