> ## Documentation Index
> Fetch the complete documentation index at: https://docs.ntop.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Thermal Boundary Conditions
A thermal **FE Model** must contain a set of **Boundary Conditions**.
The thermal analysis-related boundary conditions (in red box) can be accessed in the *Simulation*tab of the ribbon.
The relevant boundary conditions to a thermal analysis are defined in a **Boundary Condition List** block, as shown below.
**Example:** Defining a Boundary Condition Listwith three BCs (Temperature Restraint, Convection, and Radiation)
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The various thermal boundary conditions available in nTop are explained below.
Applies a distributed heat flux normal to selected boundary face entities (either CAD or FE boundary) with the input of Magnitude (can be field-based). You can reverse the heat flux direction normal with a negative sign when defining its magnitude.
Applies a convection load to selected boundary face entities (either CAD Face or FE Boundary) with inputs of Ambient temperature and Convection coefficient (can be field-based).
Applies a radiation load to selected boundary face entities (either CAD Face or FE Boundary) with inputs: Ambient temperature and Emissivity (can be field-based).
Applies a total heat generation power to a selected Region. The quantity of heat generation is distributed across the nodes based on volume fraction. The Magnitude of heat generation input is mm2s-3kg (W).
Similar to the Heat Generation boundary condition, but additionally allows the magnitude of heat generation to be field-based. The magnitude of volumetric heat generation input is mm-1s-3kg (W/m3).
Applies a temperature boundary restraint (can be field-based) to selected Boundary entities (either CAD Face or FE Boundary).
The following boundary conditions are specific to a***Thermal Stress Analysis***:
Defines a baseline temperature (can be field-based) to be used in a thermal stress analysis in order to calculate the stress due to expansion/contraction based on the difference between the **Initial Temperature** and the **Applied Temperature Load**.
Defines an Applied Temperature (can be field-based) to be used in a thermal stress analysis to calculate the stress due to expansion/contraction based on the difference between the**Initial Temperature** and the **Applied Temperature Load**.
