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.
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
emissivity
Stefan-Boltzmann Constant
Stefan-Boltzmann constant = 5.67 x 10-8W/(m2-K4)
Boundary Temperature
boundary temperature (K)
Boundary Temperature
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.
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