Piotr Grzybowski

Analysis of motion and deposition of fibrous particles on a single filter element

Abstract The definition of deposition efficiency of aerosol particles on a single element of a fibrous filter is extended to include oblong particles. The deposition efficiency is calculated separately for the effect of direct interpretation, inertia and sedimentation. For selected slenderness ratio the results are compared with the literature data for spherical particles.

Deposition of flexible and stiff fibrous particles

Abstract The object of this paper is an analysis of motion and deposition of fibrous particles. A particle moves with the air flowing around the fiber which makes the filter element. Two limiting cases are studied: for flexible particle with low value of elasticity and for stiff, neutral and electrically charged, particle. The efficiency of particle deposition is estimated.

Analysis of motion and deposition of fibrous aerosol particles flowing around a single filter element: the electrostatic effect

Abstract Equations of motion of an oblong aerosol particle in the neighbourhood of a cylinder placed crosswise to the main direction of carrier-gas flow are presented. The forces of interaction between particles and fluid as well as forces of gravitational and electrostatic interaction between collector cylinder and particle are considered. The efficiency coefficients of particle deposition due to the effects of inertial impaction, interception, sedimentation and Coulombic interaction are defined and determined. The effects of the magnitude and the distribution of electrostatic charge on a particle and of the slenderness ratio of a particle on deposition efficiency are investigated.

Theoretical study on deposition of flexible and stiff fibrous aerosol particles on a cylindrical collector

Abstract The aim of this paper is to analyze theoretically the deposition of fibrous aerosol particles from a gas stream on the cylindrical collectors in fibrous filters. Two limiting (from the point of view of mechanics) cases of a perfectly flexible and of a completely stiff elongated particle are discussed. The governing equations for these models are given. The results of numerical simulations are presented and the influence of the following parameters on the deposition efficieny is discussed: for a flexible particle its size and aspect ratio (slenderness), the gas velocity and the fiber initial orientation, and for the case of a rigid body the particle slenderness and the electric charge on it. For stiff elongated particles the electrostatic effects were taken into account. The observation was made that the fibrous particles tend to follow fluid streamlines, which is achieved by the shape deformation for the flexible fibers, or by rotation for the rigid fibers. The results of computations for the elongated particles were compared with data for spherical particles of same volume. It has been calculated that in the absence of electrostatic interactions the lowest deposition efficiencies are reached by flexible fibers, significantly higher efficiencies correspond to the spherical particles and usually even higher efficiencies are reached by the stiff fibers. It was also shown that the concept of equivalent aerodynamic diameter for fibrous particles is unimportant and invalid. Behavior of the fibrous particles is still not very well understood and, because of the known influence of such aerosols on human health, further studies are necessary.

Efficiency of Filtering Materials Used in Respiratory Protective Devices Against Nanoparticles

The basic aim of this research was to establish the efficiency of filtering materials widely used in respiratory protection devices with particular interest in their porosity, degree of electric and changeable process parameters, such as the flow rate of the test nanoaerosol and the size range of nanoparticles. Tests were carried out with an NaCl solid aerosol of 3.2 × 105 particles/cm3 for the range of particle size of 7–270 nm, at aerosol flow rate of 1800, 2700, 3600, 4500 and 5400 L/h. The tests showed that electrospun nonwovens were the most effective filtering materials for nanoparticles over 20 nm. Melt-blown electret nonwovens with lower porosity than electrospun nonwovens had higher values of penetration of 1%–4%. Those materials provided very efficient protection against nanoparticles of certain sizes only.

Deposition efficiency of nonspherical particles

Abstract Equations of motion of an oblong - stiff and flexible - aerosol particle in the vicinity of a cylinder placed crosswise to the main direction of carrier-gas flow are presented. The efficiency coefficients of particle deposition due to the effect of inertial impaction, interception, sedimentation and Coulombic interaction are defined and determined. The effect of magnitude and distribution of electrostatic charge on a particle, of slenderness ratio and of stiffness of particle on deposition efficiency is investigated.

Modelling the Viability of Microorganisms of Poly(lactic Acid) Melt-Blown Nonwoven Fabrics for the Use of Respiratory Protection

A variety of harmful microorganisms deposited in the work environment is the reason why it is becoming more and more common to use filtering respiratory protection equipment. To fulfil its protective role against biological hazards, it should not only ensure high efficiency of filtration but also present biocidal properties. Due to the fact that in laboratory studies confirming the biocidal properties of equipment it is possible to use only a limited number of testing organisms, using microbiological prognosis models seems a promising direction. The article presents a method for assessing the performance of filter materials with biocidal properties using a simple model describing the dependence of the viability of Gram - positive and Gram - negative bacteria in the biocidal structure of the material. A comparison of the results of theoretical predictions and experimental results confirmed that the model can be used as a tool for the approximate evaluation of the properties of these materials. Poly(lactic acid) (PLA) was used when validating the model melt-blown nonwovens for the construction of respiratory protection devices (RPD) against biological hazards.

Loading of mechanical fibrous filters with solid polidysperse aerosols: Mathematical model and experimental verification

The aim of this study was to verify experimentally the appropriateness of a model in the case of a continuous loading of a fibrous filter with solid, polydisperse aerosol particles. For this purpose, three samples of a commercial, polyester fibrous filter composed of the fibres with diameter in the range 10-80 μm were exposed to the air containing a polydisperse silica dust. The aerosol had a wide size distribution (0.1-10 μm).