Heat transfer insulated surface

[adp0014]

Hello everybody,
I am trying to make a Coupled temperature-displacement analysis and I want to model an insulated surface, that is a surface with its normal flux equal to zero. I have read that when no bounday condition is prescribed, abaqus automatically considers a zero flux. However, when I check the results, the perpendicular fluxes in the integration points (magnitude HFL2 in my case)are not zero in this surface.
How is it possible? Is there any way to prescribe a complete insulated surface?

Tanks in advanced

 

[corus]

Probably a mesh refinement problem. Use a finer mesh to see how the results change.