Simple Radiation to Environment

Use the Simple Radiation to Environment constraint to model thermal radiation between one or more surfaces with known emissivity and an environment at a specified temperature. Radiation is area dependent and constrained by the specified environmental temperature and surface emissivity. You specify one of the following:

• The gray body view factor (GBVF)

• The emissivity and the GBVF

• The effective emissivity

Note:

To model radiation when view factors are unknown or when the radiation environment has a complex geometry, use the Radiation simulation object instead.

Selecting geometry or elements for defining a Simple Radiation to Environment constraint

Selection	Area calculation
Surface meshed with 2D elements	Area = Surface area
Surface meshed with 3D elements	Area = Surface area
A curve or edge meshed with 1D elements	Area = Perimeter of beam section × length of body edge
The edge of body face meshed with 2D elements	Area = Thickness of 2D elements × length of body edge
A mesh point meshed with a 0D element	Area = Surface of a sphere of the specified diameter

Understanding Simple Radiation to Environment

With a Simple Radiation to Environment constraint, heat is radiated between the surface and the environment as follows:

Qse= σ GBVFse εs As (Ts4 - Te4)				where:Qse is the net radiative heat power from the surface, s, to the environment, e.σ is the Stefan-Boltzmann’s constant.GBVFse is the gray body view factor from s to e.εs is the emissivity of the surface.As is the area of the surface.Ts is the temperature of the surface.Te is the temperature of the environment.

Supported variables and functions

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

Quantity	Variables	Auto-generated expressions
Effective Emissivity****Temperature	TimeSpatial variablesTime, spatial variables	fluid_temperatureheat_flow_ratemass_flow_ratepressurenxnynzradiusrotational_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	Simple Radiation to Environment
Simulation Navigator	Right-click the Constraint Container node→New Constraint→Simple Radiation to Environment

Learn more

Radiation

Inputs to expressions

Look up more details

Auto-generated expressions

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

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