Effect Of Particle Deposition Research Articles

Four-way coupling of particle-wall and colloidal particle-particle interactions in direct absorption solar collectors

A novel model based on the Eulerian-Lagrangian approach was introduced in order to capture the physics of particle-fluid, particle-wall, and colloidal particle-particle interactions through four-way coupling in low-flux nanofluid-based direct absorption solar collectors (DASCs). This was accomplished by means of a computationally efficient particle-particle-interaction detection algorithm implemented within the frame of an in-house fluid-particle coupling algorithm that allowed for the simultaneous evolution of the carrier and particulate phases. The optical, thermal, and dispersion effects of particle-wall and colloidal particle-particle interactions were investigated over a range of particle volume fractions ϕp and flow Reynolds numbers (Re). It was found that the outcome of a particle-wall collision is either particle deposition or rebound, depending on the balance between kinetic energy of the incoming particle and particle-wall van der Waals potential energy. Brownian motion was established to be the main deposition mechanism for nanoparticles in the boundary layer. As Re decreased, Brownian motion of nanoparticles dominated over convection, which led to higher deposition rates. Deposited particles were found to cause greater attenuation of solar radiation near the collector upper surface, especially in the visible region of the solar spectrum. Whereas in the infrared region, radiation attenuation became less sensitive to particle deposition. The drop in collector efficiency when particles are allowed to deposit relative to the case when particles are not allowed to deposit was highest for low Re and ϕp. Yet, regardless of Re, an increase in particle surface potential led to a better dispersion of nanoparticles. Furthermore, colloidal interparticle interactions were found to have a negligible effect on collector performance. The results highlight the important effects of particle deposition and non-uniform particle distribution on the performance of DASC systems, which cannot be captured using conventional single-phase models.

Effects of Particle concentration, deposition and accumulation on Photovoltaic device surface

Abstract The efficiency of solar photovoltaic system is affected by many factors, among which the influence of dust deposition on photovoltaic panels is a prominent problem. In the desert which has sufficient radiation, the problem of dust deposition is quite serious. In some developed cities, photovoltaic devices are affected by dust or aerosol deposition. This short paper, thus, briefly summarizes studies of dust deposition on PV panels of urban and desert areas in recent years, and analyses the influence of dust deposition on the panel, particle characteristics and dust deposition process based on these studies. In general, there are three fields that suggests more research: (1) study on characteristics of sand or dust combined with local environmental characteristics; (2) modeling and simulation of particle dynamics around photovoltaic array; (3) comprehensive laboratory designed experiments to understand the specific influencing factors.

Gas Turbine Fouling: A Comparison Among 100 Heavy-Duty Frames

Over recent decades, the variability and high costs of the traditional gas turbine fuels (e.g., natural gas) have pushed operators to consider low-grade fuels for running heavy-duty frames. Synfuels, obtained from coal, petroleum, or biomass gasification, could represent valid alternatives in this sense. Although these alternatives match the reduction of costs and, in the case of biomass sources, would potentially provide a CO2 emission benefit (reduction of the CO2 capture and sequestration costs), these low-grade fuels have a higher content of contaminants. Synfuels are filtered before the combustor stage, but the contaminants are not removed completely. This fact leads to a considerable amount of deposition on the nozzle vanes due to the high temperature value. In addition to this, the continuous demand for increasing gas turbine efficiency determines a higher combustor outlet temperature. Current advanced gas turbine engines operate at a turbine inlet temperature (TIT) of (1400–1500) °C, which is high enough to melt a high proportion of the contaminants introduced by low-grade fuels. Particle deposition can increase surface roughness, modify the airfoil shape, and clog the coolant passages. At the same time, land-based power units experience compressor fouling, due to the air contaminants able to pass through the filtration barriers. Hot sections and compressor fouling work together to determine performance degradation. This paper proposes an analysis of the contaminant deposition on hot gas turbine sections based on machine nameplate data. Hot section and compressor fouling are estimated using a fouling susceptibility criterion. The combination of gas turbine net power, efficiency, and TIT with different types of synfuel contaminants highlights how each gas turbine is subjected to particle deposition. The simulation of particle deposition on 100 gas turbines ranging from 1.2 MW to 420 MW was conducted following the fouling susceptibility criterion. Using a simplified particle deposition calculation based on TIT and contaminant viscosity estimation, the analysis shows how the correlation between type of contaminant and gas turbine performance plays a key role. The results allow the choice of the best heavy-duty frame as a function of the fuel. Low-efficiency frames (characterized by lower values of TIT) show the best compromise in order to reduce the effects of particle deposition in the presence of high-temperature melting contaminants. A high-efficiency frame is suitable when the contaminants are characterized by a low-melting point thanks to their lower fuel consumption.

