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Particle Deposition and Reentrainment
Published in Ko Higashitani, Hisao Makino, Shuji Matsusaka, Powder Technology Handbook, 2019
Manabu Shimada, Shuji Matsusaka, Hiroaki Masuda
Particle deposition is a phenomenon in which particles that are suspended in a fluid are transported to a wall and make permanent or temporary contact with the surface of the wall. Particle deposition is an important phenomenon in many fields including fouling of channel walls exposed to dusty gas, micro-contamination problems in advanced material processing, dry deposition of particulate matter in an atmospheric environment, development and efficiency of gas filtration devices, designed positioning and accumulation of particles for the fabrication of functional devices, and inhalation of airborne particulate matter into human lungs. Particle reentrainment refers to the resuspension of particles that had been deposited on a surface. In general, it is difficult to reentrain small primary particles from a wall. However, aggregate particles are readily reentrained from a particle deposition layer. The aggregate reentrainment affects various engineering applications such as powder dispersion, particle size classification, dust collection, particle synthesis, and aerosol sampling.
Surfactant Self-Assembly at Interfaces and Its Relationship to Solution Self-Assembly
Published in Victor M. Starov, Nanoscience, 2010
Zbigniew Adamczyk, Magorzata Nattich, Anna Bratek
Theoretical models based on the RSA model can be effectively used for predicting particle deposition at quasi-continuous and heterogeneous surfaces, in particular for determining surface blocking functions, deposition kinetics, jamming coverage, and distribution of particles in monolayers, coverage fluctuations, and so on. These results can also be used as boundary conditions for bulk transport equations, making it possible to analyze particle deposition under convection- and diffusion-controlled transport conditions. The extended RSA algorithms can also be used for modeling multilayer deposition of particles, in particular to determine the average thickness of multilayers, particle density distribution, roughness, and so on, as a function of the precursor layer density and the number of layers.
Environmental Standards, Manufacturing Operations,and Good Manufacturing Practice
Published in Thomas A. Barber, Control of Particulate Matter Contamination in Healthcare Manufacturing, 1999
This annex describes procedures and equipment for sizing and counting particles which are or may be deposited from the air onto product or work surfaces in the installation. Deposited particles are collected upon witness plates with appropriate surface characteristics similar to those of the at risk surface under consideration, and are sized and counted using optical microscopes, electron microscopes, or wafer scanning instruments. A particle fallout photometer may be used to obtain particle deposition data. Data for deposited particles should be reported in terms of mass or number of particles per unit surface area per unit time.
Assessing the in vitro toxicity of airborne (nano)particles to the human respiratory system: from basic to advanced models
Published in Journal of Toxicology and Environmental Health, Part B, 2023
Maria João Bessa, Fátima Brandão, Fernanda Rosário, Luciana Moreira, Ana Teresa Reis, Vanessa Valdiglesias, Blanca Laffon, Sónia Fraga, João Paulo Teixeira
Overall, the main mechanisms for particle deposition include: interception (particle-surface contact), inertial impaction (particle sudden change in the direction of the flow), gravitational sedimentation (settling of particles under the action of gravity), diffusion (random motions of the particles, e.g. Brownian motion, where randomized particle motion is initiated by their collision with gas molecules), and electrostatic precipitation (particle charge may potentially affect their deposition in the airways) (Bui et al. 2020; Darquenne 2020; Tsuda, Henry, and Butler 2013). As illustrated in Figure 2, larger particles (5–30 μm) are deposited in the nasopharyngeal region by inertial impaction, while smaller particles (1–5 μm) are deposited in the tracheobronchial area by gravitational sedimentation where they may or may not be removed by mucociliary clearance. On the other hand, nano-sized particles (0.1–1 μm) penetrate deeper into the alveolar region, such as the alveoli where airflow is low, deposited by Brownian diffusion or electrostatic attraction (Bakand, Hayes, and Dechsakulthorn 2012; Hagens et al. 2007).
Vacuum cleaner as a source of abiotic and biological air pollution in buildings: a review
Published in Advances in Building Energy Research, 2022
Azad Bahrami, Fariborz Haghighat, Ali Bahloul
Particles generally mostly tend to deposit on upward facing surfaces instead of vertical wall or ceiling. Particle deposition is a function of numerous factors: Particle size, surface characteristics (physical configuration, electrostatic forces, etc.), temperature, air turbulent and physical disturbance (Salmela et al., 2020). For instance, bigger particles in which gravitational mechanism is more dominant deposit on the floors (upward facing surfaces), while smaller particles, on which turbulent and Brownian diffusion is more highlighted, tend to settle on walls and/or ceiling. For particles with diameter less than 100 nm, Lai and Nazaroff improved a semi-empirical model where the effect of Brownian and turbulent diffusion was considered as the main deposition mechanism and expressed deposition velocity for vertical surfaces according to the following equation (Lai & Nazaroff, 2000): where is the deposition velocity, r+ = (dp/2)(u*/ν) in which dp is the particle diameter, u* is the friction velocity and v is the kinematic velocity, ϵp is the particle turbulent diffusivity and D is the Brownian diffusivity.
The influence of wind speed on airflow and fine particle transport within different building layouts of an industrial city
Published in Journal of the Air & Waste Management Association, 2018
Dan Mei, Meng Wen, Xuemei Xu, Yuzheng Zhu, Futang Xing
The influence of complex urban structures on pollutant dispersion has been simulated using computational fluid dynamics, based on the Navier-Stokes equations. Some researchers used large-eddy simulation (Li et al. 2010; Tominaga and Stathopoulos 2011, 2012; Xie and Castro 2009) and others a Reynolds time-averaged approach. However, in these simulations, air pollutants were modeled as gas dispersion, based on an Eulerian method (Nikolova et al. 2014; Wang and Max Zhang 2012; Wang et al. 2013), and particle dynamics were neglected. Particle deposition is the combined result of inertial impaction, turbulence-eddy impaction, interception, gravitational sedimentation, and so on. Therefore, more recently, a discrete-phase, particle trajectory model based on a Lagrangian reference frame (Saidi et al. 2014; Wang, Lin, and Chen 2011; Zhang and Chen 2009) has been used to predict particle transport concentration and suspension characteristics around complex buildings.