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Documentation

Heat Transfer

The Heat transfer analysis type allows the calculation of the temperature distribution and heat flux in solids under thermal loads (for example, convection and radiation). Both steady-state and transient simulations are supported. In SimScale, Code Aster solver is used to perform heat transfer analysis.

heat transfer analysis pcb
Figure 1: Thermal change in PCB.

Creating a Heat Transfer Analysis

To create a heat transfer analysis, the first step is to select the desired geometry and then click on ‘Create Simulation‘:

creating a heat transfer analysis for a geometry
Figure 2: Creating a new heat transfer analysis.

Afterward, a window with several analysis types appears. Choose the desired type from the list.

heat transfer analysis creation
Figure 3: Steps to create a heat transfer analysis in SimScale.

In the following, the different simulation settings you have to define are described. You will also find links to relevant documentation.

simulation tree heat transfer analysis
Figure 4: Simulation tree showing entries for a transient heat transfer analysis type.

Global Settings

To access the global settings, click on ‘heat transfer‘ in the simulation tree. In there you can change the time dependency between transient and steady-state. For more information, check the global settings page.

Geometry

The geometry tab contains the CAD model used for the simulation. Details of CAD handling are described in the pre-processing section.

Contacts

If you have an assembly of multiple bodies that are not fused together. All contacts in the system are automatically detected when a geometry is selected for a heat transfer analysis. By default, they are set to bonded. Cyclic symmetry is also available. For more information about contacts check this page.

Element Technology

The element technology refers to the type of element you are using. As a general rule we recommend to use standard for first order elements and reduced integration for second order elements.

Materials

To define the material properties of the whole domain, you have to assign exactly one material to every part and define the thermal properties of those. Note that the specific heat is only needed for transient analysis.

For more information, please check the relevant documentation page for materials.

Initial Conditions

For transient analysis, it is important to define the initial conditions carefully, since these values determine the accuracy of the solution. The default initial condition for temperature is 293.15 Kelvin.

Boundary Conditions

Here temperature and thermal load boundary conditions can be set. By providing a temperature boundary condition for an entity, the temperature of all contained nodes is set to the desired value.

Thermal load boundary conditions define the heat flux into or out of the domain via different mechanisms. Note that a negative heat flux indicates a heat loss to the environment.

It is not possible to prescribe a temperature value and a heat flux on the same entity, as it would overconstrain the case. For an overview of the boundary conditions available, please visit this page.

Numerics

Under numerics, you can set the equation solver of your simulation. The choice highly influences the computational time and the required memory size of the simulation. This blog post gives more insight into the available solvers.

Simulation Control

The simulation control settings define the overall process of the calculation. For example, the time-stepping interval and the maximum runtime for the simulation are set under simulation control.

Result Control

Under result control, users can specify additional parameters of interest to be calculated. Monitors can also be defined. For example, one can set area and volume average controls, as well as point data for monitoring quantities on specific points.

For more information about result controls, check this page.

Mesh

Meshing is the discretization of the simulation domain. It essentially means to split up one large problem into multiple smaller mathematical problems.

For a heat transfer analysis, the standard and Tet-dominant algorithms are available. For more information about meshes, make sure to check the dedicated page.

Example Projects

Last updated: July 16th, 2020

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