Deposition Of Large Particles Research Articles

Composition and Effects of Aerosol Particles Deposited on Urban Plant Leaves in Terrestrial and Aquatic Habitats

Plants play a vital role in mitigating aerosol particles and improving air quality. This study investigated the composition characteristics and potential effects of particles retained on the leaf surfaces of two amphibious plants (i.e., Alternanthera philoxeroides and Hydrocotyle vulgaris) in both terrestrial and aquatic habitats. The results show that plant habitats influenced the composition of aerosol particles retained on leaf surfaces. Specifically, plants in terrestrial habitats retained a higher mass concentration of coarse and large particles rich in inorganic Ca2+, accounting for over 70% of total ions, whereas plants in aquatic habitats retained a greater abundance of fine and secondary particles with high fractions of water-soluble NO3− and SO42−, taking up over 65% of total anions. Secondary particles deposited on the surfaces of plants in aquatic habitats tend to deliquesce and transform from the particle phase to the liquid phase. Terrestrial habitats facilitate the deposition of large particles. Additionally, particle accumulation on leaf surfaces adversely affected the stomatal conductance of plant leaves, leading to reductions in both the transpiration and photosynthetic rates. This study provides insights into the impact and role of plants from different habitats in mitigating urban particulate pollution.

Particle Deposition in Large-Scale Human Tracheobronchial Airways Predicted by Single-Path Modelling.

The health effects of particles are directly related to their deposition patterns (deposition site and amount) in human airways. However, estimating the particle trajectory in a large-scale human lung airway model is still a challenge. In this work, a truncated single-path, large-scale human airway model (G3-G10) with a stochastically coupled boundary method were employed to investigate the particle trajectory and the roles of their deposition mechanisms. The deposition patterns of particles with diameters (dp) of 1-10 μm are investigated under various inlet Reynolds numbers (Re = 100-2000). Inertial impaction, gravitational sedimentation, and combined mechanism were considered. With the increasing airway generations, the deposition of smaller particles (dp < 4 μm) increased due to gravitational sedimentation, while that of larger particles decreased due to inertial impaction. The obtained formulas of Stokes number and Re can predict the deposition efficiency due to the combined mechanism in the present model, and the prediction can be used to assess the dose-effect of atmospheric aerosols on the human body. Diseases in deeper generations are mainly attributed to the deposition of smaller particles under lower inhalation rates, while diseases at the proximal generations mainly result from the deposition of larger particles under higher inhalation rates.

Processing laser ablated plasmonic nanoparticle aerosols with nonthermal dielectric barrier discharge jets of argon and helium and plasma induced effects

Dielectric-barrier-discharge (DBD) plasma jets provide viable state-of-the-art nonthermal processes for a wide range of nanomaterials including particle transport and deposition. We report the interaction of argon and helium plasma jets with the particle aerosol, produced by ns laser ablation of a silver target and subsequently their transport for deposition on a distant substrate. The nanofeatures and functionality of the nanoparticles, entrained and deposited with the two plasma jets were compared using high-resolution electron microscopy, helium ion microscopy, scanning electron microscopy, ultraviolet–visible spectroscopy, and in terms of the SERS effect. The plasma jet facilitates the transport of the particle aerosol under the upshot of plasma ionic wind, caused by the high electric field in the plasma. Compared to the helium plasma jet, the argon plasma jet leads to a relatively large particle deposition and promotes the formation of aggregates. The helium plasma jet enabled the deposition of spatially well dispersed particles. In both cases, the deposited particle was crystalline and plasmonic active. The plasma-driven altered morphology, expedient particle transport, and formation of agglomerates or spatially well dispersed particles are explained in plasma-induced ionic-wind, and dusty plasma framework. The findings are novel and interesting from the perspective of plasma–surface deposition, surface nanoengineering, and nanomaterial processing for applications in sensing, catalysis, surgical tools, futuristic coating technology, and heat-sensible biological activities.

