Deposition Behavior Of Particles Research Articles

An investigation of the filtration performance and mechanism of oil-solid mixed particles on filter materials with different wettability

In the process of air filtration, filter materials may encounter oil-solid mixed particles from various sources such as industry and household, and the influence of filter material with different wettability on the filtration performance of oil-solid mixed particles has not been fully reported. The objective of this study was to prepare filter materials with varying wettability properties and investigate their filtration performance for oil-solid mixed particles with diverse oil contents. In this study, four filter materials were prepared using the impregnation method, exhibiting 0° (superoleophilic), 46° (oleophilic), 90° and 122° (oleophobic) oil contact angles. The oil-solid mixed particles with varying oil contents were loaded on the four different filter materials. The loading behavior of the filter materials was characterized from two aspects: macroscopic loading behavior (changes in pressure drop and DHC) and microscopic particle deposition behavior. The results demonstrated that, under the conditions of 25% and 50% oil content, the enhanced liquid bridge force between the oil-solid mixed particles on the oleophobic filter material facilitated the formation of a loose and porous cake layer structure compared with other filter materials, resulting in a lower growth rate of pressure drop and a higher dust holding capacity (DHC). However, in 75% and 100% oil content environments, the superoleophilic filter material owned a remarkably high affinity for oil particles compared with other filter materials, leading to the gradual formation of an oil film structure on the filter material, yielding lower the growth rate of pressure drop and higher DHC. These findings shed light on the mechanism of particle deposition under diverse filtration conditions and are applicable to the filtration of various oil-solid mixed particles over a wide range of oil contents.

Effects of deposited microstructure on wear behaviors of detonation sprayed Fe-based amorphous coatings

Fe-based amorphous coatings (AMCs) were deposited using the detonation spray at varying spraying distances. The study aimed to characterize the deposition morphologies and elemental composition of splats for single shots under different spraying distances. Additionally, the relationship between spraying distance, particle deposition behavior, spreading morphology, and wear behavior of the coatings was comprehensively discussed. The results indicate that modifying the spraying distance affects the melting state of spray particles, thereby influencing the morphology of deposition and determining the coating's microstructure. Larger spraying distances result in reduced deposition efficiency and lead to particles depositing in a manner similar to cold spraying, resulting in an uneven coating structure with higher porosity. Consequently, the coating becomes more susceptible to fatiguedelamination wear. Conversely, a moderate spraying distance leads to full melting and acceleration of powders, results in good spreading and the formation of a uniform and dense laminar structure.

Numerical Study of Gangue Slurry Deposition Behavior in Pipelines Considering Viscosity Change

Pipeline conveying is a crucial method for realizing gangue slurry filling. In order to avoid the blockage of gangue slurry in pipeline conveying, it is necessary to clarify the deposition behavior of gangue particles in the pipeline. This paper analyzes coal gangue’s microstructure and mineral composition in the Zhaozhuang No. 2 coal mine through electron microscope scanning and X-ray diffraction tests. We studied the viscosity characteristics of gangue slurry at different mass concentrations and particle sizes and analyzed the change rule of viscosity of gangue slurry with time. Based on determining the nature of the slurry material, a simulation analysis of the deposition behavior of the gangue slurry in a pipeline was carried out using the coupled fluid dynamics–discrete element (CFD-DEM) method. The results show that gangue slurry with a particle size larger than 1.0 mm is likely to lead to the blockage of the pipeline. A small increase in viscosity will promote a uniform distribution of particles inside the pipeline. The deposition behavior of particles is jointly influenced by gravity, fluid interaction force, inter-particle force, and the interaction between particles and the pipeline surface. The research results can be used as a reference for the design and study of gangue slurry grouting systems.

Influence of nonuniform electric field due to a spherical collector on the particles dynamics in quiescent air

This study investigates particle dynamics impacting a charged spherical collector through experiments and simulations, revealing the influence of the collector’s non-uniform potential field. Electrostatic and drag forces govern trajectories, while gravity and dielectrophoretic forces play a minor role. Positive electrostatic and negative drag work are comparable, offering critical insights into particle energy budgets. Closer proximity to the collector center leads to a greater energy budget, causing uneven particle collection. Analysis of fractional energy loss indicates a critical point where electrostatic work dominates over viscous dissipation. This analysis is crucial for analyzing particle deposition behavior in non-uniform electric fields.

