Deposition Of Aerosol Particles Research Articles

Indoor concentrations of radioactive aerosols from nuclear accidents.

In previous studies, some of the important factors that affect the spread of radioactive aerosols into indoors were considered. The studies were based on a new CFD approach and provided good descriptions for the deposition of aerosol particles inside small spaces and the penetration of aerosols into buildings through wall cracks. In this article, an application of those studies is implemented, where all the graphical relations that are required to estimate the indoor concentrations of radioactive aerosols from nuclear accidents are provided. This includes the deposition velocities, deposition rate, and the penetration factor. Particular interest is in the Fukushima-Daiichi nuclear power plant accident that took place in Japan in 2011. The aerosols carrying the radioiodine iodine-131 and the radiocesium cesium-134 and cesium-137 are studied. Based on the model's assumptions, and assuming steady-state air concentrations, the radioactive aerosols' concentrations in indoor air are about 97% of the concentrations in outdoor air. The applications demonstrate the model to be convenient and practical.

Quantitative evaluation of the impact of indoor relative humidity on deposition of aerosols generated during tooth grinding in a real-world clinical setting.

Exposure to aerosol particles generated from tooth grinding has a negative impact on the health of dental personnel. The aim of this study was to quantitatively analyze the impact of indoor relative humidity (IRH) on the deposition of these suspended particles in a well-controlled dental environment. In this study, a humidity control system was employed to effectively regulate and maintain indoor relative humidity (IRH). A novel computer-assisted numerical control system was developed to pre-treat the molar specimens, and accurately simulate clinical tooth grinding procedures. Each procedure was performed in triplicate, with an online real-time particle counter (ORPC; TR-8301, TongrenCo.) measuring aerosol production. All testing devices were controlled remotely. The data obtained were statistically analyzed using descriptive statistics and non-parametric tests (Kruskal-Wallis/ Dunn's post hoc test with Bonferroni correction, p < 0.05). The findings showed that with increasing IRH, the maximum peak concentration of aerosol particles decreased by 397% from 6.51 × 107 particles/m3 at 30% to 1.64 × 107 particles/m3 at 80%. The Kruskal-Wallis test results indicated a statistically significant effect of IRH on the aerosol increment (p < 0.05). Increasing the IRH level can effectively promote the deposition of aerosol particles, with a return to baseline within 15min after reaching 60% or above. Our study suggested that maintaining IRH above 70% during the cleaning process, allowing natural recovery to ambient humidity levels within 15min after cleaning, and taking basic precautions, may lead to an adequate reduction in the possible health risks of aerosol contamination.

The impact of barrier arrangements on the transmission of respiratory infectious diseases in nursing homes in Hong Kong

Respiratory infectious diseases have affected the health of the elderly. This study investigated the optimization of physical barriers as a low-cost design strategy to reduce the risk of infection in nursing homes for the elderly in Hong Kong, which were significantly affected by the outbreak of COVID-19. First, data on two types of rooms, single and multi-occupancy, were collected from a field investigation of typical local nursing homes. Subsequently, Computational Fluid Dynamics (CFD) simulations were employed to analyse the effects of various barrier heights on the propagation, suspension, deposition and elimination of aerosol particles in these room types, thereby evaluating infection risks. The findings reveal that in single-occupancy rooms, a barrier height of 2.1 m is effective in curtailing the spread of the virus over distances. Conversely, in multi-occupancy rooms, while a 1.8-m barrier is necessary, the rate of particle suspension is considerably higher, necessitating additional ventilation measures. Based on these findings, the study provides quantitative criteria for the implementation of physical barriers as a low-cost physical measure in nursing homes and provides recommendations for the effective prevention of respiratory infectious diseases through design modifications.

Penetration of particles through vertical cracks

In a previous study, a new deposition model was developed to account for deposition of aerosol particles on the inner walls of small containers. In this article, the model applicability is extended by including deposition on horizontal surfaces, both upward-facing and downward-facing. After that, the model is applied to study a vital new issue, which is the penetration of aerosols to the indoors through vertical wall cracks. Previous studies, both theoretically and experimentally, never addressed penetration through vertical cracks. This study therefore aims to show the difference between penetration through vertical cracks and horizontal ones by applying the fourth-power model, which is very successful in describing deposition in small volumes. The penetration model formulated in this study takes into account, not only the thickness and depth of the crack, as usually happens in most penetration models, but all the three dimensions of the crack; thickness, depth and width. The obtained results are in a good agreement with the experimental data. This demonstrates the success of the extended fourth-power model in describing deposition inside cracks. Moreover, the results show a clear difference between vertical and horizontal cracks for the penetration of aerosols with diameter larger than ∼1μm. An application of the developed deposition and penetration models is presented, where a method for calculating the radioactive aerosols indoor concentrations is explained.

