Particle Deposition Efficiency Research Articles

Исследование усовершенствованного типа тонкослойного модуля

The article deals with the problems of thin-layered (lamella) module`s clogging in the sedimentation tanks at sewage treatment plants and possible ways to solve them. The purpose of this work is to improve the structure of the lamella module using mathematical modeling in ANSYS FLUENT to analyze the effectiveness of its performance. A horizontal sedimentation tank with a lamella module with flat plates is chosen as research object. The paper presents a comparison analysis of simulation results of particle deposition process in a lamella module with flat plates and in a module with an improved structure. Finite element analysis in ANSYS FLUENT shows that the improved lamella module type has higher particle deposition efficiency than the ordinary type.

Numerical study on targeted delivery of magnetic drug particles in realistic human lung

Inhalation of medical drug particles through human airway is widely utilized for the remedy of lung diseases. Due to the complexities of airway morphology, flow turbulence and particle deposition, the drug delivery efficiency to the morbid region of lung is always unsatisfactory. In this research, a 3D anatomically accurate human airway model from oral cavity to lung is reconstructed, and the large eddy simulation-discrete phase model (LES-DPM) is adopted to simulate the airway flow and drug particles transport. To improve the particle delivery to the targeted region of the left lung, a magnetic drug targeting (MDT) system is established. It is found that the LES-DPM in conjunction with MDT system is an effective tool to study airway flow patterns and magnetic particle deposition features. Moreover, the magnetic source layout, magnetic particle size and magnetic field intensity all have significant impacts on the particle deposition efficiency in the left lung. Optimal combination factors for drug particle delivery results are successfully achieved. The total deposition efficiency of magnetic particles in the left lung can be increased to more than 5 times. This work not only could provide a better understanding of air-particle dynamics, but also could contribute toward improved strategies for more efficient drug delivery in the realistic human lungs.

Aerosol Particle Transport and Deposition in Upper and Lower Airways of Infant, Child and Adult Human Lungs

Understanding transportation and deposition (TD) of aerosol particles in the human respiratory system can help clinical treatment of lung diseases using medicines. The lung airway diameters and the breathing capacity of human lungs normally increase with age until the age of 30. Many studies have analyzed the particle TD in the human lung airways. However, the knowledge of the nanoparticle TD in airways of infants and children with varying inhalation flow rates is still limited in the literature. This study investigates nanoparticle (5 nm ≤ dp ≤ 500 nm) TD in the lungs of infants, children, and adults. The inhalation air flow rates corresponding to three ages are considered as Qin=3.22 L/min (infant), 8.09 L/min (Child), and Qin=14 L/min (adult). It is found that less particles are deposited in upper lung airways (G0–G3) than in lower airways (G12–G15) in the lungs of all the three age groups. The results suggest that the particle deposition efficiency in lung airways increases with the decrease of particle size due to the Brownian diffusion mechanism. About 3% of 500 nm particles are deposited in airways G12–G15 for the three age groups. As the particle size is decreased to 5 nm, the deposition rate in G12–G15 is increased to over 95%. The present findings can help medical therapy by individually simulating the distribution of drug-aerosol for the patient-specific lung.

Numerical study on the impact of mucus layer and inlet air-temperatures on the particle deposition in a highly idealized mouth-throat model using LES

Presence of mucus layer and inlet air temperature variations can significantly affect the extent of particle transport and deposition in the mouth-throat airway for aerosol drug delivery applications. In addition, higher inlet air temperature can lead to thermal injuries as well. The main goal of the present paper is to investigate these effects in a highly idealized mouth-throat geometry in detail. Large eddy simulation was performed to accurately predict the air flow-fields and a Lagrangian particle tracking model has been employed to capture the particle deposition efficiencies and patterns. The effects of three different inlet air temperatures (15 °C, 26.7 °C and 45 °C) and three different particle sizes (3 μm, 5 μm and 6 μm) have been studied for inlet flow rates of 15 L/min and 30 L/min with and without mucus layer in the present investigation. Detailed velocity and temperature fields, as well as, particle deposition efficiencies and patterns were analyzed and it has been found out that (a) the particle deposition efficiencies varied significantly with changes in inlet air temperature and flow rates, particle diameters and in the presence of mucus layer, (b) the presence of recirculation zones and secondary vortices determined the rate of particle deposition at different inhalation flow rates and inlet air temperatures, and (c) the changes in temperature distribution near the mouth-throat wall in the presence of mucus layer have a dominant effect on particle deposition as compared to inertial deposition. The findings of the present work will provide useful information in understanding the heat transfer effects on particle transport and deposition for the design of pulmonary drug delivery devices under the influence of various environmental and human factors.