Experimental study on particle deposition of Fe3O4 in supercritical heat exchange tube

Particle deposition poses a significant challenge to the economics and safety of supercritical boilers. Understanding the deposition behavior of particles on the steam-water side wall is essential. A supercritical particle deposition system was designed and build according to the actual conditions. The effects of fluid thermal state, flow rate and exposure time on particle morphology, deposition layer morphology and deposition distribution were investigated. The results showed that FeCl2 was oxidized to micron sized Fe3O4 particle, and the salt crystals had a redissolution behavior in supercritical water. The particle deposition layer was a three-layer structure, possibly related to the gas-like fluid clusters and turbulence. The deposition distribution was related to the flow state, and there was a forward shift of the peak point with exposure time. Our results help to understand the particle deposition behavior in supercritical heat exchangers.

Understanding the effects of inhaler resistance on particle deposition behaviour – A computational modelling study

Background and objectiveUnderstanding the impact of inhaler resistance on particle transport and deposition in the human upper airway is essential for optimizing inhaler designs, thereby contributing to the enhancement of the therapeutic efficacy of inhaled drug delivery. This study demonstrates the potential effects of inhaler resistance on particle deposition characteristics in an anatomically realistic human oropharynx and the United States Pharmacopeia (USP) throat using computational fluid dynamics (CFD). MethodMagnetic resonance (MR) imaging was performed on a healthy volunteer biting on a small mockup inhaler mouthpiece. Three-dimensional geometry of the oropharynx and mouthpiece were reconstructed from the MR images. CFD simulations coupled with discrete phase modelling were conducted. Inhaled polydisperse particles under two different transient flow profiles with peak inspiratory flow rates (PIFR) of 30 L/min and 60 L/min were investigated. The effect of inhaler mouthpiece resistance was modelled as a porous medium by varying the initial resistance (Ri) and viscous resistance (Rv). Three resistance values, 0.02 kPa0.5minL−1, 0.035 kPa0.5minL−1 and 0.05 kPa0.5 minL−1, were simulated. The inhaler outlet velocity was set to be consistent across all models for both flow rate conditions to enable a meaningful comparison of models with different inhaler resistances. ResultThe results from this study demonstrate that investigating the effect of inhaler resistance by solely relying on the USP throat model may yield misleading results. For the geometrically realistic oropharyngeal model, both the pressure and kinetic energy profiles at the mid-sagittal plane of the airway change dramatically when connected to a higher-resistance inhaler. In addition, the geometrically realistic oropharyngeal model appears to have a resistance threshold. When this threshold is surpassed, significant changes in flow dynamics become evident, which is not observed in the USP throat model. Furthermore, this study also reveals that the impact of inhaler resistance in a geometrically realistic throat model extends beyond the oral cavity and affects particle deposition downstream of the oral cavity, including the oropharynx region. ConclusionResults from this study suggest that key mechanisms underpinning the working principles of inhaler resistance are intricately connected to their complex interaction with the pharynx geometry, which affects the local pressure, local variation in velocity and kinetic energy profile in the airway.

Identification and prediction of hydrate–slug flow to improve safety and efficiency of deepwater hydrocarbon transportation

The vast hydrocarbon resources (oil, gas, and gas hydrate) in deepwater areas are considered one of the most significant resources of the future. However, the dangerous flow patterns and blockage accidents caused by hydrates threaten the safety and efficiency of the transportation process. A mutual interaction exists between hydrate growth and multiphase flow. In this study, hydrate formation and gas–slurry two–phase flow tests were conducted in a pure water system with a constant pressure (4 MPa) and various liquid loadings (40–80%) in a visual flow loop. It was found that the hydrate growth process in the dynamic system included bubble promotion, subcooling promotion, and mass transfer inhibition. Meanwhile, two atypical slug patterns (rapid conversion slug and deposition slug) in the vertical upward flow were determined, which corresponded to the promotion and inhibition regions. In the rapid conversion slug flow, the churn segments replaced the original Taylor bubbles when the liquid loading was less than 60%. In the deposition slug flow, slurry shedding phenomena was observed. In addition, the hydrate particle deposition behavior was found to inhibit hydrate growth and cause flow pattern shifts, but did not trigger the differential pressure surge. The gas isolation caused by the liquid plug and energy dissipation due to the collision between hydrate particles and the tube wall may be responsible for the sudden increase in pressure drop. Furthermore, the feasibility of predicting hydrate blockage using the differential pressure method was explored. The experiment results showed that this warning method was effective when the liquid loading was below 76%. And an effective warning can improve the transport capacity by approximately 34%.

