Particle Deposition Efficiency Research Articles

Impact of the Different Molecular Weights of Polyethylene Glycol (PEG) Coating Agents on the Magnetic Targeting Characteristics of Functionalized Magnetoresponsive Nanoclusters

In this article, we investigated the influence of molecular weight (Mw) on particle deposition efficiency after PEG-functionalized (polyethylene glycol-PEG) magnetoresponsive magnetic cluster targeting. In this work, the clusters were obtained by the solvothermal polyol method using polyethylene glycol (PEG) as a coating agent. So, we investigated three kinds of magnetoresponsive clusters: MNC-2000, MNC-6000, and MNC-10,000. These clusters were coated with PEG, and had molecular weights (Mw) of 2000 Da, 6000 Da, and 10,000 Da, respectively. The authors propose that the key to achieving maximum efficiency in targeted drug delivery is to deposit a thin, uniform layer of medication that covers the vascular wall in the area of interest. We defined a set of efficiency criteria to focus on the most essential characteristics of the targeting results. These are the obstruction degree, which measures the level of vessel obstruction; the magnet coverage degree, which evaluates the quality of particle deposition along the vessel wall; and the proximal deposition degree, which assesses the effect of pulsatile flow on deposition length. We performed several tests to determine how molecular weight affected these efficiency parameters. These tests examined (a) the effect of the injected cluster quantities, (b) the effect of the magnet distance, and (c) the effect of the injection period. Our findings indicate that an increase in PEG’s molar weight significantly impacts magnetic particle targeting efficiency.

Two-Parameter Probabilistic Model and Experimental Research on Micron Particle Deposition

The deposition of micron particles in gas pipelines has always been an important problem in ultra-clean ventilation technology in the modern laser fusion, precision electronics, aerospace, and biomedical fields. Combining the mathematical expression of the migration, collision, and deposition of micron particles in a gas pipeline with a simulation of flow fields, a two-parameter particle probability deposition model based on vinl, θcr and collision probability coefficient PP is established, and the distribution law of particle deposition, considering two deposition targets of the pipe wall and deposition layer, is given. Combined with an experiment on particle migration and deposition in a gas pipeline, an interpretation and verification of the particle deposition distribution law are given, and the difference between the model and experiment is discussed through particle deposition efficiency mass distribution. Studies have shown the following: Under the premise of two kinds of deposition targets, different particle sizes in the gas pipeline present different deposition laws; the deposit morphology is a spot deposit of 10 µm particles and a flake deposit of 40 µm particles; the deposit position shows a uniform distribution and a lower wall dominance; and the deposit concentration area of 40 µm shows a more significant distribution. The results are very important for the selection and optimization of gas pipelines for clean spaces.

Research and improvement of the design of a sedimentation tank for hydropower and irrigation

The study is devoted to the analysis and optimisation of the design of the sedimentation tank to increase the efficiency of settling solid particles in hydropower and irrigation systems. Both experimental and numerical methods were used to analyse and optimise the design of sedimentation tanks to increase their efficiency in hydropower and irrigation systems. The study examined and analysed various types of sedimentation tanks according to design schemes, flow regime, deposition dynamics and sediment flushing methods, and also considered recommended improvements for hydropower and irrigation of various types of sedimentation tanks. During the study, it was revealed that optimising the geometry of the sedimentation tank significantly increases the efficiency of solid particle deposition. Experimental data have shown that changing the angle of inclination of the walls and increasing the area of the bottom of the sedimentation tank contribute to improving the deposition of silt and sand. It has also been found that the use of special turbulent inserts reduces the particle deposition time and improves the quality of treated water. Hydraulic flow modelling has confirmed that a more uniform velocity distribution in the sedimentation tank reduces turbulence and promotes more efficient particle deposition. The introduction of automated systems for monitoring and controlling the cleaning process has made it possible to increase the reliability and stability of the sedimentation tank. As a result, it was proved that the proposed design and technological changes can significantly increase the efficiency and durability of sedimentation tanks in hydropower and irrigation. The study provides practical recommendations for improving the design of sedimentation tanks, which helps to increase their efficiency and reliability in hydropower and irrigation, thereby improving water management

