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Assumptions and limitations for exporting a model
The following section describes the Thermal Model Exchanger assumptions and limitations when you export a Thermal Desktop model to a Simcenter 3D Space Systems Thermal XML file.
Exporting meshes
Thermal Model Exchanger only supports the export of 2D elements. Because Thermal Desktop does not have a concept equivalent to the Simcenter 3D mesh collector, Thermal Model Exchanger application analyzes the Thermal Desktop meshes and groups all the 2D elements that share the same following properties in a mesh collector:

User manual
- Introduction
  Thermal Model Exchanger is an application that allows you to transfer thermal models between Thermal Desktop and Simcenter 3D. The application supports the transfer of the meshes, material and optical properties, and boundary conditions of your model.
- Prerequisites and operating system
  Thermal Model Exchanger requires the installation of AutoCAD with Thermal Desktop. The Thermal Model Exchanger application uses the OpenTD Application Programming Interface (API) to exchange data between Simcenter 3D and Thermal Desktop. Since OpenTD only supports C#, Thermal Model Exchanger can only run on Windows.
- Thermal Model Exchanger user interface
- How to use Thermal Model Exchanger
- Simcenter 3D entities supported by Thermal Model Exchanger
- Thermal Desktop entities supported by Thermal Model Exchanger
- Assumptions and limitations for importing a model
  The following section describes the Thermal Model Exchanger assumptions and limitations when you import a Simcenter 3D model into Thermal Desktop.
- Assumptions and limitations for exporting a model
  The following section describes the Thermal Model Exchanger assumptions and limitations when you export a Thermal Desktop model to a Simcenter 3D Space Systems Thermal XML file.
  - Exporting meshes
    Thermal Model Exchanger only supports the export of 2D elements. Because Thermal Desktop does not have a concept equivalent to the Simcenter 3D mesh collector, Thermal Model Exchanger application analyzes the Thermal Desktop meshes and groups all the 2D elements that share the same following properties in a mesh collector:
  - Exporting primitives
    In Thermal Desktop, you can use finite difference primitives to create your thermal model. They are specific geometric shapes that have internal conductances calculated using finite difference conduction methods. Thermal Model Exchanger supports the following Thermal Desktop 2D and 3D primitives:
  - Exporting thermo-physical properties
    The thermo-physical properties are directly assigned to elements or nodes in Thermal Desktop. During the export Thermal Model Exchanger assigns the material and optical properties, and the element thickness to the Simcenter 3D mesh collector that contains the elements sharing the same properties. For more information, see Exporting meshes and Exporting primitives.
  - Exporting heat loads
    Thermal Model Exchanger supports the Total Load and Flux types of Thermal Desktop Heat Load. It converts these entities into the Heat Load and Heat Flux types of Simcenter 3D Thermal Loads respectively.
  - Exporting boundary nodes
    In Thermal Desktop, the boundary Node allows you to impose a temperature constraint on your model. This type of node has the following settings:
  - Exporting contactors
    Thermal Model Exchanger exports Thermal Desktop Contactors as a Thermal Coupling type of Thermal Coupling simulation objects in Simcenter 3D.
  - Exporting radiation
    In Thermal Desktop, radiation is computed using a Radiation Analysis Group that contains all the surfaces selected by the user and a Radiation Task that controls the radiation parameters within the active case set.
  - Exporting orbits and space environment
    Thermal Desktop offers several External Heating Environment types to define orbits and space environments for your spacecraft:
  - Exporting a case set
    A case set in Thermal Desktop corresponds to a solution in Simcenter 3D. The Simcenter 3D XML file, which is translated by Thermal Model Exchanger, is the thermal solver input file for one solution. The application creates a single XML file per case set.

Exporting meshes

Thermal Model Exchanger only supports the export of 2D elements. Because Thermal Desktop does not have a concept equivalent to the Simcenter 3D mesh collector, Thermal Model Exchanger application analyzes the Thermal Desktop meshes and groups all the 2D elements that share the same following properties in a mesh collector:

Element order
Thickness
Material
Top and bottom optical property

Linear and quadratic elements are grouped in different mesh collectors.

If a group of elements contains a mix of quads and triangles elements, Thermal Model Exchanger creates one element set for each type of elements and exports it to the XML file with the same name. When you import the XML file in Simcenter 3D, the software creates a single mesh collector for these two element sets.

Thermal Model Exchanger assesses the element thickness using a relative tolerance of 0.1% of the maximum element thickness in the model.