Use of hybrid filters to optimize the process of the filtration in cement particles

Due to growing concern about air pollution and its harmful effects on the health of the population, especially in regard to sub-micrometric particles, some studies have reported that applying an electric field to particle suspensions can improve filter performance by enhancing the deposition of particles in the filter medium. This can result in better particulate retention, which is particularly important for industrial processes such as cement production. The objective of this study was to investigate the behavior of cement particles with electrostatic charges during cake formation in fabric filters. The particles (with a d50 % of 17 μm) were generated using a dust feeder at a flow rate of 0.083 kg s−1. The fiberglass filter medium was subjected to filtration tests with constant dust concentrations (9–12 g.m−³) and air surface velocities (6 cm.s−1and 10 cm s−1) until the pressure drop reached the maximum value of 400 Pa. The electrostatic precipitator utilized discharge voltages of 0, 4, 10, and 12 kV. The particles were initially passed through the electrostatic precipitator to become charged with voltages of 0, 4, 10, and 12 kV applied. The results indicated a reduction in pressure drop of up to 55 %. The study observed a change in the deposition behavior of particles on the filter medium surface and in the filter cake formation, demonstrating that the electrostatic charge improves air filtration performance, resulting in higher efficiency and cost-effectiveness.

Improving the CFD predictive accuracy of particle fate in turbulent duct flows: Four key issues and applications in in-duct UVGI system

In order to refine the CFD methodology for predicting particle fate in duct flows, this study investigated four key issues largely influencing the predictive accuracy. The flow field modeling method applicable to in-duct UVGI systems (ID-UVs) was also investigated. The particle number independence test indicated that at least 30000 particles should be released. The use of 2D duct cannot consider particle trapping at the sidewalls, thus underestimating the particle deposition behavior. The two-equation k‐ε models significantly overestimated the fluctuation velocity perpendicular to the duct walls in the near-wall region, resulting in them providing Vd+ and η were on average 1767.9 % and 451.3 % higher than those predicted by the RSM model, respectively. Corrections for fluctuation velocity had very limited benefit in improving the predictive accuracy of the two-equation k‐ε model, which unexpectedly resulted in a decrease in the predictive accuracy of the RSM model. Therefore, it was recommended to use the uncorrected RSM model to predict the 3D duct flow field to obtain a high prediction accuracy of particle fate. Similarly, the RSM model was also recommended for modeling the flow field in ID-UVs instead of the two-equation k‐ε model that was often used. This study also revealed that missing the “Wall Reflection Effects” would lead to confusing results and analyzed the reasons for the quantitative differences in the results obtained in previous studies. The findings presented may form a CFD methodological framework for further investigation of the in-duct air purification technologies.

Preparation, nano-mechanics and particle deposition behavior of thin, antifouling hydrogel coatings

