What Is the Difference Between Isotropic and Anisotropic Thermal Conductivity?

[sml2010]

Hi to all

Can some one help me for below question:

What is different between "isotropic thermal conductivity" with " anisotropic thermal conductivity" ?
where and when we must use isotropic or anisotropic ?
which one is more accurate?

I solve an example in a FEM software and it is used anisotropic for thermal conductivity.
http://i813.photobucket.com/albums/z...Untitled-2.jpg

Please help me for difference and application of these two thermal conductivity method.


Thank you

 

[Dr Lots-o'watts]

If the thermal conductivity is not the same for every direction, then it is anisotropic.

It is isotropic if all directions are equivalent for heat flow. This the most common case (bulk metals are isotropic).

 

[AlephZero]

"Anisotropic" means the thermal conductivity of the material depends on the direction the heat flows through the material. It can also cause strange behaviour where the heat does not flow in the same direction as the temperature gradient.

Most common materials are isotropic. If your material data doesn't include anisotropic thermal properties, just ignore the option.

 

[RevMatcher]

To respond to the question "which one is more accurate": That's the wrong question... Like Dr L and AlZero said, anisotropic means the material properties are direction dependent.

For applications:
1. Bulk metals (extruded, cast, forged) are considered isotropic for stiffness and conductivity.
2. Composites are the best example of anisotropic materials. Search for ThermalGraph Fabrics.

 

[sml2010]

Thank you very much of all dear my friend that help me and post a reply here

thank you

 

[chaos_zzy]

some typical anisotropic thermal conductivity used for cooling:PCB/graphite...