Photocatalytic conversion of a model pollutant (methylene blue) is studied in a novel Photo-CREC reactor unit. The experiments developed allow us to investigate the suitability of an heterogeneous reaction model which accounts for the concentrations of the model pollutant both in the bulk and on the mesh-TiO2. In addition, a photochemical-thermo dynamic efficiency factor (PTEF) is further examined, with the help of the enthalpy of (OH)-O-. formation from water and oxygen and based on the analysis in the light energy absorbed by the mesh. The resulting PTEF is a dimensionless parameter and has to be calculated at high enough model pollutant concentrations, that is, at conditions where zero-order reactions prevail. The PTEF values found in the Photo-CREC unit with the incorporated recent technical improvements are in the 0.0182 level, and this represents quantum yields of 6.31% of the so-called ideal efficiency.