Hydrogels based on hydrophilic, crosslinked polymer networks can reduce surface contamination in aqueous environments and continue attracting research interest due to their low adhesion, biocompatibility and tunable properties. In particular, sub-micron hydrogel films can potentially screen a surface from interaction with foulant colloids and microorganisms without compromising original functions, such as water permeation in membranes. This study focuses on the preparation of thin hydrogel films with the goal of understanding their adhesive and micromechanical properties, as well as factors affecting the dynamics of microparticle deposition on such films, mimicking the initial stages of surface fouling with colloids, microparticles and microorganisms. For this purpose, a simple procedure was developed to simultaneously crosslink and covalently anchor multi-arm-PEG precursors to a surface to form a submicron coating as a representative model. The effects of synthetic parameters and external conditions on adhesion and viscoelasticity were studied by force spectroscopy using polystyrene colloidal probes. The same particles were also employed in macroscopic deposition experiments in a parallel plate flow cell under identical solution conditions. Microscopic adhesion and elasticity were unaffected by the hydrogel crosslinking density and by salinity, but strongly affected by solution pH and dwell time, whereas macroscopic deposition was strongly affected both by salinity and by pH. These differences were ascribed to the effect of long-range double-layer forces, involved in deposition but absent in measurements of adhesion and elasticity. The results highlight the differences and similarities between the two types of measurements and underlying phenomena, as a step towards the understanding and rational design of soft antifouling coatings.

Dust deposition mechanism and output characteristics of solar bifacial PV panels.

The utilization of solar photovoltaic (PV) power generation represents a highly promising technological solution for addressing environmental challenges and energy crises. Dust deposition on the front and back surfaces of solar bifacial PV panels greatly decreases the optical performance and power generation. In this study, the dust deposition characteristics and mechanism of solar bifacial PV panels are investigated using the CFD-DEM method. The effects of the dust deposition rate on the output characteristics of bifacial PV panels are discussed. The research results show that the particle deposition behaviors on the back and front surfaces of bifacial PV panels are influenced by the deposition and separation forces at the left or right inlets. The dust deposition rate of windward surfaces can be 1.48-7.60 times that of the leeward surfaces of bifacial PV panels. The particle motion trajectories on the windward and leeward sides can be mainly divided into five and three kinds, respectively. The dust deposition rate of bifacial PV panels increases when the air inlet velocity decreases and the particle size and concentration and relative humidity increase. The open circuit voltage and short circuit current of bifacial PV panels decreased by 26.7% and 16.4%, respectively, when the dust deposition rate increases by 45.8%. The attenuation rate of the maximum output power of PV panels has a positive linear correlation with the dust deposition rate, as shown in Eq. 22. The bifacial PV panels have better output characteristics than the mono-facial PV panels with consideration of dust deposition.

Evolution of particle deposits at communicating membrane pores during crossflow filtration

Understanding the influence of operating conditions on fouling is a great challenge in crossflow membrane filtration since it is determined by a complex interplay between the shear force of the crossflow and the drag toward the membrane arising from the applied trans-membrane pressure. This study uses a coupled CFD-DEM approach to simulate the motion and deposition behavior of monodisperse spherical particles within a membrane-mimicking geometry. Trans-membrane pressure and crossflow velocity are varied to reveal their respective influence on different aspects of fouling at a pore scale. A visual analysis of the simulation results demonstrates distinct behavior regarding the initial deposition of particles and the resulting filter cake morphology, which can be attributed to defined phenomena. Additionally, quantitative data reveals that the dynamic fouling behavior is dominated by the applied crossflow velocity, while the resistance to the removal of particles by crossflow and the level of flux decline is mainly influenced by the trans-membrane pressure. This study links visual pore-scale phenomena to macroscopic filtration quantities, not only underlining the importance of pore-scale investigations but also narrowing the gap between pore-scale events and the filtration process.

Numerical analysis of catalyst particle deposition characteristics in a flue gas turbine with an improved particle motion and deposition model

To more accurately understand and predict the deposition behavior of catalyst particles in the flue gas turbine cascade, test and numerical combined study is performed in this paper. Based on the systematic analysis of the deposition process and physical mechanism of the catalyst particles, the traditional DRW model, critical velocity particle deposition model and removal model were corrected with the user defined function custom function and validated with the actual deposition morphology. On this basis, the effects of the particle Stokes number and flue gas parameters on the particle deposition characteristics of the flue gas turbine cascade were detailed investigated. The results show that the revised DRW model, critical velocity and removal model can more accurately predict the deposition location and deposition rate of particles in the turbine cascade. With the increase in the Stokes number of particles, the average particle impact rate on the blade surface gradually increased, while the average deposition rate showed a trend of first increasing and then decreasing. The average deposition rate of particles in the rotor blade surface is roughly twice as high as that in the stator surface. With the increase of the flue gas expansion ratio, the deposition rate of particles less than 3 μm gradually increases, while the deposition rate of particles greater than 3 μm tends to decrease. In addition, the change in the flue gas expansion ratio has no obvious effect on the particle deposition distribution in different size ranges.

