Search

• Spectral band discretization of multiphysics model of solar photoreactors operation. • Novel numerical approach for modelling photoreactors of any spectral distribution. • Small differences in light spectra play a critical role on photocatalytic activity. • Model predictions successfully validated with solar simulator and natural sunlight. • Successful explanation for disagreement of natural and simulated solar experiments. This work describes the critical role of the matching between the spectral distribution of the incident light and the absorption spectra of the semiconductor material on the accuracy of the simulation of solar photocatalytic reactors. In silico results have been generated by a multiphysics model including the rigorous description of the hydrodynamics, radiation transfer, mass transport and chemical reaction rate, with the particular feature of using a spectral band discretization approach for the resolution of the radiation balance and the estimation of the spectral local volumetric rate of photon absorption. Model predictions with a mechanistic kinetic model have been experimentally validated using a solar reactor based on a tubular reactor coupled to a compound parabolic collector (CPC) under illumination with a solar simulator (xenon lamp) and natural sunlight. Small differences in the spectral distribution of both light sources led to significantly different predictions for the reaction rate, explaining the higher efficiency experimentally achieved with natural sunlight in comparison with the solar simulator for equivalent total UV-A irradiances. The developed model is able to explain the discrepancies between experimental results in solar simulators and under natural sunlight, usually reported in the literature, offering a novel numerical approach for rigorous modelling of photoreactors using light sources with any spectral distribution. [ABSTRACT FROM AUTHOR]

• 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]