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• Enhanced radiation transport model validated in commonly used photoreactors. • Isotropic, parallel and cone-shaped emission tested, representing common UV sources. • Increase of precision reached for sun direct light simulations. • Great improvement in LEDs simulations, from finer cone radiation and power cosine. This work presents the enhanced numerical simulation of the radiation transport in three different types of photocatalytic reactor using a novel Discrete Ordinate Method model recently developed for the open-source Computational Fluid Dynamics (CFD) platform OpenFOAM. The photoreactors represent commonly used geometries and illumination sources in the field of heterogeneous photocatalysis: an annular reactor illuminated by a mercury fluorescent lamp, a tubular reactor coupled to a compound parabolic collector illuminated by sunlight, and a tubular reactor illuminated by LEDs. Simulations were carried out for different photocatalyst concentrations, considering absorption and anisotropic scattering, showing differences smaller than 2.4% with respect to the results obtained by commercial CFD software for systems with isotropic emission, such as fluorescent lamps. Moreover, the model was able to improve the simulation of solar reactors and dramatically outperformed the simulation of LED sources, due to the combined effect of quadrature rotation and cone-limit fitting for cone-shaped sources, as well as a LED-specific power-cosine light distribution. The developed model has been thoroughly validated and is now available to the open-source CFD community. It allows a comprehensive numerical simulation of radiation transport using any type of light source, with applications in numerous engineering fields where optical phenomena affect the performance of the process. [ABSTRACT FROM AUTHOR]

• Development of a numerical simulation model for SODIS processes in flow reactors. • Coupling of solar vector calculation with radiation field resolution. • Application of mechanistic kinetic model with explicit radiation absorption effect. • Validation of the model in a tubular photoreactor coupled with a CPC reflector. • Good prediction of experimental data under both simulated and natural sunlight. A novel procedure for the simulation of solar water disinfection (SODIS) processes in flow reactors is presented. The modeling approach includes the rigorous description of hydrodynamics, radiation transfer, mass transport and bacterial inactivation phenomena within the reactor by means of a computational fluid dynamics (CFD) software. The methodology has been evaluated in a tubular reactor coupled with a compound parabolic collector (CPC). Velocity profiles have been validated versus theoretical fully developed flow, and radiation fields versus both ray tracing and experimental actinometrical measurements. Incorporation of the solar vector calculation significantly improves the model capabilities for prediction of the potential performance of the SODIS process at different geographical coordinates and operation time. A mechanistic kinetic model was used for the description of the bacterial inactivation rate with explicit radiation absorption effects, coupling the radiation field with the mass balances of viable bacterial species. Model predictions successfully reproduce the experimental data of E. coli inactivation under different irradiances of both simulated and natural solar light with a normalized root mean squared logarithmic error (NRMSLE) of 6.65% and 9.72%, respectively. Therefore, this novel methodology is confirmed as a useful tool for the scaling-up of the SODIS process to large volume systems to be installed in remote communities where safe drinking water is not available. [ABSTRACT FROM AUTHOR]