Using thermal resistance to model thermal condition of touching faces

If you have been using SOLIDWORKS Simulation Professional or Premium for your thermal analysis, you probably have asked yourself, what is the best way to model the thermal resistance condition between two touching faces? SOLIDWORKS allows you to specify resistance to touching faces to simulate imperfect thermal conduction between parts.

In reality two parts coming in contact with each other will not have a perfect contact due to factors such as surface roughness and tolerances and therefore, there will be air pockets trapped between the part which will affect the overall thermal coefficient. Even if these effects are negligible, most of the time, the parts are bonded together with a thermal adhesive or thermal glue which has a different conductance coefficient that is not negligible.

The effects of this middle layer, can be inserted into your model with defining a local contact set of “Thermal resistance”. The thermal resistance coefficient can be found either experimentally or from the properties of the glue used based on factors such as its thickness or working temperature.

Thermal resistance example

In the example below, we are defining a contact set of thermal resistance between the two touching faces. The resistance can be specified either using the total conductance or a distributed conductance per unit area. For the example below, we are using a special layer of Arctic Silver to bond the two parts with a thickness of 25 micrometer, which has a conductance of 350,000 W/m^2K. Therefore, the thermal resistance will be the inverse of this number which is 2.857e-6 m^2K/W.