ABSTRACT
Reflection at the Boundaries............................................................................................ 727 21.8 Parameter Identification for Packed Spheres Systems ................................................ 732 21.9 Conclusion.......................................................................................................................... 735 Nomenclature ............................................................................................................................. 735 References.................................................................................................................................... 736
Radiative transfer in participating media is important in many industrial applications. In many processes, radiative heat transfer is the main form of transfer. This situation is well illustrated either by porous materials or media containing particles, which play a key role in radiative transfer process. Some examples are fluidized and packed beds, combustors, surface pigmented coatings, soot and fly ash, sprayed fluids, porous sintered materials, microspheres, ceramic foam, and fibrous insulations (Moura et al., 1998a). In recent years, many works on semitransparent media (STM) have been carried out
considering the medium without interface, that is, the distance among the particles is important so that the porosity is extremely high. Consequently, the effects of reflection and refraction at interfaces cannot be considered. However, many materials, such as ceramic, thin films, coatings, and metals with low porosity, are far from being considered with unit refractive index. Besides the direction change due to refraction, in some problems it is necessary to take into account the increase of local blackbody emission by a factor of the refractive index squared.