Performance of convective-radiative porous fin heat sink under the influence of particle deposition and adhesion for thermal enhancement of electronic components

This work presents an investigation on the effect of particle deposition and adhesion on the thermal behaviour of convective-radiative porous fin heat sink using Differential Transform method (DTM). The numerical solutions of the developed thermal models are also used to study the influence of thermal conductivity, porosity, convection and radiation factors on the thermal distribution and efficiency of the fin. The analysis reveals the impact of particles or thermal fouling on the surface of the fin, which causes a rise in the temperature uniformity and distribution in the fin while reducing the rate of heat transfer from the fin. Moreover, the study also establishes that the heat transfer rate decreases due to particle deposition on the fin which depends on the particle size, particle density and cooling air flow rate. The fin efficiency decreases with increasing value of the fouled Biot, Darcy and radiation numbers, and thermo-geometric parameter. Furthermore, the analysis shows that the efficiency of the fouled porous fin is always greater than the efficiency of the clean porous fin. The result of this study shows an excellent agreement with the established results of Runge-Kutta with shooting method.

Modeling of two-phase particulate flows in a confined jet with a focus on two-way coupling

A computational fluid dynamics model is used for the simulation of laminar flow of water–Al2O3 nanofluid in a confined slot impinging jet. The (steady-state and two-dimensional) Eulerian–Lagrangian model is used considering fluid–particle and particle–wall interactions (i.e., two-way coupling). A collocated grid and the SIMPLE algorithm are used for the coupling of pressure and velocity fields. The deposition model is used to investigate the effect of particle deposition on the impingement surface. Results indicate that the particle trajectory becomes stable farther from the jet with a rising Reynolds number and jet-impingement surface distance ratio. The heat transfer coefficient of the mixture model is higher than that of the Eulerian–Lagrangian model.

Land subsidence due to groundwater pumping and recharge: considering the particle-deposition effect in ground-source heat-pump engineering

With the rapid development and use of ground-source heat-pump (GSHP) systems in China, it has become imperative to research the effects of associated long-term pumping and recharge processes on ground deformation. During groundwater GSHP operation, small particles can be transported and deposited, or they can become detached in the grain skeleton and undergo recombination, possibly causing a change in the ground structure and characteristics. This paper presents a mathematical ground-deformation model that considers particle transportation and deposition in porous media based on the geological characteristics of a dual-structure stratum in Wuhan, eastern China. Thermal effects were taken into consideration because the GSHP technology used involves a device that uses heat from a shallow layer of the ground. The results reveal that particle deposition during the long-term pumping and recharge process has had an impact on ground deformation that has significantly increased over time. In addition, there is a strong correlation between the deformation change (%) and the amount of particle deposition. The position of the maximum deformation change is also the location where most of the particles are deposited, with the deformation change being as high as 43.3%. The analyses also show that flow of groundwater can have an effect on the ground deformation process, but the effect is very weak.

Convective-diffusion model of particle deposition in modeling of building structures

The problem of the motion of a swirling flow in a vortex chamber with particle deposition effects at the lateral surface is numerically investigated. Flowfields with formation of recirculation zones are analyzed on the basis of the Navier-Stokes equations. Two cases of the transport process for solid particles of different sizes with deposition on the lateral surface of the channel are studied (passive impurities are assumed). In the first case, the particles are injected into the peripheral part of the channel together with the swirling flow; in the second case, this process is performed through an annular slot without swirling. The results are compared with available experimental data and asymptotic solutions.

