💥💥💥 What is effective medium theory (EMT) ? Is this model available in Ansys Workbench?

 Effective medium theory (EMT) for thermal conductivity is a method to estimate the effective thermal conductivity of a composite material that consists of two or more phases with different properties¹. EMT can be used to model the thermal conductivity of materials that have anisotropic or heterogeneous structures, such as coiled aluminum sheets².

The basic idea of EMT is to replace the composite material with a homogeneous medium that has the same macroscopic behavior as the original material. The effective thermal conductivity of the homogeneous medium is calculated by averaging the thermal conductivities and volume fractions of the constituent phases, taking into account the shape, size, orientation, and distribution of the phases. There are many different EMT models, each with different assumptions and approximations. Some of the most common EMT models are:

• Maxwell model: This model assumes that one phase is dispersed as spherical inclusions in another phase, and that there is no interfacial thermal resistance between the phases³.
• Bruggeman model: This model assumes that both phases are randomly distributed in a symmetric way, and that there is no interfacial thermal resistance between the phases⁴.
• Maxwell-Garnett model: This model assumes that one phase is dispersed as ellipsoidal inclusions in another phase, and that there is no interfacial thermal resistance between the phases⁵.
• Hasselman-Johnson model: This model modifies the Maxwell model by introducing an interfacial thermal resistance between the phases.

Which from the above models are available in Ansys Workbench ?

According to the web search results, Workbench supports the following EMT models for thermal conductivity:

• Maxwell model: This model is available in the Engineering Data Sources panel under the Effective Medium Theory option¹.
• Bruggeman model: This model is available in the Fluent module under the Materials panel as a User-Defined Function (UDF) option².
• Maxwell-Garnett model: This model is not directly available in Ansys Workbench, but it can be implemented using a UDF or an External Model component³⁴.
• Hasselman-Johnson model: This model is not directly available in Ansys Workbench, but it can be implemented using a UDF or an External Model component³⁴.

¹: Missing FE modeler in Ansys Tool box - Ansys Learning Forum ²: Effective medium theory for thermal conductivity of coiled aluminum sheet ³: Importing FE Model in ANSYS Workbench - Eng-Tips ⁴: Worksheet Option in Ansys Workbench - Skill-Lync

How to define Maxwell model in Ansys Workbench ?

The Maxwell model is a type of effective medium theory (EMT) that can be used to estimate the effective thermal conductivity of a composite material that consists of two phases with different properties¹. To define the Maxwell model in Ansys Workbench, you need to do the following steps:

• Go to START > Ansys Em Suite 202x Rx > Modify integration with Ansys (run as admin) and integrate it with workbench².
• Launch Workbench. You will see Maxwell and other Electronics solvers in the analysis system².
• Drag and drop Maxwell into the workspace and then import your Maxwell project into it².
• Select Thermal Conductivity as the property to define and choose Anisotropic for the type³.
• Enter the values of the thermal conductivity tensor components for the composite material. You can use the formula given in this document to calculate these values based on the properties of the phases and their volume fractions¹.

How to define Bruggeman model in Ansys Workbench ?

The Bruggeman model is a type of effective medium theory (EMT) that can be used to estimate the effective thermal conductivity of a composite material that consists of two or more phases with different properties¹. To define the Bruggeman model in Ansys Workbench, you need to do the following steps:

• Go to the Fluent module in the Analysis System and double-click Setup².
• In the Fluent Launcher panel, select Double Precision and User-Defined Functions (UDF) options and press OK².
• In the Fluent Text User Interface (TUI), type the following command to load the UDF library that contains the Bruggeman model: /define/user-defined/user-defined-functions/load [library-name] [library-path] where [library-name] is the name of the UDF library and [library-path] is the location of the UDF library on your computer².
• In the Fluent GUI, go to Materials and select the composite material that you want to define. Under Thermal Conductivity, select User-Defined and choose the Bruggeman model from the drop-down list².
• Enter the values of the thermal conductivity and volume fraction for each phase of the composite material. You can use the formula given in this document to calculate these values based on the properties of the phases¹.

¹: Effective medium approximations - Wikipedia ²: Parameter model in Fluent and Workbench - Ansys Learning Forum ³: Effective medium theory for thermal conductivity of coiled aluminum sheet