Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

heat transfer/ copper contact thermal resistant

Please login with a confirmed email address before reporting spam

I am simulating a heat transfer problem with two cylinder copper assembly together. To study the affect of contact thermal resistant, I set the four contacting faces to " Thin Thermally Resistive Layer". After every boundary being set up, the "Study" results an error:

Failed to evaluate variable Jacobian.
- Variable: mat.k_s
- Geometry: 1
- Boundary: 6 8 9 10

And the 3D plot is definitely wrong. Can anyone tell me what's the problem, am I using the right option for contact thermal resistant?

PS,: when I disable the" Thin Thermally Resistive Layer", the results make sense, which means other setting are good. But what I want is to see the difference after adding contact thermal resistance.

Thanks:-)

3 Replies Last Post Jul 13, 2010, 2:28 p.m. EDT
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Jul 13, 2010, 1:42 p.m. EDT
Hi

have you checked that your mat1.k_s ? is defined for mat1 (= the first material selected from the library).
It looks to me, from that error message that it is NOT the case

Good Luck
Ivar
Hi have you checked that your mat1.k_s ? is defined for mat1 (= the first material selected from the library). It looks to me, from that error message that it is NOT the case Good Luck Ivar

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Jul 13, 2010, 2:16 p.m. EDT
Thanks, the problem is solved by setting the thin thermal resistively layer's K a value.

But I have another problem, another model, mostly the same like previous one, but with a cross-slot surface at one tip. I gave the same boundary condition, but I got another error:

Failed to evaluate variable Jacobian.
- Variable: mat.k22
- Geometry: 1
- Domain: 1 2

Is there any way to check what Variable" mat.k22" is ?
Thanks, the problem is solved by setting the thin thermal resistively layer's K a value. But I have another problem, another model, mostly the same like previous one, but with a cross-slot surface at one tip. I gave the same boundary condition, but I got another error: Failed to evaluate variable Jacobian. - Variable: mat.k22 - Geometry: 1 - Domain: 1 2 Is there any way to check what Variable" mat.k22" is ?

Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Jul 13, 2010, 2:28 p.m. EDT
Hi

Its one of the anisotropic heat conduction variable, if I remeber right.

You have the three/four sources (all intersting) to search:

1) do an indexed search on the pdf docs
2) look up the "Physics - Equations Settings - Subdomain variablles ..." in 3.5a (turn on equations in then rpeferences in v4)
3) dump the file as a "m" file and have a look. You can also scan the .history file in 3.5
4) the web Knowledge base and finally the Forum

good luck
Ivar
Hi Its one of the anisotropic heat conduction variable, if I remeber right. You have the three/four sources (all intersting) to search: 1) do an indexed search on the pdf docs 2) look up the "Physics - Equations Settings - Subdomain variablles ..." in 3.5a (turn on equations in then rpeferences in v4) 3) dump the file as a "m" file and have a look. You can also scan the .history file in 3.5 4) the web Knowledge base and finally the Forum good luck Ivar

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.