Effect of swirling flow and particle-release pattern on drug delivery to human tracheobronchial airways

The present study aims to investigate the effect of swirling flow on particle deposition in a realistic human airway. A computational fluid dynamic (CFD) model was utilized for the simulation of oral inhalation and particle transport patterns, considering the k-ω turbulence model. Lagrangian particle tracking was used to track the particles' trajectories. A normal breathing condition (30 L/min) was applied, and two-micron particles were injected into the mouth, considering swirling flow to the oral inhalation airflow. Different cases were considered for releasing the particles, which evaluated the impacts of various parameters on the deposition efficiency (DE), including the swirl intensity, injection location and pattern of the particle. The work's novelty is applying several injection locations and diameters simultaneously. The results show that the swirling flow enhances the particle deposition efficiency (20-40%) versus no-swirl flow, especially in the mouth. However, releasing particles inside the mouth, or injecting them randomly with a smaller injection diameter (dinj) reduced DE in swirling flow condition, about 50 to 80%. Injecting particles inside the mouth can decrease DE by about 20%, and releasing particles with smaller dinj leads to 50% less DE in swirling flow. In conclusion, it is indicated that the airflow condition is an important parameter for a reliable drug delivery, and it is more beneficial to keep the inflow uniform and avoid swirling flow.

A CFD study of particle deposition in three-dimensional heat exchange channel based on an improved deposition model

Airborne particle deposition in the heat exchange channel will cause serious heat transfer efficiency reduction. Better understanding of deposition characteristics is of significance for energy and thermal engineering application. In this study, particle deposition in three-dimensional heat exchange channel with surface ribs was conducted by Reynolds stress model and discrete phase model. An improved deposition model based on turbulent fluctuation correction and particle rebound was developed by user-defined function (UDF). After grid independence study and numerical verification, the flow structures, the secondary flow in the channel corners, particle deposition patterns and deposition efficiency on each wall were investigated and analyzed. The influences of several important parameters, such as particle diameter, the ratio of rib spacing to rib height p/e, and air flow velocity on the turbulent flow and deposition characteristics were investigated. The results showed that turbulent flow structures induced by the ribs, the secondary flow, the interception of rib windward surface, particle rebound and gravitational settling are the main mechanisms for particle deposition in ribbed channel. The main deposition locations are the windward surface of ribs and the cavity walls in front of the ribs, due to the interception of the ribs, particle rebound and flow eddies in the cavities. Moreover, the deposition efficiency of each wall is significantly affected by the influencing parameters.

Numerical Simulation of the Aerosol Particle Motion in Granular Filters with Solid and Porous Granules

In this work, a study was carried out to compare the filtering and hydrodynamic properties of granular filters with solid spherical granules and spherical granules with modifications in the form of micropores. We used the discrete element method (DEM) to construct the geometry of the filters. Models of granular filters with spherical granules with diameters of 3, 4, and 5 mm, and with porosity values of 0.439, 0.466, and 0.477, respectively, were created. The results of the numerical simulation are in good agreement with the experimental data of other authors. We created models of granular filters containing micropores with different porosity values (0.158–0.366) in order to study the micropores’ effect on the aerosol motion. The study showed that micropores contribute to a decrease in hydrodynamic resistance and an increase in particle deposition efficiency. There is also a maximum limiting value of the granule microporosity for a given aerosol particle diameter when a further increase in microporosity leads to a decrease in the deposition efficiency.

