Directional spectral emittance of absorbing and scattering isotherm packed spheres system is predicted by a radiative model based on the discrete ordinates method associated with the control volume technique to solve the radiative transfer equation. Radiative properties for the packed opaque spheres bed are computed by the large size parameter factor scaling model. This model requires the knowledge of several parameters. Particle diameter and porosity can be easily obtained, but particle hemispherical spectral reflectivity is very difficult to obtain directly. It is determined by an identification method (Gauss method of linearization) applied to bidirectional spectral reflectance data obtained from an experimental device using a Fourier transform infrared spectrometer. Results obtained from this approach are consistent. Directional spectral emittance of absorbing and scattering isotherm packed spheres system is predicted using a radiative model based on the discrete ordinates method to solve the radiative transfer equation. Directional spectral emittance is measured using a direct radiometric technique which has been recently proposed. A good agreement is observed between experimental results of directional spectral emittance packed opaque spheres system at high temperature and theoretical data computed.