Radiant Field in Annular and Tubular Photocatalytic Reactors With the Novel Six‐Flux Model in ( <i>r</i> , <i>z</i> ) Coordinates (SFM‐2D) Under Artificial Light

ABSTRACT In this study, the local volumetric rate of photon absorption ( LVRPA ) was established by solving the radiative transfer equation (RTE) in ( r , z ) coordinates using the six‐flux model approach (SFM‐2D). This methodology enabled the estimation and description of the radiant field in annular and tubular photocatalytic reactors under both nonuniform and uniform incident radiation. Titanium dioxide and LiVMoO 6 were used as catalyst models, and their optimum values were consistent with literature values obtained from Monte Carlo (MC) simulations in annular photocatalytic reactors. The LVRPA was subsequently utilized to formulate a modified Langmuir–Hinshelwood (LH) kinetic equation, which predicts the photocatalytic degradation of benzyl alcohol in an annular reactor using the LiVMoO 6 catalyst, with minor discrepancies compared to experimental data. Additionally, the boundary layer of photon absorption (δ abs ) was formulated for a tubular reactor, revealing that the commercial TiO 2 ‐P25 catalyst exhibited no photon absorption beyond 74% of the reactor radius. The SFM‐2D improves upon the SFM‐1D by assuming only one symmetry consideration to solve the RTE, compared to the two assumptions required by the SFM‐1D.