5.7.1 Definitions
- View Factor: View Factor,
is the fraction of the radiation which leaves surface "
" and strikes surface "
". The View Factors between opaque surfaces in the solution domain are calculated using ray tracing. - Rays: Rays along a selected number of discrete directions are used to determine the view factors for the Surface to Surface (S2S) modelling. The default number of Rays used is 256.
- Grain Size: Size of the cell face groups used to determine view factors. The default Grain Size is 1, which corresponds to view factors being calculated for every opaque cell face.
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Radiation: A boundary condition which accounts for the heat gained or lost based on the incident radiation, the temperature of the boundary, and the emissivity according to the following formula:
5.400
where
Heat flux (W/m2) 
Emissivity 
Stefan-Boltzmann constant = 5.67 x 10-8 W/(m2-K4) 
Boundary temperature (K) 
Area of the boundary (m2) - Emissivity: The ratio of the emitted radiative heat transfer to the incident radiative heat transfer.
-
Reflective Boundary: An emissivity of zero would be equivalent to a totally reflective boundary, i.e. no energy absorbed due to the incident radiation.
-
Absorbing Boundary: An emissivity of 1 would be equivalent to a fully absorbing boundary.