scholarly journals Influence of the aerosol flow and exposure time on the structural changes in the filtering half masks material

2018 ◽  
Vol 83 (4) ◽  
pp. 463-471 ◽  
Author(s):  
Negovan Ivankovic ◽  
Dusan Rajic ◽  
Radovan Karkalic ◽  
Dusan Jankovic ◽  
Zeljko Radovanovic ◽  
...  
Keyword(s):  
Structural Changes ◽  
Aerosol Particles ◽  
Direct Consequence ◽  
Filtration Process ◽  
Flow Rates ◽  
Process Duration ◽  
Aerosol Flow ◽  
Flow Change ◽  
Aerosol Filtration ◽  
Theory Of Filtration

The flow of air and aerosol particles through the filtering half masks material depends on the structure porosity. It is very difficult to determine the behaviour of the filtering material during the process of extraction and retention of aerosols. The samples of five filtering half mask models were used in this investigation. Dynamics of the aerosol filtration through the filtering materials was tested using a method for testing the leakage of aerosol particles through the filtering material and a method for testing the inhalation resistance of filtering material, both specified in the SRPS EN 149:2013. Recording of the structural changes in the samples of the tested materials was carried out by the technique of scanning electron microscopy. The experiments showed a deviation of the results in relation to the theory of filtration the finely dispersed submicron sized particles. It was concluded that the aerosol leakage through the filtering half masks and their resistance to aerosol flow change depend on the aerosol flow rates and the on filtration process duration, as a direct consequence of the newly-made changes in the structure of the filtering material and due to reversibility effect between the filtration process and the changes in the filtering material.

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

2017 ◽  
Vol 38 (1) ◽  
pp. 31-50
Author(s):  
Rafał Przekop
Keyword(s):  
Fluid Dynamics ◽  
Classical Theory ◽  
Aerosol Particles ◽  
Single Fibre ◽  
Fibrous Filters ◽  
Aerosol Filtration ◽  
Depth Filtration ◽  
Perfect Mixing ◽  
Theory Of Filtration

AbstractAerosol 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.

Filtration Model of Aerosol Particles by Fibrous Filters

2004 ◽  
Author(s):  
Wen Zhong ◽  
Ning Pan
Keyword(s):  
Aerosol Particles ◽  
Filtration Process ◽  
Fiber Cells ◽  
Fibrous Filters ◽  
Aerosol Filtration ◽  
Numerous Cell ◽  
System Energy ◽  
Simulation Results ◽  
The Difference ◽  
Filtration Model

Aerosol filtration by fibrous filters is one of the most common methods of separating and removing particles in micro and sub-micro size ranges. The statistical genesis of this process can be regarded as the interactions and the resulting equilibrium among particle and fiber cells that comprise the system. Therefore a statistical mechanics approach, the Ising’s model, combined with Monte Carlo simulation, is employed in studying the process of the aerosol filtration through fibrous filters. The process is modeled as consisting of numerous cell state exchanges driven by the difference of system energy after and before a particle moves from one cell to the other and/or deposits on a fiber cell. With the use of a simpler binary algorithm, this approach is capable of realistically simulating the complicated mechanisms involved in the filtration process. For verification, simulations are carried out for the behaviors of aerosol particles of different sizes through isotropic fiber filters with various volume fractions. Simulation results are in good agreements with reported experimental data.

Aerosol Flow Through a Micro-Capillary

2009 ◽  
Author(s):  
Iskander S. Akhatov ◽  
Justin M. Hoey ◽  
Drew Thompson ◽  
Artur Lutfurakhmanov ◽  
Zakaria Mahmud ◽  
...  
Keyword(s):  
Flexible Electronics ◽  
Aerosol Particles ◽  
Particle Interaction ◽  
Direct Write ◽  
Center Line ◽  
Aerosol Flow ◽  
Aerodynamic Focusing ◽  
Ink Jet ◽  
Micron Size ◽  
Flow Through

A combined theoretical/experimental study of micron size aerosol flows through micro-capillaries of diameter about 100 μm and length about 1 cm is presented. It is shown that under proper conditions at a relatively high velocity of about 100 m/s such an aerosol flow reveals a new manifestation of microfluidics: the Saffman force acting on aerosol particles in gas flowing through a micro-capillary becomes significant thereby causing noticeable migration of particles toward the center line of the capillary. This finding opens up new opportunities for aerosol focusing, which is in stark contrast to the classical aerodynamic focusing methodologies where only particle inertia and the Stokes force of gas-particle interaction are typically used to control particle trajectories. A mathematical model for aerosol flow through a micro-capillary accounting for complicated interactions between particles and carrier gas is presented. This model describes the experimental observables obtained via shadowgraphy for aerosol beams exiting micro-capillaries. It is further shown that it is possible to design a micro-capillary system capable of generating a Collimated Aerosol Beam (CAB) in which aerosol particles stay very close to a capillary center line. The performance of such a CAB system for direct-write fabrication on a substrate is demonstrated. The lines deposited by CAB for direct-write fabrication are shown to exhibit widths of less than 5 μm — superior to ink-jet. Materials deposition based upon directed aerosol flow has the potential of finding application in the fields of flexible electronics, sensors, and solar cells. In this paper, the genesis of a new materials deposition method termed Collimated Aerosol Beam Direct-Write (CAB-DW) is discussed.

