Modeling and validation of a photocatalytic oxidation reactor for indoor environment applications Lexuan Zhong, Fariborz Haghighat n Department of Building, Civil and Environmental Engineering, Concordia University, Montreal, Quebec, Canada H3G 1M8 article info Article history: Received 2 March 2011 Received in revised form 5 August 2011 Accepted 8 August 2011 Available online 19 August 2011 Keywords: Ultraviolet photocatalytic oxidation Model Irradiance Energy Efficiency Air purification abstract Modern building ventilation design must take into account the health, safety and comfort of the occupants, as well as energy consumption and the environment. The system needs to protect occupants against chemical contaminants from numerous internal sources—office equipment, furniture, building materials, appliances, as well as intentional release. A promising technology which has great potential in this respect is UV photocatalytic oxidation (UV-PCO). Designing a UV-PCO system for a building requires full understanding of its performance, which strongly depends on the UV intensity field, types and concentration levels of reactants, oxygen and moisture levels, temperature, reflectance of duct surfaces, system configuration, orientation, air stream characteristics like temperature, humidity, air velocity and mixing, just to mention a few. This paper reports the development of a mathematical model for predicting the performance of a honeycomb monolith PCO reactor used in building mechanical ventilation systems. The model is validated by comparing its prediction with experimental data and with the prediction made by an existing model. The influence of several kinetic parameters such as airflow rate, pollutant inlet concentration, light intensity, humidity and catalyst deactivation has been investigated. The developed model can be used as a practical tool to simulate and optimize a UV-PCO system for application in building mechanical ventilation system. & 2011 Elsevier Ltd. All rights reserved. 1. Introduction The needs to provide a healthy, safe and comfortable indoor environment and to reduce building energy consumption have all increased the interest in systems to filter gaseous contaminants from the air. Ultraviolet photocatalytic oxidation (UV-PCO) is a promising technology, which has great potential for such an application (Zhong et al., 2010). Such devices use titanium dioxide (a semiconductor) where electron transition from the valence band to the conduction band results from the absorption of light in the near UV range. The subsequent generation of positive holes and their interactions lead to the formation of hydroxyl radicals. These act as powerful oxidizing agents and can be used in the mineralization of organic molecules on the surface of titanium dioxide. In addition, claims have been made with respect to the use of UV-PCO devices in enhanced inactivation rate of micro- organism (Wang et al., 2009). However, it must be noted that in case of incomplete oxidation, the pollutants may be transformed into other by-products that can also pose health hazards. There is little reliable information available in the literature about the performance of this system. Although a number of devices such as chemical filtration, UVGI and UV-PCO are available in the market, no systematic studies have been carried out regarding their comparative performance. In the quest for more successful commercial applications of UV-PCO technology in buildings, more attention is being brought to the modeling and simulation of reactors in order to obtain a more comprehensive and systematic understanding of the UV-PCO system. Nicolella and Rovatti (1998) proposed a mathematical model- ing of monolith reactors, which predicted the rate of chemical reaction and energy transfer. This model provided the distribution of photo-flux along the channels, and defined the contributions of thermal and pure photonic effect on the overall rate of conver- sion. Although enthalpy balance was an innovative aspect in their modeling, they neglected the contribution of molecular diffusion transfer in the mass balance, and therefore their model cannot accurately account for the behavior of PCO under the case of continuous injection of contaminants. Changrani and Raupp (2000) presented the development of a two-dimensional heterogeneous convection-reaction model for an annular reticulated monolithic gas–solid photo-reactor. This model was developed on the basis of efficient utilization of UV irradiance, and it evaluated the reaction rate with local volu- metric rate of energy absorption (LVREA). The magnitude of Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/ces Chemical Engineering Science 0009-2509/$ - see front matter & 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.ces.2011.08.017 n Corresponding author. E-mail address: haghi@bcee.concordia.ca (F. Haghighat). Chemical Engineering Science 66 (2011) 5945–5954