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"Conjugate Heat transfer" failed to converge if a fluid is included.

Posted 07.02.2014, 09:55 GMT-5 Heat Transfer, Studies & Solvers Version 4.4 4 Replies

Hans Gennerich
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A cylinder with a cavity filled with water is the geometry.
At the beginning, the outer wall hast a temperature different from the contents.
"Conjugate Heat transfer" is used to model the thermal equilibration with a time dependend solver.
The modelling does not converge:
"Failed to find consistent initial values./Last time step is not converged./ - Feature: Time-Dependent Solver 1 (sol1/t1)"
What is missing, to make it converge?

Note: "If I apply the "Heat transfer in solid" node with an included sub-node "Heat transfer in fluids" instead to the same model, convergence is reached."
4 Replies Last Post 19.02.2014, 11:18 GMT-5
Tero Hietanen
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Posted: 1 decade ago 07.02.2014, 16:02 GMT-5
Hi,

You forget to add "volume force". Without this water is not moving by temperature difference. Check model.

Best regards

Tero Hietanen
Hi, You forget to add "volume force". Without this water is not moving by temperature difference. Check model. Best regards Tero Hietanen
Hans Gennerich
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Posted: 1 decade ago 10.02.2014, 13:17 GMT-5
Hi Tero Hietanen!

Thank You for the helpful reply.

=> The point to make the equations converge and work was Your adding of "Pressure Point constant" for one point at the wall of the fluid, as You inserted into my model. I didn't expect, that this was needed.

=> Yes, You are right, a body force is needed to drive a convection inside the fluid.

=> A subsequent question is: How do I know, how the physical properties in the material library treat the temperature, salinity and pressure dependency of the material?
==> Is there a way to check the values of several variables before running the program, just by asking the software?

Greetings
Hans
Hi Tero Hietanen! Thank You for the helpful reply. => The point to make the equations converge and work was Your adding of "Pressure Point constant" for one point at the wall of the fluid, as You inserted into my model. I didn't expect, that this was needed. => Yes, You are right, a body force is needed to drive a convection inside the fluid. => A subsequent question is: How do I know, how the physical properties in the material library treat the temperature, salinity and pressure dependency of the material? ==> Is there a way to check the values of several variables before running the program, just by asking the software? Greetings Hans
Tero Hietanen
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Posted: 1 decade ago 12.02.2014, 02:20 GMT-5
Hello Hans,

Pressure point constant is needed because without this fluid has no connection to pressure and due to this solution is not working.

To that other question I don't have good solution, sorry.

Best regads

Tero
Hello Hans, Pressure point constant is needed because without this fluid has no connection to pressure and due to this solution is not working. To that other question I don't have good solution, sorry. Best regads Tero
Hans Gennerich
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Posted: 1 decade ago 19.02.2014, 11:18 GMT-5
Pressure point constant is needed because without this fluid has no connection to pressure and due to this solution is not working.


Does this setting mean, the pressure inside the fluid is all the time constant at the pressure set?

What is the way to deal with variable overpressures in the container depending on changing temperatures which result from different thermal expansions of the fluid contents in the sealed volume relative to the thermal expansion of the container?

May be I should calculate the internal pressure from the volume change of the fluid due to differences in thermal expansions of the fluid and the container and insert a variable with this value? Or isn't it necessary to have the overpressure in the volume which is constant in the volume set at that point?

[QUOTE] Pressure point constant is needed because without this fluid has no connection to pressure and due to this solution is not working. [/QUOTE] Does this setting mean, the pressure inside the fluid is all the time constant at the pressure set? What is the way to deal with variable overpressures in the container depending on changing temperatures which result from different thermal expansions of the fluid contents in the sealed volume relative to the thermal expansion of the container? May be I should calculate the internal pressure from the volume change of the fluid due to differences in thermal expansions of the fluid and the container and insert a variable with this value? Or isn't it necessary to have the overpressure in the volume which is constant in the volume set at that point?

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