Effects of particles deposition on thermal performance of a convective-radiative heat sink porous fin of an electronic component

The advent of high-power electronic system components and slim margin errors require the proper understanding of particle deposition characteristics and its effects on the thermal performance of electronic heat sinks of electronic devices. In this work, we investigate the effects of particle deposition on the thermal performance of convective-radiative porous fin heat sink of an electronic component using Chebyshev spectral collocation method. The numerical solutions from the developed thermal models are also used to study the influence of thermal conductivity, porosity, convection, and radiation parameter on the temperature distribution and overall fin efficiency. The analysis establishes that presence of particles or thermal fouling on the surface of the fin increases the temperature distribution and temperature uniformity of the fin whilst decreasing the heat transfer rate from the fin. The study also establishes that decrease in heat transfer rate from the fin is due to the particle deposition on the fin, which depends on the particle size, particle density and cooling air flow rate. Moreover, the fin efficiency decreases with an increasing value of the fouled Biot, Darcy and radiation numbers, and thermo-geometric parameter. The study further shows that the efficiency of the fouled porous fin is always greater than the efficiency of the clean porous fin. The analysis established that the result of Chebyshev spectral collocation method is in good agreement with that of the convectional numerical method using Runge-Kutta coupled with shooting method.

Combined effects of ZnO particle deposition and heat treatment on dimensional stability and mechanical properties of poplar wood

This study proposed a one-step wood modification method by combining the deposition of ZnO particles on wood surface and heat treatment. The effects of ZnO particles and heat treatment on mechanical properties and dimensional stability of poplar wood were examined. Samples were sorted into 4 groups, i.e., control, heat-treated, impregnation/heat-treated, and hydrothermal-treated samples. The mechanical properties and dimensional stability of impregnation/heat-treated and hydrothermal-treated wood samples were measured in comparison with those of the control and heat-treated wood samples. Compared with the control ones, the reduction of the flexural strength of the heat-treated, impregnation/heat-treated and hydrothermal-treated samples were about 11.57%, 8.53% and 15.90%, respectively. The modulus of elasticity of the heat-treated and hydrothermal-treated samples decreased by 13.78% and 23.78%, respectively, while the impregnation/heat-treated samples increased by about 8.57% due to the ZnO particles growth. The dimensional stabilities of the heat-treated, impregnated/heat-treated and hydrothermal-treated samples were improved in comparison with that of the control sample. All samples were characterized by the scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X - ray diffraction (XRD).

Thermal and solutal stratification on MHD nanofluid flow over a porous vertical plate

Nanoparticles have the highest credibility to develop the thermal properties compared to conventional particle fluid suspension. Thermal and solutal stratification on heat and mass transfer induced due to a nanofluid over a porous vertical plate is analyzed. The transport equations engaged in the study include the effect of Brownian motion and thermophoresis particle deposition. The nonlinear governing equations and their related boundary conditions are initially looked into dimensionless forms by similarity variables. The resulting equations are solved numerically utilizing the fourth-fifth order Runge–Kutta–Fehlberg method with shooting technique (MAPLE 18). It is investigated that the temperature of the nanofluid and the concentration fraction decelerate with increase in thermal and solutal stratification.

Numerical method and calculation of two-phase swirling flows with rigid particles for technical applications

Swirling flow with particle deposition effects at the lateral surface is numerically investigated. The flow field calculation results have been obtained as the solutions of the Navier-Stokes equations. Various flow regimes with the formation of axial recirculation zones are presented. The convection-diffusion model is used for the determination of the flow particle concentration and the formation of typical sedimentation zones.

Simulation of particle deposition on the tube in ash-laden flow using the lattice Boltzmann method

The LBM-Lagrange tracking method with multiple relaxation time (MRT) model has been developed to predict the flow field and particle deposition a circular or elliptical tube in ash-laden gas turbulent flow with Re of 10,229. The model can be used for predict particle deposition effect on thermal resistance or fouling factor of heat exchangers mostly operating in turbulent flow.Particle deposition morphology on the circular and the elliptical tubes were obtained with the lattice Boltzmann method (LBM). The particle deposition mechanism has been investigated. The dominating mechanism of particle deposition on the circular tube is Brownian diffusion for the Stokes number of 0.002, whereas the dominating mechanism of particle deposition is drag inertia for the Stokes number larger than 0.031. When the long axis of the elliptical tube is parallel to the flow, both the collision efficiency and the deposition efficiency for the elliptical tube are fewer than those of the circular tube which means less particle deposition. It also can be concluded that both ratios of the collision efficiency and the deposition efficiency decrease with increasing axial length ratio of the elliptical tube. The elliptical tube is better than the circular tube as heat transfer surface in the aspect of preventing ash particle deposition.

