Directional Emittance of a Two-Dimensional Ceramic Coating

Abstract

variation between some of the measured and calculated data; therefore, the results are used only to establish the general range of optical conditions used in this directional emittance study. The geometry considered is that of a semi-infinite slab that absorbs, emits, and scatters thermal radiation. Isotropic scattering is assumed, and the effects of multiple scattering are included. The scattering centers may be either voids or particles suspended in the solid matrix. The method of analysis is similar to Ref. 2 with the addition of Fresnel reflections at the boundaries. Monte Carlo techniques are used to obtain the solutions for the directional emittance. The application of Monte Carlo methods in the analysis of coatings is not new. References 3 and 4 both used statistical approaches to determine optical characteristics of pigmented coatings. Both approaches, however, are concerned with infinite coating geometries. No previous solution for the directional emittance of a two-dimensiona l coating considering Fresnel reflectivities at the boundaries has been published. This study is intended to show the effects of optical thickness, refractive index, and scattering albedo on the directional emittance of a ceramic coating.