Effect of Indoor Air Ventilation on Particulate Pollutant Concentration Distribution, Including Nucleation, Coagulation and Surface Growth

2011 ◽  
Author(s):  
Behtash Tavakoli ◽  
Goodarz Ahmadi
Keyword(s):  
Particle Size ◽  
Concentration Distribution ◽  
Fine Particles ◽  
Surface Growth ◽  
High Concentration ◽  
Indoor Airflow ◽  
Air Ventilation ◽  
The Moment ◽  
Ultra Fine Particles ◽  
Analysis Of Dispersion

Typical furniture inside residential or office buildings is made from materials that emit terpenes. Terpenes react with ozone in the air, and produce secondary organic aerosols (SOA). During summer the concentration of SOAs may exceed by a factor of two to five times the concentration in outdoor air. The high concentration of SOA could adversely influence the human health. The air ventilation inside the room as well as the particles’ Brownian motion causes the particles to mix and coagulate. The coagulation of SOAs due to their collision leads to an increase in sizes in time. Coagulation, surface growth and nucleation of particles are the mechanisms which change the particle size and concentration distribution. The particle size distribution is important as large particles sediment rapidly and they are not a health threat for residents while fine and ultra fine particles stay suspended in the air and could enter the human respiratory system. A typical office room with furniture and a manikin was modeled in this study. The indoor airflow was simulated and was followed by the analysis of dispersion and coagulation of particles using the moment method. Two types of ventilation systems were modeled, and the results were compared discussed.

Vaporization and Ultra-Fine Particle Generation during the Plasma Spraying Process

1997 ◽  
Author(s):  
K.A. Gross ◽  
P. Fauchais ◽  
M. Vardelle ◽  
J. Tikkanen ◽  
J. Keskinen
Keyword(s):  
Fine Particles ◽  
High Concentration ◽  
Thermal Spray Process ◽  
Particle Generation ◽  
Spray Process ◽  
Ultra Fine Particle ◽  
Fast Cooling ◽  
Ultra Fine Particles ◽  
Plasma Spraying Process ◽  
Very High

Abstract The thermal spray process melts powder at very high temperatures and propels the molten material to the substrate to produce a coherent deposit. This heating produces a certain amount of vaporization of the feedstock. Upon exiting the plasma plume the fast cooling conditions lead to condensation of the vapor. An electrical low pressure impactor was used to monitor the concentration of ultra-fine particles at various radial and axial distances. Metal, namely iron powder, showed very high concentration levels which increase with distance. Ultra-fine particles from ZrO2-8Y2O3 reached a peak concentration at 6 cm. Use of an air barrier during spraying decreases the population of ultra-fine particles facilitating the production of a stronger coating.

Sedimentation of a Stratified Suspension in a Quiescent Fluid

2007 ◽  
Author(s):  
Takashi Mitsui ◽  
Shusaku Harada ◽  
Kuniomi Asakura
Keyword(s):  
Particle Size ◽  
Settling Velocity ◽  
Fine Particles ◽  
Small Particle Size ◽  
Fluid Interface ◽  
High Concentration ◽  
Particle Assembly ◽  
Sedimentation Behavior ◽  
Surrounding Fluid ◽  
Quiescent Fluid

The sedimentation of fine particles in a stratified suspension, which has both the upper and lower interfaces, is studied experimentally. We measure the settling velocity of particles and observe the diffusion behavior near the interfaces. Especially we examine whether the macroscopic or the microscopic natures of suspension is dominant during sedimentation, i.e., the particles settle as an particle assembly relative to surrounding fluid or as a continuous suspension. The experimental observation shows that the gravity-induced instability of suspension-fluid interface, which has been already reported, governs the particle motion for high concentration and small particle size. However, the microscopic nature of suspension comes out in case of larger particles. In our study, the dependency of the sedimentation behavior on the particle size and the concentration is discussed quantitatively.

The effect of particulate material and the loading of bacteria on a high dose PAC-MF system

2002 ◽  
Vol 2 (5-6) ◽  
pp. 359-365 ◽  
Author(s):  
M.M.T. Khan ◽  
H.-S. Kim ◽  
H. Katayama ◽  
S. Takizawa ◽  
S. Ohgaki
Keyword(s):  
Particle Size ◽  
Membrane Fouling ◽  
Fine Particles ◽  
Age Distribution ◽  
Particulate Material ◽  
High Dose ◽  
High Concentration ◽  
High Accumulation ◽  
Actual Surface ◽  
Total Bacteria

The effects of particulate material, their size distribution and the loading of total bacteria based on the age distribution of powdered activated carbon (PAC) were investigated in a hybrid membrane process consisting of an immersed microfiltration membrane system in a completely aerated reactor containing high concentration (40 g/L) of PAC. The laboratory-scale experiments on PAC-MF system were carried out using actual surface water (Tama River, Tokyo), before and after the treatment by a biofilter media. As a result of continuous filtration and backwash experiments, improvement of filtrate water quality and controls of membrane fouling were demonstrated by the addition of PAC. 52% of the PAC fell into a particle size between 22 μm and 45 μm. PAC larger than 125 μm and smaller than 22 mm were 6% and 4% respectively. Due to continuous aeration and Brownian motion of the particles, the size of the PAC inside the reactor was becoming smaller day by day. After 162 days of operation, the particle size from 1-10 μm was higher, which is the suitable size range for the adsorption of bacteria. At the same time, the number of total bacteria was also increasing inside the reactors. The membranes were fouled shortly during end of the operation due to the heavy load of fine particles and high accumulation of bacteria. However, PAC acts as an adsorbent media inside the reactors that causes successive accumulation of total bacteria.

scholarly journals High Concentration Fine Particle Separation Performance in Hydrocyclones

Minerals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 307
Author(s):  
Yuekan Zhang ◽  
Meng Yang ◽  
Lanyue Jiang ◽  
Hui Wang ◽  
Jinguang Xu ◽  
...  
Keyword(s):  
Particle Size ◽  
Fine Particle ◽  
Fine Particles ◽  
Volume Fraction ◽  
Separation Performance ◽  
Centrifugal Separation ◽  
Discrete Phase Model ◽  
High Concentration ◽  
Ansys Fluent ◽  
Discrete Phase

The vast majority of current research on hydrocyclone field centrifugal separation focuses on low concentration fluids having volume fraction less than 3%. For high-concentration fluids having volume fractions greater than 10%, which are often encountered in engineering, the law governing particle motion and the classification mechanism are still unclear. In order to gain insights into the interaction between fine particles in the high concentration hydrocyclone field and to improve the hydrocyclone separation performance of these particles, a Dense Discrete Phase Model (DDPM) of the Euler-Eulerian method under the Ansys Fluent 14.5 software was employed. Numerical simulations were carried out to study the characteristics of the hydrocyclone field of dense particles and the influence of parameters, such as the diameter of the overflow outlet, diameter of the underflow outlet, and material concentration, on separation performance. The trajectories and separation efficiencies of two kinds of fine particles with different densities and six different particle sizes at high concentration were obtained. The results show that for the hydrocyclone classification of high-concentration fine particles, particles with large density and small particle size are more likely to enter the internal cyclone and discharge from the overflow. Particles with small density and large particle size are more likely to enter the external cyclone and discharge from the underflow. The research results of this topic could provide a feasible reference and theoretical basis for the centrifugal separation of high-concentration fine particle fluid.

Studies of copper selenide ultrafine particles by newly developed gas evaporation method

1990 ◽  
Vol 48 (4) ◽  
pp. 306-307
Author(s):  
Chihiro Kaito ◽  
Yoshio Saito
Keyword(s):  
Crystal Structure ◽  
Ultrafine Particles ◽  
Fine Particles ◽  
Production Method ◽  
Atmospheric Temperature ◽  
Copper Selenide ◽  
Quartz Boat ◽  
Selenium Vapor ◽  
Ar Gas ◽  
Ultra Fine Particles

The direct evaporation of metallic oxides or sulfides does not always given the same compounds with starting material, i.e. decomposition took place. Since the controll of the sulfur or selenium vapors was difficult, a similar production method for oxide particles could not be used for preparation of such compounds in spite of increasing interest in the fields of material science, astrophysics and mineralogy. In the present paper, copper metal was evaporated from a molybdenum silicide heater which was proposed by us to produce the ultra-fine particles in reactive gas as shown schematically in Figure 1. Typical smoke by this method in Ar gas at a pressure of 13 kPa is shown in Figure 2. Since the temperature at a location of a few mm below the heater, maintained at 1400° C , were a few hundred degrees centigrade, the selenium powder in a quartz boat was evaporated at atmospheric temperature just below the heater. The copper vapor that evaporated from the heater was mixed with the stream of selenium vapor,and selenide was formed near the boat. If then condensed by rapid cooling due to the collision with inert gas, thus forming smoke similar to that from the metallic sulfide formation. Particles were collected and studied by a Hitachi H-800 electron microscope.Figure 3 shows typical EM images of the produced copper selenide particles. The morphology was different by the crystal structure, i.e. round shaped plate (CuSe;hexagona1 a=0.39,C=l.723 nm) ,definite shaped p1 ate(Cu5Se4;Orthorhombic;a=0.8227 , b=1.1982 , c=0.641 nm) and a tetrahedron(Cu1.8Se; cubic a=0.5739 nm). In the case of compound ultrafine particles there have been no observation for the particles of the tetrahedron shape. Since the crystal structure of Cu1.8Se is the anti-f1uorite structure, there has no polarity.

The effect of Tin additionon on Structural and magnetic properties of the stannoferrite Li0.5+0.5XFe2.5-1.5XSnXO4

2016 ◽  
Vol 12 (3) ◽  
pp. 4307-4321 ◽  
Author(s):  
Ahmed Hassan Ibrahim ◽  
Yehia Abbas
Keyword(s):  
Particle Size ◽  
Fine Particles ◽  
Magnetic Moments ◽  
Lithium Ferrite ◽  
Tem Analysis ◽  
Weiss Temperature ◽  
X Ray ◽  
Two Phases ◽  
Nanocrystalline Ferrite ◽  
20 Nm

The physical properties of ferrites are verysensitive to microstructure, which in turn critically dependson the manufacturing process.Nanocrystalline Lithium Stannoferrite system Li0.5+0.5XFe2.5-1.5XSnXO4,X= (0, 0.2, 0.4, 0.6, 0.8 and 1.0) fine particles were successfully prepared by double sintering ceramic technique at pre-sintering temperature of 500oC for 3 h andthepre-sintered material was crushed and sintered finally in air at 1000oC.The structural and microstructural evolutions of the nanophase have been studied using X-ray powder diffraction (XRD) and the Rietveld method.The refinement results showed that the nanocrystalline ferrite has a two phases of ordered and disordered phases for polymorphous lithium Stannoferrite.The particle size of as obtained samples were found to be ~20 nm through TEM that increases up to ~ 85 nmand isdependent on the annealing temperature. TEM micrograph reveals that the grains of sample are spherical in shape. (TEM) analysis confirmed the X-ray results.The particle size of stannic substituted lithium ferrite fine particle obtained from the XRD using Scherrer equation.Magneticmeasurements obtained from lake shore’s vibrating sample magnetometer (VSM), saturation magnetization ofordered LiFe5O8 was found to be (57.829 emu/g) which was lower than disordered LiFe5O8(62.848 emu/g).Theinterplay between superexchange interactions of Fe3+ ions at A and B sublattices gives rise to ferrimagnetic ordering of magnetic moments,with a high Curie-Weiss temperature (TCW ~ 900 K).

scholarly journals Contribution of Fine Particles to Air Emission at Different Phases of Biomass Burning

