Thermal Contact
This node defines correlations for the conductance h at the interface of two bodies in contact. It can be added to pairs by selecting Pair Thermal Contact from the Pairs menu. Note that in this case the source term is applied on the destination side.
The conductance h is involved in the heat flux across the surfaces in contact according to:
where u and d subscripts refer to the upside and downside of the slit, respectively. Pair Thermal Contact should be activated on a Identity Pair or on a Contact Pair where a structural mechanics physics interface defines a contact pair feature.
Pair Selection
If this node is selected from the Pairs menu, choose the pair on which to apply this condition. A pair has to be created first. See Identity and Contact Pairs in the COMSOL Multiphysics Reference Manual for more details.
Thermal Contact
Constriction Conductance
Select a Constriction conductance: Cooper-Mikic-Yovanovich correlation (the default), Mikic elastic correlation, or User defined. For User defined enter a value or expression for hc.
Gap Conductance
Select the Gap conductance: User defined (the default) or Parallel-plate gap gas conductance (available if Cooper-Mikic-Yovanovich correlation or Mikic elastic correlation is selected as the Constriction conductance). For User defined enter a value for hg.
Radiative Conductance
When the Surface-to-surface radiation check box is selected under the Physical Model section on a physics interface, choose the Radiative conductance: User defined (the default) or Gray-diffuse parallel surfaces.
For User defined enter a value for hr.
Contact Surface Properties
This section is available if Cooper-Mikic-Yovanovich correlation or Mikic elastic correlation are chosen as the Constriction conductance correlation under Contact. Enter values for the:
•
Surface roughness, asperities average height σasp
•
Surface roughness, asperities average slope masp
•
Contact pressure p
For Cooper-Mikic-Yovanovich correlation select a Hardness definition: Microhardness (the default), Vickers hardness, or Brinell hardness.
•
For Microhardness enter a value for Hc.
•
For Vickers hardness enter a value for the Vickers correlation coefficient c1 and Vickers size index c2.
•
For Brinell hardness enter a value for HB. It should be between 1.30 and 7.60 GPa.
For Mikic elastic correlation select Contact interface Young’s modulus Econtact: Weighted harmonic mean (the default) or User defined.
•
For Weighted harmonic mean enter values or expressions for the Young’s modulus E and Poisson’s ratio ν.
•
For User defined enter another value or expression for Econtact.
Gap Properties
This section is available when Parallel-plate gap gas conductance is selected as the Gap conductance correlation under Thermal Contact.
The default Gas thermal conductivity kgap is taken From material. For User defined select Isotropic, Diagonal, Symmetric, or Anisotropic based on the characteristics of the gas thermal conductivity, and enter another value or expression.
Also enter the following:
•
Gas pressure pgap
•
Gas thermal accommodation parameter α
•
Gas fluid parameter β
•
Gas particles diameter D
Radiative Conductance
This section is available when Gray-diffuse parallel surfaces is selected as the Radiative conductance correlation under Thermal Contact.
By default the Surface emissivity ε is taken From material. For User defined enter another value or expression.
Thermal Friction
Select a Heat partition coefficient r: Charron’s relation (the default) or User defined. For User defined enter a value for r.
Select either the General source (the default) or Heat rate.
•
For General source enter a frictional heat source Qb.
•
For Heat rate enter the heat rate Pb.
Theory for Thermal Contact
Upside and downside settings can be visualized by plotting the global normal vector (nx, ny, nz), that always points from downside to upside. Note that the normal vector (ht.nx, ht.ny, ht.nz) may be oriented differently.
See Tangent and Normal Variables in the COMSOL Multiphysics Reference Manual.
Thermal Contact Resistance Between an Electronic Package and a Heat Sink: Application Library path Heat_Transfer_Module/Thermal_Contact_and_Friction/
thermal_contact_electronic_package_heat_sink
Location in User Interface
Context menus
Heat Transfer>Thermal Contact
Heat Transfer in Solids>Thermal Contact
Heat Transfer in Fluids>Thermal Contact
Heat Transfer in Porous Media>Thermal Contact
Bioheat Transfer>Thermal Contact
Heat Transfer with Surface-to-Surface Radiation>Thermal Contact
Heat Transfer with Radiation in Participating Media>Thermal Contact
Heat Transfer in Solids>Pairs>Pair Thermal Contact
Heat Transfer in Fluids>Pairs>Pair Thermal Contact
Heat Transfer in Porous Media>Pairs>Pair Thermal Contact
Bioheat Transfer>Pairs>Pair Thermal Contact
Heat Transfer with Surface-to-Surface Radiation>Pairs>Pair Thermal Contact
Heat Transfer with Radiation in Participating Media>Pairs>Pair Thermal Contact
Ribbon
Physics Tab with interface as Heat Transfer, Heat Transfer in Solids, Heat Transfer in Fluids, Heat Transfer in Porous Media, Heat Transfer in Building Materials, Bioheat Transfer, Heat Transfer with Surface-to-Surface Radiation or Heat Transfer with Radiation in Participating Media selected:
Pairs>interface>Pair Thermal Contact