Deposition Of Solid Particles Research Articles

Impacts and depositional behaviors of debris flows on natural boulder-negative Poisson's ratio anchor cable baffles

The impacts of natural boulders carried by debris flows pose serious risks to the safety and reliability of structures and buildings. Natural boulders can be highly random and unpredictable. Consequently, boulder control during debris flows is crucial but difficult. Herein, an eco-friendly control system featuring anchoring natural boulders (NBs) with (negative Poisson's ratio) NPR anchor cables is proposed to form an NB-NPR baffle. A series of flume experiments are conducted to verify the effect of NB-NPR baffles on controlling debris flow impact. The deployment of NB-NPR baffles substantially influences the kinematic behavior of a debris flow, primarily in the form of changes in the depositional properties and impact intensities. The results show that the NB-NPR baffle matrix successfully controls boulder mobility and exhibits positive feedback on solid particle deposition. The NB-NPR baffle group exhibits a reduction in peak impact force ranging from 29% to 79% compared to that of the control group in the basic experiment. The NPR anchor cables play a significant role in the NB-NPR baffle by demonstrating particular characteristics, including consistent resistance, large deformation, and substantial energy absorption. The NB-NPR baffle innovatively utilizes the natural boulders in a debris flow gully by converting destructive boulders into constructive boulders. Overall, this research serves as a basis for future field experiments and applications.

Numerical study of turbulent heat transfer and particle deposition in enhanced pipes with helical roughness

Large-eddy simulations of turbulent heat transfer and solid particle deposition in helically rib-roughened pipe flows have been performed for different Reynolds numbers Re and various particle diameters Dp. An Euler–Lagrange approach, using cyclic boundary conditions for the continuous and the dispersed phase, have been applied to achieve a fully developed turbulent flow. An adhesion and removal model have been added to the multiphase large-eddy simulations to take into account the physical effect of particle re-entrainment. The complex interactions between particle-laden turbulent flow and the structured pipe wall in multiple-started helically ribbed pipes are numerically investigated with regard to heat transfer, pressure loss, and particulate deposition. The results of the Nusselt numbers Nu, friction factors fd, and particle deposition rates Ṅd are presented for each geometry variant. For same Reynolds numbers Re, significant differences of those values have been observed for the differently structured pipes.

Investigation on coupling deposition and plugging of hydrate and wax in gas–liquid annular flow: Experiments and mechanism

The coupling deposition and plugging caused by hydrate formation and wax precipitation during the development of deep water natural gas resources bring new industrial challenges and theoretical difficulty. We designed a single-pass pipeline with two types to investigate deposition behavior and systematically performed the coupling deposition and plugging of hydrate and wax experiments in gas–liquid annular flow. The experimental results illustrate that the single solid phase of hydrate is covered layer sheet deposition, while the coupling solid phase of hydrate and wax is bulk aggregations arch bridge deposition. Meanwhile, the natural eddy zone in reducing pipeline accelerates coupling solid particles deposition. Our finds provided the first knowledge on the double effect that wax crystals inhibit particles adhesion and gel network increases aggregations arch bridge blockage. For the low water content in emulsion system, the gel network provides gathering place for hydrate particles, and the arch bridge structure formed by aggregations accelerates the pipeline blockage. The plugging time is shortened by up to 72.6% with the wax concentration increase from 0 wt% to 3 wt%. For the high water content in emulsion system, the majority of wax crystals adsorbed on the hydrate particles and reduce particles cohesion force, which increase the plugging time. Combined with the microscopic morphology evolution perspective of hydrate particles coupled wax, the coupling deposition of hydrate and wax in gas–liquid annular flow has four stages: gas–liquid flow, coupling solid phase formation, coupling solid phase deposition and sloughing, and coupling solid phase plugging. This study can provide theoretical support and design basis for flow assurance program of deep water gas fields and low temperature natural gas transportation pipelines.

Stochastic subgrid-scale modeling for particles dispersion and deposition for a filtered DNS channel flow field

The effect of subgrid-scale velocity fluctuations on the deposition and dispersion of solid particles in a filtered DNS turbulent channel flow at Reτ=180, and for particles with Stokes numbers of St = 1, 2, 5, 24 was studied. First, the turbulent flow field was simulated using the DNS on a high-resolution grid. Then, the filtered DNS flow fields were generated using several low-resolution grids. Particle tracking was performed for the DNS and filtered DNS channel flow fields, and the effects of filtering on particle deposition and concentration were studied. It was shown that filtering significantly decreases the particle deposition velocities at lower Stokes numbers (St = 1, 2, 5). However, at higher Stokes numbers (St = 24), the deposition velocity was less affected. Next, the ability of a stochastic model to generate the correct particle deposition velocities and concentration profiles was studied. A Langevin stochastic equation for modeling the subgrid-scale (SGS) fluid velocity fluctuations as seen by particles was developed and tested. The two input parameters of the stochastic model are the variance of SGS fluctuations in the wall-normal direction and the Lagrangian SGS time-scale. It was seen that the model prediction is sensitive to the SGS time scale used in the Langevin equation. The model was capable of predicting the correct deposition velocities and concentration profiles of lower inertia particles when the proper time-scale was used. For higher inertia particles and when a larger amount of energy was removed by filtering, the model was unable to predict the deposition velocities.

Investigation of a solid particle deposition velocity in drag reducing fluids with salinity

Optimal and cost-effective drilling operations in extended-reach horizontal wells depend on efficient solid cuttings removal from the borehole. Several solids-suspended multiphase processes such as crude petroleum transportation, separation, and processing of oil and gas streams also require the efficient removal of these solids. The terminal settling velocity (Vts) of the solid particle is a vital parameter that controls the removal efficiency of these solids. In a drilling scenario when there is a hold on fluid circulation such as connection time, the accurate estimation of Vs provides the driller with time available to prevent solid deposition. In severe conditions, this can result in a stuck pipe, especially for extended-reach horizontal wells. In this work, both spherical and non-spherical particle deposition were experimentally investigated in several fluid rheology and salinity. Two concentrations (0.1vol% and 0.05vol%.) of partially-hydrolyzed polyacrylamide (PHPA) were used as a drag-reducing additive for water-based drilling mud. The PHPA drag-reducing fluid (reduced pressure loss) acts as a turbulence inhibitor. The PHPA polymer chain suppresses any turbulence in the flow, reducing the turbulent eddy viscosity. The effects of salinity (3wt.%NaCl and 3wt.%CaCl2 contamination) on solid particle settling velocity (Vs) in drag-reducing fluids were also investigated. Terminal velocity was achieved for all experiments and seemed to increase with increased diameter/sphericity. However, cases when this trend was not consistent were observed and therefore a new parameter of Φ (sphericity index × diameter) was proposed. Vs increases with Φ value for all cases. During drilling, PHPA also aids in sealing the fracture in the formation. With and without salt in the fluid, how lowering drag affected the settling velocity of solid particles (drill cuttings) could be observed. The settling velocity tests will be improved in drag-reducing PHPA solutions with the knowledge from this study.

On the Influence of Fine Particle Migration and Deposition on Gas Hydrate Production: Insights from the First Trial Production in the South China Sea

Summary As a promising alternative energy source with vast reserves, the primary challenge in exploiting natural gas hydrates (NGHs) lies in achieving long-term safety and efficiency. Several production tests conducted globally have demonstrated that the production of solid particles is one of the main factors contributing to this issue. However, most studies on assessing NGH production capacity have overlooked this phenomenon and its impact on production performance, potentially compromising the accuracy of simulation results. Therefore, this study aims to quantitatively analyze the impact of fine particle migration and deposition on gas production by numerically examining the first NGH production test conducted in the Shenhu area of the South China Sea (SCS). Through comparison of simulation results with the reconstructed gas production curve, the model was calibrated and enabled an explanation of unique gas production performance during field testing. It is found that the deposition of solid particles reduced the gas production rate by nearly an order of magnitude during the initial stage of exploitation. Long-term simulation results indicate that only the three-phase layer (TPL) remains partially unobstructed and serves as the primary source of gas production in later stages. Sensitivity analysis reveals that both depressurization and particle control strategies exert significant effects on particle migration, which in turn affects gas production. Specifically, the increase in depressurization amplitude does not necessarily lead to improved gas production behavior beyond a certain threshold (approximately 6 MPa). This study illustrates the inherent trade-off between preventing particle production and increasing gas production, highlighting the need for a safe and efficient production scheme that strikes a balance between these two objectives. Based on the current study, it is preliminarily recommended to maintain a depressurization amplitude of approximately 6 MPa with a maximum depressurization rate of 3 MPa/d and ensure a fine particle filtration ratio of no less than 95%.

Методика визначення показникА поглинання світла мікрочастинками ПОРОШКУ Люмінофора YAG:Сe3+ та її технологічне забезпечення

The development of methods for photometric control of turbid media based on YAG:Ce3+ phosphor (luminophore) microcrystals in transparent matrices requires solving a number of technological problems in the manufacture of self-supporting films of the composite material, adequate measurement of their optical properties and calculation of the corresponding values of absorption indices. This general problem is solved in this work by developing original measuring equipment, elaborating a number of technological protocols and a calculation algorithm based on modelling in the concept of a composite film of a dispersion medium. It is proved that the production of a suspension of microparticles of YAG:Ce3+ powder in epoxy resin at reduced pressure using an original turbine microstirrer allows to obtain a homogeneous and degassed suspension with a low rate of solid particle deposition, efficient light absorption of excitation radiation and an increased level of quantum yield of luminescence. A methodology for manufacturing self-supporting films from the obtained suspension has been developed. Such films are characterised by a low scatter of colourimetric parameters on the surface due to their high spatial homogeneity. 5 ml of the suspension is enough to produce a set of 30 flat-parallel films with an area of up to 1 cm2 and a thickness of 110÷600 µm with an error not exceeding ±3 µm. On the basis of the matrix spectroradiometer НAAS-2000, a photometric measuring setup was developed and created, which, in addition to the spectroradiometer, includes an optical module and an LED blue light source with λmax= 456 nm to excite the luminescence of the light-converting composition layers. The elements of the optical module ensure that the solid angle of the source radiation corresponds to the numerical aperture of the receiver (Ω = 0.126 steradian) in the form of the end window of the fibre-optic cable of the spectroradiometer and cause the transmission of the image on a 1:1 scale. An algorithm for determining the volumetric and linear absorption coefficients of a microcrystal-averaged YAG:Ce3+ phosphor powder under conditions corresponding to the isotropic scattering mechanism was proposed and worked out. Calculations in the composite film model, which takes into account the effects of light absorption and reflection by individual microcrystals in the volume of a transparent matrix, using the results of experimental measurements, allowed us to establish the values of the volume and linear absorption coefficients of the size-averaged (5.3 μm) YAG:Ce3+ microcrystal, which are 774 cm-1 and 129 cm-1, respectively.

КРИТЕРИАЛЬНОЕ УРАВНЕНИЕ ПРОЦЕССА СЕДИМЕНТАЦИИ В ПЕРЕХОДНОМ РЕЖИМЕ

Using the method of dimensional analysis, a general form of the criterion equation for the pro-cess of deposition of solid particles in a layer of liquid is obtained. The coefficients of the equa-tion for the process of sedimentation of sand particles in the transition regime were determined experimentally

Assessing underdeposit corrosion inhibitor performance for carbon steel in CO2/Sulfide environment

Under deposit corrosion (UDC) that occurs due to the deposition of solid particles, like iron sulfide or organic solids, and CO2 corrosion, cause disasters for pipelines and fluid-handling apparatus. This research investigated the impact of mineral deposits, like iron disulfide, iron sulfide, and sand, on the inhibition performance of the commercial UDC inhibitor in sulfated CO2-saturated brine solution at 60 °C and 1000 rpm flow rates for different immersion times. The deposit characteristics, type, and coverage technique on the steel (full/partial) were explored. The surface morphology, elemental analysis, and particle size of deposits in the absence and presence of the inhibitor were analyzed. The inhibitive effect at different inhibitor concentrations and the corrosion rates of steel in the absence and presence of the deposits were calculated from the fitting process of the electrochemical impedance spectroscopy (EIS) results. The utilized UDC inhibitor has the highest efficiency (about 95 %) at a concentration of 400 ppm. The FeS, FeS2 and SiO2 deposits in the presence of the inhibitor offered a 77.5 %, 94.5 % and 94.6 % inhibition efficiency after 6h of immersion time, resulting in about 77.5 %, 25.6 % and 60.1 % increase in their efficiencies before the addition of the inhibitor. Therefore, the inhibitor can effectively inhibit the UDC triggered by FeS and SiO2 deposits in an aqueous environment containing sulfated CO2. However, it is unavailable in the steel underneath the FeS2 deposit to inhibit corrosion. EDX and XPS analyses confirm the success of the inhibitor movement through deposits and its adsorption on steels.

Improving inter-particle deformation and bonding by preserving transient in-situ deposition temperatures during cold spray

Cold Spray (CS) represents a solid-state coating process with promising applications in localized repairs and additive manufacturing. However, the weak inter-particle bonding limits the deposit properties due to low plastic deformation. In this study, the high temperature of the transient in-situ deposition surface shortly after particle impact is proposed to promote inter-particle deformation and bonding. A new in-situ deposit surface is formed after solid particle deposition, showing transient in-situ temperature due to the heat transfer between this particle and the overlay deposit. An equivalent time method is devised to obtain the transient in-situ deposition temperature by significantly accelerating the computation speed by nearly 1000 times. Meanwhile, based on spatio-temporal independence, the time interval between deposited particles reaches thousands of microseconds, showing that the in-situ deposition surface tends to the low substrate temperature. Reducing the time interval between particle impacts enables new particles to be deposited onto surfaces at elevated in-situ temperatures, thus promoting better inter-particle bonding. The results provide a basis for increasing the in-situ surface transient temperature to improve the deposit quality.

Numerical simulation of clogging of two types of emitters with similar properties

AbstractThe benefits of drip irrigation are numerous and include water savings, control of fertilizer applications, and improved water and energy use efficiency of irrigation. In these systems, the emitter is the most vulnerable component to clogging, which in critical states can cause a reduction in performance and shorten the life of the distribution system. It can also have several impacts on water, its economy, and its wastage. In the absence of adequate filtration and when the flow is through the narrow labyrinth channel of the emitter, clogging can be created by continuous deposition of solid particles, organic matter, dissolved salts, chemical precipitates, bacteria, and other impurities. It is obvious that it is impossible to physically visualize the hydraulic behavior of the flowing water in the labyrinths. However, due to the increasing performance of computational tools and simulation software, it is possible to simulate this flow through Computational Fluid Dynamics (CFD), which has become one of the main techniques for describing the flow and deposition of the solid phase inside the emitter. This study aims to numerically simulate the behavior and the flow of the fluid inside two emitters, widely used in the industry, with different types but approximately identical flow rates. The fluid takes in its flow an inert solid suspension of fixed concentration. One of the emitters is compensating‐pressure, and the other is non‐compensating‐pressure; the numerical simulation model used is the RNG κ‐ε two‐phase model. The results showed that the regions affected by clogging are mainly the corners of the labyrinth channel and the recirculation vortex zones. The trajectory field plot reveals that as the clogging increases, the serpentine fluid threads become thinner.

Numeric Investigation of Non-Stationary Dust-Containing Airflow and Deposition of Dust Particles in the Lower Airways

Within creation of the mathematical model to describe the human respiratory system, we accomplished numeric investigation of non-stationary dust-containing airflow as well as dust particle deposition in the lower airways with the real anatomic geometry based on CT scans. Inhaled air is considered a multi-phase mixture of a homogenous gas and solid dust particles. Motion of a basic carrier gas phase is described using the Euler approach. Solid dust particles are a dispersed carried phase, which is described with the Lagrange approach. The k-ω model is used to describe turbulence. We consider non-stationary airflow during calm inhalation. The article presents calculated flow streamlines for the velocity of particles in inhaled air in the lower airways at different moments. We quantified a share of deposited particles (SDP) with various dispersed structure (between 10 nm and 100 µm) and density (1000 kg/m3, 2000 kg/m3, 2700 kg/m3) in the lower airways; the article provides computed motion paths of particulate matter. Solid particle deposition in the airways has different efficiency depending on particle sizes and density. SDP goes down as their sizes and masses decrease. Particle density mostly influences differences in deposition of micro-sized particles (2.5–20 µm): as particle mass and density grow, SDP in the airways also increases. SDP with their diameter being less than 1 µm amounts to approximately 20 % of all the particles that reach the inlet to the trachea. According to the results obtained by numeric modeling, the greatest share of dust particles penetrates the right main bronchus, predominantly the right middle and inferior lobar bronchi. Dust particles are able to induce diseases of the lungs, pneumoconiosis included.

Particle deposition model for a fully developed turbulent channel flow

This study aims to develop a mathematical model for solid particle deposition under a fully-developed turbulent flow in a rectangular channel, considering the effect of the change in geometry over time. The present study introduces a mathematical approach to predict the equilibrium thickness/mass of the deposition, saturation and equilibrium times, and their corresponding non-dimensionalized parameters. Scaling analysis, and parametric study are reported. For a fixed Reynolds number Re, the particle deposition increases with non-dimensional relaxation time. In general, as more particles are deposited, the surface takes less time to become saturated and approach equilibrium faster. The saturation and equilibrium times decrease with an increase in non-dimensional particle relaxation time. For a fixed particle concentration, as the inlet velocity increases, the saturation and equilibrium time decreases, and the asymptotic deposited mass decreases.

Clay-induced permeability decline in sandstone reservoirs: Insights from a coupled NMR-SEM experimental approach

The blockage induced by solid particles transport and deposition is one of the main causes of injectivity decline in geothermal sandstone reservoirs during reinjection. This paper investigates clay-induced clogging mechanisms to provide a better understanding to formation damage problems encountered in geothermal fields. In-depth NMR measurements were carried out during core-flooding experiments where illite clay particles (120 nm) were injected in sand-packed columns. SEM imaging was performed to compare the porous space before and after damage and study the morphology and distribution of the deposited particles in the sand column. Pressure drop measurements and NMR T2 relaxation time distributions revealed that clogging occurs in two stages: surface deposition and pore bridging. This was further confirmed by SEM images showing that pore-blocking illite ribbons were formed in the porous space.

Anaerobic dynamic membrane bioreactor applied to wastewater treatment: a review

Membrane bioreactors have been widely used in biological wastewater treatment. The membranes used in this type of technology are produced from organic or inorganic materials. However, membranes can also be formed from the deposition of solid particles, colloids, and polymeric materials, as well as microbial cells and flocs, on an inert support during the filtration process. When coupled to a bioreactor, they establish a unique system called a dynamic membrane bioreactor (DMBR). This type of bioreactor, while retaining the solids and microorganisms present in the system, removes both easy and difficult-to-degrade organic material, which reduces treatment costs and makes it advantageous compared to conventional membrane bioreactors (MBRs). In Brazil, this technology is relatively new and still little explored. Therefore, the present study aims to evaluate the DMBR's performance in anaerobic wastewater treatment systems. In addition to the advantages and disadvantages presented by this type of system compared to conventional MBRs (micro and ultrafiltration), the fouling phenomenon, its implications, and the theories that explain the formation of the dynamic layer are described. Finally, some challenges that still need to be overcome in the use of this technology are pointed out in order to be affirmed as a safe and robust tool for the biological treatment of domestic and industrial wastewater.

Influence of Oil Content on Particle Loading Characteristics of a Two-Stage Filtration System

Filter media may encounter aerosols mixed with solid and oil ingredients from various sources, such as industries, transportation, and households, in the air purification process, while the influence such oil content has on the loading performance of single-stage and two-stage filtration systems is under-reported. Thus, this study aims to evaluate oil fraction effects on the loading performance of single-stage and two-stage filtration systems. First, to reveal the oil–solid mixed particle deposition mechanisms, the filter media parameters, i.e., specific cake resistance ε and cake porosity K2, were tested, indicating that a slight amount of oil can increase the dust holding capacity (DHC) of filters by forming a more porous cake, while an excess of oil results in reduced DHC by forming impermeable liquid films on the solid skeleton. Further two-stage experimental results indicate that the effectiveness of a pre-stage filter can be significantly affected by the properties of incoming aerosol and main-stage filters. The utilization of a pre-stage filter unintentionally deteriorated the service lifetime of the main-stage filter when challenged with contaminants with certain oil particles. This counter-intuitive negative phenomenon is due to the special loading behaviors of oil–solid mixed particles. The existing pre-stage filters allow a higher fine oil particle fraction to reach the main-stage downstream, while the induced cake filtration scenario leading to a film clogging scenario adversely reduced the lifetime of the main-stage filter. The findings suggest that the feasibility of a pre-stage in the filtration system requires compressive evaluations according to the specific oil-coated contaminants.

Effect of deposit chemistry on microbial community structure and activity: Implications for under-deposit microbial corrosion.

The deposition of solid particles carried by production fluids from oil and gas companies in horizontal surfaces of different assets has shown to cause severe localised corrosion. Sand, one of the most common deposits in the energy sector pipelines, is frequently mixed with crude, oil, asphaltenes, corrosion inhibitors, and other organic compounds. For this reason, they might favour the metabolic activity of native microbial communities. This study aimed to determine the impact of sand-deposit chemical composition on the microbial community structure and functional attributes of a multispecies consortium recovered from an oilfield and the resulting risk of under-deposit microbial corrosion of carbon steel. Sand deposits recovered from an oil pipeline were used in their raw form and compared against the same deposits exposed to heat treatment to remove organic compounds. A four-week immersion test in a bioreactor filled with synthetic produced water and a two-centimeter layer of sand was set up to assess corrosion and microbial community changes. The raw untreated deposit from the field containing hydrocarbons and treatment chemicals resulted in a more diverse microbial community than its treated counterpart. Moreover, biofilms developed in the raw sand deposit exhibited higher metabolic rates, with functional profile analysis indicating a predominance of genes associated with xenobiotics degradation. Uniform and localized corrosion were more severe in the raw sand deposit compared to the treated sand. The complex chemical composition of the untreated sand might have represented an additional source of energy and nutrients to the microbial consortium, favoring the development of different microbial genera and species. The higher corrosion rate obtained under the untreated sand suggests that MIC occurred due to syntrophic relationships between sulphate reducers or thiosulphate reducers and fermenters identified in the consortium.

A numerical investigation of the particle behaviors and entropy generation in mixed convection inside a vented enclosure