Simulation of particle deposition in a plate-fin heat exchanger using a particle deposition model with a random function method

The particle deposition characteristics of plate-fin heat exchangers were studied using a particle deposition model with a random function method. The effects of the inlet velocity, particle size, and temperature difference on particle deposition and the distribution of the particles deposited in plate-fin heat exchangers were investigated. The simulation results showed that the thermal diffusion–induced motion of small particles was obvious at low velocities, the deposition of large particles was mainly limited by the critical velocity, there was a maximum deposition velocity in particle deposition and the maximum deposition velocity decreases with increasing particle size. Finally, large particles would rebound and deposit after secondary impacts. The temperature difference will increase the average deposition efficiency of 1 μm particles, and reduce the average deposition efficiency of 7 μm particles. The plate-fin heat exchanger should be designed with consideration for the particle size range and velocity seen in the intended application.

Combined Influence of Meso- and Macroporosity of Soft-Hard Templated Carbon Electrodes on the Performance of Li-O2 Cells with Different Configurations.

Li-O2 batteries can offer large discharge capacities, but this depends on the morphology of the discharged Li2O2, which in turn is strongly affected by the nanostructured carbon used as support in the air cathode. However, the relation with the textural parameters is complex. To investigate the combined effect of channels of different sizes, meso-macroporous carbons with similar mesopore volume but different pore size distribution were prepared from the polymerization of resorcinol-formaldehyde (RF) in the presence of surfactants and micro-CaCO3 particles. The carbon materials were used as active materials of air cathodes flooded by ionic liquid-based electrolytes in Li-O2 cells with two different configurations, one with a static electrolyte and the other with a stirred electrolyte, which favor a film-like and large particle deposition, respectively. The presence of large pores enhances the discharge capacity with both mechanisms. Conversely, with respect to the reversible capacity, the trend depends on the cell configuration, with macroporosity favoring better performance with static, but poorer with stirred electrolytes. However, all mesoporous carbons demonstrated larger reversible capacity than a purely macroporous electrode made of carbon black. These results indicate that in addition to pore volume, a proper arrangement of large and small pores is important for discharge capacity, while an extended interface can enhance reversibility in Li–O2 battery cathodes.

The role of fine sediment characteristics and body size on the vertical movement of a freshwater amphipod

Abstract Sedimentation and clogging (colmation) of interstitial pore spaces with fine sediment particles is widely considered to be one of the most significant threats to lotic ecosystem functioning. This paper presents the results of a running water mesocosm study examining the effect of benthic and hyporheic fine sediment loading and particle size on the vertical movement and distribution of the freshwater amphipod Gammarus pulex. A gradient of fine sediment loading and different particle sizes were used to examine the ability of G. pulex from two body size classes to access and migrate vertically within subsurface sediments. We tested three hypotheses: (a) sediment loading would modify the distribution of G. pulex by limiting vertical movement; (b) the deposition of large particles and heterogenous sediments would limit the vertical movement of individuals more than homogeneous fine‐grained sediments; and (c) large bodied individuals would be prevented from migrating vertically with increasing sediment loading and particle size/heterogeneity. Sediment loading, particle size and heterogeneity of deposited sediment had a significant effect on the vertical movement of individuals, with heterogeneous sand (0.125–4 mm) acting as the strongest barrier to the vertical movement of individuals through the infilling and clogging of interstitial spaces followed by coarse (1–4 mm) and fine sand (0.125–4 mm). Fine sediment loading and particle size acted as a filter on body size and limited the ability of large bodied individuals to migrate vertically to a greater extent than small bodied individuals. This study demonstrates that the effects of fine sediment on habitat availability and faunal movement is dependent on both sedimentological characteristics and an individual's body size. The results illustrate the importance of both abiotic and biotic factors when evaluating the ecological effects of fine sediment deposition.