Aerosol dosimetry in the whole conducting zone of a murine left-lung using CF-PD and LSFM images

Aerosol dosimetry in respiratory airways is relevant for pulmonary drug delivery and inhalation toxicology. Consequently, computational fluid-particle dynamics (CF-PD) modelling of pulmonary aerosol delivery is an active research field. Additionally, mice are the most commonly used animals in medical research. Technological advances have provided information on whole mice lung morphologies with unprecedented high resolution. Therefore, in this study, we used high-resolution light sheet fluorescent microscopy (LSFM) images of a healthy C57BL/6 mouse lung with a constant air flow rate of 72 ml/min, to extract an anatomical 3-dimensional (3D) geometry of the entire airway tree of the left lung from the primary bronchi to the most distal bronchioles excluding the trachea. The airways were segmented based on an order- and generation-based method. Also, to compare the morphological data and regional deposition, a generation-based investigation including 25 generations was employed in the present model. One-way coupling of CF-PD modeling was applied to model an intubated and mechanically-ventilated mouse. Maximum values of the velocity and vorticity magnitude of 3.2 m/s and 200,000 1/s were reached in the second order, respectively, and maximum pressure and wall shear stress levels were 30 Pa and 3.5 Pa, respectively. Finally, order- and generation-based particle deposition efficiency and dose per lung area were obtained for the particle size range of 1 μm ≤ dp ≤ 10 μm yielding pronounced hotspot deposition patterns mainly near the proximal bifurcations. The results showed a positive correlation between deposition efficiency and particle size due to a size-dependent increase in inertial and gravitational effects. Maximum regional deposition and normalized dose was seen for 10 μm particles in the 1st order of the murine left lung. Smaller peak sizes of deposition efficiency were seen in the third and fourth orders of the mouse left lung due to almost complete loss of the largest particles in lower order airways. It also justifies the close to zero deposition efficiency in the highest orders (fifth to sixth). Both lung morphology as well as total and regional aerosol deposition showed reasonably good agreement with empirical data from the literature. The present CF-PD model with accurate realistic lung morphology, improves our knowledge of airway aerosol deposition hotspots. The obtained modeling method and the qualitative results can be implemented on human airways.

Numerical study of deposition rates of monodisperse particles in curved pipes with different expansion or shrinkage variables

The study of particle deposition in ventilation ducts is crucial as it can have a significant impact on indoor air quality (IAQ) and human health. However, little research has been done on bends in ducts with different cross-sections. This study employs the Eulerian - Lagrange method to investigate particle deposition in a 90 elbow with gradually increasing and decreasing cross-sectional areas. The turbulence model used is based on the RNG k-, and the particulate phase is modelled by the discrete phase model (DPM). The study aims to discuss the effect of the cross-sectional asymptotic coefficient (K) and the Stokes number on particle deposition. The study found that as K increased, the particle deposition efficiency of the 90-degree bends decreased. Additionally, particles were primarily deposited on the outer curved surface of the bends. Specifically, when the particle size was 2 m, the pipe with K=0.75 had a particle deposition efficiency five times greater than that of K=1.25.

In silico investigation of inhalation condition impacts on hygroscopic growth and deposition of salbutamol sulphate in human airways

