Computational fluid dynamics modelling of the visible light photocatalytic oxidation process of toluene for indoor building materials with locally doped titanium dioxide

Abstract

Computational fluid dynamics (CFD) is one of the promising methods that can precisely predict non-uniform air flow and contaminant distribution in indoor environments. The overarching objective of this study was to develop a mathematical model for describing the photocatalytic oxidation (PCO) reaction mechanism of gas phase toluene with titanium dioxide (TiO2)-bound indoor building materials. This mathematical model was developed based on Langmuir-Hinshelwood type kinetics and for the integration with CFD simulations as a wall surface boundary condition. The effects of gas phase toluene concentration, illuminance and humidity on the toluene oxidation reaction were considered with locally TiO2-doped building materials. Especially, humidity dependence was explicitly integrated as a competitive adsorption model between toluene and water vapour. Moreover, surface compositions of TiO2 and the substrate (ceramic tile in this study), and the physical adsorption properties of those materials, were modelled and integrated into the mathematical model. A 0.02 m3 chamber experiment and adsorption isotherm measurements were conducted to identify the model parameters. CFD analysis was carried out according to experimental scenarios, and an optimization procedure for the model parameters was proposed for their application as the boundary conditions in the CFD analysis.

Hybrid emergency ventilation system for controlling inhaled contaminant dose in the case of chemical leakage

“…We numerically modelled the PCO degradation of toluene on TiO 2 -bound building material surfaces and integrated this numerical model into CFD simulation as a wall surface boundary condition. 31,32 To evaluate the effect of concentration reduction when the photocatalyst building material is installed on the wall surfaces of the factory, the integrated effects of chemical pollutant concentration reduction with the EVS were numerically investigated.…”

“…The model used in this research is based on the Langmuir-Hinshelwood adsorption type, incorporated into the CFD model considering the competitive adsorption of water and toluene on building materials. 31,32 Equation (3) shows a model formula for reducing the concentration of toluene using a photocatalytic building material, where r is the toluene decomposition flux ((kg/m 2 ).s). r is the sum of r 1 in equation ( 4) and r 2 in equation ( 5), each weighted by the titanium oxide coverage f (�)…”

“…Recently, the development of visible-light-type TiO 2 -bound building materials, along with the precedence of photocatalytic building material technology for indoor environments, has also been explored. 31,32 However, the PCO technology has rarely been applied to air quality control in factory spaces.…”

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“…In their review, Boyjoo et al summarized the CFD methods extensively used to address different aspects of gas-phase photocatalytic oxidation modeling for the prediction of uniform and non-uniform air flow and contaminant distribution, generally reporting close agreement with the experimentally obtained contaminant's conversion [23]. Over the recent years, CFD-based assessment of PCO reaction and fluid dynamics prediction has been applied for optimization of the reactors' design [9,[24][25][26][27][28][29] and optimization of the PCO model parameters [22,[30][31][32][33]. These methods are especially useful when the configuration of the photocatalytic reactor does not yield a laminar plug flow and there are large gradients of velocities and pollutant concentration [31,32,34].…”

“…Over the recent years, CFD-based assessment of PCO reaction and fluid dynamics prediction has been applied for optimization of the reactors' design [9,[24][25][26][27][28][29] and optimization of the PCO model parameters [22,[30][31][32][33]. These methods are especially useful when the configuration of the photocatalytic reactor does not yield a laminar plug flow and there are large gradients of velocities and pollutant concentration [31,32,34].…”