Computational analysis of radon progeny deposition patterns in the human respiratory system

In the last year, the use of computational fluid dynamics (CFD) techniques has gained prominence as a powerful tool for modeling biological phenomena and influencing the design of biomedical devices. In this study, we utilized a computational fluid dynamics (CFD) model to simulate airflow and the deposition of aerosol particles within the human respiratory tract. To achieve this, we meticulously constructed a 3D model of the human tracheobronchial airways using SolidWorks software. Our computational analyses encompassed a range of breathing conditions, ranging from 15 to 60 (L/min). Through the application of discrete phase modeling (DPM), we investigate the behavior of two-phase flow dynamics. Our focus lies in the examination of aerosol particles, with diameters ranging from 1 to 10 (μm), in order to evaluate the influence of aerosol particle size on deposition rates. Our findings encompass velocity contour maps, deposition rates of aerosol particles, and insights into the process of aerosol particle entrapment at various locations within the respiratory tract. Our study reveals a direct correlation between higher inhalation rates and larger aerosol particle sizes, resulting in increased deposition rates. Additionally, we observe a heightened deposition of aerosol-particles at bronchi region. These computational results hold significant value in estimating the distribution of doses resulting from radon progeny exposure in distinct anatomical regions of the respiratory tract.

Growth of branched nanowires via solution-based Au seed particle deposition

Nanowires offer unprecedented flexibility as nanoscale building blocks for future optoelectronic devices, especially with respect to nanowire solar cells and light-emitting diodes. A relatively new concept is that of charge carrier diffusion-induced light-emitting diodes, for which nanowires offer an interesting architecture by use of particle-assisted core-branch growth. The branches should be homogenously distributed along the cores. However, most deposition techniques, such as aerosol particle deposition, mainly yield particles at the nanowire tips for dense nanowire arrays. In this study, we demonstrate a liquid-based approach for homogeneously distributed formation of catalytic Au particles on the core nanowire sidewalls which is cost and time-efficient. Subsequently, we demonstrate the synthesis of dispersed nanowire branches. We show that by changing the deposition parameters, we can tune the number of branches, their dimensions, and their growth direction.

Magnetic Resonance Imaging of Aerosol Deposition.

Nuclear magnetic resonance imaging (MRI) uses non-ionizing radiation and offers a host of contrast mechanisms with the potential to quantify aerosol deposition. This chapter introduces the physics of MRI, its use in lung imaging, and more specifically, the methods that are used for the detection of regional distributions of inhaled particles. The most common implementation of MRI is based on imaging of hydrogen atoms (1H) in water. The regional deposition of aerosol particles can be measured by the perturbation of the acquired 1H signals via labeling of the aerosol with contrast agents. Existing in vitro human and in vivo animal model measurements of regional aerosol deposition in the respiratory tract are described, demonstrating the capability of MRI to assess aerosol deposition in the lung.

Influence of the Sphericity Coefficient on the Deposition Characteristics of Aerosol Particles on the Surface of Photovoltaic (PV) Modules: Numerical Simulation

The deposition of aerosol particles has a significant impact on the output capacity of photovoltaic modules. Therefore, studying the deposition characteristics of aerosol particles on photovoltaic modules is of great importance for improving their output capacity. Particle morphology is one of the important parameters affecting the deposition characteristics of aerosol particles. This study introduces the spherical coefficient as a quantification method for characterizing the morphology of aerosol particles. Numerical simulations using FLUENT 2022 software were conducted to investigate the influence of the spherical coefficient on the deposition characteristics of aerosol particles on photovoltaic modules. The reliability of the numerical simulations was further validated through experimental studies. Based on the research, the following conclusions can be drawn: the airflow velocity near the surface of the photovoltaic panel increases from bottom to top, with the lowest wind speed recorded near the ground at a minimum value of 2.2 m/s and a maximum value of 3.89 m/s. The air pressure near the surface of the photovoltaic panel shows a decreasing trend from bottom to top, with the highest pressure recorded near the ground at a maximum value of 10 pa and a minimum value ranging from 3.33~5.56 pa. During the deposition process, the accumulation of particles increases with an increase in the sphericity factor. Furthermore, as the sphericity factor gradually increases, the distribution of particles on the surface of the photovoltaic panel becomes more dispersed, covering the entire surface.