The objective of this study is to explore the transport, size growth, and deposition of Salbutamol Sulphate (SS) using Computational Fluid Dynamics (CFD). A CT-based realistic model of human airways from the oral cavity to the 5th generation of the lung was utilized as the computational domain. Four Test Cases (TC) with varying temperature and relative humidity (RH) under two inspiratory waveforms were considered to completely evaluate the impact of inhalation conditions on particle growth. Salbutamol Sulphate (SS) is a β2-adrenergic agonist and has been extensively used for asthma treatment. A monodispersed distribution of SS particles with an initial diameter of 167 nm was considered at the mouth inlet based on pharmaceutical data. Results indicated that inhalation of saturated/supersaturated air (RH>100%) leads to significant hygroscopic growth of SS particles with a factor of 10. In addition, the deposition efficiency of SS particles under the Quick and Deep (QD) inhalation profile was enhanced as the flow temperature and humidity increased. However, the implementation of Slow and Deep (SD) inspiratory waveform revealed that the same particle size growth is achieved in the respiratory system with lower deposition efficiency in the mouth-throat (less than 3%) and tracheobronchial airway (less than 2.18%). For the escaped particles form the right lung, in the SD waveform under TC 3, the maximum particle size distribution was for 600 nm particles with 25% probability. In the left lung, 30% of the particles were increased up to 950 nm in size. For the QD waveform in TC 3 and TC4, the most frequent particles were 800 nm with 36% probability. This holds practical significance in the context of deep lung delivery for asthmatic patients with enhanced deposition efficiency and large particle size. The findings of the present study can contribute to the development of targeted drug delivery strategies for the treatment of pulmonary diseases using hygroscopic dry powder formulations.

Advances in Aerosol Formulation for Targeted Delivery of Therapeutic Agents from Nose to Brain.

The intricate anatomical and physiological barriers that prohibit pharmaceuticals from entering the brain continue to provide a noteworthy hurdle to the efficient distribution of medications to brain tissues. These barriers prevent the movement of active therapeutic agents into the brain. The present manuscript aims to describe the various aspects of brain-targeted drug delivery through the nasal route. The primary transport mechanism for drug absorption from the nose to the brain is the paracellular/extracellular mechanism, which allows for rapid drug transfer. The transcellular/intracellular pathway involves the transfer across a lipoidal channel, which regulates the entry or exit of anions, organic cations, and peptides. Spectroscopy and PET (positron emission tomography) are two common methods used for assessing drug distribution. MRI (Magnetic resonance imaging) is another imaging method used to assess the efficacy of aerosol drug delivery from nose to brain. It can identify emphysema, drug-induced harm, mucus discharge, oedema, and vascular remodeling. The olfactory epithelium's position in the nasal cavity makes it difficult for drugs to reach the desired target. Bi-directional aerosol systems and tools like the "OptiNose" can help decrease extranasal particle deposition and increase particle deposition efficiency in the primary nasal pathway. Direct medicine administration from N-T-B, however, can reduce the dose administered and make it easier to attain an effective concentration at the site of activity, and it has the potential to be commercialized.

Particle tracking schemes for micron particle deposition in a 90° pipe bend and nasal airway geometry

Computational studies of micron particle deposition is used to predict inhaled particles through the nasal cavity for understanding drug delivery or toxicology risks. To ensure reliable results in future studies, this study evaluated particle tracking schemes and determined the most appropriate settings for predicting micron particle deposition in a pipe bend and nasal cavity geometry. Micron particles were injected into a fully developed 90° pipe bend under a turbulent flow regime with Reynolds number, Re = 10,000, for comparison with existing data in the literature. Similarly, the micron particles were released into a more complex geometry, a human nasal cavity.The study found that although the high-resolution tracking is the default and preferred option set out by Ansys-Fluent, the 5μm particle tested travelled further than when the high-resolution tracking was off. This was rectified by setting the wall nodal velocity to zero. All particle tracking schemes performed well and were suitable for predicting deposition for particle diameters >5μm, with high-resolution tracking and setting the wall nodal velocity to zero. However, the results become sensitive to the particle scheme when dealing with particle diameters ¡ 5μm. The lower-order schemes overpredict deposition, while the higher-order schemes have zero deposition in the pipe bend unless the wall nodal velocity is set to zero. This study provides a list of recommended settings to best simulate particle deposition efficiency in Ansys Fluent (version 2023R2), although future releases of the CFD software may incorporate these settings as default options.