Self-assembled CuS porous grade sub-nanoflowers as efficient nano-adsorbents for adsorption/self-deposition characteristics research

In recent decades, growing population and industrial development have led to releasing huge amounts of highly toxic chemical pollutants into the environment globally. Several approaches to handling the removal of contaminants from wastewater for environmental remediation, including biological, chemical, physical, and advanced oxidation processes have been employed. Among them, using nano-adsorbents as a tool for effectively removing organic contaminants represents a promising strategy in sewage purification field. More importantly, the nano-adsorbents with auto-deposition property can greatly improve the efficiency of sewage treatment. Therefore, the developing of environment friendly nano-adsorbents is thus an important issue to remove organic contaminants in water via simply adsorbing. Here in this work, porous flower-like copper sulfide (CuS) grade sub-nanomaterials are successfully fabricated by simply mixing two inorganic salts. Furthermore, the as-prepared nano-adsorbents with auto-deposition property can create a super adsorption capability for organic contaminants in wastewater. We further study the adsorption/auto-deposition characteristics of porous flower-like CuS grade sub-nanomaterials systematically by using various organic dyes (methyl blue, crystal violet, lemon yellow, sunset yellow and amaranth) as target molecules. For instance, in a typical procedure, 0.8-mg methyl blue can be removed 100% via adding 10-mg porous flower-like CuS grade sub-nanomaterials sample in 30 min. Therefore, the adsorption efficiency can be enhanced by 55% and 26% in comparison with the adsorption efficiency of CuS micro pompons and micron particles, respectively. Additionally, the porous flower-like CuS grade sub-nanomaterials can self-deposite on the bottom of the solution within 3 h after adsorption has finished, and the deposition efficiency can be improved by 95% and 3.17 times in comparison with the deposition efficiency of CuS micro pompons and micron particles, respectively. Comparing with micron particles, the unique self-depositing characteristics of porous flower-like grade sub-nanomaterials are attributed to larger specific surface area, greater porosity and stronger electrostatic adsorption capacity. Remarkably, this work provides an effective method of effectively removing various organic dyes from wastewater.

Numerical Study of Nanoparticle Deposition in a Gaseous Microchannel under the Influence of Various Forces

Nanoparticle deposition in microchannel devices inducing contaminant clogging is a serious barrier to the application of micro-electro-mechanical systems (MEMS). For micro-scale gas flow fields with a high Knudsen number (Kn) in the microchannel, gas rarefaction and velocity slip cannot be ignored. Furthermore, the mechanism of nanoparticle transport and deposition in the microchannel is extremely complex. In this study, the compressible gas model and a second-order slip boundary condition have been applied to the Burnett equations to solve the flow field issue in a microchannel. Drag, Brownian, and thermophoretic forces are concerned in the motion equations of particles. A series of numerical simulations for various particle sizes, flow rates, and temperature gradients have been performed. Some important features such as reasons, efficiencies, and locations of particle deposition have been explored. The results indicate that the particle deposition efficiency varies more or less under the actions of forces such as Brownian force, thermophoretic force, and drag force. Nevertheless, different forces lead to different particle motions and deposition processes. Brownian or thermophoretic force causes particles to move closer to the wall or further away from it. The drag force influence of slip boundary conditions and gas rarefaction changes the particles’ residential time in the channel. In order to find a way to decrease particle deposition on the microchannel surface, the deposition locations of different sizes of particles have been analyzed in detail under the action of thermophoretic force.

Orally Inhaled Drug Particle Transport in Computerized Models of Laryngotracheal Stenosis.