In silico prediction of e-cigarette aerosol particle transport and deposition within the airways.

Electronic cigarettes (ECs) generate aerosols by heating up a liquid ('e-liquid') that typically consists of propylene glycol (PG), vegetable glycerol (VG), nicotine and flavouring agents. These aerosols transport through the airway tree, and lung and deposit non-uniformly in the bronchi and alveoli. Studying the transport of aerosols through lung airways is necessary because it provides information about the concentration and deposition of particles in the upper and lower airways. Here, particle transport and deposition were simulated within an anatomically-realistic airway model, which was constructed from computed tomography imaging. Particle transport was simulated using the advection-diffusion equations. Particle deposition was estimated using three different mechanisms; including sedimentation, impaction and Brownian diffusion. Results show that by increasing the particle size (PS) from 50 nm to 500 nm, the total deposition efficiency decreased from 50% to 10%, and then by increasing the PS to 3 μm, it increased to 60%. In addition, Brownian deposition was the dominant mechanism for nanoparticles (PS≪0.5μm), while the sedimentation deposition mechanism was the dominant one for microparticles (PS≫0.5μm).Clinical relevance-There is an urgent need to understand the risk that ECs pose to human health and to determine the safest methods for using these devices to support smoking cessation whilst also minimising harm. The results of this study will be used to simulate the conditions such as aerosol concentration and flow rate in airways and alveoli to use in in vitro studies.

Study on aerosol thermophoretic force and thermophoresis deposition model in reactor building

During nuclear reactor severe accident, the input of external passive containment cooling system will result in significant aerosol thermophoresis deposition in reactor building, which plays important factor affecting the safety assessment of nuclear reactor. Ratio of aerosol particles radius and gas molecule mean free path (Kn number) in reactor building is not greater than 2, corresponding to the near-continuous medium zone and transition zone. Firstly the typical thermophoretic force equations for these zones are evaluated. Combined with key influencing factors analysis, the correction factor connected to Kn number is introduced to address the deviation in the prediction for the transition zone of the current equations. The modified thermophoretic force equation obviously improves the underestimation of the original equation and is then used to obtain the thermophoresis deposition coefficient. According to experimental validation, the obtained coefficient is more accurate than the model that is widely employed in analysis codes in predicting the thermophoresis deposition of aerosol particles. Finally, fluid continuity, momentum, energy and particle continuity equations are established with deduced thermophoresis deposition coefficient and solved numerically. The thermophoresis deposition model considering natural convection (CT model) is established by theoretical derivation and fitting with the numerical solutions. By introducing the effects of natural convection on temperature distribution and aerosol concentration distribution the CT model could accurately describe the aerosol thermophoresis deposition behavior under natural convection conditions for Kn number is not greater than 2, which can be applied to aerosol thermophoresis deposition prediction in reactor building.

Estimating aerosol particle removal in indoor air by ion-enhanced deposition

Small air ions have the ability to charge airborne particles, thereby increasing their accumulation on surfaces. Indoor air purification by applying ionization uses electrostatic particle deposition. Respiratory pathogens, including viruses and respiratory droplets carrying viruses or other pathogens, represent bioaerosols, whose particle size distributions contain increasingly larger proportion of fine and ultrafine particles, as the evaporation process proceeds. We have generated two model aerosols: the nebulized NaCl solution, resembling human saliva, and the cigarette smoke, having relatively low water content. We have conducted real life experiments of such surrogate aerosol particle deposition without ionization, using bipolar ionization, as well as using unipolar negative air ions. Particle number concentrations have been measured in the 10 nm–10 μm particle size range. The calculated deposition rates and aerosol particle half-life times were correlated with bioaerosol pathogens based on the core pathogen sizes. Bipolar ionizers emitting equal concentrations of positive and negative ions had low impact to the particle concentration decrease. Intense negative air ionization resulted in pronounced deposition rate increases, particularly in the particle size range of viruses including the SARS-CoV-2. The impact of negative air ionization was most pronounced in the same size range where the deposition rates without ionization were the lowest. Therefore, the results are very promising from the standpoint of air purification and bioaerosol pathogen removal, bearing in mind that the effect of ions will be most pronounced if the unipolar ion rich air stream is directed towards the breathing zone.