Dynamic analysis of self-forming dynamic membrane (SFDM) filtration in submerged anaerobic bioreactor: Performance, characteristic, and mechanism

This study attempts to provide an improved fundamental understanding of the self-forming dynamic membrane (SFDM) filtration process in submerged anaerobic bioreactors. Excellent system performances were achieved in terms of high COD removal efficiency (∼ 90%), fast formation/reformation of SFDM (<1 h), and sustainable low-resistance (3.92 × 1010 m−1) high-flux (10–30 L/m2·h) filtration. A typical flux-variation profile consisted of an initial abruptly fast decrease followed by a gradually slow reduction, corresponding to the formation and sustainable operation period, respectively. The increase of SFDM resistance in formation period was attributable to the fast deposition of large particles on coarse-pore support materials. After SFDM formation, the subsequent increase of SFDM resistance was controlled more by the increase of specific resistance, which was firstly mainly resulted from the increasing accumulation of small particles with higher hydrophobicity and the external deposition of eEPS but later most attributable to the increase of internal release of eEPS.

Direct numerical simulation of polydisperse aerosol particles deposition in low Reynolds number turbulent flow

Aerosol behaviors have a great effect on the evaluation of the leak rate of the coolant in the concept of Leak Before Break (LBB) in the Nuclear Power Plant (NPP) as the coolant will be released into the containment mainly in the form of aerosols if there exists a leak in the primary loop. The transportation and deposition of aerosol particles strongly affect the accuracy of evaluating the leakage source term. In this paper, direct numerical simulation coupled with Lagrangian particle tracking is proposed aiming at the transportation and deposition of polydisperse micron-sized particles in low Reynolds number turbulent horizontal flow. Results are validated by several theoretical and empirical equations. The study reveals the diffusion and deposition mechanism of particles with different sizes. It indicates that gravity plays a main role in the deposition of large particles (dp > 10 μm) in the low Reynolds number turbulent flow (Re < 6000). For small particles, deposition is mainly determined by the turbulence and Brownian motion. The size distribution of the deposited particles is different with the initial particle size distribution, which indicates that the particle size distribution in the containment may be not the same as the leaked particle size distribution.

A numerical study of particle deposition in HTGR steam generators

The present study numerically investigated the graphite particle deposition in the steam generator of a pebble-bed high-temperature gas-cooled reactor (HTGR) and discussed the effect of size and velocity of particles on turbulent and thermophoretic depositions. Turbulent closure is achieved by Reynolds stress transport equations and particle motions were simulated by a discrete particle model with rebound boundary by user-defined functions to determine deposition. The results showed that turbulent deposition plays the dominant role for large particle deposition, while thermophoretic deposition is the main factor causing small graphite dust particles to deposit on the wall. It also indicated that the particles with dimensionless relaxation time near 1 are the most deposited.

Study of formation damage caused by retention of bi-dispersed particles using combined pore-scale simulations and particle flooding experiments

The infiltration of solid particles (fines) into a reservoir during drilling or water reinjection is a long-standing problem in the petroleum industry because of the associated production decline or injectivity loss. Solid particle infiltration is also an active area of research in other fields such as waste water treatment and fines migration in clay-rich reservoirs.In this work, we perform experiments to study particle infiltration into sintered glass bead core plugs and measure the changes in porosity and permeability using computed tomography (CT) scanning and pressure transducers, respectively. Suspensions of prescribed bimodal particle sizes, concentrations, and flowrates are flooded through the core plugs. Permeability changes are measured continuously over time, and the porosity change is measured after flowing a fixed mass of invaded particles.A dual pore-scale numerical model approach (a combination of a direct pore-scale discrete element method (DEM) and a pore-scale network model) is used to predict permeability reduction by particle filtration in porous media. Large particle deposition is modeled using the DEM in a disordered sphere pack geometry; the result is a prediction of deposition as a function of large particle concentration. Small particle deposition is modeled using the network model; the result is a prediction of deposition as a function of small particle concentration. Crucially, the geometry of the network model depends on the amount of large particles deposited. In this way, the deposition of large and small sized particles is coupled together.The permeability and porosity reduction of the network due to the deposition of small and large particles are then calculated from the functions above. We compare the experimental results with simulation predictions and find that the dual pore-scale model is capable of predicting the permeability of the invaded core in the regions away from the injection face. Permeability prediction in the region adjacent to the injection face is improved by incorporating the influence of the external filter cake.

