Discussion Forum

Hi everybody

I use COMSOL version 4.3 for thermal analysis in 2D axisymmetric structure. I have a cilinder and I want to calculate the total conductive heat flux [W] through the top surface and the total one through the bottom surface.

What I did for calculating the total conductive heat flux [W] through the top surface is:

- I selected with "CutPlane " the top surface (I called this Cutplane as" TopSurface")
-I selected Derived Values/Surface Integration (dataset TopSurface) and in Expression I selected ht.dfluxz (since I am interested to the flux ortogonal to the surface)

I also tried another way:
-I selected with "CutLine" ( in 2D) the top edge of the rectangle (which is the radius of the topsurface of the cilinder). I called this CutLine"TopLine"
-I selected Derived Values/Line Integration (dataset TopLine ) with integrand ht.dfluxz and selecting also "Compute Surface Integral"

I thought to have the same result in both the ways but I haven't. I would like to understand what is the difference between the integrals :

Derived Values/Surface Integration and Derived Values/Line Integration/ComputeSurfaceIntegral


- How does COMSOL work to elaborate the integral when I select Surface Integration for a 2DAxis?
Also
-Should I integrate ht.dfluxz or htdfluxMag ?

Thanks

I hope I was clear in my question.

Ida