Shaped Anisotropy

CrysMAS supports the anisotropic heat conductivity calculation. The scalar heat conductivity is then substituted by the orthotropic conductivity tensor with two main components: heat conductivity in radial and in axial direction. The values of the conductivity tensor are entered in the Materials dialog in the Conductivity - r and Conductivity - z dialog fields. Such material should be marked as an anisotrop by selection of Yes for the Anisotropy field in the same dialog.

Additionally an option for rotation of the principal axes of the orthotropic tensor is available. The rotation angle in counter-clockwise direction for the axes is entered in the Phi field in degrees.

Sometimes parts from graphite or from the pyrolytically deposited boric nitride have the direction of the best heat conduction what is aligned with the curved geometry of the assembly. For example the direction of the largest conductivity in the pBN crucible is aligned along the crucible wall. For an orthogonal shape of the crucible it can be separated into two bottom and side regions with materials having different conductivity components or anisotropy angles. But for the curved wall shape of the crucible no appropriate setting can be done.

Therefore additional model was develop in CrysMAS for treatment of anisotrop heat conductivity aligned with the curved shape of thin layers. In this model two components of the thermal conductivity are interpreted as the conductivity components across and parallel to the wall. The radial conductivity component is directed across to the layer and the axial one parallel to it.

The material should be marked as anisotropically conducting and the anisotropy angle should be set equal to zero.

Then regions should be specified where the curved anisotropy is to be considered. Open the dialog Shaped Anisotropy. Then select all regions with shaped anisotropy. Number of selected regions is appeared in the left top dialog window.

Definition of regions with shaped anisotropy dialog 

Figure 46. Definition of regions with shaped anisotropy dialog

After all required regions are selected, press OK button. The heat conduction will treated now according to the shaped anisotropy approach in all selected regions.

Note

The directions "across to the layer and along the layer" are determined from the region shape. It is assumed that in direction along the wall the region is much longer than in direction across to it. Therefore the selected regions should have a band-like shape with aspect ratio at least 1:5.