Interface Conditions
The
Interface attributes for the
Heat module are listed below. You can assign a specific independent
Interface attribute to each
Interface. You can specify the
Interface type for a selected
Interface under the
Heat module in the Properties panel.
Conjugate Wall
Conjugate Wall also has the option to include Heat Source, Radiation and the effect of small gaps (Contact Resistance).
The
Conjugate Wall option uses a harmonic averaging of the effective
Conductivity at the
Interface.
Conjugate Wall is the default at any
Interface separating a liquid and solid. Harmonic averaging is required for accurate calculation of the heat flux between materials with different conductivities. The alternative to the
Conjugate Wall option is the
Default Interface option, in which the
conductivity at the
Interfaces between the cells uses a simpler linear average, as in the rest of the domain. This is not as accurate if there is a sharp change in
conductivity across the
Interface.
• Heat Source—The
Heat Source option allows the introduction of a
Heat Source at an
Interface. You can add the Heat Source as an average
Heat Source Per Area(
Flux per Area) or
Total Heat Source (total flux). The
Heat Source that you add is distributed to either side of the
Interface based on the respective thermal properties of the neighboring cells. You cannot use the
Heat Source option at an
Interface in conjunction with the
Radiation option.
• Radiation—The radiative heat source is distributed to either side of the Interface based on the respective thermal properties of the neighboring cells. You cannot use the Heat Source or Contact Resistance at an Interface in conjunction with the Radiation option.
• Contact Resistance—The
Contact Resistance option models the effect of a thin gap or layer of material at an
Interface between two materials. You can specify the gap
Thickness and the
Conductivity of the material.
Contact Resistance is useful for including the effects of very small gaps between objects, without the expense or complication of a very fine mesh in between. The
Contact Resistance only includes the effect of the
conductivity across the thickness of the gap, and does not include the effect of any lateral conduction. The Conductivity in the gap is input in units of W/m-K and the Thickness in terms of meters (m). You cannot use the
Contact Resistance at an
Interface with the
Radiation option.
Default Interface
The Default Interface is the default option for an Interface connecting similar materials. You can also elect this for the Interface between dissimilar materials.
For the
Default Interface option, the conductivity at the
Interfaces between the cells uses a simple linear average. It has the advantage of simplicity and speed, but is not accurate if there is a sharp change in
Conductivity across the
Interface. For such
Interfaces, you should specify
Conjugate Wall instead. Despite its name, the
Default Interface is not always the default choice for the
Interface between the cells. For example, the
Interface between a solid and fluid is automatically set, by default, as a
Conjugate Wall.
Output
Click User Select to view the output available for the various Interface Types.