The characterization of haboobs and the deposition of dust in Tempe, AZ from 2005 to 2014

Abstract Dust storms known as ‘haboobs’ occur in Tempe, AZ during the North American monsoon season. This work presents a catalog of haboob occurrence over the time period 2005–2014. A classification method based on meteorological and air quality measurements is described. The major factors that distinguish haboobs events from other dust events and from background conditions are event minimum visibility, maximum wind or gust speed, and maximum PM10 (particulate matter with aerodynamic diameters of 10 μm or less) concentration. We identified from 3 to 20 haboob events per year over the period from 2005 to 2014. The calculated annual TSP (total suspended particulate) dry deposition ranged from a low of 259 kg ha−1 in 2010 to a high of 2950 kg ha−1 in 2011 with a mean of 950 kg ha−1 yr−1. The deposition of large particles (PM>10) is greater than the deposition of PM10. The TSP dry deposition during haboobs is estimated to contribute 74% of the total particulate mass deposited in Tempe.

Deposition of particles in liquid flows in horizontal straight channels

A flow in a horizontal channel is an important method for the transport of materials, products and/or waste gases/liquids. The deposition of particles in a horizontal channel may clog the flow path. The purpose of this paper is to extend the use of a developed Eulerian deposition model to liquid flows in horizontal straight channels to predict the particle deposition rate. For a horizontal pipe, the deposition rates may differ greatly along a cross section, due to the influences of gravity and buoyancy. The current deposition model is first applied to air flows to enable a comparison with available experimental data. Then, the model is applied to liquid flows in horizontal straight pipes. The effects of gravity, buoyancy, water flow rates, wall roughness, particle size and temperature difference in the near-wall boundary layer on the deposition rate have been studied and explained. The results show that the deposition rates of particles increase with an increased flow rate. The gravity separation has a large influence on the deposition of large particle at high and low parts of the horizontal pipe in some flows. Moreover, both the wall roughness and thermophoresis have a significant influence on the deposition rate of small particles. In addition, the roughness also shows an important influence on the large particle deposition at the top of the investigated pipe, due to that a large value of roughness can make the deposition location somewhat far away from the wall, where a stronger turbophoresis exists. The intensity of the turbophoresis relative to the gravity separation before a particle is reaching the deposition location is important for the large particle deposition when the gravity separation play a negative role on the deposition rate.

Thermophoretic and turbulent deposition of graphite dust in HTGR steam generators

The present study calculated the graphite dust deposition in the steam generator of HTGR by using a thermophoretic deposition model and a turbulent deposition model based on the temperature and flow field distributions calculated by a computational fluid dynamics (CFD) model. The results showed that the heat flux along the heat transfer surface was not evenly distributed which affect the particle deposition. Thermophoretic deposition is the main factor causing small graphite dust particles to deposit on the surface while turbulent deposition plays the dominant role for large particle deposition. The results also indicate that the deposited particles are mainly small graphite dust particles in steam generator when the reactor is running at low power, with both small and large graphite dust particles at high reactor power levels with fewer medium size particles.

Size distribution and optical properties of mineral dust aerosols transported in the western Mediterranean

