Thermal contact conductance 

Contact heat transfer deals with the thermal conductivity in the contact zone of two solids. Technical surfaces always have a certain roughness, which means that the components do not actually touch each other over their entire surface, but instead only at a few points, usually at the roughness peaks. At these points of contact, heat conduction actually occurs between the two bodies. In the intermediate areas, heat radiation also contributes to energy transport. If the contact point is not in a vacuum, convection and heat conduction through the fluid also provide a corresponding proportion of the energy transport.

The contact heat transfer thus depends on many factors, whereby the heat conduction in the points of contact is essential. The main influencing variables are the thermal conductivity of the contact partners, their hardness, roughness and contact pressure. The softer and therefore smoother the surfaces and the higher the contact pressure, the higher the conductivity becomes.

Computation time / model size

A good knowledge of the various influencing variables and their effect on the contact conductivity, in particular the contact pressure, is a prerequisite for realistic representation of the contact heat transfer. If these principles are known, the contact conductance can be integrated into the contact definition.

The best assumption for the contact conductance is obtained with the aid of a coupled structure and temperature simulation. In this way, both the local distribution of the surface pressure and its temporal change can be taken into account. If this is not necessary or possible, the average contact pressure can be used. In this case the influence on the computing time is small. Otherwise, the effort for a coupled simulation is increased accordingly.

Relevance

For a realistic temperature field calculation, especially for large assemblies with many contact pairs, a good description of the contact heat transfer is essential.