**radiation#
[fem:bc:radiation]
Description#
This BC for thermal problems applies a radiation heat flux on a line set
(liset) in 2D, or a face set (faset) in 3D problems. The
expression for the heat flux is:
Syntax#
**radiation group a Te table
- group
Character name of the previously defined line set in 2D or face set in 3D.
- a
Real value for the coefficient \(a\).
- Te
Real value for the exterior temperature, \(T_e\), scale factor. This value will be a multiplicative scale of the current table value to determine the external temperature.
- table
Character name of a pre-defined table name (see
***table). This table describes the magnitude of the external temperature
The coefficient a is constant. There is currently no provision for temperature or time dependence in this parameter. We recall that the coefficient is the product of the two terms:
with \(\sigma\) the Stefan’s constant (\(~5.73~10^{-8}~~W/m^2~K^4\)) and \(\epsilon\) the grey body constant (no dimension).
The formula of radiation is not valid except for temperatures defined in on the absolute scale (Kelvin). This requires therefore that the units throughout the problem be defined consistently in Kelvin when radiation boundary conditions are applied.
Example#
**radiation myliset 1.0e8 273.0 table1