Establishment of Generalized Correlated-Scattering Model for Radiative Properties of Packed Beds

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The present study aims at establishing a generalized correlated-scattering model fot the radiative properties needed for analysis of radiative transfer in packed beds. To this end, the following experimental and theoretical studies have been made:1) Experimental measurements of slab transmittances of packed beds consisting of alumina, silica or polystyrene spheres and inverse analysis of the obtained data using the hemispherical transmittace fitting method2) Experimental measurements of total normal emittances of high-temperature packed beds consisting of carbon steel or alumina spheres and inverse analysis of the obtained data using the directional emittance fitting method3) Establishment of generalized correlated-scattering model for the radiative properties of packed beds; particularly albedo ω^* and asymmetry factor g__〜^*. As a result, we can obtain the following conclusions:1) The values of the albedo and asymmetry factor of alumina, silica and polystyrene bead beds determined by the hemispherical transmittance fitting method are close to those predicted by the correlated scattering model,2) The values of the albedo and asymmetry factor of high-temperature carbon steel and alumina bead beds, of which temperatures were varied from 400 to 870K, are also close to those predicted by the correlated scattering model,3) The developed generalized correlated-scattering model are described as follows:ω^*=P_H+τ_Hγ_3g^^〜^*=[P_Hg^^〜_s+(τ_Hγ_3)g^^〜_1γ_4]/(P_H+τ_Hγ_3)γ_4 = 1+?√<1-φ>Here,γ_3 is a function of the albedo of a single particle and f is a function of the reflective index of a particle. In additin, P_H and τ_H respectively represent the hemispherical reflectivity and hemispherical transmissivity of a particle, whereas g^^〜_S and g^^〜I denote the surface scattering phase function and the refracted scattering phase function, respectively.