Modeling of UV-LED photocatalytic reactors for the degradation of gaseous volatile organic compounds (VOCs) in indoor environments

Abstract

A computational model was developed to predict the photocatalytic oxidation of organic compounds in an ultraviolet light-emitting diode (UV-LED) reactor. To simulate the overall reactor performance, the fluid flow, mass transfer, radiation, and kinetics were modeled and integrated by solving the governing equations of mass, momentum, species, and radiant energy conservation, using computational fluid dynamics (CFD) software. The kinetic parameters were experimentally measured and were defined in the model. The model could reliably predict the reactor’s performance and was in close agreement with the experiments within the range of studied photocatalyst orientation, flowrates (Re = 1125 – 36000), and ultraviolet (UV) irradiances (Iavg = 1.4 – 13.8 mW/cm2). Our results revealed that toluene, as the model organic compound, can effectively diffuse to the catalyst surface resulting in minimal mass transfer limitation (less than 4%) even at the lowest examined flow rate (Re = 1125). The experimental data and simulation results both showed close-to-zero mass transfer limitation at the turbulent flow regime (Re≥ 4600). The modeling results identified the areas of the highest mass transfer limitation using the local values of velocity and concentration. The developed model can be applied to the virtual prototyping as well as design and optimization of UV-LED air purification reactors.