Abstract. This study presents in situ aircraft measurements of Saharan mineral dust transported over the western Mediterranean basin in June–July 2013 during the ChArMEx/ADRIMED (the Chemistry-Aerosol Mediterranean Experiment/Aerosol Direct Radiative Impact on the regional climate in the MEDiterranean region) airborne campaign. Dust events differing in terms of source region (Algeria, Tunisia and Morocco), time of transport (1–5 days) and height of transport were sampled. Mineral dust were transported above the marine boundary layer, which conversely was dominated by pollution and marine aerosols. The dust vertical structure was extremely variable and characterized by either a single layer or a more complex and stratified structure with layers originating from different source regions. Mixing of mineral dust with pollution particles was observed depending on the height of transport of the dust layers. Dust layers carried a higher concentration of pollution particles below 3 km above sea level (a.s.l.) than above 3 km a.s.l., resulting in a scattering Ångström exponent up to 2.2 below 3 km a.s.l. However, the optical properties of the dust plumes remained practically unchanged with respect to values previously measured over source regions, regardless of the altitude. Moderate absorption of light by the dust plumes was observed with values of aerosol single scattering albedo at 530 nm ranging from 0.90 to 1.00. Concurrent calculations from the aerosol chemical composition revealed a negligible contribution of pollution particles to the absorption properties of the dust plumes that was due to a low contribution of refractory black carbon in regards to the fraction of dust and sulfate particles. This suggests that, even in the presence of moderate pollution, likely a persistent feature in the Mediterranean, the optical properties of the dust plumes could be assumed similar to those of native dust in radiative transfer simulations, modelling studies and satellite retrievals over the Mediterranean. Measurements also showed that the coarse mode of mineral dust was conserved even after 5 days of transport in the Mediterranean, which contrasts with the gravitational depletion of large particles observed during the transport of dust plumes over the Atlantic. Simulations with the WRF mesoscale meteorological model highlighted a strong vertical turbulence within the dust layers that could prevent deposition of large particles during their atmospheric transport. This has important implications for the dust radiative effects due to surface dimming, atmospheric heating and cloud formation. The results presented here add to the observational data set necessary for evaluating the role of mineral dust on the regional climate and rainfall patterns in the western Mediterranean basin and understanding their atmospheric transport at global scale.

A One-D approach for modeling transport and deposition of Black Powder particles in gas network

Black Powder (BP) is a universal issue in sales gas transmission pipelines. It can cause serious problems in pipelines operations and instruments and contaminate customer supply. The objective of the present study is to develop a novel methodology for tracking the dispersion of Black Powder within gas transmission pipelines using a 1D approach based on the dusty gas assumption and the usage of analytical solutions of one-dimensional scalar advection/reaction equation. The study takes into account the deposition of Black Powder particles under different flow conditions, different particle diameters and different surface roughness. The proposed approach is applied to particle-laden flow in pipe segments with and without junctions and contrasted against CFD simulations based on the Discrete Phase Model (DPM). The results show that the finer particles with diameters dp < 1 (μm) can be transported easily to the downstream of the tree shaped network, while the larger particles dp > 1 (μm) are likely to settle rapidly near to the source location where Black Powder is generated and, consequently, forming beds. It is shown also that surface roughness increases the deposition rate of small particles dp ≤ 1 (μm) controlled by the Brownian forces. However, the deposition of larger particles in the inertial regime is not affected by the change in the surface roughness. These reported results are of significant practical interest, due to the lack of available data of Black Powder concentration in natural gas networks that have been reported in the literature to date.

CFD investigation on particle deposition in aligned and staggered ribbed duct air flows

This study investigated the effects of surface rib arrangements on particle deposition in two-dimensional ribbed duct air flows by CFD method. The turbulent duct air flows were simulated by Reynolds stress model (RSM) with UDF correction, and the particle motions were solved by discrete particle model (DPM). The surface ribs were arranged in aligned or staggered layouts. The air velocity profiles for both smooth and ribbed duct flows as well as the particle deposition velocity for smooth duct cases were all in good agreement with the relative literature data. The simulation results showed that the surface ribs with aligned arrangement have better performance on small particle deposition enhancement, compared with staggered surface ribs. Nevertheless, the large particle deposition rates are not enhanced obviously by both kinds of surface ribs. Considering the flow drag increase, the maximum particle deposition enhancement can reach 425 times for particles with 1 µm diameter. Finally, the mechanisms of particle deposition enhancement by aligned and staggered surface ribs were analyzed and discussed from the views of rib interception, deposition area increase, turbulent eddy capture and the flow passage width. Surface ribs with aligned arrangement are recommended to be applied in particle removal and air clean devices.

