Directional spectral emittance of a packed bed: Correlation between theoretical prediction and experimental data

Directional spectral emittance of an absorbing and scattering isothermal sy stem of packed spheres is predicted by a radiative model based on the discr ete ordinates method Radiative properties for the bed of packed opaque sphe res are obtained using geometric optics laws corrected with a scaling facto r to take into account the dependent scattering. This model requires the kn owledge of several parameters. Particle diameter and porosity can be easily obtained but particle hemispherical spectral reflectivity is very difficul t to obtain a priori. This particle reflectivity is determined by an identi fication method (Gauss method of linearization) applied to bidirectional sp ectral reflectance data obtained from an experimental device using a Fourie r transform infrared spectrometer. Directional spectral emittance is measur ed using a direct radiometric technique that has been recently proposed. Fo r a system of packed opaque spheres at high temperature, good agreement is observed between experimental, results of directional spectral and computed theoretical data.