Numerical investigation of radiation transfer in packed bed of semitransparent coated spherical particles

A packed bed of multilayered spherical particles plays a very important role in several engineering applications, such as the thermal insulation material of polystyrene foam and solar absorber for thermal energy conversion. In this study, we investigate the transmission of diffused beam in a one-dimensional densely packed bed. Spherical particles with double-layer structure and same radius are distributed randomly in transparent host media. The semitransparent inner layer is coated with a semitransparent shell. The size parameter χ of these spheres is sufficiently large to simulate their interaction with radiation through a Monte Carlo ray-tracing technique based on the geometrical optics approximation. After verification of the code for radiative transfer in a single coated sphere, the effects of optical thickness, refractive index, thickness, and porosity on the transmission are examined in detail. Transmittance and reflectance are employed to describe the radiative properties of a packed bed filled with multilayered semitransparent spherical particles.