Non-uniform face orientations of the shell elements on the interface between two volumes can affect the functioning of a mesh for radiation calculations and also the visualization of variables on those element faces during post-processing. This is because the face normals are inconsistent and this leads to element faces getting associated with the wrong side of the interface. The surface mesh orientations can be fixed in ICEM CFD as follows: Edit mesh > Re-Orient mesh > Re-Orient consistent A reference element must be selected and the function then aligns all other shell element orientations with that one. Since there is not always a unique solution, the orientations on the interface should be checked and fixed by Re-orient consistent again, if needed. Visualization of the surface element orientations is available via the model tree: right click on mesh>shells > select “Normals Using Arrow” or Normals Using Color”