scholarly journals Characterization and intercomparison of aerosol absorption photometers: result of two intercomparison workshops

2011 ◽  
Vol 4 (2) ◽  
pp. 245-268 ◽  
Author(s):  
T. Müller ◽  
J. S. Henzing ◽  
G. de Leeuw ◽  
A. Wiedensohler ◽  
A. Alastuey ◽  
...  
Keyword(s):  
Aerosol Particles ◽  
Spot Size ◽  
High Variability ◽  
Flow Rates ◽  
Aerosol Absorption ◽  
Large Sets ◽  
Different Types ◽  
Total Particle ◽  
Noise Measurements ◽  
Real Time Application

Abstract. Absorption photometers for real time application have been available since the 1980s, but the use of filter-based instruments to derive information on aerosol properties (absorption coefficient and black carbon, BC) is still a matter of debate. Several workshops have been conducted to investigate the performance of individual instruments over the intervening years. Two workshops with large sets of aerosol absorption photometers were conducted in 2005 and 2007. The data from these instruments were corrected using existing methods before further analysis. The inter-comparison shows a large variation between the responses to absorbing aerosol particles for different types of instruments. The unit to unit variability between instruments can be up to 30% for Particle Soot Absorption Photometers (PSAPs) and Aethalometers. Multi Angle Absorption Photometers (MAAPs) showed a variability of less than 5%. Reasons for the high variability were identified to be variations in sample flow and spot size. It was observed that different flow rates influence system performance with respect to response to absorption and instrumental noise. Measurements with non absorbing particles showed that the current corrections of a cross sensitivity to particle scattering are not sufficient. Remaining cross sensitivities were found to be a function of the total particle load on the filter. The large variation between the response to absorbing aerosol particles for different types of instruments indicates that current correction functions for absorption photometers are not adequate.

High-Speed Aerosol Flow Through Micro-Nozzles for Direct-Write Processes

2013 ◽  
Author(s):  
Justin M. Hoey ◽  
Sourin Bhattacharya ◽  
Artur Lutfurakhmanov ◽  
Michael Robinson ◽  
Orven F. Swenson ◽  
...  
Keyword(s):  
High Speed ◽  
Aerosol Particles ◽  
Particle Interaction ◽  
Direct Write ◽  
Particle Rotation ◽  
High Speed Flow ◽  
Magnus Force ◽  
Aerosol Flow ◽  
Speed Flow ◽  
Flow Through

Aerosol direct-write printing for mesoscale features has been commercially available since around 2002 from Optomec®. We have developed variances to this process first in Collimated Aerosol Beam-Direct Write (CAB-DW) for printing sub-10 μm features and in Micro Cold Spray for printing with solid metallic aerosols. These deposition tools offer extensive uses, but are still limited in certain applications by either line widths or the amount of overspray. Modeling of aerosol flow through micro-nozzles used in these applications yields a greater understanding of the focusing of these aerosol particles, and may provide a vehicle for new nozzle designs which will further enhance these tools. Recent modeling applied both Stokes and Saffman force to the aerosol particles. Under certain conditions particle rotation and Magnus force may also be necessary to accurately predict the aerosol particles. In this paper we will present our recent results of high-speed flow of 1–10 μm diameter aerosol particles through micro-nozzles in which the model includes all three forces (Stokes, Saffman, Magnus) of fluid-particle interaction, and a comparison of these results to experiments.

scholarly journals Predicting the Aqueductal Cerebrospinal Fluid Pulse: A Statistical Approach

2019 ◽  
Vol 9 (10) ◽  
pp. 2131
Author(s):  
Clive B Beggs ◽  
Simon J Shepherd ◽  
Pietro Cecconi ◽  
Maria Marcella Lagana
Keyword(s):  
Cerebrospinal Fluid ◽  
Flow Rate ◽  
Structural Changes ◽  
Statistical Approach ◽  
Healthy Individuals ◽  
Anova Analysis ◽  
Venous Flow ◽  
Flow Rates ◽  
Relative Contribution ◽  
The Brain

