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.
