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Thermal Resistance Networks

A thermal resistance network can be used to approximate the effect of heat sources and heat transfer from that source to the surrounding domain without explicitly having to resolve the source geometry itself. An example application is a PCB with multiple small resistors, LEDs, and/or processor chips mounted on top, which, compared to the overall domain, are small enough for their individual geometry to play only a minor role on the result.


  • Thermal resistance networks are only available in the Conjugate heat transfer analysis type.
  • Only perfectly rectangular objects (solids) can be approximated via a thermal resistance network. (In case the original geometry resolves more detailed features of the object you’d like to model via a thermal resistance network, simply replace them with rectangular boxes.)

Creation of a Thermal Resistance Network

  • In your Conjugate heat transfer analysis, navigate to Advanced concepts and add a Thermal resistance network.
  • Assign the top face of the part you want to approximate as thermal resistance network. (Top face in this case means the one facing in opposite direction of where the object is fixed on. See the approximation diagram below for context.)
example of which face to assign to a thermal resistance network
The thermal resistance network assumes a simplified thermal model, in which the resistance between top face and bounding region, side faces and bounding region, as well as bottom face and bounding region can be specified. Assignment of the top face only is required in order to assign the resistance correctly in each direction.
  • Define thermal resistance in all directions. The network will model each face of your rectangular body with an average temperature, which then transfers heat via convection to the surrounding medium based on the thermal resistance specified.
thermal resistance network panel
Assign the top part of your solid body and specify the thermal resistance in each direction. All four side faces will be assumed as equal.
Resistance diagram
This diagram depicts the thermal resistance model. For both top and all four side faces together one thermal resistance value needs to be specified. For the bottom surface, one additional resistance component can be specified. This is to allow for applications to be modeled, in which e.g. thermal conduction paste is applied between a chip and the PCB.

Topology that is assigned to a thermal resistance network is not going to be resolved in the mesh. Additionally, all contacts defined between topology assigned to thermal resistance networks and surrounding regions will be ignored, meaning thermal resistance networks are always taking priority over contacts.


When creating a simulation run, a warning will be shown that some faces have been assigned to both a thermal resistance network and an interface. This warning can be ignored. The simulation will prioritize thermal resistance networks over contacts.

Find below an example project for the setup of a thermal resistance network.

Last updated: October 9th, 2020

What's Next

part of: Simulation Setup

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