Numerical research on the particle transport and deposition in the impingement-film cooling passage

With the aim of exploring the particle transport and deposition characteristics in the internal cooling channel of turbine blades, the computational fluid dynamics-discrete element method is used to implement the numerical simulation of particle transport and deposition in the impingement-film cooling passage. First, the unsteady development process of the particle transport and deposition with the increase in injection particle mass is obtained. Then, the effect of jets Reynolds number, particle Stokes number, and initial particle volume fraction on the particle deposition characteristics is presented. Finally, the particle deposition mechanism in the impingement-film cooling passage of turbine blades is revealed. The results show that the conical-shape particle deposition layer is formed at the impingement stagnation point region and the banded-shape particle deposition layer is formed between adjacent impingement holes. The cooling gas carrying particles is injected from the impact hole and subjected to the fluid shear force. Then, the cooling gas carrying particles gradually developed into the conical-shape free jets. In addition, the symmetrical vortex structure is formed due to the collision of the adjacent jets. Therefore, the particle deposition layer is formed on the impingement target surface, which is caused by the energy attenuation due to the continuous collision of the particle with the particle and the particle with the wall. The increase in the jets Reynolds number inhibits the particle deposition behavior, and the increase in the Stokes number accelerates the particle deposition behavior.

Numerical simulation of wear particle deposition in ferrograph based on coupled analysis of magnetic, fluid and solid field

Ferrography is a significant means of wear particle detection for mechanical equipment. In view of the issue that the wear particle deposition process by a ferrograph is difficult to accurately adjust to avoid accumulation or escape, the deposition behavior of wear particles coupled with the magnetic, fluid and solid field in a ferrograph is studied by the finite element method. The wear particle force and its deposition principle are first analyzed, and the theoretical deposition law is obtained. By building 3D finite element model, setting the magnetic, flow field and wear particle parameters, the coupled simulation based on the particle tracking is carried out. According to the process of wear particles flowing out of the oil tube and then depositing on the ferrogram slide, the effect of oil pressure, viscosity, density, ferrogram slide inclination angle, distance between oil tube and ferrogram slide and the particle release mode on the particle deposition behavior is studied. Based on the velocity and displacement of particles, the reasonable parameter ranges are obtained, and the sensitive variables are determined. In order to verify the numerical law through experiments, the area and perimeter of wear particles are adopted, meanwhile the oil viscosity is selected as the adjustable parameter, and the tested results prove the numerical simulation correct.

A unified model of slagging particle deposition behavior with thermophoresis and dynamic mesh based on OpenFOAM

This study used a unified algorithm to calculate the deposition process of slagging particles by coupling five sub-models and revising thermophoretic force and particle adhesion models based on dynamic mesh technology. The model predicted deposition thickness with an error of 7.66%. Results showed that thermophoretic forces can extend slagging particle transport range and facilitate the impact of particles below 18 μm on the probe, with impact and deposition efficiencies of 55% and 15%, respectively. Particles sized 25–40 μm and with 0.004–0.007 mJ energy are easily captured by the probe, and escaped particles have a temperature 100 K lower than deposited particles. Moreover, the deposition process of slagging particles is significantly staged with the properties of the deposited particles at different stages corresponding to the initial and sintered deposition layers. Average particle size within the second stage (40–100 min) was higher than that of the first stage (0–40 min) with 32 and 27 μm, but the average particle temperature was lower than that of the first stage with 1280 and 1320 K, which is an important reason of deposition stratification.