The cerebrospinal fluid (CSF) pulse in the Aqueduct of Sylvius (aCSF pulse) is often used to evaluate structural changes in the brain. Here we present a novel application of the general linear model (GLM) to predict the motion of the aCSF pulse. MR venography was performed on 13 healthy adults (9 female and 4 males—mean age = 33.2 years). Flow data was acquired from the arterial, venous and CSF vessels in the neck (C2/C3 level) and from the AoS. Regression analysis was undertaken to predict the motion of the aCSF pulse using the cervical flow rates as predictor variables. The relative contribution of these variables to predicting aCSF flow rate was assessed using a relative weights method, coupled with an ANOVA. Analysis revealed that the aCSF pulse could be accurately predicted (mean (SD) adjusted r2 = 0.794 (0.184)) using the GLM (p < 0.01). Venous flow rate in the neck was the strongest predictor of aCSF pulse (p = 0.001). In healthy individuals, the motion of the aCSF pulse can be predicted using the GLM. This indicates that the intracranial fluidic system has broadly linear characteristics. Venous flow in the neck is the strongest predictor of the aCSF pulse.

scholarly journals Antimicrobial Nanofiber Based Filters for High Filtration Efficiency Respirators

Nanomaterials ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 900
Author(s):  
Maria Pardo-Figuerez ◽  
Alberto Chiva-Flor ◽  
Kelly Figueroa-Lopez ◽  
Cristina Prieto ◽  
Jose M. Lagaron
Keyword(s):  
Zinc Oxide ◽  
Zno Nanoparticles ◽  
Electrospun Nanofibers ◽  
Filtration Efficiency ◽  
Electrospun Fibers ◽  
Flow Rates ◽  
Breathing Resistance ◽  
Symmetric Structure ◽  
Aerosol Filtration ◽  
Potential Use

Electrospinning has been used to develop and upscale polyacrylonitrile (PAN) nanofibers as effective aerosol filtration materials for their potential use in respirators. The fibers were deposited onto non-woven spunbond polypropylene (SPP) and the basis weight (grammage, g/m2) was varied to assess the resulting effect on filtration efficiency and breathing resistance of the materials. The results indicated that a basis weight in excess of 0.4 g/m2 of PAN electrospun fibers yielded a filtration efficiency over 97%, with breathing resistance values that increased proportionally with the amount of basis weight added. With the aim of retaining filter efficiency whilst lowering breathing resistance, the basis weight of 0.4 g/m2 and 0.8 g/m2 of PAN electrospun fibers were strategically split up and stacked with SPP in different configurations. The results suggested that a symmetric structure based on SPP/PAN/PAN/SPP was the optimal structure, as it reduces SPP consumption while maintaining an FFP2-type of filtration efficiency, while reducing breathing resistance, specially at high air flow rates, such as those mimicking FFP2 exhalation conditions. The incorporation of zinc oxide (ZnO) nanoparticles within the electrospun nanofibers in the form of nanocomposites, retained the high filtration characteristics of the unfilled filter, while exhibiting a strong bactericidal capacity, even after short contact times. This study demonstrates the potential of using the symmetric splitting of the PAN nanofibers layer as a somewhat more efficient configuration in the design of filters for respirators.

scholarly journals Do increased flow rates in displacement ventilation always lead to better results?

2021 ◽  
Vol 932 ◽  
Author(s):  
Rui Yang ◽  
Chong Shen Ng ◽  
Kai Leong Chong ◽  
Roberto Verzicco ◽  
Detlef Lohse
Keyword(s):  
Thermal Stratification ◽  
Direct Consequence ◽  
Living Environment ◽  
Displacement Ventilation ◽  
Flow Rates ◽  
Air Contamination ◽  
Wide Range ◽  
Ventilation Rates ◽  
Respiratory Droplets ◽  
Ventilation Scheme

Indoor ventilation is essential for a healthy and comfortable living environment. A key issue is to discharge anthropogenic air contamination such as CO $_2$ gas or, of potentially more direct consequence, airborne respiratory droplets. Here, by employing direct numerical simulations, we study mechanical displacement ventilation with a wide range of ventilation rates $Q$ from 0.01 to 0.1 m $^3$ s $^{-1}$ person $^{-1}$ . For this ventilation scheme, a cool lower zone is established beneath a warm upper zone with interface height $h$ , which depends on $Q$ . For weak ventilation, we find the scaling relation $h\sim Q^{3/5}$ , as suggested by Hunt & Linden (Build. Environ., vol. 34, 1999, pp. 707–720). Also, the CO $_{2}$ concentration decreases with $Q$ within this regime. However, for too strong ventilation, the interface height $h$ becomes insensitive to $Q$ , and the ambient averaged CO $_2$ concentration decreases towards the ambient value. At these values of $Q$ , the concentrations of pollutants are very low and so further dilution has little effect. We suggest that such scenarios arise when the vertical kinetic energy associated with the ventilation flow is significant compared with the potential energy of the thermal stratification.

Sign in / Sign up

Export Citation Format

Share Document