Numerical study of solid particles motion and deposition in a filter with regular and irregular arrangement of blocks with using Lattice Boltzmann method

In this investigation, motion and deposition of solid particles in regular and irregular structure filters have been studied. This study compares deposition efficiency of particles in two structures and investigates effects of Lift and Brownian forces on particles deposition. The laminar flow field in the filter is simulated using Lattice Boltzmann method and then motion of solid particles is investigated. The motion of particles is simulated using the Lagrangian method. The Lift, Drag, Brownian and Gravity forces affect particles motion. It is concluded that the Brownian force affects the motion and deposition of 0.01–0.1μm diameters particles in both of structures. A few numbers of the small particles are deposited on the blocks walls, but it is increased by decreasing Stk Number from 10−5 to 10−6 due to the effect of Brownian force on deposition of small particles. The Lift force has no significant effect on the deposition of particles in the investigated range of sizes, but ignoring this force increases the deposition efficiency of very small particles in both of structures of filters. The deposition efficiency has a rapid increasing for Stk Number greater than 0.1, due to the effect of inertial impaction on deposition of large particles. Regular filter has a more deposition efficiency for small particles (less than 15μm diameters) and irregular filter is more suitable for filtering large particles (more than 15μm diameters). The deposition efficiency on the surface of block in the channel containing a single block is more than regular and irregular structure filters. Finally, it is obtained that most of the particles deposited on the first block in the filter.

On the deposition of particles in liquid metals onto vertical ceramic walls

The deposition of non-metallic particles in liquid-metal flows is a serious industrial problem because the build-up of particles on ceramic walls clogs the flow path and interrupts the production, and this leads to large economic losses. This paper is an effort to extend the current state-of-the-art knowledge of particle deposition in air in order to predict particle deposition rates in liquid-metal flows using an improved Eulerian deposition model and considering Brownian and turbulent diffusion, turbophoresis and thermophoresis as transportation mechanisms. The model was used to predict the rate of deposition of particles in an air flow, and the predictions were compared to published measurements to demonstrate its performance. The model was then modified to take into account the differences in properties between air and liquid metals and thereafter applied to liquid-metal flows. Effects on the deposition rate of parameters such as steel flow rate, particle diameter, particle density, wall roughness and temperature gradient near the wall were investigated. It is shown that the steel flow rate has a very important influence on the rate of deposition of large particles, for which turbophoresis is the main deposition mechanism. For small particles, both wall roughness and thermophoresis have a significant influence on the particle deposition rate. Particle deposition rates under various conditions were successfully predicted.

Effect of Modified Silica Abrasive Particles on Nanosized Particle Deposition in Final Polishing of Silicon Wafers

The silane coupling agent γ-aminopropyl triethoxysilane (APTS) and polyethylene oxide (PEO) are proposed to modify the SiO2 abrasive particles for final polishing of silicon wafers. The effects of the modified silica abrasive particles on nanosized particle deposition, roughness, and removal rate of the silicon wafer are explored in detail. PEO is proved to be a potential modifying agent for controlling deposition of large particles (∼410 nm diameter), leading to low roughness (Ra = 0.097 nm), and APTS is found to be effective in controlling deposition of both large and small particles (∼410 and ∼200 nm diameter, respectively), resulting in lower roughness (Ra = 0.054 nm).

Modelling of Straitened Sedimentation Process in Bidisperse Suspension with Inter-Fractional Coagulation

In this paper we study the general characteristics of deposition of large particles (or aggregates) that result from the mutual aggregation of small and large fractions in bidisperse (or double fractional) suspension. We give equations of motion and change in mass of the large particle in the presence of inter-fractional coagulation process and effect of straitened sedimentation. In the limiting Stokes and Newton modes (relevant for small and large Reynolds numbers) we have movement formulas for speed of sedimentation and their analysis. Discuss some of the results of calculations obtained by numerical integration of the equations of motion of a large particle in suspension.