Adjuvant management for laryngotracheal stenosis (LTS) may involve inhaled corticosteroids, but metered dose inhalers are designed for pulmonary drug delivery. Comprehensive analyses of drug particle deposition efficiency for orally inhaled corticosteroids in the stenosis of LTS subjects are lacking. Descriptive research. Academic medical center. Anatomically realistic 3-dimensional reconstructions of the upper airway were created from computed tomography images of 4 LTS subjects-2 subglottic stenosis and 2 tracheal stenosis subjects. Computational fluid dynamics modeling was used to simulate airflow and drug particle transport in each airway. Three inhalation pressures were simulated, 10 Pa, 25 Pa, and 40 Pa. Drug particle transport was simulated for 100 to 950 nanoparticles and 1 to 50 micron-particles. Particles were released into the airway to mimic varying inhaler conditions with and without a spacer chamber. Based on smallest to largest cross-sectional area ratio, the laryngotracheal stenotic segment shrunk by 57% and 47%, respectively, for subglottic stenosis models and by 53% for both tracheal stenosis models. Airflow resistance at the stenotic segment was lower in subglottic stenosis models than in tracheal stenosis models: 0.001 to 0.011 Pa.s/mL vs 0.024 to 0.082 Pa.s/mL. Drug depositions for micron-particles and nanoparticles at stenosis were 0.06% to 2.48% and 0.10% to 2.60% for subglottic stenosis and tracheal stenosis models, respectively. Particle sizes with highest stenotic deposition were 6 to 20 µm for subglottic stenosis models and 1 to 10 µm for tracheal stenosis models. This study suggests that at most, 2.60% of inhaled drug particles deposit at the stenosis. Particle size ranges with highest stenotic deposition may not represent typical sizes emitted by inhalers.

A new periodic cell model of aerosol diffusion deposition in a fibrous filter

A new periodic cell model for the convective-diffusive transport of small aerosol particles in a fibrous filter is developed. The proposed periodic model takes into account the influence of the fiber diffusion wake on the particle deposition. This allows us to predict the efficiency of a filter more accurately compared to the single-fiber approximations. The fluid flow is described in the framework of Stokes flow in a rectangular periodic cell. New form of periodic boundary conditions for the particle transport equation in the cell is suggested. The equations of fluid flow and particle transport are solved using the Boundary Element Method (BEM) and Boundary Domain Integral Method (BDIM).The diffusive deposition of nanoaerosols in the filter, modeled as a row of the large number of circular cylinders located perpendicular to the flow direction, is studied numerically using the many fibers model. It is shown, that predictions of the new periodic model are in the better agreement with the many fibers model for the filters of greater length. It is also shown, that the widely used approximation for single fiber deposition efficiency (Stechkina, 1967) overestimates the efficiency of multi-fiber filter compared to periodic model. The overestimation increases with increase of Peclet number.The approximate formula for the single fiber particle deposition efficiency in a periodic cell for a square and staggered cylinder arrays is derived. The formula accounts for the effect of the Peclet number and the hydrodynamic factor. The predictions of the derived formula are compared to the numerical data from the work of Hosseini and Tafreshi (2010) for the fibrous filter comprised of many randomly arranged cylinders. The predictions of the diffusive deposition efficiency obtained using the derived formula for the staggered fibers array are shown to be in a good agreement with the numerical model predictions.

Health effects after inhalation of micro- and nano-sized zinc oxide particles in human volunteers

Inhalation of ZnO particles can cause inflammation of the airways and metal fume fever. It is unclear if different sizes of the particles alter these effects. However, various studies report higher biological activity of other nano-sized particles compared to microparticles. No effects at all were observed after inhalation of micro- and nano-sized zinc oxide (ZnO) particle concentrations of 0.5 mg/m3. Studies with different particle sizes of ZnO at higher exposures are not available. Accordingly, we hypothesized that inhalation of nano-sized ZnO particles induces stronger health effects than the inhalation of the same airborne mass concentration of micro-sized ZnO particles. 16 healthy volunteers (eight men, eight women) were exposed to filtered air and ZnO particles (2.0 mg/m3) for 2 h (one session with nano- and one with micro-sized ZnO) including 1 h of cycling at moderate workload. Effect parameters were symptoms, body temperature, inflammatory markers in blood and in induced sputum. Induced sputum was obtained at baseline examination, 22 h after exposure and at the end of the final test. The effects were assessed before, immediately after, about 22 h after, as well as two and three days after each exposure. Neutrophils, monocytes and acute-phase proteins in blood increased 22 h after micro- and nano-sized ZnO exposure. Effects were generally stronger with micro-sized ZnO particles. Parameters in induced sputum showed partial increases on the next day, but the effect strengths were not clearly attributable to particle sizes. The hypothesis that nano-sized ZnO particles induce stronger health effects than micro-sized ZnO particles was not supported by our data. The stronger systemic inflammatory responses after inhalation of micro-sized ZnO particles can be explained by the higher deposition efficiency of micro-sized ZnO particles in the respiratory tract and a substance-specific mode of action, most likely caused by the formation of zinc ions.

