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1

Estimation of Filtration Efficiency – from Simple Correlations to Digital Fluid Dynamics

Przekop R.

Chemical and Process Engineering

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2017

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Vol. 38, nr 1

31--50

EN

Aerosol filtration in fibrous filters is one of the principal methods of accurate removal of particulate matter from a stream of gas. The classical theory of depth filtration of aerosol particles in fibrous structures is based on the assumption of existing single fibre efficiency, which may be used to recalculate the overall efficiency of entire filter. Using “classical theory” of filtration one may introduce some errors, leading finally to a discrepancy between theory and experiment. There are several reasons for inappropriate estimation of the single fibre efficiency: i) neglecting of shortrange interactions, ii) separation of inertial and Brownian effects, ii) perfect adhesion of particles to the fibre, iv) assumption of perfect mixing of aerosol particles in the gas stream, v) assumption of negligible effect of the presence of neighbouring fibres and vi) assumption of perpendicular orientation of homogenous fibres in the filtration structure. Generally speaking, “classical theory” of filtration was used for characterization of the steady - state filtration process (filtration in a clean filter, at the beginning of the process) without deeper investigation of the influence of the nternal structure of the filter on its performance. The aim of this review is to outline and discuss the progress of deep-bed filtration modelling from the use of simple empirical correlations to advanced techniques of Computational Fluid Dynamics and Digital Fluid Dynamics.

2

Dynamics of particle loading in deep-bed filter. Trasport, deposition and reentrainment

Przekop R., Gradoń L.

Chemical and Process Engineering

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2016

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Vol. 37, nr 3

405--417

EN

Deep bed filtration is an effective method of submicron and micron particle removal from the fluid stream. There is an extensive body of literature regarding particle deposition in filters, often using the classical continuum approach. However, the approach is not convenient for studying the influence of particle deposition on filter performance (filtration efficiency, pressure drop) when non-steady state boundary conditions have to be introduced. For the purposes of this work the lattice-Boltzmann model describes fluid dynamics, while the solid particle motion is modeled by the Brownian dynamics. For aggregates the effect of their structure on displacement is taken into account. The possibility of particles rebound from the surface of collector or reentrainment of deposits to fluid stream is calculated by energy balanced oscillatory model derived from adhesion theory. The results show the evolution of filtration efficiency and pressure drop of filters with different internal structure described by the size of pores. The size of resuspended aggregates and volume distribution of deposits in filter were also analyzed. The model enables prediction of dynamic filter behavior. It can be a very useful tool for designing filter structures which optimize maximum lifetime with the acceptable values of filtration efficiency and pressure drop.

3

Ion Move Brownian Dynamics (IMBD) : Simulations of Ion Transport

Kurczyńska M., Kotulska M.

Acta of Bioengineering and Biomechanics

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2014

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Vol. 16, no. 4

107--115

EN

Purpose: Comparison of the computed characteristics and physiological measurement of ion transport through transmembrane proteins could be a useful method to assess the quality of protein structures. Simulations of ion transport should be detailed but also time-efficient. Methods: The most accurate method could be Molecular Dynamics (MD), which is very time-consuming, hence is not used for this purpose. The model which includes ion-ion interactions and reduces the simulation time by excluding water, protein and lipid molecules is Brownian Dynamics (BD). In this paper a new computer program for BD simulation of the ion transport is presented. We evaluate two methods for calculating the pore accessibility (round and irregular shape) and two representations of ion sizes (van der Waals diameter and one voxel). Results: Ion Move Brownian Dynamics (IMBD) was tested with two nanopores: alpha-hemolysin and potassium channel KcsA. In both cases during the simulation an ion passed through the pore in less than 32 ns. Although two types of ions were in solution (potassium and chloride), only ions which agreed with the selectivity properties of the channels passed through the pores. Conclusions: IMBD is a new tool for the ion transport modelling, which can be used in the simulations of wide and narrow pores.

4

Brownian dynamics for calculation of the single fiber deposition efficiency of submicron particles

Sztuk E., Przekop R., Gradoń L.

Chemical and Process Engineering

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2012

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Vol. 33, nr 2

279-290

EN

The motion of submicron particles involves the deterministic terms resulting from the aerodynamic convection and/or electrostatic attraction, and the stochastic term from the thermal displacement of particles. The Langevin equation describes such behavior. The Brownian dynamics algorithm was used for integration of the Langevin equation for the calculation of the single fiber deposition efficiency. Additionally the deterministic and stochastic of the particle motion were derived, using the Lagrangian and Eulerian approaches of particle movement and balance, for the calculation of the single fiber deposition efficiency due to both mechanisms separately. Combination of the obtained results allows us for calculation of the coupling effect of inertia and interception with the Brownian diffusion in a form of correlation. The results of calculation show that the omitting of the coupling effect of particular mechanism and using the simple additive rule for determination of the single fiber deposition efficiency introduces significant error, especially for particles with diameter below 300 nm.

5

Dynamika agregatów aerozolowych

Moskal A.

Inżynieria i Aparatura Chemiczna

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2006

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Nr 6s

165-166

EN

A new model of translational and rotational motion of rigid aggregates of nanoparticles suspended in air has been developed taking into account the stochastic Brownian forces as well as the gravity and hydrodynamic drag. The model was used to simulate the dynamic motion of aggregates of various internal shapes, in order to extract the corresponding diffusion coefficient values.

6

Depozycja nanostrukturalnych agregatów aerozolowych w górnych drogach oddechowych człowieka

Moskal A., Makowski Ł.

Inżynieria i Aparatura Chemiczna

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2006

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Nr 6s

166-167

EN

The deposition of aerosol fractal-like aggregates in a numerical model of the human nose was studied theoretically under steady-state breathing conditions. The object geometry was reconstructed using anatomical data and implemented numerically into the CFD code (FLUENT) that was used to calculate the three-dimensional airflow structure in the model. The Brownian dynamics algorithm was used to calculate the dynamic distribution of aggregates deposition.

7

Zastosowanie metody dynamiki brownowskiej do wyznaczania sprawności depozycji aglomeratów fraktalopodobnych w filtrach włókninowych

Bałazy A., Podgórski A.

Inżynieria i Aparatura Chemiczna

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2005

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Nr 4

6--8

PL

Wykorzystując zmodyfikowaną metodę dynamiki brownowskiej określono sprawność depozycji aglomeratów fraktalopodobnych na pojedynczym włóknie dla różnych parametrów charakteryzujących aglomerat oraz rozmaitych warunków prowadzenia procesu. Wyniki symulacji wskazują na to, iż sprawność depozycji aglomeratów fraktalopodobnych znacząco różni się od sprawności depozycji cząstki kulistej o równoważnej masie.

EN

The deposition efficiency of fractal-like aggregates onto a single fiber was determined for different aggregates' parameters and different process conditions utilizing a modified Brownian dynamics method. The results of simulations indicate that the deposition efficiency of fractal-like aggregates is considerably different from the deposition efficiency of a mass-equivalent spherical particle.