Definitions
• View Factor 
—Fraction of the radiation which exits surface 
and strikes surface 
. View factors between opaque surfaces in the solution domain are calculated using ray tracing.
—Fraction of the radiation which exits surface and strikes surface . 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) modeling. Default number of rays used is 256.
• Grain Size—Size of the cell face groups used to determine view factors. Default grain size is 1, which corresponds to view factors being calculated for every opaque cell face.
• Radiation—A boundary condition which accounts for the heat gained or lost based on factors like incident radiation, the temperature of the boundary, and the emissivity according to the following formula:
Equation 2.272
where,
 | heat flux (W/m2) |
 | emissivity |
 | Stefan-Boltzmann constant = 5.67 x 10-8W/(m2-K4) |
 | boundary temperature (K) |
 | area of the boundary (m2) |
• Emissivity—Ratio of the emitted radiative heat transfer to the incident radiative heat transfer.
• Reflective Boundary—An emissivity of zero is equivalent to a totally reflective boundary, in which no energy is absorbed due to the incident radiation.
• Absorbing Boundary—An emissivity of 1 is equivalent to a fully absorbing boundary.
• Reflective Boundary—A boundary in which no energy is absorbed due to the incident radiation and its zero emissivity is equivalent to a totally reflective boundary.