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Étude des mécanismes de formation des dépôts de particules appliquée à la filtration THE

Abstract : The filtration of air by fibrous media with high efficiency particulate air (HEPA) is a key point for the safety of sensitive installations. However, filters have a major drawback linked to the increase in their aeraulic resistance during their clogging, which can lead to unbalance the ventilation networks, or even in extreme cases to the rupture of filters and therefore to a loss of containment. In case of fire the filters may be subjected to a large supply of particles or to very clogging particles, causing a rapid increase in their pressure drop. In current pressure drop models used for risk assessment, porosity is a key parameter. Many authors, via simulations, have proposed porosity values for deposits of nanoparticles formed by filtration and have shown, for a given aerosol, a dependence of the porosity as a function of the Peclet number (ratio of the transport mechanisms by convection and diffusion. A specific experimental methodology has been developed in order to study the influence of the porosity of the deposits of the size and morphology of the particles, the physico-chemical characteristics of the particles and the carrier gas (nature, density, viscosity) and operating conditions (filtration rate, pressure). For this study, an experimental bench and a laser measurement device have been developed. This device measures the change in the thickness of the deposit coupled with its deposited mass over time in order to determine the porosity of the deposit. Studies on the deposits of spherical nanoparticles and formed by aggregates have made it possible to define the Stokes number (ratio between the kinetic energy of the particle and the energy dissipated by friction with the fluid) as the most relevant parameter to account for the evolution of the porosity of the deposit. This study led to various correlations allowing the estimation of the porosity of a deposit of pseudo-spherical nanoparticles or nanostructured particles.
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Submitted on : Wednesday, September 8, 2021 - 4:03:13 PM
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Jonathan Nuvoli. Étude des mécanismes de formation des dépôts de particules appliquée à la filtration THE. Génie des procédés. Université de Lorraine, 2021. Français. ⟨NNT : 2021LORR0049⟩. ⟨tel-03338422⟩

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