The present study is to focus on the numerical investigation of the transportation, deposition and removal of solid particles in the range of 5 μm to 0.01 μm for mixed convection flow in the vented square cavity by utilizing the Eulerian–Lagrangian method with one-way coupling. The change in the deposition and removal mechanisms affected by the forces acting on the particles is addressed for mixed convection of ventilation airflow. In the analysis of entropy generation, the irreversibilities due to the presence of solid particles are studied with a new approach for both dominant natural and forced convection. The governing equations for fluid phase and the Lagrangian particle tracking are scrutinized by employing the finite volume method with SIMPLE algorithm and explicitly integrating the set of ordinary differential equations, respectively. The examination of the thermal and flow fields is carried out in the cases of various Reynolds numbers and Richardson numbers. The minimum and maximum values of the average Nusselt number are determined with related operating parameters. By using the results of thermal behaviors and flow structures obtained at steady-state condition, the particle velocity, temperature and location are presented for the combined natural and forced convection. By investigating the particles deposited on the walls and ones removed from the exit section for different Reynolds numbers and Richardson numbers, it is demonstrated that the sum rate of deposition and removal is low at 1≤Ri≤10 and high Reynolds number for 1 μm and 0.1 μm particles. For given Reynolds number, increasing the buoyancy effect results in substantial changes in the thermal field and flow pattern, therefore the particles remaining suspended show different behaviors when the effect of natural convection alters from weak to dominant. It is observed that the Brownian and thermophoretic forces play an important role in the small particle deposition and removal. As a result of entropy generation analysis, the minimum total entropy generation is determined at Ri=5 for given Reynolds number except for Re=50. Moreover, it is proposed to investigate the irreversibilities due to the heat transfer between the particles and the fluid surrounding them and the frictional total force acting on the suspended particles.

Compressibility and Rarefaction Effects on Particle Dynamics and Heat Transfer in Aerosol Deposition Process

The aerosol deposition (AD) method is an emerging coating technique to create a dense ceramic or metal layer on a substrate through the kinetic impaction and cumulative deposition of ultrafine solid particles under near-vacuum conditions. Prediction of the particles’ impact velocity and temperature during the AD process is crucial in enhancing the coating quality. In the present work, a two-way coupled Eulerian-Lagrangian model is developed for an AD system equipped with a converging-barrel nozzle to simulate the supersonic gas flow, particle in-flight behavior, as well as particle conditions upon impact on a flat substrate. The focus of the current study is to understand the effects of compressibility and rarefaction on particle velocity and temperature during the AD process. The effects of compressibility and rarefaction can be assessed using the Mach and Knudsen numbers. Therefore, different models for the drag coefficient and the heat transfer coefficient that take into account the Knudsen, Mach, and Reynolds number effects are implemented into the computational fluid dynamics (CFD) models. The results show that compressibility and rarefaction have significant influence on the particle temperature and velocity. As the particle size reduces, the effects of compressibility and rarefaction become more important.

Transport and deposition of solid phosphorus-based mineral particles in urine diversion systems

ABSTRACT The deposition of solid phosphorus-based mineral particles is a common problem in urine diversion systems, which occurs in transport systems, particularly in horizontal pipelines. In this work, particle deposition behaviour in turbulent flow in a 3D horizontal pipe was simulated by using the Euler–Lagrange method. The effects of particle diameter, particle density, particle shape factor and fluid flow velocity on particle deposition behaviour were investigated. The results showed that the deposition rate increased by 9.92%,6.88% and 6.88% with increasing particle diameter (10-90 ), particle density (1400 kg/m3–2300 kg/m3), and particle shape factor (0.2–1), respectively. For particles with larger diameters (>90 ) or larger density (>2300 kg/m3), the deposition rate of these particles was almost reached 100%. It was found that gravitational sedimentation was the dominant deposition mechanism in low fluid flow velocity range (0.1–0.5 m/s). As fluid flow velocity increased (>0.5 m/s), turbulent fluctuation became the dominant factor that affected particle motion behaviour, whereas the effect of gravitational sedimentation on particle deposition behaviour declined significantly, and the increase in fluid flow velocity no longer significantly affects deposition rate. It was found that the deposition rate decreased by 29.13% as the fluid flow velocity was increased from 0.1 m/s to 0.5 m/s, while the corresponding deposition rate only decreased by 14.24% when the fluid flow velocity was increased from 0.5 m/s to 2 m/s. The optimal flow velocity was found to range between 0.75 and 1.25 m/s, which may mitigate the deposition of mineral solids in urine diversion systems.