Thermal Coupling — Radiation

Use a Thermal Coupling — Radiation simulation object to model simple radiation between surfaces by creating radiative heat paths (radiative conductances) between each primary element and the closest secondary elements. A Thermal Coupling — Radiation simulation object is only practical when the magnitude of the conductances are known or easily calculated.

Applications of Thermal Coupling — Radiation

A Thermal Coupling — Radiation is useful for modeling radiation between surfaces as well as radiation heat transfer to or from ambient surroundings. However:

• To model radiation to or from an environment, use the Simple Radiation to Environment constraint. See Simple Radiation to Environment for more information.

• To model complex radiative exchange between surfaces and/or the environment, use the Radiation simulation object.

Understanding the magnitude of Thermal Coupling — Radiation

A Thermal Coupling — Radiation has a magnitude given by:

σ × GBVF × ε¹× A¹ ( T12+ T22)( T1 + T2 )

• σ is the Stefan-Boltzmann constant.

• GBVF is the specified gray body view factor.

• ε¹ is the emissivity of the primary elements.

• A¹ is the area of overlap of the primary element with the secondary element.

• T1 is the absolute temperature of the primary elements.

• T2 is the absolute temperature of the secondary elements.

Types of Thermal Coupling — Radiation

There are two radiation thermal coupling types: Gap Radiation and Object to Object Radiation.

• Gap Radiation models radiative heat paths between close parallel surfaces with known emissivity. With Gap Radiation, the view factor is effectively 1 so radiative conductance is based solely on emissivity. Typical applications are multi-layer insulating panels, honeycomb panels, or any pair of broad thin surfaces separated by a narrow gap, across which radiative conductances are significant. See Understanding the Gap Radiation type of Thermal Coupling — Radiation for more information.

• Object to Object Radiation models radiative heat paths between objects with know emissivity and known view factors to each other. Since the radiative conductance depends on emissivity and view factors, the magnitude of the conductance can vary widely depending on proximity. See Understanding the Object to Object type of Thermal Coupling — Radiation for more information.

Using Thermal Coupling — Radiation and 2D elements

When the solver calculates a Thermal Coupling — Radiation on 2D elements with the Gray Body View Factor, it always uses the elements' top side emissivity, regardless of elements' normal direction.

Note:

If you want to create a Thermal Coupling — Radiation on the bottom side but are unable to change the top side emissivity because another radiation object is using the same mesh and needs top side emissivity defined differently, then you must either specify a Effective Emissivity value, or adjust the specified Gray Body View Factor value to account for the incorrect emissivity.

Where do I find it?

In a Simulation file, with an active solution that has the appropriate solver, analysis type, and solution type selected:

• Choose Home tab→Loads and Conditions group→Thermal Coupling — Radiation .

• In the Simulation Navigator, right-click Simulation Objects and choose →New Simulation Object→Thermal Coupling — Radiation.

Application	Pre/Post
Command Finder	Thermal Coupling — Radiation
Simulation Navigator	Right-click the Simulation Objects node→New Simulation Object→Thermal Coupling — Radiation

How do I

Create a Thermal Coupling — Radiation

Learn more

Understanding the Gap Radiation type of Thermal Coupling — Radiation

Understanding the Object to Object type of Thermal Coupling — Radiation

Inputs to expressions

Specifying a Coupling Resolution

Using the Only Connect Overlapping Elements option

Using the Overlap Projection Direction option

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

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Thermal Coupling — Radiation, Simcenter 3D 2021.1 Series

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