Analysis of collimated irradiation under local thermal non-equilibrium condition in a packed bed

Forced convective heat transfer in a packed bed in the presence of collimated irradiation and under local thermal non-equilibrium is analyzed in this work. Both the collimated and diffusive radiative transfer processes are accounted for using the modified P-1 approximation. Two boundary condition models considering different limiting conditions at the wall which couple radiation and convection under LTNE were constructed. The effect of pertinent parameters such as the porosity φ, pore diameter dp, ratio of the solid to fluid thermal conductivities ζ; radiative properties including optical thickness τ, scattering albedo ω, and the wall emittance ɛw were analyzed. Also, their effects on the temperature and heat flux distributions in the incident direction were analyzed systematically and the limiting interactions between thermal radiation and conduction were revealed. The differences between the two boundary models with the effects of the cited parameters were analyzed. Our analysis demonstrated that an increase in either φ or dp enhances the transfer of radiative energy into the channel.