Small Test Chamber Experiment and Modeling of Photocatalytic Oxidation for CFD Simulation : Part 1-CFD Modeling of Photocatalytic Oxidation and Numerical Prediction of Concentration Reduction Performance in Indoors

Indoor air quality affects occupants' health and comfort. Poor indoor environmental conditions and gas-phase/aerosol-phase contaminants in indoors are also identified as one of the causes of illnesses such as asthma and allergy, and known to result in significant loss of productivity because of its adverse effect on health. In recent years, photocatalytic oxidation (PCO) process have attracted attention because they are effective in purification of indoor air polluted with volatile organic compounds (VOCs), especially at low concentration levels. Thus far, TiO_2, one of the photocatalyst bound building materials, has been extensively studied for the oxidation of indoor air pollutants. The purpose of this research is to establish of Numerical Prediction of Concentration Reduction Performance of VOCs indoors. In this study, kinetic studies were carried out on photocatalytic oxidation (PCO) of toluene as VOCs in the gas phase over TiO_2-bound building materials in a 20 L test chamber and computational fluid dynamics (CFD) simulations were performed using the same boundary conditions as the experiments to identify model parameters of the PCO process. A performance test for evaluating the reduction of toluene concentration was carried out according to the ISO 16000-24 procedure (ISO, 2009) using a rectangular test chamber and a TiO_2-coated building material through a thermal spraying technique. TiO_2 powder was retained on the the surface of a material in the absence of any specific binder. Toluene concentration-controlled air was supplied into the chamber via an inlet located at the bottom of the chamber using a precise gas generator. The concentrations of toluene and products in the gas phase were determined using gas chromatography (GC/FID) by collecting samples from the outlet located on the ceiling of the test chamber. In this paper, we show the experimental results of photo-catalytic degradation on toluene concentration and the identification result of the kinetic model parameters of the Langmuir-Hinshelwood model on the PCO process in combination with CFD simulations. The Langmuir-Hinshelwood model was applied to the first control volume from the building material surface as a source term (sink term). The error of the reaction rate constant obtained in the experiment was corrected and adjusted through CFD analysis. The reaction rate constant k and Langmuir adsorption constant K were 1.78×10^<-10> kg/m^2/s, 1.16×10^6 m^3/kg, respectively.