Radiation

Use a Radiation simulation object to create view factor calculation requests for enclosures comprised of selected geometry or elements. The thermal solver computes infrared radiative conductances between elements associated with selected geometry. It uses black body view factor technique which assumes diffuse emission and reflection from surfaces of the elements within enclosure. These conductances are then used to calculate radiant heat load emitted, reflected, and absorbed through the enclosure.

Note:

You can control the accuracy of the view factor shadowing calculations with the Error Criterion or Fixed Subdivision options.

When you define the Radiation simulation object, you do not introduce thermal energy into the model. You define how thermal energy is exchanged between model surfaces, or between model surfaces and the radiative environment.

Required element properties

For all elements associated with the Radiation simulation object you have to define:

• Thermal material properties.

• Emissivity in a Thermo-Optical Properties modeling object that you assign to the associated mesh collector.

Upon a radiation request, the solver will detect enclosures, calculate view factors, perform shadowing checks, calculate diffuse and reflected radiative exchanges and compute radiative heating (if any) within the model. Only elements defined with emissivity between 0 and 1 can radiate.

Determining the top and bottom side of the mesh

The 2D mesh can radiate from its top side, its bottom side, or both. The top and bottom sides of the mesh are controlled by the direction of the elements' normal. You should check the mesh's element normal direction to determine the top and bottom sides of the mesh before you define the Radiation simulation object and shell's top or bottom thermo-optical properties.

Geometry and mesh for radiation

How thermal solver models radiative exchange between surfaces depends on geometry you select, and how the geometry is meshed.

You can select:

• Surfaces meshed with 2D elements. Actual radiative loads apply to physical surfaces. 2D elements have many options for thermal modeling and present a smaller conduction matrix than 3D solid elements.

• Curves meshed with 1D elements. For radiation modeling, the solver interprets these elements as cylinders with a circumference equal to the perimeter of the beam section, and uses this configuration to determine view factors.

• A point meshed with 0D element. For radiation modeling, the solver interprets this element as a sphere with effective diameter, and uses this configuration to determine view factors.

• The free faces of 3D elements require no special properties.

Techniques for reducing radiation analysis time

• If the gray body view factors are known, use a Thermal Coupling—Radiation simulation object to model radiation instead of calculating them with Radiation simulation object. This can reduce model preparation and analysis time.

• To deactivate elements for radiation, use the Deactivation Set simulation object. This can reduce analysis time if some elements are not needed for a particular analysis.

• If on a subsequent run you want to change some element emissivity values, you can reuse previously calculated black body view factors.

Where do I find it?

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

How do I

Define Radiation

Learn more

Radiation types

Understanding enclosures

Understanding view factors

Understanding the Hemicube Rendering calculation method

Example 1 - Using the All Radiation type

Example 2 - Using multiple Enclosure Radiation type objects

Understanding the Monte Carlo calculation method

Monte Carlo Settings

Inputs to expressions

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

Simcenter 3D tutorials

Browse Simcenter 3D help by product area

Radiation, Simcenter 3D 2021.1 Series

© 2020 Siemens

window.mainLanguage="en_US"

window.delivId=""

window.projectId=""

MathJax.Hub.Config({ TeX: { extensions: ["autoload-all.js"] }, tex2jax: { displayMath: [ ] }, "SVG": { scale: 125 } });