Photocatalytic Surface Reactivity


Calculations based on model developed in the PHOTOPAQ LIFE project for a tunnel, i.e. adapted here.

The treatment of the surface reactivity is based on the photocatalytic deposition velocity (n) concept, which is independent on the geometry of the reactor, flow rates, etc. and which is typically used in atmospheric modelling.
Transport limitations are negleted (assumption: well mixed volume). Thus, only the surface resistence - measured in the lab (ISO/CEN etc) - is considered here.
Calculations are based on a first order reaction kinetics of the NOx remediation rate.
Details on the kinetic description are explained in: Ifang, et al. (2014).


Limitations of the model


Dispersion of contaminants has only partly been taken into account, i.e. dispersion in the horizontal axis has been considered but not in the vertical one.
Possible overestimation of the NOx reduction by mass transfer limitation (negligible under high traffic load and/or small deposition velocity).
Uncertainties of the used deposition velocity, if the reaction order is < 1. This is however typically negligible at low Nox

a) Overestimation of the NOx reduction, if c(laboratory) < c(tunnel).
b) Underestimation of the NOx reduction, if c(laboratory) > c(tunnel).

Overestimation of the reduction caused by the use of only NO-reactivity data (NO is typically more reactive than NO2).
Overestimation of the NOx reduction by overestimated reaction time (depends on the correctness of the average wind speed determination).
Overestimation of the reduction caused by passivation of the active surface against NOx under high pollution (e.g. by "organic grime").
Underestimation of the NOx reduction when the reactivity shows curved behaviour with UVA irradiance and when Irradiancelaboratory > Irradiancetunnel

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NOx-reduction in the VOLUME

Full volume in front of the textiles. Volume in front of the textiles at 0.5m from the facade. Full volume of the street.
NOx reduction in the whole volume of the street situated in front of the building where the textiles are installed. NOx reduction in the volume of the street situated in front of the installed textiles, at 0.5m from the facade. NOx reduction generated by the textiles installed in a building, calculated in the whole volume of the street defined by the user.