New synthetic nano-aerosol for accelerated realistic ageing of air filters

J. A. Marval Díaz, E. Norata, P. Tronville*, Politecnico di Torino, Italy

To assess reliably the energy impact of air filters it is essential to ascertain changes of their airflow resistance during their whole service life and not just when they are clean. This is true in the case of current filters on the market and for future filter designs too.

An air filter’s ageing behavior is strongly dependent on the characteristics of the challenging aerosol during its service life and on the characteristics of the particles collected on the fibers. The relevant aerosol characteristics include its particle size distribution, the shape of the particles, and whether the particles are solid or liquid. The size (diameter) of aerosol particles is especially important in determining the kinetics of the air filter loading and clogging process. In general, the airflow resistance increases more significantly as the size of the loading aerosol decreases.

Current laboratory standards simulate the ageing of air filters by dispersion and loading of synthetic dusts with particle size distribution completely different from a typical urban atmospheric one. This is considered acceptable for rating filters and comparing their performance against each other, but it will not result in accurate prediction of the airflow resistance increase, likely to occur in a real environment. Therefore, the energy-use assessment cannot be reliably estimated by means of current laboratory test dusts.

We can better predict the impact on air filter resistance of their service time if we perform an accelerated ageing procedure by using synthetic aerosols with a thoughtful size distribution like, for example, a reasonable simulation of typical urban atmospheric aerosols. Knowing how a pressure drop realistically changes in time will allow to estimate optimal air filter changes and to establish a meaningful energy labeling system. ISO 16890-1:2016 defines...

...We describe various methods for generating nanoparticles having approximately the same particle size distribution of a typical urban aerosol, but at higher mass concentrations. The purpose is to allow accelerated ageing in a similar way to what happens in actual service conditions. The paper describes the thermal aerosol generator chosen to produce the desired particle size distribution of the synthetic aerosol in an existing test rig according to ISO 16890:2016 specifications. This generator produces a high amount of nanoparticles by burning a salt stick (e.g. made with KCl) with an oxy-propane flame. The salt vapor condenses in the air stream to form a cloud of ultrafine particles...

Session: G16 - Particles for Filter Testing
Day: 24 October 2019
Time: 13:00 - 14:15 h

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