On the balance of hydrophilicity and electrostatic interactions during particle filtration and backwash at microfiltration pores

Colloidal fouling is a notoriously limiting factor in many membrane processes. Although intensely studied in mostly macroscopic filtration systems, the underlying phenomena leading to generally decreased fouling remain unknown. This study systematically investigates fouling and backwashing of anionic polystyrene particles in microfluidic structures with engineered surface charge and hydrophilicity. We interpret the observed phenomena with the extended Derjaguin–Landau–Verwey–Overbeek (xDLVO) theory for interaction potentials. Polyelectrolyte coatings of the membrane-mimicking structure allow us to investigate particle–membrane interactions in (1) hydrophobic structures with negative zeta potential, (2) hydrophilic structures with positive zeta potential, and (3) hydrophilic structures with negative zeta potential. We assess the qualitative changes in membrane–particle interaction potentials regarding their hydrophilic and electrostatic double-layer interactions on the basis of the extensive study of particle deposition and resuspension during filtration and backwash. The results generally confirm the known trend of decreased fouling with increased hydrophilicity. However, we also show that hydrophilicity alone is an insufficient measure to estimate a membrane’s particle deposition and removal behavior. More important to achieve a low-fouling membrane that can be cleaned with pure flow reversal during regular backwashing is the design of a hydrophilic membrane with an engineered surface charge.

Dispersant promotes mild formation of aminated-carbon quantum dots nanofiltration membranes for high-efficient resource recovery

Nanomaterial-based membranes are a research hot spot for their sub-nanometer structural precision that can realize selective separation within a molecular scale. However, their preparation needs complex processes (heat treatment, time-consuming, vacuum-assisted filtration, etc), restricting their development. For the first time, the dispersant-poly (maleic acid-co-acrylic acid) sodium salt (PMAS) was designed to promote the mild formation of amine-carbon quantum dots (CQDs-NH2) membrane at room temperature via a facile interfacial polymerization. First, PMAS incorporation may form an electric double layer and strengthen the electrostatic force between CQDs-NH2 and substrate, accelerating CQDs-NH2 particle deposition. Second, the PMAS may be conjunct with the adjacent CQDs-NH2 particles, lowing the long-range force, and improving CQDs-NH2 particle deposition behavior. Third, its surfactant property may regulate the interface compatibility, improving the reactivity to promote the mild preparation of the separation layer. The prepared membrane possessed high water permeance (55 L/m2·h1·bar1) and high selective separation to the NaCl/reactive black 5 mixture, showing great potential for wastewater treatment and resource recovery.

DEPOSITION BEHAVIOR OF INDOOR AIRBORNE PARTICULATE MATTER ON HUMAN BODY SURFACES

In this study, we investigated the deposition behavior of particles in air using a thermal manikin and a silicon wafer as a surface on which particles are deposited. As a result, it was confirmed that the particle deposition velocity on the heated manikin was reduced compared to that on the unheated manikin, due to the effect of thermophoretic forces. The deposition velocities obtained from the experiments were compared with existing models of particle deposition on the human body, and the order and trend of the experimental values were generally consistent, confirming the validity of the models.

Prediction of Microstructure and Mechanical Properties of Atmospheric Plasma-Sprayed 8YSZ Thermal Barrier Coatings Using Hybrid Machine Learning Approaches

The preparation of thermal barrier coatings (TBCs) is a complex process involving the integration of physics and chemistry, mainly involving the flight behavior and deposition behavior of molten particles. The service life and performance of the TBCs were determined by various factors, especially the preparation process parameters. In this work, to set up the quantitative characterization model between the preparation process parameters and the performance characteristic parameters, the ceramic powder particle size, spraying power and spraying distance were treated as the model input parameters, the characteristic parameters of microstructure properties represented by the porosity, circularity and Feret’s diameter and the mechanical property represented by the interfacial binding strength and macrohardness were treated as the model output. The typical back propagation (BP) model and extreme learning machine (ELM) model combined with flower pollination algorithm (FPA) optimization algorithm were employed for modeling analysis. To ensure the robustness of the obtained regression prediction model, the k-fold cross-validation method was employed to evaluate and analyze the regression prediction models. The results showed that the regression coefficient R value of the proposed FPA-ELM hybrid machine learning model was more than 0.94, the root-mean-square error (RMSE) was lower than 2 and showed better prediction accuracy and robustness. Finally, this work provided a novel method to optimize the TBCs preparation process, and was expected to improve the efficiency of TBCs preparation and characterization in the future.