Euler-Lagrangian Model of Particle Motion and Deposition Effects in Electro-Static Fields based on OpenFoam

In order to study the powder coating process of metal substrates, a comprehensive, numerical 3D Eulerian-LaGrangian model, featuring two particle sub-models, has been developed. The model considers the effects of electro-static, fluid-dynamic and gravity forces. The code has been implemented in C++ within the open source CFD platform OpenFoam®, is transient in nature with respect to the applied LaGrangian particle implementation and the electro-static field calculation and is stationary regarding fluid-dynamic phenomena. Qualitative validation of the developed solver has already been achieved by comparison to simple coating experiments and will hereby be presented alongside a thorough description of the model itself. Upon combining knowledge of the relevant dimensionless groups and the numerical model, a dimensionless chart, representing all possible states of coating, was populated with comprehensive, exemplary cases, which are shown here as well.

Aerosol dynamics within and above forest in relation to turbulent transport and dry deposition

Abstract. A 1-D atmospheric boundary layer (ABL) model coupled with a detailed atmospheric chemistry and aerosol dynamical model, the model SOSAA, was used to predict the ABL and detailed aerosol population (characterized by the number size distribution) time evolution. The model was applied over a period of 10 days in May 2013 to a pine forest site in southern Finland. The period was characterized by frequent new particle formation events and simultaneous intensive aerosol transformation. The aim of the study was to analyze and quantify the role of aerosol and ABL dynamics in the vertical transport of aerosols. It was of particular interest to what extent the fluxes above the canopy deviate from the particle dry deposition on the canopy foliage due to the above-mentioned processes. The model simulations revealed that the particle concentration change due to aerosol dynamics frequently exceeded the effect of particle deposition by even an order of magnitude or more. The impact was, however, strongly dependent on particle size and time. In spite of the fact that the timescale of turbulent transfer inside the canopy is much smaller than the timescales of aerosol dynamics and dry deposition, leading us to assume well-mixed properties of air, the fluxes at the canopy top frequently deviated from deposition inside the forest. This was due to transformation of aerosol concentration throughout the ABL and resulting complicated pattern of vertical transport. Therefore we argue that the comparison of timescales of aerosol dynamics and deposition defined for the processes below the flux measurement level do not unambiguously describe the importance of aerosol dynamics for vertical transport above the canopy. We conclude that under dynamical conditions reported in the current study the micrometeorological particle flux measurements can significantly deviate from the dry deposition into the canopy. The deviation can be systematic for certain size ranges so that the time-averaged particle fluxes can be also biased with respect to deposition sink.

Influences of rotation and thermophoresis on MHD peristaltic transport of Jeffrey fluid with convective conditions and wall properties

This article aims to predict the effects of convective condition and particle deposition on peristaltic transport of Jeffrey fluid in a channel. The whole system is in a rotating frame of reference. The walls of channel are taken flexible. The fluid is electrically conducting in the presence of uniform magnetic field. Non-uniform heat source/sink parameter is also considered. Mass transfer with chemical reaction is considered. Relevant equations for the problems under consideration are first modeled and then simplified using lubrication approach. Resulting equations for stream function and temperature are solved exactly whereas mass transfer equation is solved numerically. Impacts of various involved parameters appearing in the solutions are carefully analyzed.

Eulerian-LaGrangian model of particle laden flows and deposition effects in electro-static fields based on OpenFoam

Eulerian-LaGrangian model of particle laden flows and deposition effects in electro-static fields based on OpenFoam

Effect of Oral Pathway on Charged Particles Deposition in Human Bronchial Airways.

