Modeling and optimization of a tangential photocatalytic reactor for uniform distribution of pollutant-laden air on the reactive area

Photocatalysis has shown significant promise due to its ability to chemically degrade volatile organic compounds (VOCs) using TiO₂ and UV irradiation. However, the efficiency of chemical degradation in photocatalytic reactors is often limited by a poor distribution of airflow in the vicinity of the reactive surface. Traditional reactors commonly employ divergent or planar inlets with an axial introduction of polluted air, based on the incorrect assumption of ensuring uniform flow distribution. By integrating insights from fluid mechanics, this research replaces the former inlets of a tangential reactor with a convergent inlet combined with a transverse introduction of polluted air. Numerical simulations based on computational fluid dynamics (CFD) under laminar flow conditions were conducted to optimize the reactor design. A local residence-time analysis demonstrated that the optimized design promoted a more homogeneous residence-time distribution within the treatment region. Subsequently, two sets of photocatalytic degradation experiments using toluene were carried out. The first experimental campaign, considering a constant flow rate of 1 L min −1 under varying irradiance intensities, showed that the optimized reactor achieved up to a 25% improvement compared with the other designs, as a result of more uniform velocity profiles and improved air–surface interaction. The second experimental campaign examined the effect of airflow rate in the range 0.75 to 1.5 L min −1 on the performance of the optimized reactor at irradiance intensity of 215 μW cm −2 . Toluene degradation decreased as the residence-time decreased with increasing airflow rate; however, 65% of the degradation capacity was maintained at the highest airflow rate. These findings highlight the critical role of reactor design in achieving effective degradation of VOCs. • A novel photocatalytic tangential reactor was designed to improve internal airflow distribution. • This novel reactor was compared numerically and experimentally with two reference geometries. • The flow uniformity in the treatment zone is significantly enhanced. • Experimental results confirmed a 25% increase in toluene degradation efficiency.