Set the Node name for the heat rate node.

Select an option from the Specify list: Heat rate (default), Convective heat rate, Nucleate boiling heat rate, or Joule heating.

Enter a value or expression for P0 to prescribe it as the heat rate at the selected node of the thermal system.

The heat rate P is defined in function of the difference between the node temperature T and a specified external temperature, Text, by mean of a convective thermal resistance, Rconv:

Set the Area A of the surface of the convective heat flux and define the Heat transfer coefficient h used to express the convective thermal resistance as:

The default option is to enter a User defined value for the Heat transfer coefficient h.

In addition, the following options are also available to control the type of convective heat rate to model: External natural convection, Internal natural convection, External forced convection, or Internal forced convection.

For all options except User defined, select a Fluid: Air (default), Transformer oil, Water, Moist air, or From material.

When From material is selected, choose a material available from the Materials list.

Depending of the selected option, different parameters are needed. You can refer to the Sketch section to get an illustration of the configuration.

See the Fluid feature for more details on the settings related to each correlation.

Set the Absolute pressure, pA. For User Defined, enter a value or expression. Else, select an Ambient absolute pressure defined in an Ambient Properties node under Definitions. The pressure is used to evaluate the Fluid material properties and this setting is not available for the Transformer oil and Water options.

In addition, enter an External temperature, Text. For User defined, enter a value or expression. Else, select an Ambient temperature defined in an Ambient Properties node under Definitions.

Finally, when the Fluid is Moist air, also set the External relative humidity, ϕw,ext, and the Surface relative humidity, ϕw,s, used to evaluate the material properties.

The heat rate P is defined as follows:

where A is surface area, and q0 is computed with the Rohsenow’s correlation, that evaluates the heat flux due to nucleate boiling on a surface immersed in a liquid pool. See Nucleate Pool Boiling Correlation for details about the correlation. Set the Area A of the surface of the nucleate boiling heat flux, and select materials from the Fluid and Surface lists. When a predefined material (Water, Benzene, n-Pentane, or Ethanol) is used for the fluid, no additional parameters are required, because the liquid and vapor properties are predefined (at saturation temperature) and the Rohsenow’s correlation parameters Csf and s are available for different surface materials. Else, see Nucleate Boiling Heat Flux (Heat Flux feature) for details about the settings.

The heat rate P is defined as follows to model resistive heating at the node:

where Re is the electric resistance and I is the electric current.

Set values or expressions for the Electric current, I, and the Electric resistance, Re.

Set a user-defined value or expression for the Initial temperature, Tinit, to be used at initialization, in particular to evaluate the heat transfer coefficient.

Select appropriate options in the Add the following to default results in order to include the following global variables (space-independent) in the default plots:

Physics tab with Lumped Thermal System selected: