Distribution Of Solid Particles Research Articles

Exploring the tendency of Brownian agglomeration in polydispersed systems of solid atmospheric aerosols

Recent extensive research has focused on atmospheric aerosol systems, driven by their far-reaching implications for climate and public health, with a goal to identify optimal air quality management practices. This study employs Langevin dynamics to investigate the impact of size distribution and concentration of submicrometer solid aerosol particles on Brownian agglomeration tendencies within an isothermal, hydrostatically balanced atmosphere. To accomplish this, a Langevin dynamic model is devised, and parameters are carefully determined to ensure numerical integration precision, stability, and efficiency. Using this model, we numerically simulate the average agglomeration nucleus and overall agglomeration rate within the system while considering variations in the standard deviation of size distribution and volume fraction of aerosol particles.

Source and characteristics of inorganic acidic gases and aerosols emission in a semiconductor plant

Inorganic acids, widely used in semiconductor manufacturing processes, have become a concern as improper handling of these acids can have severe environmental impacts. This study investigates the major contamination source of inorganic acids (hydrofluoric acid, hydrochloric acid, nitric acid, phosphoric acid, and sulfuric acid), the different ratios of solid and gaseous inorganic acids, and the particle size distribution of solid particles emitted after local scrubber (LSC) treatment. An assessment of pollutant status revealed that hydrofluoric acid emissions dominate in the chemical vapor deposition (CVD) process at 65%, hydrochloric acid in the diffusion (DIFF) process at 69%, phosphoric acid in the epitaxy (EPI) process at 100%, and sulfuric acid in wet etching at 85%. In contrast, particulate matter constitutes the primary component, ranging from 82% to 99% of the LSC emission. The LSC configuration is then adjusted based on the overview of inorganic acid emissions from different processes to match their characteristics. After related improvement activities, the results presented a significant reduction of 56% to 87% in inorganic acid emissions at the outlet of the LSC, and 18-68% reduction in the stack emissions.

Numerical Simulation of Solid-Liquid Two-Phase Flow in Pump

Abstract This paper is based on EDEM-FLUENT coupling calculation, the solid-liquid two-phase flow at pump is analyzed. Three kinds of solid phase volume concentration and three solid phase particle diameters are given respectively, and the solid-liquid two-phase flow numerical simulation of the internal flow field of the pump is carried out. The position distribution of solid particles in the flow field and the change of particle average velocity with time and the distribution of particle velocity are analyzed. The results show that the inlet of the runner and the pressure surface of the blade are the concentrated distribution areas of particles. With the increase in particle concentration, the particle distribution at the outlet of the volute is more uniform. The average velocity of particles at different particle concentrations varies similarly with time, but the average velocity of particles increases with the increase of concentration. With the increase in particle size, the average velocity of particles decreases, but the velocity value with the largest proportion of particles becomes larger.

Effect of electric field on separation characteristics of oil–water–solid three phases separating device

Lubricating oil can decay as a result of the mixing of water with solid impurities in the working process, and this process can adversely affect the performance of the machinery. Therefore, desolidification and dewatering are key steps in overall oil purification. In general, a basic swirl device cannot sustain efficient dewatering and desolidification. Thus, a three-phase separating device enhanced by an electric field has been proposed. To study the performance of the oil-water-solid separation process, a numerical model of the device was conceived based on combining the governing equations of the flow field and the electric field with the particle-tracking equation giving due consideration to the population balance model. The tangential velocity and the distribution of solid particles at various voltage amplitudes were analyzed, and the effect of the electric field on the oil, water and particle separation process was studied. The results show that at 3 kV, the tangential velocity increased by 5.06%, compared with that at 12 kV. Application of an electric field to the device was found to accelerate more solid particles which assembled near the wall of the device, and where the number of the particles near the axial plane decreased. The maximum particle concentration near the wall at the z = 630 mm plane is 20.24%. Moreover, the average residence time of the solid particles initially exhibited an increasing and then a decreasing trend. Additionally, the increase in the droplet size and enhancement of the oil-water separation process are promoted through the action of the electric field. The rate for desolidification, deoiling and dewatering at 3 kV are 93.60%, 93.30% and 95.59%, respectively.

Assessing the conveyance of fluidized natural gas hydrate in a horizontal tubing

This study evaluates the transportability of clayey-silt natural gas hydrate (NGH) solid particles during solid fluidization in horizontal tubing, a crucial step in recovering marine NGH. Non-uniform solid particle distribution in horizontal flows can cause unstable operations and financial losses. Thus, assessing transportability is necessary to avoid these issues and harness the potential of NGH as an alternative energy source. This study introduces a model based on each phase's two-layer approach and momentum balance equation, considers potential hydrates (re)formation, and overcomes previous models’ limitations. Moreover, it assumes that the critical settling velocity marks the moment when the lower bed of solid particles stagnates, thereby leading to the disappearance of frictional pressure in the lower bed. The proposed model is evaluated and compared with existing models using a laboratory dataset and the South China Sea offshore field dataset and found to provide the highest prediction accuracy and precision. Moreover, it reveals that the tubing diameter, solid particle diameter, and solid particle concentration are the major influential parameters affecting the solid particle conveyance. Consequently, the proposed model is suitable for evaluating the transportability of those solid particles in horizontal tubing, making it ideal for assessing their transportability in pipelines.

Experimental investigation of particle dynamics in particle-laden turbulent boundary layer

In a horizontal wind tunnel, experiments were performed on both particle-free and particle-laden flows at the same incoming velocity. Glass micro-spheres were carried by air along the turbulent boundary layer at a high Reynolds number (Reτ=3200). The Stokes numbers of the solid particles considered were O(10) and O(102). Under a similar volume fraction, Φv=O(10−5), the velocity and spatial distribution of solid inertial particles were investigated using simultaneous particle image/tracking velocimetry measurements and time-resolved particle imaging. This allowed for the exploration of particle dynamics and their corresponding spatial structure in the particle-laden turbulent boundary layer. The results showed that particle–wall (P-W) interaction occurs in both types of particle-laden flows. However, the particle Stokes number directly affects the intensity of the P-W interaction, significantly altering the behavior and spatial organization of particles. The results from the Voronoi tessellation technique confirmed that preferential clustering still happens for the small particle case. In particular, the premultiplied spectra for the particle concentration showed that the temporal pattern of particle clustering presents a similar time-scale to very large-scale motion (around 22δ, where δ is the boundary layer thickness) in the near-wall region.

Simulation Study on Hydrodynamic Performance of Slurry Bubble Column with Vertical Tube Internals

The gas-liquid-solid mixing characteristics in slurry bubble column were studied using the CFD-PBM model under different cross section coverage ratios of tubes. The research shows that with the increase of the proportion of the cross section area of the vertical tube, the flow field in the slurry bubble column tends to be stable, the liquid phase flow rate in the column becomes faster, and the large-scale liquid circulation strengthens, resulting in the decrease of gas holdup. As the proportion of cross section area in the vertical column increases, the distribution of gas-solid holdup becomes more uneven in the radial direction. However, increasing the number of vertical tubes can improve the axial distribution of solid particles in the reactor while reducing the size of bubbles in the column. Therefore, it can be concluded that in order to achieve effective gas, liquid, and solid mixing in slurry bubble column, the ratio of cross section area of vertical internals is crucial under given conditions.

Distribution of micro-sized range solid particles in the human airways: field experiment

Introduction. Ambient air pollution is a widespread and pressing issue. This necessitates the development of methods for estimating and predicting progression of pathologies on the base of evolutionary mathematical models. Adaptation of the theoretical model to practice requires identification and verification procedures in real conditions of contamination of inhaled air with dust particles of various compositions.
 The purpose of the work was to investigate regularities of distribution of dust particles with a different disperse, component and morphological structure in the human airways after inhalation from ambient air. The study involved performing a field experiment.
 Materials and methods. We accomplished several investigations in 3 zones with different levels and structures of ambient air pollution. Disperse, component, and morphological structures of particles occurring in ambient (inhaled), deposited in various sections of the human airways, in exhaled air and blood were examined by electronic microscopy.
 Results. Air quality in zones 1 and 2 did not comply with hygienic standards for suspended particles, PM10, PM2.5, metal compounds, etc. (up to 3.29 MPCm.s., 3.2 MPCav.s., 2.91 MPCav.y.) and formed increased hazard quotient for manganese, copper, nickel and their compounds, inorganic fluorides, suspended particles (up to 5.48 HQac, 3.42 HQch), respiratory and other hazard indices (up to 5.48 HIac, 8.59 HIch). The degree of sedimentation of small particles (PM2.5 or less) in different parts of the respiratory tract is uneven, they are able to penetrate into the lower airways and lungs of humans. More than 65% of all the particles deposited in the upper airways had a diameter bigger than 10 µm. PM2.5 accounted for more than 60 % in sputum in the lower airways and the share of PM1.5 reached 46.7 %. Particles smaller than 1.5 μm (90.5%) were predominantly recorded in blood biosubstrates, of which up to 88.1% of the particles had a sphericity of 0.9–1.0.
 Limitations. Limited degree of precision of location of the examined sections in the respiratory system.
 Conclusion. Common deposition regularities are mostly determined by sizes and morphology of dust particles. The component structure of inhaled air has practically no effects on regularities of particle deposition in various sections of the respiratory system; however, it can have substantial influence on types of pathologies progressing in the body. High shares of PM1.5 identified in inhaled air, the lower airways and blood require considering levels of PM1.5 and smaller particles in ambient air in settlements to be covered by hygienic standards. In future, the study results will be used in numeric modelling of accumulation of functional respiratory disorders and associated pathologies of other organs and systems and in predicting development of pathologies based on evolution mathematical models.

Removal of the effect of the high solids holdup ring in the fluidized bed on electromagnetic tomography

Electromagnetic tomography (EMT) system based on tunneling magneto resistance (TMR) sensor, as a non-invasive multiphase flow measurement technique, can effectively detect the solid-phase distribution in the gas–liquid–solid three-phase fluidized bed with magnetic catalysts by reconstructing the permeability distribution image. The radial distribution of solid particles in the gas–liquid–solid three-phase fluidized bed with uneven fluidization is non-uniform, in which a high solids holdup ring exists near the wall of the riser. When the TMR-EMT system is used directly for image reconstruction, the high solids holdup ring will greatly reduce the image quality, further leading to the inability to detect phase information in the riser. To improve the reconstructed image by the TMR-EMT system, a removal method for the high solids holdup ring is proposed. The method firstly estimates the equivalent thickness of the high solids holdup ring based on the boundary measurement data. Then the influence of the high solids holdup ring on the boundary measurement data is subtracted. By the removal method, the internal phase distribution information is prominent. The simulation and experimental results demonstrate that the proposed method can realize the permeability distribution detection by the TMR-EMT system in the presence of the high solids holdup ring.

Effects of the distribution of solid particles on the rheological properties and buildability of 3DPM fresh pastes with different FA/GGBFS content

Effects of the distribution of solid particles on the rheological properties and buildability of 3DPM fresh pastes with different FA/GGBFS content

Three‐dimensional numerical modelling of a fast fluidized bed biomass gasifier to generate energy from wastes

AbstractThe modelling of a biomass fluidized bed gasification system, one of the most effective ways to produce energy from biomass resources and wastes, has been performed in this study. The effect of the turbulence phenomena, including calculations relating to flow turbulence, chemical fuel reactions, and energy and momentum exchange between multiple solid and gas phases, has been taken into account in the current research as a novel approach. A computational fluid dynamics case study model that combines equations with comprehensive geometry has been considered. Results have been compared with published operational records of an existing power plant to validate the model. The solid particle distribution, the velocity of the mixture and gas phase, the turbulent flow viscosity ratio, and the temperature distribution in the model indicated the accuracy of the simulation performance compared with the experimental studies. The production of the molar fraction of the constituent elements of the synthesis gas has been evaluated in transient conditions. Additionally, 35 s after the process began, the system's performance was estimated, and the results indicated the average molecular weights of hydrogen, carbon monoxide, carbon dioxide, and methane are 26%, 23%, 12.5%, and 3.3%, respectively, which presented high precision with the experimental results.

Three-dimensional solid particle self-assembly in thermovibrational flow: The case with unidirectional temperature gradient and concurrent vibrations

As a follow-up to earlier work [Crewdson and Lappa, “Spatial and temporal evolution of three-dimensional thermovibrational convection in a cubic cavity with various thermal boundary conditions,” Phys. Fluids 34, 014108 (2022)], where the main focus was on the modes of convection in a three-dimensional cubic enclosure filled with a Pr = 7 liquid undergoing vibrations in a direction “parallel” to the imposed temperature gradient, the present study considers the modes of particle clustering, which occur when solid spheres, with density ratio ξ = 1.85 or 0.3 and Stokes number (St) between 0.5 and 3.5 × 10−5, are added to the fluid. Starting from a uniform distribution of solid particles and fluid in quiescent conditions, the governing equations for the involved phases are numerically solved in their complete, time-dependent, and non-linear form for a representative vibrational Rayleigh number (8.34 × 104), angular frequency Ω = 50, and non-dimensional acceleration amplitude (γ) spanning the interval 0.4 × 107 ≤ γ ≤ 3.4 × 107. It is shown that, while for relatively high values of St and/or γ, only degenerate states are obtained, where all particles collapse on planar structures, for intermediate values of such parameters, interesting (heretofore unseen) patterns are enabled. The hallmark of these phenomena is an endless squeezing and expansion of the particle formations along the direction of the temperature gradient. As confirmed by the numerical simulations, the underlying formation mechanisms rely on the combined action of the body force acting on particles due to their different densities with respect to the host fluid and the additional drag that is produced when the carrier thermovibrational flow enters a specific stage, known as “convective burst,” where the magnitude of the fluid velocity increases dramatically.

Spatially resolved measurement of the distribution of solid and liquid Si nanoparticles in plasma synthesis through line-of-sight extinction spectroscopy.

In many high-temperature gas-phase nanoparticle synthesis processes, freshly nucleated particles are liquid and solidify during growth and cooling. This study presents an approach to determine the location of the liquid-to-solid phase transition and the volume fraction and number density of particles of both phases within a gas phase reactor. Spectrally-resolved line-of-sight attenuation (LOSA) measurements are applied to a silicon nanoparticle aerosol generated from monosilane in a microwave plasma reactor. A phantom-based analysis using particle number density, particle size, and temperature distribution from direct numerical simulation (DNS) of the reacting flow indicates that the contributions from the two particle phases can be decoupled under practical conditions, even with noisy data. The approach was applied to analyze spatially and spectrally resolved LOSA measurements from the hot gas flow downstream of the plasma zone where both solid and liquid silicon particles coexist. Extinction spectra were recorded along a line perpendicular to the flow direction by a spectrometer with an electron-multiplying charge-coupled device (EMCCD) camera, and two-dimensional projections were deconvolved to obtain radial extinction coefficient distributions of solid and liquid particles across the cross-section of the flow. Particle number densities of both particle phases were retrieved simultaneously based on the size-dependent extinction cross-sections of the nanoparticles. The particle-size distribution was determined via thermophoretic sampling at the same location with subsequent transmission electron microscopy (TEM) analysis. The particle temperature distribution was determined from the particle's thermal radiation based on line-of-sight emission (LOSE) measurements. The approach for phase-selective data analysis can be transferred to other materials aerosol systems as long as significant differences exist in extinction spectra for the related different particle classes.

Chemically bonded PA‐PTFE‐oil compounds by reactive processing: Chemical, thermal, morphological, and mechanical analysis

AbstractIn this research, the novel materials based on polyamide (PA), polytetrafluoroethylene (PTFE), and olefinic oil molecules are produced as a solid lubricant in metal‐plastic sliding contacts or sacrificial elements in metal–metal sliding contacts. For these applications, high durability of the compound material combined with low wear is required for long‐term use under high friction and mechanical loads. Earlier studies of IPF have shown that chemical bonding between the polymer matrix and the solid lubricant is mandatory to meet these requirements. For this purpose, the compounds are fabricated by a novel two‐step reactive processing procedure based on radiation‐modified PTFE, which exhibits reactive‐functional groups (COOH) and persistent perfluoroalkyl‐(peroxy)‐radicals (COO·). The PA‐PTFE‐oil‐cb compound materials (cb: chemically bonded) are analyzed by differential scanning calorimetry (DSC) concerning breaking down behavior and Fourier‐transform infrared spectroscopy with regards to the chemical covalent bonding state between the three components. Results of scanning electron microscopy investigations in correlation with DSC show that chemical bonding between PA and PTFE‐oil‐cb leads to a homogeneous distribution of solid lubricant particles in the three various PA matrices. Due to the chemical coupling, the compounds offer almost comparable or improved mechanical properties in the case of toughness compared to non‐modified PA.

Numerical Simulation of Solid-Liquid Two-Phase Flow in Non-Clog Pump

This paper mainly based on the CFD numerical simulation method to analyze the solid-liquid two-phase flow of the vortex pump. Three kinds of solid-phase volume concentration and three solid-phase particle diameters were given respectively to carry out the numerical simulation of solid-liquid two-phase flow in the internal flow field of the pump. The distribution of solid particles in the impeller and the lateral cavity were analyzed to study the influence of different solid-phase particle diameters and solid-phase particle concentrations on the pump performance. The results showed that there was no obvious concentration distribution at the junction area between blades and hub. The solid phase concentration on the back is lower than that on the working face. Due to the characteristics of circulating flow in the vortex pump, some particles enter the lateral cavity from the blade working face, and some particles enter the blade back face from the lateral cavity under the action of low pressure on the back and circulating flow. Solid particles are mainly distributed in the center of the cavity and are circularly distributed. The overall fluctuation of the solid phase slip velocity on the working face is not large, while the magnitude of the solid phase slip velocity on the back is relatively disordered.

Numerical Simulations of Liquid-Solid Flows in A Vertical Pipe by MPS-DEM Coupling Method

In the process of deep-sea mining, the liquid-solid flows in the vertical transportation pipeline are very complex. In the present work, an in-house solver MPSDEM-SJTU based on the improved MPS and DEM is developed for the simulation of hydraulic conveying. Firstly, three examples including the multilayer cylinder collapse, the Poiseuille flow and two-phase dam-break are used to validate the precision of the DEM model, the pipe flow model and MPS-DEM coupling model, respectively. Then, the hydraulic conveying with coarse particles in a vertical pipe is simulated. The solid particle distribution is presented and investigated in detail. Finally, the coupling method is successfully applied for the simulation of the liquid-solid flows in a vertical pipe with rotating blades, which shows the stability of the solver under rotating boundary conditions. This fully Lagrangian model is expected to be a new approach for analyzing hydraulic conveying.