Particle deposition and fluid flow characteristics in turbulent corrugated pipe flow using Eulerian-Lagrangian approach

A numerical simulation of aerosol particle deposition in a horizontal circular pipe with a corrugated wall under turbulent flow has been carried out in this research. This paper uses the RNG k-ε turbulence model with Enhanced Wall Treatment to simulate fluid flow. Furthermore, the Lagrangian particle tracking model simulates particle deposition in the corrugated pipe. Air-particle interaction is influenced by Stokes number, surface roughness, flow velocity, particle diameter, and pipe diameter. For the parametric simulation, particle diameter varies from 1 to 30 μm, whereas the Reynolds number ranges from 5000 to 10,000. The effect of corrugation height and pipe diameter on deposition efficiency is also investigated. This study shows that corrugation height significantly increases particle deposition compared to the smooth wall pipe. As the pipe diameter decreases, keeping the corrugation ratio constant, deposition efficiency also increases. Moreover, high flow velocity enhances deposition efficiency for particle diameters lower than 5 μm.

Ash aerosol particle size distribution, composition, and deposition behavior while co-firing coal and steam-exploded biomass in a 1.5 MWth combustor

Five different blends of Utah bituminous coal and steam-exploded pine (100/0, 75/25, 50/50, 25/75, 0/100 by mass) were fired in a 1.5 MWth combustor. Primary objectives were to understand mineral matter behavior by analyzing aerosol size distribution, aerosol size-segregated composition, ash deposition mass, and ash composition. For particle size <0.1 μm, pure coal had the lowest aerosol concentration and pure biomass showed the highest (higher nucleation of potassium salts), a trend which reversed for particles >0.1 μm. During pure biomass combustion, aerosol particles >15 μm contained higher mass fractions of potassium (+126%), calcium (+132%), and iron (+115%) and lower fractions of aluminum (−49%) and silicon (−29%) than pure coal. Ash deposition mass decreased with increasing biomass blends. Downstream ash deposits contained −3% to 55% higher sodium and potassium than the upstream ash, which highlights the dilution effect of the condensation layer by inertial impaction on the upstream side. Submicron ash load and deposited mass for 30-min and 90-min tests showed R2 values of 0.974 and 0.966, indicating that smaller particles' concentration determines the final mass. The results suggest that plant operators should not face any difficulties while co-firing these blends with respect to ash deposition by fouling.

Численное моделирование переноса твёрдых частиц в атмосферном городском пограничном слое с использованием лагранжева подхода: физические задачи и параллельная реализация

This paper presents the results of the development of a numerical model of the Lagrangian particle transport and the application of parallel computation methods to increase the efficiency of the software implementation of the model. The model is a software package allowing calculations of transport and deposition of aerosol particles taking into account the properties of particles and input data describing atmospheric conditions and the underlying surface geometry. The dynamic core, physical parameterizations, numerical implementation, and algorithm of the model are described. Initially, the model has been used for computationally low-intensive problems. In this paper, given the need to use the model in computationally intensive problems, we conduct optimization of the sequential software implementation of the model, as well as creation of software implementations of the model with the use of parallel computing technologies OpenMP, MPI, CUDA. The results of testing of different implementations of the model show that optimization of the most computationally complex blocks in the sequential version of the model can reduce the execution time by 27%, at the same time the use of parallel computing technologies allows to achieve acceleration by several orders of magnitude. The use of OpenMP in dynamic block of the model resulted in acceleration of block up to 4 times, the use of MPI – up to 8 times, the use of CUDA – up to 16 times, all other conditions being equal. Recommendations on the choice of parallel computing technology depending on the properties of the computing system are proposed.

Experimental study on aerosol inhalation of the human upper airway

The study of aerosol deposition in the human upper respiratory tract is of great significance for understanding the impact of toxic aerosols on human health and improving the therapeutic effect of drug aerosol inhalation. 3D printing technology was used in the experimental model of the human upper airway. A laser particle size analyzer was used to study the deposition of aerosol particles with a particle size of 1-20 μm inhaled in the upper respiratory tract of the human body, and the particle deposition rules of the aerosol particles in the upper respiratory tract were analyzed. The experimental results show that aerosol particles remain more in the pharynx, larynx and position. For particles with a particle size of 1-5 μm, more deposition will occur in the trachea, and for particles with a particle size of 10-20 μm, most of them will be deposited in the mouth.

