New Radiative Analysis Approach for Reticulated Porous Ceramics Using Discrete Ordinates Method

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Abstract
A novel radiative modeling technique using discrete ordinates has been developed for reticulated porous ceramics (RPCs) from experimental measurements of transmittance and reflectance on small samples of partially stabilized zirconium oxide (PS ZrO2) and oxide-bonded silicon carbide (OB SiC). The new technique defines and quantifies the direct transmittance fraction, fdt, of a reticulated porous ceramic, demonstrates how it redefines the extinction process, and creates a new effective extinction coefficient, Kλ,eff. This ultimately produces a modified form of the radiative transfer equation (RTE) and an innovative discrete ordinates formulation to solve the RTE unique to RPCs. The direct transmittance modeling approach has been compared to a more conventional homogeneous modeling approach, in which the direct transmittance effects are essentially ignored and the RPC is treated as a homogeneous lump of material. The two modeling approaches yield identical results in predicting small test sample reflectances and transmittances. The direct transmittance technique does demonstrate explicitly, through a unique relationship between absorption coefficients in the two modeling approaches, the importance of scattering processes in enhancing the absorption mechanism in RPCs. It can also be an important secondary modeling technique that imposes additional parameter constraints in an inverse analysis to help refine derived radiative coefficients.