Definitions
View Factor Fij—Fraction of radiation which leaves surface i and strikes surface j. You can calculate view factors between opaque surfaces in the solution domain using ray tracing.
Rays—In radiative heat transfer, 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. Default grain size = 1, which corresponds to view factors being calculated for every opaque cell face.
Radiation—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:
where,
Heat flux W/m2
ε
Emissivity
σ
Stefan-Boltzmann constant = 5.67 x 10-8W/(m2-K4)
T
Boundary temperature K
A
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 would be equivalent to a totally reflective boundary, where no energy is absorbed due to the incident radiation.
Absorbing Boundary—An emissivity of 1 would be equivalent to a fully absorbing boundary.
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