wrong values in thermal analysis
 

Hi to all people!

I'm contacting you for this reason:

I have built a model that refers to a pipe that is covered by insulating material, I have used bidimensional surfaces to model isulation.

I have made 3 simulation tests :

-The first : with insulating surface at distance of 10 mm from heating source ( exaust pipe) where i assigned only emissivity (aluminium ) insulating surface

-the second :where I moved surface to 5 mm from heating source and added thermal resistance (relative to Glass Fiber)

- The third : only changed thermal resistance of insulating material changing it to a value that is 2 times greater than the material I used in the second test.

My problem is that , in the first two simulations, I have obtained correct values in post processing relative to avarage and maximum temperature. But in the last one I have obtained a peak in some cells that are really out of range, so this influences my average and maximum temperatures, bring my simulation to totally wrong values:eek:.

My model use about 800000 polyhedral cell.
I used surface to surface radiation model , coupled flow for convection.

Could It be a meshing problem? Maybe due to thermal resistance raised value?

Anybody can help me ?:)

Thank you guys...

Francesco