For a steady-state problem the temperature does not change with time and the first term disappears.

This section has fields and values that are inputs to expressions that define material properties. If such user-defined property groups are added, the model inputs appear here. For all model inputs, you can select Common model input to use a model input defined under Global Definitions.

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, and all temperature variables from the physics interfaces included in the model. These physics interfaces have their own tags (the Name). For example, if a Heat Transfer in Fluids interface is included in the model, the Temperature (ht) option is available.

The default Absolute pressure pA is taken from Common model input. It corresponds to the minput.pA variable, set to 1 atm by default. To edit it, click the Go to Source button (), and in the Default Model Inputs node under Global Definitions, set a value for the Pressure in the Expression for remaining selection section. When additional physics interfaces are added to the model, the absolute pressure variables defined by these physics interfaces can also be selected from the list. For example, if a Laminar Flow interface is added you can select Absolute pressure (spf) from the list. The last option is User defined.

From the Concentration c (SI unit: mol/m3 or kg/m3) list, select an existing concentration variable from another physics interface, if any concentration variables exist, or select User defined to enter a value or expression for the concentration. This section can be edited anytime a material property is concentration dependent; for example, when the Fluid type is set to Moist air with Input quantity set to Concentration.

The default Velocity field u is User defined. For User defined enter values or expressions for the components based on space dimensions. You can also select an existing velocity field in the component (for example, Velocity field (spf) from a Laminar Flow interface).

The thermal conductivity k describes the relationship between the heat flux vector q and the temperature gradient ∇T in q = −k∇T, which is Fourier’s law of heat conduction. Enter this quantity as power per length and temperature.

The default Thermal conductivity k is taken From material. For User defined select Isotropic, Diagonal, Symmetric, or Full based on the characteristics of the thermal conductivity, and enter another value or expression. For Isotropic enter a scalar which will be used to define a diagonal tensor. For the other options, enter values or expressions into the editable fields of the tensor.

The heat capacity at constant pressure Cp describes the amount of heat energy required to produce a unit temperature change in a unit mass.

The ratio of specific heats γ is the ratio of the heat capacity at constant pressure, Cp, to the heat capacity at constant volume, Cv. When using the ideal gas law to describe a fluid, specifying γ is sufficient to evaluate Cp. For common diatomic gases such as air, γ = 1.4 is the standard value. Most liquids have γ = 1.1 while water has γ = 1.0. γ is used in the streamline stabilization and in the variables for heat fluxes and total energy fluxes. It is also used if the ideal gas law is applied.

The only Fluid type option is Gas/Liquid. This option specifies the Density, the Heat capacity at constant pressure, and the Ratio of specific heats for a general gas or liquid.

Physics Tab with interface as Heat Transfer in Solids, Heat Transfer in Fluids, or Heat Transfer in Solids and Fluids selected: