scholarly journals Deposition of aerosols in cylindrical tubes and in human lung airways

2010 ◽  
Author(s):  
◽  
Veera Rajesh Gutti
Keyword(s):  
Carbon Nanoparticles ◽  
Particle Deposition ◽  
Human Lung ◽  
Numerical Technique ◽  
Cylindrical Tube ◽  
Deposition Efficiency ◽  
Surface Geometry ◽  
The Real ◽  
Cylindrical Tubes ◽  
Lung Airways

Aerosol transport and deposition is of interest in many industrial and medical applications. This research is focused on two specific topics: deposition of aerosols in cylindrical tubes with emphasis on thermophoresis and deposition in real human lung airways. A numerical technique and a CFD code FLUENT are explored and used to estimate particle deposition efficiency due to thermophoresis in cylindrical tubes. Discrete phase modeling (DPM) employing Lagrangian particle tracking algorithm in CFD code FLUENT and user defined functions for thermophoretic force were used to predict the particle deposition efficiencies. Further, limited experiments were conducted to measure the thermophoretic deposition efficiency of carbon nanoparticles in a cylindrical tube. Real lung airway geometry for computational purposes was developed using Computed Tomography (CT) scan images of chest. Using image segmentation, volume rendering and surface processing tools in two commercially available software programs, the real lung airway surface geometry was extracted with good anatomical detail. Particle deposition was modeled using species transport and reaction modeling for molecular phase radioactive polonium-218 species in air. DPM model was also used to compute deposition of particles inhaled in the real lung airway geometry. The computational models used were verified against available experimental data for simpler single bifurcation geometries. Particle deposition efficiencies were computed using the DPM model for carbon nanoparticles of sizes 100 to 1000 nm.

scholarly journals Numerical Simulation of the Aerosol Particle Motion in Granular Filters with Solid and Porous Granules

Processes ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 268
Author(s):  
Olga V. Soloveva ◽  
Sergei A. Solovev ◽  
Ruzil R. Yafizov
Keyword(s):  
Numerical Simulation ◽  
Aerosol Particle ◽  
Particle Deposition ◽  
Particle Diameter ◽  
Deposition Efficiency ◽  
Hydrodynamic Resistance ◽  
Hydrodynamic Properties ◽  
Granular Filters ◽  
Limiting Value ◽  
Good Agreement

In this work, a study was carried out to compare the filtering and hydrodynamic properties of granular filters with solid spherical granules and spherical granules with modifications in the form of micropores. We used the discrete element method (DEM) to construct the geometry of the filters. Models of granular filters with spherical granules with diameters of 3, 4, and 5 mm, and with porosity values of 0.439, 0.466, and 0.477, respectively, were created. The results of the numerical simulation are in good agreement with the experimental data of other authors. We created models of granular filters containing micropores with different porosity values (0.158–0.366) in order to study the micropores’ effect on the aerosol motion. The study showed that micropores contribute to a decrease in hydrodynamic resistance and an increase in particle deposition efficiency. There is also a maximum limiting value of the granule microporosity for a given aerosol particle diameter when a further increase in microporosity leads to a decrease in the deposition efficiency.

Experimental and Mechanism Investigation on Boiling Heat Transfer Characteristics of Alumina/Water Nanofluid on a Cylindrical Tube

NANO ◽  
2019 ◽  
Vol 14 (10) ◽  
pp. 1950124
Author(s):  
Hao Zhang ◽  
Zeng-en Li ◽  
Shan Qing ◽  
Zhuangzhuang Jia ◽  
Jiarui Xu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Particle Deposition ◽  
Heat Transfer Performance ◽  
Pool Boiling ◽  
Heating Surface ◽  
Cylindrical Tube ◽  
Influential Factors ◽  
Transfer Performance ◽  
Pool Boiling Heat Transfer

Nucleate pool boiling heat transfer experiments have been conducted to nanofluids on a horizontal cylinder tube under atmospheric pressure. The nanofluids are prepared by dispersing Al2O3 nanoparticles into distilled water at concentrations of 0.001, 0.01, 0.1, 1 and 2[Formula: see text]wt.% with or without sodium, 4-dodecylbenzenesulfonate (SDBS). The experimental results showed that: nanofluids at lower concentrations (0.001[Formula: see text]wt.% to 1[Formula: see text]wt.%) can obviously enhance the pool boiling heat transfer performance, but signs of deterioration can be observed at higher concentration (2[Formula: see text]wt.%). The presence of SDBS can obviously enhance the pool boiling heat transfer performance, and with the presence of SDBS, a maximum enhancement ratio of BHTC of 69.88%, and a maximum decrease ratio of super heat of 41.12% can be found in Group NS5 and NS4, respectively. The tube diameter and wall thickness of heating surface are the influential factors for boiling heat transfer coefficient. Besides, we find that Rohsenow formula failed to predict the characteristics of nanofluids. The mechanism study shows that: the decrease of surface tension, which leads to the decrease of bubble departure diameter, and the presence of agglomerates in nanofluids are the reasons for the enhanced pool boiling heat transfer performance. At higher concentration, particle deposition will lead to the decrease of distribution density of the vaporization core, and as a result of that, the boiling heat transfer performance will deteriorate.

Particle deposition efficiency at air–liquid interface of a cell exposure chamber

2015 ◽  
Vol 81 ◽  
pp. 90-99 ◽  
Author(s):  
Yuji Fujitani ◽  
Yutaka Sugaya ◽  
Masanori Hashiguchi ◽  
Akiko Furuyama ◽  
Seishiro Hirano ◽  
...  
Keyword(s):  
Particle Deposition ◽  
Deposition Efficiency ◽  
Liquid Interface ◽  
Exposure Chamber ◽  
A Cell ◽  
Air Liquid Interface

scholarly journals Particle Deposition Characteristics and Efficiency in Duct Air Flow over a Backward-Facing Step: Analysis of Influencing Factors

2019 ◽  
Vol 11 (3) ◽  
pp. 751
Author(s):  
Hao Lu ◽  
Li-zhi Zhang
Keyword(s):  
Particle Deposition ◽  
Air Flow ◽  
Deposition Velocity ◽  
Particle Diameter ◽  
Deposition Efficiency ◽  
Reynolds Stress Model ◽  
Expansion Ratio ◽  
Particle Model ◽  
Duct Flow ◽  
Backward Facing Step

Dry deposition of airborne particles in duct air flow over a backward-facing step (BFS) is commonly encountered in built environments and energy engineering. However, the understanding of particle deposition characteristics in BFS flow remains insufficient. Thus, this study investigated particle deposition behaviors and efficiency in BFS flow by using the Reynolds stress model and the discrete particle model. The influences of flow velocities, particle diameters, and duct expansion ratios on particle deposition characteristics were examined and analyzed. After numerical validation, particle deposition velocities, deposition efficiency, and deposition mechanisms in BFS duct flow were investigated in detail. The results showed that deposition velocity in BFS duct flow monotonically increases when particle diameter increases. Moreover, deposition velocity falls with increasing expansion ratio but rises with increasing air velocity. Deposition efficiency, the ratio of deposition velocity, and flow drag in a BFS duct is higher for small particles but lower for large particles as compared with a uniform duct. A higher particle deposition efficiency can be achieved by BFS with a smaller expansion ratio. The peak deposition efficiency can reach 33.6 times higher for 1-μm particles when the BFS expansion ratio is 4:3. Moreover, the “particle free zone” occurs for 50-μm particles in the BFS duct and is enlarged when the duct expansion ratio increases.

Effect of Gas Temperature on the Particle Deposition Characteristics and Coating Microstructure by Cold Spray

2011 ◽  
Vol 675-677 ◽  
pp. 1295-1298
Author(s):  
Xian Ming Meng ◽  
Jun Bao Zhang ◽  
Yong Li Liang ◽  
Wei Han ◽  
Jie Zhao
Keyword(s):  
Critical Velocity ◽  
Particle Deposition ◽  
Deposition Efficiency ◽  
Shear Instability ◽  
304 Stainless Steel ◽  
Interface Bonding ◽  
Instability Mechanism ◽  
Gas Temperature ◽  
Coating Microstructure ◽  
Steel Substrates

In this study, 304 stainless steel particles were deposited on IF steel substrates by cold dynamic spray technology. The effect of gas temperature on bonding features and deposition critical velocity were studied and compared. The results demonstrated that the successful bonding between 304SS particle and substrate could be attributed to the adiabatic shear instability mechanism, increasing gas temperature led to enhance the particle interface bonding, deduce the deposition critical velocity, and also increase both deposition efficiency and density of coatings.

Investigation of particle deposition efficiency enhancement in turbulent duct air flow by surface ribs with hybrid-size ribs

2016 ◽  
Vol 26 (5) ◽  
pp. 608-620 ◽  
Author(s):  
Hao Lu ◽  
Lin Lu
Keyword(s):  
Particle Deposition ◽  
Air Flow ◽  
Deposition Efficiency ◽  
Dynamics Simulation ◽  
Particle Model ◽  
Particle Removal ◽  
Cleaning Equipment ◽  
Discrete Particle Model ◽  
Turbulent Air Flow ◽  
Flow Drag

This study presents the particle deposition enhancement by hybrid-size and same-size surface ribs in turbulent air duct flows using computational fluid dynamics simulation. The Reynolds stress turbulence model with UDF corrections and discrete particle model were adopted to simulate the turbulent air flow fields and particle deposition behaviours, respectively. After numerical validation with the relative literature results, pure particle deposition enhancement ratios, flow drag increase, comprehensive deposition efficiency and deposition enhancement mechanisms were investigated and discussed in details. The findings showed that the hybrid-size ribs with small rib spacing have the best enhancement performance on particle deposition for small particles ([Formula: see text]). Considering the flow drag increase, the maximum deposition efficiency can reach 485 for 1 µm particles for the hybrid-size ribbed cases, while it is just 425 for the same-size ribbed case. Nevertheless, no obvious particle deposition enhancement can be found for large particles ([Formula: see text]) for all types of surface ribs. The hybrid-size surface ribs are more efficient compared with the same-size ribs, which can be applied in the air cleaning equipment to improve the aerosol particle removal performance.

Toroidal equilibrium of rotating plasma with adiabatic constraints

1994 ◽  
Vol 52 (1) ◽  
pp. 129-140 ◽  
Author(s):  
A. Gałkowski ◽  
R. Żelazny
Keyword(s):  
Equilibrium Problem ◽  
Stability Criterion ◽  
Numerical Technique ◽  
Magnetic Axis ◽  
Governing Equations ◽  
Surface Geometry ◽  
Adiabatic Evolution ◽  
Flux Surface ◽  
Toroidal Plasma

A numerical technique, alternative to Grad's well-known ADM method has been proposed to deal with the slow adiabatic evolution of a toroidal plasma with flow. The equilibrium problem with prescribed adiabatic constraints may be solved by simultaneous calculations of flux surface geometry and original profile functions. Implications for the problem of bifurcation due to nonlinearity of the governing equations are discussed. In the case of field-aligned sub-Alfvénic flow the system is in the second elliptic regime if β <A2/(1 – A2) at the magnetic axis, where A is the Mach Alfvén number of the flow. Super-Alfvénic flows do not satisfy the local firehose stability criterion.

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