Heat transfer within a heat-sink


The content of this tutorial is not up to date with the current live version of SimScale. The tutorial setup and the results are still valid! Please do not get confused if styles like buttons and entity names have changed in the meantime.

This tutorial shows how to analyze the Heat transfer in a heat sink.

Import tutorial case into workspace


1) Import tutorial project

  • To start this tutorial, you have to import the tutorial project into your ‘Dashboard’ via the link above.
  • Alternatively, you can also add the tutorial project from the ‘Public Projects’ library by searching for “tutorial” name.
  • Clicking on the project, then clicking on ‘Actions’ and ‘make a copy’ option to add it to your ‘Dashboard’. This process is illustrated by the figures below.
  • Once the project is in your ‘Dashboard’, simply move the mouse over to the upper right corner click on the blue icon to open it in your workbench as shown in figure below.

2) The CAD model

  • Once the ‘Work bench’ is open you will be in the ‘Mesh creator’ tab.
  • The Mesh Creator tab is the place where you upload CAD models and create meshes for them.
  • The geometry is already available under the ‘geometry’ tree item.
  • Click on the CAD model named “heat-sink” to load the CAD model in the viewer.
  • After a few moments, the CAD model is displayed in the viewer like shown in the figure below
  • You can interact with the CAD model as in a normal desktop application

The CAD model displayed in the viewer

3) Create a mesh

  • Choose the geometry in the Navigator tree and click on the blue Mesh geometry button
  • A new tree item automatically appears in the Navigator tree under Meshes
  • SimScale has various mesh operations which allow you to specify in very detail how the mesh shall be generated.
  • When creating the new mesh, a default Mesh Operation is automatically added to your Mesh (default name is Operation 1)
  • Click on the mesh operation and select the options as shown in figure below.
  • After setting all parameters save your selection and start the meshing operation. Use the notifications or the job status panel in the lower left corner to check the status of the meshing process. As soon as the mesh is finished it is loaded into the viewer and you can interact with it in the same way as with the geometry before.

The mesh after the meshing operation is finished

  • Use the operations log to get some general informations about the mesh e.g. number of nodes and elements in the mesh.

4) Set up the actual simulation

  • Switch to the Simulation Designer and add a new simulation.
  • In a first step you have to choose the general simulation type. You can get some information about the different types on the right. In this tutorial we want to calculate the heat flux and the temperature distribution in the heat sink due to the convective boundary conditions caused by the surrounding flows. Hence we choose Heat transfer from the Thermostructural analysis selection. As the time-invariant state should be calculated we select Steady-state under Properties.

Analysis type choice: Steady state heat transfer

  • The next item in the Navigator tree is the Domain where you have to specify the CAD model or the mesh that you want to use for this simulation. Choose here the previously created mesh. After you have saved your selection the mesh should be displayed in the Viewer on the right.

Domain assignment: The previously created mesh

  • The material is specified in the Materials section. You can add a new material by clicking on Add new material and assign a name to it. For a steady-state heat transfer simulation one has to determine the density (unit kg/m³) and the conductivity coefficient (unit W/mK). We assign a standard steel and leave all values as they are.

Material properties and assignement to the heat sink

  • Use the Boundary conditions section in order to apply heat flux or temperature boundary conditions. A new boundary condition can be added with the Add new ... boundary condition-Buttons.
  • We use a simple boundary condition setup: The heat source is set to be the single face on the bottom of the face where we apply a fixed temperature of 70 degrees Celsius or 343.15 Kelvin. The peviously created face groups are very helpful in assigning the faces. Just switch the entity filter from faces to face sets and you can see them.

Boundary condition 1: Fixed temperature

  • The second boundary condition is the convective heat flux taking place on all other faces.
  • so select the bottom heat source face and then invert selection from the ‘selection’ menu at top tool bar.

Boundary condition 2: Convective heat flux

  • In the Numerics section you can choose the linear equation system solver. In this tutorial we use the iterative solver Iterative Cholesky. The iterative solvers do have advantages over the direct solvers especially in terms of memory usage. For TDaller problems with less nodes, the direct solver Spooles might be beneficial though.

Choosing an iterative solver for the linear system

  • If you followed the settings of this tutorial so far especially considering the mesh fineness it is possible to select one computing core for the calculation in the Simulation Control section. For finer meshes it may be necessary to choose a larger instance in order to provide memory and reduce calculation time.

5) Start a simulation run

  • At last create a simulation run that holds the current configuration of your simulation and simply start your calculation by clicking on the Start button.
  • If you select Results you can download a zipped folder containing the vtk-files of your results and use a local postprocessor on your desktop.

6) Post-Processing

  • In order to analyse your results on the SimScale platform switch to the Post-Processor and choose your current project and run. For a Heat transfer run the results can be accessed by selecting Solution fields. Afterwards the post-processing environment is loaded in the Viewer.
  • Goto the last step by clicking on the play button and selecting ‘last frame’ and load the temperature as shown.

Use the integrated post-processing environment for visualizing the results