Wall-modeled large eddy simulation of 90° bent pipe flows with/without particles: A comparative study

Wall-modeled large eddy simulation (WMLES) has been proven to be a cost-effective approach capable of resolving turbulence up to certain resolutions. Among the simplest wall models used are the equilibrium wall models, assuming the pressure gradient and convective terms balance out in the momentum equations. There is a lack of studies to assess the performance of these standard wall models in internal turbulent flows including separation regions with/without particles. Regarding this research gap, we have conducted WMLES of incompressible turbulent flows, to the authors’ knowledge, for the first time, in 90° bent pipes with and without particles using an algebraic equilibrium wall model (Spalding’s function). A pipe flow simulation was conducted to confirm the simulation setup and assess the sensitivity with respect to the modeling parameters. In each case, comparisons are made with experiment or direct numerical simulation (DNS), and depending on the case, with other existing simulation methods in the literature: WMLES, standard (wall-resolving) LES, and Reynolds stress model (RSM) for Reynolds-averaged Navier-Stokes (RANS) simulations. Despite the controversy on the performance of equilibrium wall models in nonequilibrium flows, our results show acceptable accuracy of this type of wall models. Specifically in the bent pipe flow with particles, WMLES succeeded in predicting particle deposition efficiency at Stokes numbers greater than 0.5, but obtained less accurate results for smaller Stokes numbers. The WMLES errors were, however, on par with those of the standard LES employed with a tenfold higher grid cell count. Improved results would be expected if combined with auxiliary mechanisms such as stochastic models.

Numerical Simulation of Turbulent Structure and Particle Deposition in a Three-Dimensional Heat Transfer Pipe with Corrugation

When colloidal particles are deposited in a heat transfer channel, they increase the flow resistance in the channel, resulting in a substantial decrease in heat transfer efficiency. It is critical to have a comprehensive understanding of particle properties in heat transfer channels for practical engineering applications. This study employed the Reynolds stress model (RSM) and the discrete particle model (DPM) to simulate particle deposition in a 3D corrugated rough-walled channel. The turbulent diffusion of particles was modeled with the discrete random walk model (DRW). A user-defined function (UDF) was created for particle–wall contact, and an improved particle bounce deposition model was implemented. The research focused on investigating secondary flow near the corrugated wall, Q-value standards, turbulent kinetic energy distribution, and particle deposition through validation of velocity in the tube and particle deposition modeling. The study analyzed the impact of airflow velocity, particle size, corrugation height, and corrugation period on particle deposition efficiency. The findings suggest that the use of corrugated walls can significantly improve the efficiency of deposition for particles less than 20 μm in size. Specifically, particles with a diameter of 3 μm showed five times higher efficacy of deposition with a corrugation height of 24 mm compared to a smooth surface.

Enhancing the capturing characteristics of charged droplets on submicron particles: An experimental and numerical investigation

Charged water mist dust removal, combined electrostatic dust removal and wet dust removal, has low energy consumption and high capturing efficiency. Particle motion laws under turbulent flow are investigated. The theoretical model of droplet capturing submicron particles is established, and the kinetic process of submicron particles is analyzed. Considering that the actual conditions of the droplet capturing process is a combination of multiple capturing mechanisms, to better fit the actual engineering cases, an experimental platform is built to study the particle capturing characteristics of droplet under different operating conditions. The motion and deposition behavior of submicron particles relative to single droplet are investigated using COMSOL simulations to reveal the influence laws of relevant parameters. The results show that: the higher the temperature difference, the stronger the charging field, the fewer the escaping particles, and the greater the particle deposition efficiency. The particle capturing efficiency under combined action increases 20% compared to temperature alone and increases 24% compared to electrostatics alone. Also, the particle deposition efficiency under combined action increases 30% to 40% compared to temperature alone and increases 10% to 20% compared to electrostatics alone. The deposition efficiency under combined action is higher than the sum, up to 89%.

The effects of imposed swirling flow on the transport and deposition of particulate pollutants in the 90° industrial duct bends: An Eulerian-Lagrangian approach

Duct bend is one of the important parts of ventilation and dust removal systems, and particles deposited in curved ducts can reduce system efficiency or cause erosion on the bend wall. To investigate whether particle deposition is affected by imposed swirl on fluid flow, this article combines the RSM turbulence model and the Discrete Phase Model (DPM) to predict the deposition efficiency of particles in the bend under high Reynolds number conditions. The results show that the imposed swirl flow modifies the secondary flow initially dominated by the pressure gradient caused by the curvature effect. With the gradual increase of the swirl number ( S n), the deposition efficiency of the particles gradually decreased. However, when the swirl number is low ( S n ≤ 0.17), particles with smaller Stokes numbers are more susceptible to the intensity of turbulence. The higher the turbulence intensity near the wall, the easier it is for low inertia particles ( St ≤ 0.456) to deposit. The higher swirl intensity dominates the centrifugal force, reduces the turbulent intensity in the central region of the duct, improves the stability of the airflow and makes it easier for particles with larger inertia ( St ≥ 0.811) to pass through the bend.

Effects of the burner on SiO2 formation and deposition in the OVD process

The burner of outside vapor deposition (OVD) is of great significance for enhancing the yields and quality of the optical fiber preform. This study aims to numerically investigate the effects of the burner on silica particles formation and its corresponding deposition performance in the OVD process. This work is based on our recently developed integrated Eulerian-Eulerian multiphase OVD process model combined with a particle nucleation model. The effects of the distance between the burner and target, the horizontal offset of the target to the burner, the shape of burners, swirl burners as well as double burners are investigated. The results demonstrate that there exists an optimal value for the distance between the burner and target to yield the largest deposition efficiency. However, the deposition efficiency monotonically declines as the horizontal offset of the target to the burner increases. The elliptic burner potentially provides a better match with the target surface for particle deposition. An optimal number of helical vanes installed inside the O2–1 inlet is observed in the counter-swirling burner of O2–1 and H2 inlets, which yields the largest deposition efficiency of 33.4%. Double burners could promote the deposition rate, but could not enhance the particle deposition efficiency. The results provide a deeper understanding of the burner design and OVD process optimization.

Ternary Dry Powder Agglomerate Inhalation Formulation of Melatonin With Air Jet Mixing to Improve In Vitro And In Vivo Performance

An improved agglomerate formulation with melatonin and fine lactose for dry powder inhalation using Turbuhaler® was developed. Co-grinding lactose with 1 % magnesium stearate prior to air jet mixing served as a key factor to improve the in vitro aerosolization and in vivo efficacy. Elevated mixing pressure facilitated the dispersion and homogenization of the cohesive mixture for even distribution of agglomerate size after spheroidization and subsequent higher emitted dose with lower variation. Magnesium stearate was employed as a tertiary component to adjust the interparticle force for better aerosolization. At optimized mixing pressure, co-grinding lactose with magnesium stearate before jet mixing displayed further improvement of fine particle fraction to 71.6 ± 3.1 %. The superior fine particle deposition efficiency contributed to rapid onset of action and a high bioavailability of 67.0 % after intratracheal administration to rats. Overall, an inhalable melatonin dry powder formulation exhibiting good aerosol property and lung deposition with clinical translation potential was developed.

Effect of Nanoparticles Deposition on Cooling Performance of Photovoltaic Panels

Abstract The current research aims to investigate the deposition and dispersion of nanoparticles for thermally developing laminar flow inside a cooling channel of a photovoltaic (PV) panel. The particle transport is modeled in an Eulerian-Lagrangian framework using a two-way coupling approach to perform the particle trajectories. In the absence of turbulent fluctuations, Brownian diffusion is the main force that contributes to particles deposition due to the small size of the particles used in the current study (below 100 nm). Several parameters were investigated such as inlet temperature, Reynolds number, nanoparticle size, and concentration in order to record the subsequent effects on the deposition efficiency, heat transfer coefficient, and pressure drop. There is no direct particle deposition model available in commercial computational packages such as Fluent, so a deposition model was developed and programmed in C-language using the User-Defined Functions (UDF) capabilities available in the Fluent solver to model how the particles are affected by wall impacts. Model validation was performed against the experimental studies found in the literature and showed good agreement. The efficiency of particle deposition on the channel wall was found to increase with decreasing nanoparticle size and/or Reynolds number. Furthermore, the deposition efficiency increased with the increase in fluid inlet temperature and nanofluid concentration. Moreover, the heat transfer rate was decreased as a result of decreasing nanofluid concentration caused by nanoparticle deposition on the channel walls, while the pumping power was also decreased due to concentration loss.

Numerical analysis of airflow and particle deposition in multi-fidelity designs of nasal replicas following nasal administration

Background and ObjectiveAn improved understanding of flow behaviour and particle deposition in the human nasal airway is useful for optimising drug delivery and assessing the implications of pollutants and toxin inhalation. The geometry of the human nasal cavity is inherently complex and presents challenges and manufacturing constraints in creating a geometrically realistic replica. Understanding how anatomical structures of the nasal airway affect flow will shed light on the mechanics underpinning flow regulation in the nasal pharynx and provide a means to interpret flow and particle deposition data conducted in a nasal replica or model that has reduced complexity in terms of their geometries. This study aims to elucidate the effects of sinus and reduced turbinate length on nasal flow and particle deposition efficiencies. MethodsA complete nasal airway with maxillary sinus was first reconstructed using magnetic resonance imaging (MRI) scans obtained from a healthy human volunteer. The basic model was then modified to produce a model without the sinus, and another with reduced turbinate length. Computational fluid dynamics (CFD) was used to simulate flow in the nasal cavity using transient flow profiles with peak flow rates of 15 L/min, 35 L/min and 55 L/min. Particle deposition was investigated using discrete phase modelling (DPM). ResultsResults from this study show that simplifying the nasal cavity by removing the maxillary sinus and curved sections of the meatus only has a minor effect on airflow. By mapping the spatial distribution of monodisperse particles (10 μm) in the three models using a grid map that consists of 30 grids, this work highlights the specific nasal airway locations where deposition efficiencies are highest, as observed within a single grid. It also shows that lower peak flow rates result in higher deposition differences in terms of location and deposition quantity, among the models. The highest difference in particle deposition among the three nasal models is ∼10%, and this is observed at the beginning of the middle meatus and the end of the pharynx, but is only limited to the 15 L/min peak flow rate case. Further work demonstrating how the outcome may be affected by a wider range of particle sizes, less specific to the pharmaceutical industries, is warranted. ConclusionA physical replica manufactured without sections of the middle meatus could still be adequate in producing useful data on the deposition efficiencies associated with an intranasal drug formulation and its delivery device.

The Motion and Deposition of Small Particles in the Human Lung Acinus, Part B: Weibel’s Model of Bifurcating Airways

Weibel’s model A for the human lung is applied in which the lung comprises a binary bifurcating tree of 23 generations of airways. It assumes that each airway bifurcates into two airways their sizes defined by the generation number. The goal of this analysis is to predict deposition efficiencies of various size particles which reach the human acinus vis-a-vis generation number, a result that can be used in designing inhaled therapeutical particles or preventing dangerous substances like Covid 19 of reaching the blood stream. The simulations account for particle convection, the effects of gravity and Brownian motion. Applying ANSYS Fluent, a commercial program which includes a two-phase model for finite volumes, it is found that particle diameters within the range (0.4 ¸ 1.0 mm) and densities as low as 500 kg/m3 reach deep into the human lung acinus and are likely to reach the blood stream. Particles of higher densities and diameters outside the foregoing range deposit at lower branches of the acinar tree, the smaller particles due to dominant diffusion and the bigger due to gravity.

Effects of organic carbon/elemental carbon and particle size on inhalation bioaccessibility of particle-bound PAHs

Bioaccessible fractions of particle-bound hydrophobic organic compounds (HOCs) are critical to evaluating human inhalation exposure risk. However, the key factors for controlling the release of HOCs into the lung fluid are not adequately examined. To address this issue, eight particle size fractions (0.056–18 μm) from different particle emission sources (barbecue and smoking) were collected and incubated with an in vitro method for determining inhalation bioaccessibilities of polycyclic aromatic hydrocarbons (PAHs). The bioaccessible fractions of particle-bound PAHs were 35–65% for smoke-type charcoal, 24–62% for smokeless-type charcoal, and 44–96% for cigarette. The size distributions of bioaccessible fractions of 3–4 ring PAHs were symmetric with the patterns of their masses, characterized as a unimodal distribution with both the trough and peak at 0.56–1.0 μm. Analysis from machine learning showed that chemical hydrophobicity appeared to be the most significant factor affecting inhalation bioaccessibility of PAHs, followed by organic carbon and elemental carbon contents. Particle size seemed to have little effect on the bioaccessibility of PAHs. A compositional analysis of human inhalation exposure risk from total concentration, deposition concentration, and bioaccessible deposition concentration in alveolar region showed a shift in the key particle size from 0.56−1.0 μm to 1.0–1.8 μm and an increasing in the contributions of 2–3 ring PAHs to risk for cigarette due to the high bioaccessible fractions. These results suggested the significance of particle deposition efficiency and bioaccessible fractions of HOCs in risk assessment.

