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Nous présentons une méthodologie expérimentale et numérique grâce à laquelle nous pouvons comparer les efficacités de filtration en prenant en compte une description précise de la force électrostatique entre une particule sphérique et une fibre., We present an experimental and numerical methodology through which we can compare the filtration efficiencies taking into account a precise description of the electrostatic force between a spherical particle and a fiber.

Dans les réseaux de ventilation, l'utilisation de pré-filtres métalliques est envisagée pour protéger les filtres THE d'un éventuel rejet d'aérosol liquide qui pourrait affecter les performances du système de filtration. Cette étude porte sur l'influence des caractéristiques du média (épaisseur, compacité et diamètre moyen des fibres métalliques) et de la vitesse de filtration sur l'évolution de la perte de charge de médias métalliques au cours de la filtration d'un aérosol liquide. Ce travail a mis en évidence que ces paramètres influent non seulement sur la perte de charge à saturation mais également sur la quantité de liquide accumulée dans le filtre., In ventilation systems, the use of metallic pre-filters is being considered to protect the HEPA filters from the possible release of liquid aerosol that could affect the performance of the filtration system. This study focuses on the influence of media characteristics (thickness, compactness and average diameter of the metal fibers) and filtration velocity on the evolution of the pressure drop of metallic media during the filtration of a liquid aerosol. This work has shown that these parameters influence not only the saturation pressure drop but also the amount of liquid accumulated in the filter.

Pour endiguer la récente pandémie de Covid-19, la France a pris des mesures pour mettre rapidement à la disposition de la population des masques de protection respiratoire efficaces. Les laboratoires en capacité de réaliser des mesures d'efficacité et de perméabilité de matériaux filtrants ont été sollicités pour mettre en ?uvre des bancs d'essais permettant de caractériser les media filtrants utilisés pour la confection des masques dits « barrière » ou « grand public » en termes d'efficacité de filtration et de perméabilité selon les spécifications établies par l'AFNOR (efficacité de filtration vis-à-vis d'aérosols de 3 µm supérieure à 70% et 90% pour deux catégories de masques, et perméabilité à 100 Pa supérieure à 96 L.m-2.s-1). Face à l'urgence, ces différents laboratoires ont mis en ?uvre des protocoles différents pour caractériser ces dispositifs. La présente communication vise à comparer les résultats obtenus par trois laboratoires impliqués dans ces essais en utilisant des protocoles différents. Les résultats montrent un bon accord entre les trois laboratoires impliqués dans l'intercomparaison avec des dispersions probablement imputables à l'hétérogénéité des échantillons., In the context of the Covid-19 pandemic, France has taken measures to quickly produce respiratory protection masks for the population. Laboratories able to carry out filtration media efficiency and permeability measurements were asked to implement test benches to characterize the filter media used for making these so-called ?community face covering? in terms of filtration efficiency and permeability according to the AFNOR specifications (3 µm filtration efficiency greater than or equal to 70% and 90% for two categories, and permeability at 100 Pa greater than 96 L.m-2.s-1). In this context of emergency, these laboratories implemented different protocols and this communication aims at comparing the results obtained by the three laboratories involved in these tests. The results show good agreement between laboratories participating in the intercomparison with a dispersion probably due to the sample heterogeneity.

Une campagne d'intercomparaison sur la mesure de la taille de nanoparticules a été organisée en 2018 dans le cadre du GT1- Santé et Environnement du club nanométrologie. L'objectif est de faire un état des lieux d'un point de vue métrologique des capacités de mesure de la taille de divers nano-objets en France, parmi lesquelles le SMPS (Scanning Mobility Particle Sizer) utilisé en métrologie des aérosols. Quatre échantillons ont été proposés, à savoir, une suspension colloïdale de SiO2 (European Reference Material ERM-FD304) constituée d'une population monomodale, deux échantillons constitués de deux populations de nanoparticules de SiO2 ayant des proportions à déterminer, et une suspension colloïdale de TiO2 alimentaire (E171). Cet article présente la description du banc expérimental, le protocole de préparation des échantillons ainsi que les résultats préliminaires de cette intercomparaison., An intercomparison campaign on nanoparticle size measurement was organized in 2018 as part of the nanometrology working group n°1 - Health and Environment-. The aim of this study is to make an inventory of the metrological capabilities of all measurement techniques in France involved in the ?nano? range, including the SMPS (Scanning Mobility Particle Sizer) concerning the aerosols metrology. Four samples have been proposed namely (1) - a SiO2 colloidal suspension (FD304) consisting of a monomodal population, (2) - two samples consisting of two nanoparticle populations of SiO2 having proportions to be determined and (3) - a TiO2 colloidal suspension. This article presents preliminary results of this intercomparison study associated with the description of the experimental set-up and the sample preparation protocol with an identified schedule.

Au cours du colmatage, la structure du dépôt formé au sein des filtres conditionne l'évolution de la perte de charge. Dans le présent travail, des simulations numériques de colmatage des filtres plissés THE par des particules poly-dispersées ont été réalisées en utilisant le code de calcul GeoDict. Dans le dépôt ainsi simulé on observe la formation de dendrites le long du pli ce qui engendre une obstruction prématurée de ce dernier et augmente donc la perte de charge du filtre. Une comparaison avec des résultats expérimentaux a été réalisée. Un modèle de perte de charge a été développé en prenant en compte la perte de surface de filtration déduite des simulations numériques réalisées., During clogging, the structure of the cake build-up on the filter surface determines the evolution of its pressure drop. In the present work, numerical simulation of HEPA filters clogging with poly-dispersed particles, have been carried out with GeoDict software at the pleat scale. In the simulated cake an apparition of dendrites all along the pleat cake has been observed inducing an important increase of pressure drop. A pressure drop model have been developed taking into account the loss of filtration surface derived from simulation. A comparison between the numerical results and an experimental data has been realized.