Atmosphere ◽  
2019 ◽  
Vol 10 (5) ◽  
pp. 278 ◽  
Author(s):  
Niloofar Ordou ◽  
Igor E. Agranovski
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Fine Particles ◽  
Combustion Process ◽  
Coarse Particles ◽  
Biomass Smoke ◽  
Smoke Particles ◽  
Air Emission ◽  
Entire Duration ◽  
Diffusion Properties

Particle size distribution in biomass smoke was observed for different burning phases, including flaming and smouldering, during the combustion of nine common Australian vegetation representatives. Smoke particles generated during the smouldering phase of combustions were found to be coarser as compared to flaming aerosols for all hard species. In contrast, for leafy species, this trend was inversed. In addition, the combustion process was investigated over the entire duration of burning by acquiring data with one second time resolution for all nine species. Particles were separately characterised in two categories: fine particles with dominating diffusion properties measurable with diffusion-based instruments (Dp < 200 nm), and coarse particles with dominating inertia (Dp > 200 nm). It was found that fine particles contribute to more than 90 percent of the total fresh smoke particles for all investigated species.

scholarly journals A study on highly concentrated lactic acid and the synthesis of lactide from its solution

2021 ◽  
pp. 174751982110210
Author(s):  
Xiaolong Xu ◽  
Lijuan Liu
Keyword(s):  
Lactic Acid ◽  
Acid Solution ◽  
Concentration Distribution ◽  
Raw Material ◽  
High Concentration ◽  
Composition Distribution ◽  
Lactic Acid Solution ◽  
H Nmr ◽  
Back Titration ◽  
Condensed Water

Lactic acid is an important platform compound used as raw material for the production of lactide and polylactic acid. However, its concentration and composition distribution are not as simple as those of common compounds. In this work, the mass concentration distribution of highly concentrated lactic acid is determined by back titration. The components of highly concentrated lactic acid, crude lactide, and polymer after the reaction are analyzed by HPLC. Different concentrations of lactic acid solution were prepared for the synthesis of lactide and its content in the product was determined by 1H NMR analysis. We found that lactide is more easily produced from high-concentration lactic acid solution with which the condensed water is easier to release. Hence, the removal of condensed water is crucial to the formation of lactide, although it is not directly formed by esterification of two molecules of lactic acid.

scholarly journals Experimental Analysis of the Mechanical Properties and Resistivity of Tectonic Coal Samples with Different Particle Sizes

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2303
Author(s):  
Congyu Zhong ◽  
Liwen Cao ◽  
Jishi Geng ◽  
Zhihao Jiang ◽  
Shuai Zhang
Keyword(s):  
Mechanical Properties ◽  
Particle Size ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Uniaxial Compressive Strength ◽  
Coalbed Methane ◽  
Coal Sample ◽  
Fine Particles ◽  
Particle Sizes ◽  
Tectonic Coal

Because of its weak cementation and abundant pores and cracks, it is difficult to obtain suitable samples of tectonic coal to test its mechanical properties. Therefore, the research and development of coalbed methane drilling and mining technology are restricted. In this study, tectonic coal samples are remodeled with different particle sizes to test the mechanical parameters and loading resistivity. The research results show that the particle size and gradation of tectonic coal significantly impact its uniaxial compressive strength and elastic modulus and affect changes in resistivity. As the converted particle size increases, the uniaxial compressive strength and elastic modulus decrease first and then tend to remain unchanged. The strength of the single-particle gradation coal sample decreases from 0.867 to 0.433 MPa and the elastic modulus decreases from 59.28 to 41.63 MPa with increasing particle size. The change in resistivity of the coal sample increases with increasing particle size, and the degree of resistivity variation decreases during the coal sample failure stage. In composite-particle gradation, the proportion of fine particles in the tectonic coal sample increases from 33% to 80%. Its strength and elastic modulus increase from 0.996 to 1.31 MPa and 83.96 to 125.4 MPa, respectively, and the resistivity change degree decreases. The proportion of medium particles or coarse particles increases, and the sample strength, elastic modulus, and resistivity changes all decrease.

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