In vitro studies to investigate the effect of charged particle deposition in the oral pathway of human adults have demonstrated substantial increases in deposition due to an induced charge effect. In the current study, charged particle deposition in the oral pathway was incorporated in the stochastic human airway generation model IDEAL (Inhalation, Deposition, and Exhalation of Aerosols in the Lung) to quantify their effect on bronchial airways deposition. Calculation of increased oral deposition due to charged particles was performed by a modified version of IDEAL for oral pathway, whereas deposition in the bronchial airways was carried out by the already employed efficiency equation. Deposition calculations were performed for 3, 4.5, and 6 μm particles at flow rates of 15 and 30 L/min. The enhancement in deposition is found to be 40 times higher in oral pathway and 6 times higher in bronchial airways for 3 μm size particles carrying 2500 elementary charges. For particles larger than 3 μm, deposition by impaction dominates over deposition by particle charges, and hence higher deposition in oral pathway is observed primarily due to impaction. As a consequence of this increased oral deposition, bronchial airways deposition decreases. By controlling breathing, aerosol properties, and electrostatic charge, targeted deposition in the human airways can be improved. Hence, charged particles can therefore be utilized to give better control on regional drug delivery in the lungs or to filter out toxic constituents.

A Behavioural Membrane Fouling Model for Integrated Simulation of Membrane Bioreactors for Wastewater Treatment

This paper presents a simple membrane fouling model intended for use in conjunction with an activated sludge model to form an integrated model of a membrane bioreactor (MBR). It is based on an earlier development of Liang et al.[1] who divided fouling into short-term reversible fouling tantamount with cake deposition and long-term irreversible fouling representing th effects of irreversible particle deposition inside membrane pores. The original model was extended to account for cake detachment, back- flushing, and dependency of soluble microbial products (SMP) deposition on permeate flux. The model was identified on two sets of data from two experiments: a short-term flux stepping experiment under fluxes higher from the ‘threshold flux’ and a long-term filtration experiment under fluxes not exceeding the ‘threshold flux’. Additionally, the paper proposes a simple ‘pen and ruler’ identification method for unique estimation of model parameters based on the information obtained from flux stepping experiments.

Influence of thermophoretic particle deposition on MHD free convection flow of non-Newtonian fluids from a vertical plate embedded in porous media considering Soret and Dufour effects

This study numerically investigates the combined heat and mass transfer of an electrically conducting, non-Newtonian power-law fluid in MHD free convection adjacent to a vertical plate within a porous medium in the presence of the thermophoresis particle deposition effect. The governing boundary layer equations along with the boundary conditions have been first transformed by a similarity transformation into a set of coupled, non-linear ordinary differential equations, and the resulting similarity equations are then solved by the local adaptive differential quadrature method (La-DQM). Some important parameters have been discussed in this study, which include the magnetic parameter Ma, the buoyancy ratio N, the Dufour number Df and the Soret number Sr. Effects of these major parameters on the fluid, heat and mass transfer processes are carried out. The results indicate that the wall friction decreases as the magnetic parameter increases or the buoyancy ratio decreases. Increasing the Soret number or decreasing the Dufour number tends to decrease the temperature distribution inside the boundary, but tends to increase the concentration variation. In addition, the thermophoretic deposition velocity decreases as the magnetic parameter or the Dufour number increases, while it increases as the buoyancy ratio or the Soret number increases.

Retraction of “Influence of thermophoresis particle deposition and chemical reaction on unsteady non-Darcy MHD mixed convective flow over a porous wedge in the presence of temperature-dependent viscosity”

An analysis is presented to investigate the effect of thermophoresis particle deposition and temperature dependent viscosity on unsteady non-Darcy mixed convective heat and mass transfer of a viscous and incompressible fluid past a porous wedge in the presence of chemical reaction. The wall of the wedge is embedded in a uniform non-Darcian porous medium in order to allow for possible fluid wall suction or injection. The governing partial differential equations of the problem, subjected to their boundary conditions, are solved numerically by applying an efficient solution scheme for local nonsimilarity boundary layer analysis. Numerical calculations are carried out for different values of dimensionless parameters arising in the problem. The results are compared with available ones in the literature and excellent agreement is obtained. An analysis of the obtained results shows that the flow field is influenced appreciably by the chemical reaction and thermophoresis particle deposition.