Le TEOM-FDMS (Tapered Element Oscillating Microbalance with Filter Dynamics Measurement Systems) est un instrument de mesure très répandu au sein du réseau national de surveillance de la qualité de l'air. à l'heure actuelle, cet appareil est étalonné à l'aide de masses étalons raccordées au SI mais dont les valeurs et les différences de masse ne sont pas représentatives des masses particulaires atmosphériques prélevées. De plus, l'utilisation de ces masses étalons ne permet pas de prendre en compte un éventuel dysfonctionnement du système de prélèvement en amont de la mesure de la masse et du système de filtration intrinsèque au TEOM-FDMS. Par conséquent, une nouvelle méthode d'étalonnage pour les TEOM-FDMS a été développée de par la mise en place d'un système portable de génération de particules ayant des concentrations massiques connues et stables dans le temps. Cet article présente la caractérisation de ce générateur portable en termes de gamme de masses de référence, son couplage à un TEOM-FDMS et la comparaison globale entre les masses particulaires de référence définies et les masses moyennes lues sur le TEOM-FDMS impliqué dans cette étude., The TEOM-FDMS (Tapered Element Oscillating Microbalance with Filter Dynamics Measurement Systems) is a common measuring instrument employed by the French air quality monitoring network. This instrument is currently calibrated with calibration weights traceable to SI but having values and masses differences between each of them which are not representative of real atmospheric particle mass measurements. Moreover, these calibration weights do not allow detecting any technical problem of the TEOM-FDMS sampling system upstream the mass measurement and of the intrinsic TEOM-FDMS filtration system. In this way, a calibration method was developed using a portable reference aerosol generator (PRAG) producing known and stable particle mass concentrations over time. In this paper, we present the characterization of the PRAG system in terms of reference range of particle masses, its coupling with TEOM-FDMS and the global comparison between the defined reference range of particle masses and the measured masses obtained with each TEOM-FDMS implicated in this study.

International audience; For industrial or domestic applications, the wide range of use of pleated filters makes the understanding of their airflow behavior a major issue for designer and users. In all industrial installations dealing with radioactive matter, the containment of pollutants must be ensured. High-efficiency particulate air (HEPA) filters are used as the last purification stage before the air is rejected in the environment. These filters can be used either alone, in the case of nonsensible installation, or coupled with other filtration devices disposer before it where contamination level could be important. The prediction of their pressure drop is very important in nuclear safety to be able to anticipate any dysfunction or rupture of these devices. It has been observed that geometry of the medium has an influence on the pressure drop of a pleated filter. In the case of HEPA filters, no convincing explanation has been brought to explain their airflow behavior. The pressure drop evolution of the filtre during the clogging remains difficult to explain by assuming constant pleat geometry. Some studies show that deformation occurs during the filter use, which could induce an increaseof the available volume in the pleat and a reduction of the efficient filtration surface. The increase in computation capacity introduces nowadays the possibility to perform complex simulation, taking into account the effect of fluids on sensible devices. This can be the case for simple structural analysis or for more complex analysis such as vibration induced by gas or fluid flow. It is mostly applied to avoid breaking or deformation of safety devices,and this can also be applied to anticipate the fluid behavior of some special devices such as filters. In classical filtration application, properties of the filter are coupled with particle deposition (e.g., changes in geometry and permeability depend on the thickness of the deposit). The studies concerning mechanical properties of filters are mainly perfore for liquid filtration and clean filters. For pleated filters, the complexity of this kind of analysisremains the modification of the link between geometry, pressure drop, mechanical strength, and particle transport and accumulation inside the pleat. As a first approach, it has been chosen to combine an experimental and a numerical approach to improve the understanding of filter behavior. In this paper, the pleat deformation will be investigated using a direct nonintrusive laser measurement performed on a single pleat experiment.The rate of filtration surface lost will be estimated using these data and taken into account to evaluate the pressure drop against the filtration velocity. Results obtained show that the pleat deformation is an important parameter, which influences the geometry of the pleat.

The harmlessness of nanometric aerosols is currently being called into question. Their massive production in industrial production processes or during combustion, whether deliberate or incidental, requires that they be contained. Today, the most widely-used means and that providing the best cost-benefit ratio is the use of porous, mainly fibrous material, in air filter design. The efficiency of these filtration devices has been the subject of numerous studies and does not require further demonstration, but the prediction of their lifetime, conditioned by the pressure drop which evolves during clogging, still needs to be managed. Predicting pressure drop in the case of very thin, and therefore very clogging, particles remains a major issue in the design of filtration devices. Two phases have been highlighted on a plane fibrous medium: deep filtration and surface filtration preceded by a transition regime where particles are collected both in the depth and on the surface of the medium. Each of these phases is characterized by a different pressure drop evolution. This study focuses on measuring the porosity of the deposits, an important parameter which conditions the resistance of a clogged filter. For this, pseudo-spherical alumina particles and aggregates of 10 nm carbon nanoparticles with respectively 350 nm and 73 nm of electrical mobility diameter were used. A device enabling the continuous measurement of the thickness of the deposit during the clogging process was developed. Results are shown for filtration velocities of 0.8 and 0.16 cm s− 1. The change in pressure drop of a fibrous medium is then studied for deep filtration, when aerosols penetrate the medium at the beginning of the filtration process. On this basis, a simplified model was developed to predict the pressure drop increase of a filter exposed to ultrafine aerosols.