Computational fluid dynamics (CFD) simulation was applied to a photocatalytic reactor with surface reaction for trichloroethylene (TCE) oxidation at various pollutant concentrations, and flow rates. First-order and Langmuir-Hinshelwood kinetics for TCE removal rate were considered. The results were compared with those from experiments of Demeestere et al. (Appl Catal B Environ. 2004;54:261-274) in a flat plate photocatalytic reactor with serpentine geometry. The flow regime was laminar. Through the CFD simulation, the velocity field and the concentration gradient of TCE in the reactor were studied in detail. At Reynolds numbers around 900, the laminar flow becomes unstable. Under such a condition, when flow passes the 180 degrees sharp turns, due to formation of secondary flow and consequently vortices, there is a lot of cross-sectional mixing in the reactor. This kind of studies can help us to model the photocatalytic reactor as accurately as possible. (c) 2008 American Institute of Chemical Engineers AIChE J, 55: 312-320, 2009