Novel six flux model two-dimensional (SFM-2D) approach for evaluation of radiation field in slurry photocatalytic reactors with rectangular flat slab geometries

The radiative transfer equation (RTE) in slurry photocatalytic reactors with flat-slab geometries was solved analytically through a new two-dimensional Six-Flux Model approach (SFM-2D), which overcomes the limitations of the SFM and SFM-HG approaches regarding long photon pathways and non-uniform radiation distributions on the front wall of the slab. The model builds a set of partial differential equations of photon balances solved by combining different mathematical methods and suitable boundary conditions, and yields an analytical solution of the local volumetric rate of photon absorption (LVRPA). The model also allows for radiation absorption by the suspended photocatalytic particles and by the fluid matrix, including all reactive species. The radiant field of a flat plate photocatalytic reactor using the proposed model was compared with the SFM-HG approach, using both constant and variable incident radiation boundary conditions. The LVRPA profiles calculated with the SFM-2D and the SFM-HG matched closely in the region near the slab front wall where the incident radiation source enters the reactor, but were significantly different in the regions far away from it. The SFM-2D provides a more accurate optimization of the radiation field in a flat plate with non-uniform irradiation of the front wall, allowing a more accurate estimation of the optimum catalyst load and slab thickness, thus facilitating the design of photocatalytic reactors with suspended photocatalysts.