Deposition Characteristics of Aerosol Particles on the Surface of PV Modules: Numerical Study

AbstractThe deposition of aerosol particles can significantly affect the surface transmittance of photovoltaic (PV) modules and thus reduce photoelectric efficiency. With the aid of the control variable method, orthogonal experimental design, and stepwise linear regression method, a numerical simulation study of the deposition process of aerosol particles on the surface of a PV module is carried out in this paper. The influence laws of inflow wind velocity (v), particle diameter (d), installation angle (α), and particle concentration (c) on the deposition process of aerosol particles are analyzed, respectively. The deposition mechanism of aerosol particles on the surface of the PV module is disclosed, and the prediction model of deposition rate (n) is proposed. The results show that v, d, and c all positively affect n of the aerosol particles within the value ranges of each investigation variable in this study. α positively affects n of the aerosol particles when v is less than 3.65 m s−1. α negatively affects the n of the aerosol particles when v is larger than 3.65 m s−1. The prediction model could accurately predict the n of aerosol particles. This research has a theoretical guiding significance for the formulation process of cleaning strategies for the surface of PV modules.

Characterization of nebulization generated aerosol particles dispersion and deposition by total reflection X-ray fluorescence

Characterization of nebulization generated aerosol particles dispersion and deposition by total reflection X-ray fluorescence

Particle deposition and characteristics of turbulent flow in converging and diverging nozzles using Eulerian-Lagrangian approach

The current study conducts a thorough assessment of the deposition of aerosol particles in turbulent flows in both converging and diverging nozzles using the Lagrangian particle tracking model and the RNG k-ε turbulence model. The air-particle interaction depends on flow velocity, particle diameter, and types of flow sections when the particles are injected into the airflow. For the parametric simulation, Stokes number is varied from 0.0354 to 0.8265 with the corresponding particle diameter ranging from 2.00 to 10.00 μm, whereas Reynolds number is varied from 5000 to 10,000. Computational results show how the particle deposition efficiency in converging and diverging nozzles is influenced by Stokes number, diameter ratio of pipe, particle diameter, and Reynolds number. The deposition efficiency of a diverging nozzle is found to be lower than that of a converging nozzle, and the flow Reynolds number increases the deposition efficiency slightly in the diverging nozzle but gradually in the converging nozzle.

A 3D Monte Carlo Simulation for Aerosol Deposition onto Horizontal Surfaces by Combined Mechanisms of Brownian Diffusion and Gravity Sedimentation

A three-dimensional Monte Carlo model was developed to simulate the deposition of aerosol particles onto horizontal solid surfaces. The random walk method was employed to solve the particle transport equation, which allowed obtaining the trajectory of particle motion by a combined mechanism of Brownian diffusion and gravity sedimentation. The particle transport mechanism was described in terms of a Peclet number (Pe). The local structures of the dust layer, the relationship between the structure of the dust layer and particle transport mechanisms, and the number of the particles attached to the solid surface were investigated. The results showed that for a small Pe, when Brownian diffusion was a controlling mechanism for aerosol transport, the dust layer might exhibit a more open and looser structure, while for a large Pe, the dust layer was dense and tight. The differences of deposition morphologies under different transport mechanisms were caused by the different random intensities of particle motion. There was an upper limit of the maximum number of particles attached to the surface, and it strongly depended on particle transport mechanisms and size distributions. Additionally, the deposit morphologies obtained with the 3D Monte Carlo model were in good agreement with the experimental results found in the literature.

A Numerical Simulation of the Airflow and Aerosol Particle Deposition in a Realistic Airway Model of a Healthy Adult

Determining the behavior of aerosol drug particles is of vital importance in the treatment of respiratory tract diseases. Despite the development of imaging techniques in the pulmonary region in recent years, current imaging techniques are insufficient to detect particle deposition. Computational fluid dynamics (CFD) methods can fill the gap in this field as they take into account the very different physical processes that occur during aerosol transport. This study aims to numerically investigate the airflow and the aerosol particle dynamics on a realistic human respiratory tract model during multiple breathing cycles. The simulations were conducted on the different breathing conditions for people under light, normal, and heavy physical activities, and the aerosol particles with different aerodynamic diameters (i.e., dp=2, 5, and 7 µm). The numerical results were validated by comparing extensively with experimental and numerical results. The results indicated that the airflow during inspiration and expiration was characteristically different from each other and changed with the inspiration flow rate. It was determined that small-sized particles followed the streamlines and moved towards the distal of the lung under low respiratory conditions. On the other hand, larger particles tended to deposit in higher generations due to the higher inertia. It was found that with the increase of inspiration flow rate the deposition of particles increased for all particles during multiple breaths. For light breathing conditions, low deposition efficiencies were obtained because the particles followed the streamlines and moved towards the distal part of the lung. The particle deposition efficiency under heavy breathing conditions was 28.2% for 2 µm, 33.05% for 5 µm, and 38.4% for 7 µm particles. The results showed that inertial impaction plays an active role in particle deposition.