Opacity
This subnode enables to define the surface-to-surface radiation direction on boundaries surrounding the domains where it is defined. When several spectral bands are defined, the opacity can be set for all or only a selection of wavelengths.
When the Radiation direction is defined by Opacity controlled in surface-to-surface boundary features (Diffuse Mirror, Diffuse Surface, Prescribed Radiosity), surface-to-surface radiation propagates in non-opaque domains. Alternatively the Radiation direction can be defined using the normal orientation or on both sides of boundaries. In this case the Opacity node is ignored.
Opacity
Select Opaque or Transparent to set the domain’s opacity type. Depending on the Wavelength dependence of emissivity defined in the Radiation Settings section of the physics interface settings, different sections display underneath:
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When Wavelength dependence of emissivity is set to Constant in the physics interface settings, set the opacity for all wavelengths.
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When Wavelength dependence of emissivity is set to Solar and ambient or Multiple spectral bands in the physics interface settings, set the opacity for each spectral band by selecting the corresponding check box in Opacity on solar spectral band and Opacity on ambient spectral band, or Opacity on spectral band i sections. By default the opacity is set to the same type for all spectral bands.
The default opacity type depends on the parent node’s type. It is set to Opaque for Solid, Porous Medium, Biological Tissue and Building Material domain features and Surface-to-Surface Radiation interface; and to Transparent for Fluid, Phase Change Material, and Isothermal Domain domain features.
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The Wavelength dependence of emissivity is defined in the physics interface settings, in the Radiation Settings section.
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If this feature is combined with heat transfer in 2D and 1D, the thickness is assumed to be infinite for the view factor computation. The user-defined value for d is still used in the heat transfer equation.
Free Convection in a Light Bulb: Application Library path Heat_Transfer_Module/Thermal_Radiation/light_bulb
Thermo-Photo-Voltaic Cell: Application Library path Heat_Transfer_Module/Thermal_Radiation/tpv_cell
Location in User Interface
Context menus
Heat Transfer with Surface-to-Surface Radiation>Solid>Opacity
Heat Transfer with Surface-to-Surface Radiation>Fluid>Opacity
Heat Transfer with Surface-to-Surface Radiation>Porous Medium>Opacity
Heat Transfer with Surface-to-Surface Radiation>Phase Change Material>Opacity
Heat Transfer with Surface-to-Surface Radiation>Biological Tissue>Opacity
Heat Transfer with Surface-to-Surface Radiation>Building Material>Opacity
Heat Transfer with Surface-to-Surface Radiation>Isothermal Domain>Opacity
Heat Transfer in Moist Air>Moist Air>Opacity
Surface-to-Surface Radiation>Opacity
More locations are available if the Surface-to-surface radiation check box is selected under the Physical Model section. For example:
Heat Transfer in Solids>Solid>Opacity
Ribbon
Physics Tab with Solid, Fluid, Porous Medium, Phase Change Material, Biological Tissue, Building Material, or Isothermal Domain selected in the model tree:
Attributes>Opacity
Physics Tab with Surface-to-Surface Radiation selected in the model tree:
Domains>Opacity