Comparison of Numerical and Experimental Results for the Evaluation of the Depollution Effectiveness of Photocatalytic Coverings in Street Canyons

Abstract

Towards the aim of improving the air quality in the urban environment via the application of innovative TiO 2 based photocatalytic coverings, a field campaign took place within the frame of the EU PICADA project (http:// www.picada-project.com) to asses the expected depollution efficiency of such materials under realistic conditions. Furthermore, extensive numerical modeling was performed via the application of the RANS CFD code for microscale applications MIMO, in an effort to asses the sensitivity of the developing flow field and the corresponding dispersion mechanism and hence of the depollution efficiency of the PICADA products on a wide range of factors, with most notably the length of the street canyon, the thermal exchange between the heated street canyon walls and the air and the approaching wind direction. For the needs of the PICADA project a new, simple module had to be implemented into MIMO to be able to model the removal of NO x from a street canyon whose walls have been treated with a photocatalytic product. The model simulations results presented in this paper, show that MIMO is indeed capable of predicting the effectiveness of the photocatalytic products in question. At the same time, they reveal a strong dependence of the developing flow and concentration fields inside the field site street canyon configuration on most of the aforementioned factors with most notably the direction of the approaching wind.

Full scale demonstration of air-purifying pavement

“…This is because from one day to the other, several parameters changed simultaneously and therefore it is not possible to analyze the effect of only one parameter. In order to predict the effect of different factors independently over the NO x degradation a CFD model would be needed [31,32]. On the other hand, due to the application of the photocatalytic coating that is not very durable under normal outdoor exposition, the photocatalytic performance decreases with the ageing of the coating.…”

Photocatalytic roads: from lab tests to real scale applications

“…Furthermore, the best results will be achieved by modeling the environment, validating the model by measurements and implementing the different parameters to asses the real life effect (e.g. [18]). One must bear in mind that photocatalytic applications are only effective in case of good contact between pollutants and the active surface.…”

Photocatalytic degradation of NOx in a pilot street canyon configuration using TiO2-mortar panels

“…The three-dimensional microscale model MIMO was used to simulate the configuration of the field experiment (Moussiopoulos et al 2005). The experimental NOx measurements were compared with the numerical simulation results for both walls.…”