Study of the Influence of the Add оf Micropores on Filtering Characteristics of High Porous Structures

In this work we carried out a numerical study of the gas flow through an open cell foam material with solid-state partitions and partitions containing micropores. The effect of a geometry change by adding micropores on the pressure drop, particle deposition efficiency, and filter quality factor is estimated. The results showed that the addition of micropores positively affects the filtering and hydrodynamic properties of the highly porous material for the same macroporosity of the medium, and for the case of total porosity of the medium, the material with micropores allows one to obtain an increased value of the deposition efficiency and filter quality factor for small particles.

Deposition characteristics of particles in inclined heat exchange channel with surface ribs

Ash particles in flue gas flow would deposit on the heat recovery exchanger in the waste heat recovery system (WHRS), which may lead to the reduction of heat transfer efficiency and service life. Understanding of ash particle deposition in the heat exchange channel is crucial for the safe operation of WHRS. In this study, deposition characteristics of ash particles in an inclined heat exchange channel with surface ribs were investigated by using Reynolds stress model combined with discrete phase model. The turbulent fluctuation correction and particle rebound model were developed by using UDF program to improve the prediction accuracy. After grid sensitivity analysis and numerical verification, the flue gas thermal-fluid fields, the 3D particle deposition patterns and deposition efficiency on each ribbed channel surface were obtained and analyzed. Parameter study on the deposition characteristics was conducted by considering flue gas flow velocity, particle size and inclination angle of the ribbed channel. The results showed that significant secondary flow eddies can be observed near the rib windward surfaces and high-value turbulent intensity area appears near the rib crest. The windward surfaces and the crests of the ribs are the main deposition locations in the inclined heat exchange channel. The deposition efficiency in the ribbed channel is obviously changed by the particle diameter and flue gas flow velocity. The inclination angle has little influence on deposition efficiency for small particles (dp<5μm) but great effect on deposition efficiency for large particles (dp>10μm).

Оценка времени работы пылеуловителя со скругленными сепарационными элементами

The study is focused at the development of new technical devices for separating dust particles up to 10 microns in size from flue gases of thermal power plants, along with the creation of an engineering methodology for the proposed separation device and obtaining calculated dependences for determining operational maintenance intervals. In order to determine the efficiency of particle deposition on the surface of the separation device, previously verified methods of mathematical modelling were used based on the laws of momentum and heat conservation, as well as a solution to hydrodynamics equations. The proposed original trapezoidal separator design is equipped with several rows of arcuate elements for concentrating dust during the operation of the apparatus due to the action of inertial and centrifugal forces. With an increase in the input velocity of the gas flow from 3 to 11 m/s and efficiency values of 0.5, 0.7 and 0.9, the operation time of the separator is decreased by an average of 3.7 times. The minimum operation time is established to be about 50 days at a dust flow rate of 11 m/s and a dust concentration of 8 mg/m3. The maximum operation time of the separator was determined to be about 465 days at a dust flow rate of 3 m/s and a dust concentration of 5 mg/m3. The proposed design of the trapezoidal separator ensures the separation of particles both larger and smaller than 10 microns from the flue gases of thermal power plants with an efficiency of 99.0-99.9 and 61.7%, respectively, resulting in reduced atmospheric emissions. Using the developed methodology, the main structural dimensions of the proposed separator can be determined under given gas flow parameters.

