where ε is the surface emissivity, σ is the Stefan-Boltzmann constant (a predefined physical constant), and Tamb is the ambient temperature.

This section is available when temperature-dependent material properties are used. By default the temperature of the parent interface is used and the section is not editable. To edit the Temperature field, click Make All Model Inputs Editable (). The available options are User defined (default), Common model input (the minput.T variable, set to 293.15 [K] by default) and all temperature variables from the physics interfaces included in the model. To edit the minput.T variable, click the Go to Source button (), and in the Common Model Inputs node under Global Definitions, set a value for the Temperature in the Expression for remaining selection section.

For User defined, enter an Ambient temperature Tamb. The default value is approximately room temperature, 293.15 K (20ºC). Else, select an Ambient temperature defined in an Ambient Thermal Properties node under Definitions.

The default Surface emissivity ε (a dimensionless number between 0 and 1) is taken From material. For User defined, it should be specified. An emissivity of 0 means that the surface emits no radiation at all while an emissivity of 1 means that it is a perfect blackbody.

Physics Tab with Thin Rod selected in the model tree:
Attributes>Surface-to-Ambient Radiation