Computational fluid-particle dynamics modeling of ultrafine to coarse particles deposition in the human respiratory system, down to the terminal bronchiole

Background and objectivesSuspended respirable airborne particles are associated with human health risks and especially particles within the range of ultrafine (< 0.1 μm) or fine (< 2.5 μm) have a high possibility of penetrating the lung region, which is concerned to be closely related to the bronchial or alveoli tissue dosimetry. Nature complex structure of the respiratory system requires much effort to explore and comprehend the flow and the inhaled particle dynamics for precise health risk assessment. Therefore, this study applied the computational fluid-particle dynamics (CFPD) method to elucidate the deposition characteristics of ultrafine-to-coarse particles in the human respiratory tract from nostrils to the 16th generation of terminal bronchi. MethodsThe realistic bronchi up to the 8th generation are precisely and perfectly generated from computed tomography (CT) images, and an artificial model compensates for the 9th-16th bronchioles. Herein, the steady airflow is simulated at constant breathing flow rates of 7.5, 15, and 30 L/min, reproducing human resting-intense activity. Then, trajectories of the particle size ranging from 0.002 – 10 μm are tracked using a discrete phase model. ResultsHere, we report reliable results of airflow patterns and particle deposition efficiency in the human respiratory system validated against experimental data. The individual-related focal point of ultrafine and fine particles deposition rates was actualized at the 8th generation; whilst the hot-spot of the deposited coarse particles was found in the 6th generation. Lobar deposition characterizes the dominance of coarse particles deposited in the right lower lobe, whereas the left upper-lower and right lower lobes simultaneously occupy high deposition rates for ultrafine particles. Finally, the results indicate a higher deposition in the right lung compared to its counterpart. ConclusionsFrom the results, the developed realistic human respiratory system down to the terminal bronchiole in this study, in coupling with the CFPD method, delivers the accurate prediction of a wide range of particles in terms of particle dosimetry and visualization of site-specific in the consecutive respiratory system. In addition, the series of CFPD analyses and their results are to offer in-depth information on particle behavior in human bronchioles, which may benefit health risk assessment or drug delivery studies

Heat transfer and deposition analysis of CuO-Water nanofluid inside a baffled channel: Two-phase Eulerian–Lagrangian method

BackgroundUsing nanofluids is an applicable way of improving heat transfer. Besides, manipulating internal flows using baffles placed on the walls is a common way of increasing thermal efficiency in industrial energy processes. MethodsTwo-phase numerical study of CuO-water nanofluid flow inside a constant heat flux channel with consecutive baffles has been done by a modified Lagrangian solver in OpenFOAM. In this way, the Thermophoretic force was implemented as a new submodel into OpenFOAM's library. The effects of various parameters consisting of the baffles' height and spacing as well as Reynolds number and nanoparticles’ volume concentration were analyzed on the pressure drop, heat transfer, and particles’ deposition inside the channel. Significant FindingsIt was observed that increasing the baffle height ratio AH can improve the Nusselt number up to 85%, however nanoparticle disposition inside the channel becomes 2.5 times more. Also, decreasing the baffle spacing ratio BH has the same effect, increasing the Nusselt number and deposition by about 34% and 17%, respectively. Furthermore, looking at the flow field and particle distribution shows that one or two vortexes were generated after each baffle, having lower concentration than the other regions of the channel. Finally, particle deposition efficiency of different surfaces of the channel was compared with each other and it was reported that particle deposition on the baffles is noticeably higher than on the walls of the channel.