Analysis of pre-filter models using numerical simulation

The article presents a numerical simulation of the gas flow in pre-filter models. It was proposed nine models of pre-filters with grating sizes of 1mm, 1.5mm and 2mm, with a change in the number of plates. Pre-filters were compared in terms of particle deposition efficiency, pressure drop and filter quality parameter.

Comparison of experimentally measured and computational fluid dynamic predicted deposition and deposition uniformity of monodisperse solid particles in the Vitrocell® AMES 48 air-liquid-interface in-vitro exposure system

Accurately determining the delivered dose is critical to understanding biological response due to cell exposure to chemical constituents in aerosols. Deposition efficiency and uniformity of deposition was measured experimentally using monodisperse solid fluorescent particles with mass median aerodynamic diameters (MMAD) of 0.51, 1.1, 2.2 and 3.3 μm in the Vitrocell® AMES 48 air-liquid-interface (ALI) in vitro exposure system. Experimental results were compared with computational fluid dynamic, (CFD; using both Lagrangian and Eulerian approaches) predicted deposition efficiency and uniformity for a single row (N = 6) of petri dishes in the Vitrocell® AMES 48 system. The average experimentally measured deposition efficiency ranged from 0.007% to 0.43% for 0.51–3.3 μm MMAD particles, respectively. There was good agreement between average experimentally measured and the CFD predicted particle deposition efficiency, regardless of approach. Experimentally measured and CFD predicted average uniformity of deposition was greater than 45% of the mean for all particle diameters. During this work a new design was introduced by the manufacturer and evaluated using Lagragian CFD. Lagragian CFD predictions showed better uniformity of deposition, but reduced deposition efficiency with the new design. Deposition efficiency and variability in particle deposition across petri dishes for solid particles should be considered when designing exposure regimens using the Vitrocell® AMES 48 ALI in vitro exposure system.

Numerical simulation of particle deposition in the human nasal cavity

This paper presents the results of numerical simulation of airflow with suspended particles through a human nasal cavity. The stationary and nonstationary problem statements were considered. Within the nonstationary case, two variants were studied: for the first variant, the breath cycle is taken with symmetric inhale/exhale, and for the second variant, we modelled a real asymmetric breath cycle. The solution was based on Navier-Stokes equations for laminar flow of incompressible gas. Particle flow is described using the Lagrangean approach with account for Brownian motion. Numerical simulation results were compared with experimental and simulation data from other authors. Results for different variants of problem statement were compared. Asymmetry of breath cycle should be accounted in calculation of particle deposition efficiency. A simple rule was found that replaces the computation-consuming nonstationary calculation with three stationary flow calculations.

Numerical study on characteristics of particle deposition efficiency on different walls of 90° square bend

A better understanding of the characteristics of particle deposition in bend would help in designing a sampling bend. In this paper, gas-solid flow in 90° bend was simulated using the RNG k-ɛ turbulence model and the Lagrangian particle-tracking model. The preliminary results show that the deposition efficiency in 90° square bend is lower than that in 90° circular bend. Afterwards, the flow field, particle trajectories, and effect of curvature ratio on deposition efficiency on different walls were analyzed in 90° square bend. The results show that the main deposition location is related to the Stokes number. On inner wall, the deposition efficiency increases first and then decreases as the Stokes number increases, and particles mainly deposit in middle deflection angles range. Moreover, increasing the curvature ratio changes the flow field in the bend and, in turn, the deposition efficiency on inner wall and distributions of deposition efficiency on outer wall.

Improving the efficiency of particle deposition on the filter fiber through its modification

In this work, we performed a numerical study of the parameters of a fiber filter that make the greatest contribution to the efficiency of particle deposition, using the example of a single fiber. The mechanism of inertial particle deposition is considered. The aerosol motion was numerically simulated in the ANSYS Fluent software package. The particle deposition efficiency was calculated for a single solid and porous fiber without a protrusion, with one protrusion and five protrusions. Based on the data obtained, the dependences of the particle deposition efficiency for a single fiber are graphically presented. A new method is proposed for increasing filter efficiency by creating modified fibers.