NUMERICAL SIMULATION OF PARTICLE DYNAMICS IN THE HYDROGEN-AIR MIXING LAYER

In this paper, supersonic plane turbulent mixing layer of gases with injection of solid particles is studied numerically. The gas phase are determined by DNS solving the multi-species Navier-Stokes equations in the Eulerian approach , and the dynamic of solid particles  are traced in the Lagrangian approach. The dynamics of hydrogen – air mixing and the formation of the vortex system in the mixing layer and its effect on the distribution of solid particles in the two free-flow speeds are investigated. The study focuses on detailed analysis an influence of the vortex system in the supersonic turbulent mixing layer on the dispersion solid particles with different size. The results show that heavy particles almost do not react to vortex structures. It is revealed that medium particles tend to accumulate along the circumference of the vortex and along the braid between the two vortices. A quasi-equilibrium state with a gas flow of light particles is established.

Research on the statistical damage constitutive model for composite solid propellant

The study of constitutive model of composite solid propellant is an important basis for analyzing the structural integrity of propellant grains of the solid rocket motor. From the view of microscopic, composite solid propellant is composed of a large number of solid particles with various sizes embedded in the matrix. In this paper, based on the distribution of solid particles with different sizes and the failure strength of the particle-matrix interfaces, the damage evolution was assumed to obey the Weibull distribution function and power law distribution function, and the two statistical damage constitutive models were first established. Then, the model parameters were identified and validated through the uniaxial tensile tests data of HTPB propellant. Finally, the prediction abilities of the developed two models were compared. The results show that both of the two statistical damage models can describe the stress-strain curves of HTPB propellant well.

Thermal conductivity of scrap tire rubber-sand composite as insulating material: Experimental investigation and predictive modeling

Scrap tire rubber of good thermal insulating properties can be reused with soils as a new sustainable construction material. While the heat conduction mechanism of this tire rubber-soil composite has not been fully understood. The present study investigated the thermal behavior of scrap tire rubber-sand composite for using it as an insulating material in thermo-active applications. Several series of thermal conductivity tests were conducted on scrap tire rubber-sand composite prepared with different sand/shredded tire particle size ratios, shredded tire mixing ratios, and degrees of saturation. A predictive model was developed within the framework of normalized thermal conductivity concept that could capture the experimental data. The results showed that addition of shredded tires leads to a considerable reduction in thermal conductivity of sand, indicating great potential of using recycled scrap rubber tires in the construction of insulation layers. With an increase in degree of saturation, the order of thermal conductivity increase was found to be: sand > scrap tire rubber-sand composite > shredded tires. The spatial distribution of solid particles changed from ‘rubber-connected insulation layer’ to ‘sand-encompassed conduction path’ with increasing sand/shreds tire particle size ratio. The normalized thermal conductivity exhibited a linearly increasing trend with shredded tire mixing ratio, and the increase rate mainly depended on degree of saturation and particle size ratio. The predicted thermal conductivity showed satisfactory accuracy for engineering design, as reflected by the absolute percentage difference being controlled under 25%. The validity of the prediction model was also demonstrated based on the experimental results reported in the published literature. Additional research is recommended to assess the effects of particle morphology on thermal conduction of the binary-solid particle system.

CFD modelling of the flow of ice slurry in a vertical slit channel

In this article, the Euler-Euler method was applied to CFD modelling of adiabatic ice slurry flow, for different flow directions in a vertical slit channel. The mean relative accuracy of determining pressure drops compared to experimental studies was 5.6%. Calculations showed that the relative slip velocity and the effect of flow direction on slip velocity increase with decreasing carrier fluid concentration, decreasing mean flow velocity, and decreasing mean solid particles volume fraction. The mean particle slip velocity does not exceed 4%, and local slip velocity values can be 58% of the mean suspended solids flow velocity. For heterogeneous flow, the highest slip velocities occur at a distance of 15% of the channel width from the channel sidewalls. The shape of the solid particles distribution profile is determined by the mean flow velocity and the mean solid particles volume fraction. Excluding the area at a distance of 8% of the channel width from the sidewall where local maximum (for low velocities) and minimum (for higher velocities) values may occur, the profile is stabilised in the central part of the channel. In this study, the boundary curves between heterogeneous and homogeneous flow were determined for ice slurry flow in a vertical slit channel.