光触媒反応による室内汚染物質濃度低減性能の数理モデル化と数値予測 第1報: 小形チャンバーを用いた濃度低減性能試験と濃度依存性を考慮した光触媒反応モデルの提案

摘要

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 photocatalytic 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- Hin-shelwood 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.%サステナブル建築への移行に社会的関心が高まっている中，エネルギーコストを増大させずに室内空気質制御を行う技術の開発は，その要素技術として必須である。本研究では，室内環境中のガス状汚染物質濃度をパッシブに濃度制御する技術として光触媒反応に着目し，酸化チタン(TiO_2)を担持させた建築材料の性能評価法を確立すると共に，室内汚染物質濃度の低減性能を数値的に精度良く定量評価するための数理モデル開発に取り組む。本報(第1報)では数値流体力学CFDによる室内濃度予測に組み込み可能なLangmuir- Hinshel-wood型の光触媒反応モデルを提案した上で，代表的な室内ガス状汚染物質としてトルエンに着目し，独自開発した20L小形チャンバーを用いて濃度低滅性能試験ならびにモデルパラメータ同定を行った。その上で，実験条件に対応するCFD解析を併せて実施することで，小形チャンバー内の速度場·濃度場の不均一性を考慮した上で精度良くモデルパラメータ同定する方法を提案した。