You can use the Extruded or Axisymmetric simplification options for thermal studies.
You cannot apply contact sets between faces, edges, or vertices.
- Extruded
Use this option for constant thermal loads along the extruded direction.
The figure shows an example of a long aluminum block held at a uniform temperature and suddenly exposed to a convection environment. You can create a section parallel to the XZ plane, and then apply a uniform temperature to the rectangular cross section and a convection load to the outer edge of the rectangle.

- Axisymmetric
Use this option to model geometries, material properties, and thermal loads that are symmetric about an axis.
The figure shows an example of a hollow cylinder insulated at the inner surface and exposed to a convection environment on the outer surface. You can select any section plane on which the axis of revolution lies.
