Thin Film (Heat Transfer Interface) and Fluid (Heat Transfer in Shells Interface)
This node behaves like Fluid but is applicable on boundaries.
Boundary Selection
For a manually added Fluid node in the Heat Transfer in Films interface, or for a Thin Film node in the Heat Transfer interface, select the Restrict to layered boundaries check box to make the node applicable only if a layered material is defined on the boundary. If a layered material (Material with Layer thickness specified, Single Layer Material, Layered Material Link, or Layered Material Stack) is available, its name is then displayed beside the boundary index (for example, slmat1), otherwise the boundary is marked as not applicable.
The default Fluid node of the Heat Transfer in Films interface is applied on all boundaries where the Heat Transfer in Films interface is applied, and neither the boundary selection nor the Restrict to layered boundaries check box are editable.
Note that when the Shell type is Nonlayered shell in the Shells Properties section of the parent interface or node, the Restrict to layered boundaries check box is not editable.
Shell Properties
Fluid (Heat Transfer in Shells Interface)
Different settings are available, depending on the settings in the Shell Properties section of the parent interface, and whether Fluid is the default node or was added manually:
When the Shell type is Layered shell in the Shells Properties section of the parent interface, the same layered material is used in the Fluid node, but you can limit the contribution to individually selected layers by clearing the Use all layers check box. For a given Layered Material Link or Layered Material Stack, you get access to a list of check boxes for the selection of the individual layers. In this case, both the General and Thermally thin approximation options are available in the Layer Model section.
When the Shell type is Nonlayered shell in the Shells Properties section of the parent interface, the Thickness is taken From physics interface in the Fluid node. This option is not editable when Fluid is the default node, but you can change to User defined and override the interface setting with a specific value or expression for Lth when the node was added manually. In this case, only the Thermally thin approximation option is available in the Layer Model section.
Thin Film (Heat Transfer Interface)
Two options are available for the Shell type:
When the Shell type is Layered shell, the Extra Dimension tool is used to solve the equations through the thickness of a layered material. It is possible to consider several layers with different thermal properties varying through the thickness. This makes the General and Thermally thin approximation options available for Layer type in the Layer Model section. You can limit the contribution to individually selected layers by clearing the Use all layers check box. For a given Layered Material Link or Layered Material Stack, you get access to a list of check boxes for the selection of the individual layers.
Alternatively, set Shell type to Nonlayered shell, and set a user defined value or expression for the Thickness Lth. This option should be used for thermally thin layers, for which no through-thickness temperature variation is expected in the layered material. This makes Thermally thin approximation the only option available for Layer type in the Layer Model section.
You can visualize the selected layered materials and layers in each layered material by clicking the Layer Cross Section Preview and Layer 3D Preview buttons.
Model Input
This section contains fields and values that are inputs for expressions defining material properties. If such user-defined property groups are added, the model inputs appear here.
Temperature
This section is available when material properties are temperature-dependent. 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 Default Model Inputs node under Global Definitions, set a value for the Temperature in the Expression for remaining selection section.
Absolute Pressure
Absolute pressure is used in certain predefined quantities that include enthalpy (the energy flux, for example).
It is also used if the ideal gas law is applied. See Thermodynamics, Fluid.
The default Absolute pressure pA is User defined. 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 Common model input option 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.
Layer Model
The available options for Layer type are Thermally thin approximation, and General (when the Shell type is Layered material in the Shell Properties section). The former is a lumped model that accounts only for tangential temperature gradients (along the film), whereas the latter accounts also for the normal gradients of temperature (through the film’s thickness). The second model may be used for the modeling of bearings for example.
If the Layer type is Thermally thin approximation, and the Shell type is Layered shell, the Layerwise constant properties check box is available to solve the equations with weighted averaged material properties, assuming that these properties are constant within each layer. When suitable, this allows to compute efficiently the homogenized properties of the layered material. When this check box is not selected, the properties are integrated through the thickness of the layered material. It means that you can provide material parameters with a through-thickness variation by using expressions containing the extra dimension coordinate, as described in Using the Extra Dimension Coordinates.
Heat Convection
The settings are the same as in the Fluid domain feature.
Heat Conduction, Fluid
The settings are the same as in the Fluid domain feature.
Thermodynamics, Fluid
The settings are the same as in the Fluid domain feature, except for the available options in the Fluid type list: Ideal gas, Gas/Liquid, and Moist air.
See the Fluid domain feature for more details on the Ideal gas and Gas/Liquid options.
Moist Air
If Moist air is selected, the thermodynamics properties are defined as a function of the amount of vapor in moist air. The Input quantity options available to define this amount are as follows:
Vapor mass fraction to define the ratio between vapor mass and total mass. Enter a value or expression for the Vapor mass fraction ω.
Concentration to define the amount of water vapor in the total volume. If selected, a Concentration model input is added to the Model Inputs section.
Moisture content (default), also called mixing ratio or humidity ratio, to define the ratio between water vapor mass and dry air mass. For User defined, enter a value or expression for the Moisture Content xvap. Else, select an Ambient moisture content defined in an Ambient Properties node under Definitions.
Relative humidity ϕw, a quantity defined between 0 and 1, where 0 corresponds to dry air and 1 to air saturated with water vapor. The Relative humidity, temperature condition and Relative humidity, absolute pressure condition should be specified.
Within a layered material selection, a single Layer type should be used. If two layer types are needed for the same layered material, the original material should be duplicated so that one layered material is defined for each layer type. A Shell Continuity (Heat Transfer Interface) and Continuity (Heat Transfer in Shells Interface) node may be added between the two layered materials.
Location in User Interface
Context Menus
Ribbon
Physics tab with interface as Heat Transfer in Fluids selected:
Physics tab with interface as Heat Transfer in Films selected: