Surface-to-Surface Contact

Use a Surface-to-Surface Contact simulation object to model heat transfer between surfaces in close or perfect contact. You can manually specify pairs of faces as contact pairs, or you can allow the software to automatically identify faces of separate polygon bodies that are in contact with each other.

You can model the heat transfer using the following Type options:

• Perfect Contact merges the two surfaces making their temperatures identical.

• Conduction models only conduction between the two surfaces.

• Radiation models only radiation between the two surfaces.

• Conduction and Radiation models both conduction and radiation between the two surfaces.

When you select Conduction or Conduction and Radiation, you can choose one of the following Conduction Type options:

• Total Conductance defines an absolute conductance between the two element sets. The conductance is defined in units of power per degree of temperature difference between the two element sets.

• Total Resistance defines a resistance to heat flow between the two element sets. The resistance is defined in units of degree of temperature difference between the two element sets per power.

• Heat Transfer Coefficient defines the quantity of heat that flows between two sets of elements. The coefficient is defined in units of power per unit area, per degree of temperature difference between the two element sets.

• Conductive Gap defines the thermal conductivity of the gap medium. The conductivity is defined in units of power per unit thickness and per degree of temperature difference between the two element sets.

When you select Radiation or Conduction and Radiation, you can choose one of the following Radiation Type options to specify how the software calculates radiative conductances:

• With the Close Parallel Plates option, the software calculates the radiative conductances based on the emissivities of the two element sets. The software assumes that the two element sets are on flat parallel plates that are close to each other.

• With the Gray Body View Factor option, the software calculates the radiative conductances based on the specified gray body view factor.

• With the Effective Emissivity option, the software calculates the radiative conductances based on the specified effective emissivity. Effective emissivity = emissivity x gray body view factor.

Supported variables and functions

The following table lists the independent variables and auto-generated expressions for the Surface-to-Surface Contact quantities that you can define using fields and expressions.

Quantity	Variables	Auto-generated expressions
Total ConductanceTotal ResistanceHeat Transfer Coefficient****Conductive Gap	TimeTemperatureHeat flow rateTemperature differenceThermal capacitance	fluid_temperatureheat_flow_ratemass_flow_ratenxnynzpressureradiusrotational_speedtemperaturetemperature_differencethermal_capacitancethicknesstimevolume_flow_ratexyz

In expressions, you can also use all built-in functions that are listed in Mathematical functions in expressions and most built-in functions that are listed in Thermal-flow functions in expressions.

Where do I find it?

Application	Pre/Post
Command Finder	Surface-to-Surface Contact
Simulation Navigator	Right-click the Simulation Objects node→New Simulation Object→Surface-to-Surface Contact

How do I

Create Surface-to-Surface Contact

Learn more

Inputs to expressions

Using the Only Connect Overlapping Elements option

Using the Overlap Projection Direction option

Specifying a Coupling Resolution

Automatic face pairing

Look up more details

Auto-generated expressions

Quick links

Simcenter 3D Thermal/Flow, Electronic Systems Cooling, and Space Systems Thermal boundary conditions

Thermal/Flow, Electronic Systems Cooling, and Space Systems Thermal

Command reference

Pre/Post video examples

Bulk Entry Descriptions

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Surface-to-Surface Contact, Simcenter 3D 2021.1 Series

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