COAGULATION AND SURFACE LOSSES IN DISPERSE SYSTEMS IN STILL AND TURBULENT AIR

1947 ◽  
Vol 25b (5) ◽  
pp. 455-471 ◽  
Author(s):  
G. O. Langstroth ◽  
T. Gillespie
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Mass Concentration ◽  
Particle Number ◽  
Disperse Systems ◽  
Air Motion ◽  
Chamber Studies ◽  
Smoke Chamber ◽  
Analytical Separation ◽  
The Ideal

Smoke chamber studies have been made of the ageing of ammonium chloride smokes under various controlled degrees of turbulent air motion as well as in still air. The changes in mass concentration and particle number were followed for 5.5 hr. under each set of conditions, and some data on particle size distribution were obtained. The logarithm of the mass concentration was found to vary linearly with time under all conditions. None of the particle number data lent themselves to interpretation on the basis adopted by previous workers. They were described quantitatively by equations developed from general postulates which take into account loss to various surfaces. The equations permitted analytical separation of coagulation and surface effects, and the constant descriptive of the latter was closely related to that associated with mass loss. The coagulation constant for still air was found to be only slightly greater than the ideal Smoluchowski value. A description was obtained of the manner in which the various constants increased with the degree of air motion.

scholarly journals Particle size distribution and particle mass measurements at urban, near-city and rural level in the Copenhagen area and Southern Sweden

2003 ◽  
Vol 3 (6) ◽  
pp. 5513-5546 ◽  
Author(s):  
M. Ketzel ◽  
P. Wåhlin ◽  
A. Kristensson ◽  
E. Swietlicki ◽  
R. Berkowicz ◽  
...  
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Particle Number ◽  
Size Range ◽  
Urban Background ◽  
Total Particle ◽  
Urban Level ◽  
20 Nm ◽  
Traffic Source

Abstract. Particle size distribution (size-range 3–900 nm) and PM10 was measured simultaneously at an urban background station in Copenhagen, a near-city background and a rural location during a period in September-November 2002. The study investigates the contribution from urban versus regional sources of particle number and mass concentration. The total particle number (ToN) and NOx are well correlated at the urban and near-city level and show a distinct diurnal variation, indicating the common traffic source. The average ToN at the three stations differs by a factor of 3. The observed concentrations are 2500 # cm−3, 4500 # cm−3 and 7700 # cm−3 at rural, near-city and urban level, respectively. PM10 and total particle volume (ToV) are well correlated between the three different stations and show similar concentration levels, in average within 30% relative difference, indicating a common source from long-range transport that dominates the concentrations at all locations. Measures to reduce the local urban emissions of NOx and ToN are likely to affect both the street level and urban background concentrations, while for PM10 and ToV only measurable effects at the street level are probable. Taking into account the supposed stronger health effects of ultrafine particles reduction measures should address particle number emissions. The traffic source contributes strongest in the 10–200 nm particle size range. The maximum of the size distribution shifts from about 20–30 nm at kerbside to 50–60 nm at rural level. We also observe particle formation events in the 3–20 nm size range at rural location in the afternoon hours, mainly under conditions with low concentrations of pre-existing aerosol particles. The maximum in the size distribution of the "traffic contribution" seems to be shifted to about 28 nm in the urban location compared to 22 nm at kerbside. Assuming NOx as an inert tracer on urban scale let us estimate that ToN at urban level is reduced by 15–30% compared to kerbside. Particle removal processes, e.g. deposition and coagulation, which are most efficient for smallest particle sizes (<20 nm) and condensational growth are likely mechanisms for the loss of particle number and the shift in particle size.

Effects of Emulsifier Concentration on Nucleation Mode of Emulsion Polymerization of Styrene

2013 ◽  
Vol 395-396 ◽  
pp. 399-402 ◽  
Author(s):  
Li Bao Mei ◽  
Xiao Qin Xiao ◽  
Yong Li ◽  
Yan Lin Sun
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Emulsion Polymerization ◽  
Homogeneous Nucleation ◽  
Particle Number ◽  
Nucleation Mode ◽  
P Fraction ◽  
Emulsifier Concentration

The nucleation mode of emulsion polymerization of styrene under different emulsifier (SDS) concentrations is studied in this paper. Some factors such as conversion, particle number (Np), fraction of coverage, polydispersion index (PDI) and particle size distribution (PSD) of the reactions were investigated. The results show that when [SD is less than its CMC, homogeneous nucleation dominates. But when [SD is more than its CMC, micelle nucleation plays the major role.

scholarly journals Particle size distribution and particle mass measurements at urban,near-city and rural level in the Copenhagen area and Southern Sweden

2004 ◽  
Vol 4 (1) ◽  
pp. 281-292 ◽  
Author(s):  
M. Ketzel ◽  
P. Wåhlin ◽  
A. Kristensson ◽  
E. Swietlicki ◽  
R. Berkowicz ◽  
...  
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Particle Number ◽  
Size Range ◽  
Urban Background ◽  
Rural Location ◽  
Total Particle ◽  
Urban Level ◽  
Traffic Source

Abstract. Particle size distribution (size-range 3-900nm) and PM10 was measured simultaneously at an urban background station in Copenhagen, a near-city background and a rural location during a period in September-November 2002. The study investigates the contribution from urban versus regional sources of particle number and mass concentration. The total particle number (ToN) and NOx are well correlated at the urban and near-city level and show a distinct diurnal variation, indicating the common traffic source. The average ToN at the three stations differs by a factor of 3. The observed concentrations are 2500#cm, 4500#cm and 7700#cm at rural, near-city and urban level, respectively. PM10 and total particle volume (ToV) are well correlated between the three different stations and show similar concentration levels, in average within 30% relative difference, indicating a common source from long-range transport that dominates the concentrations at all locations. Measures to reduce the local urban emissions of NOx and ToN are likely to affect both the street level and urban background concentrations, while for PM10 and ToV only measurable effects at the street level are probable. Taking into account the supposed stronger health effects of ultrafine particles reduction measures should address particle number emissions. The traffic source contributes strongest in the 10-200nm particle size range. The maximum of the size distribution shifts from about 20-30nm at kerbside to 50-60nm at rural level. Particle formation events were observed in the 3-20nm size range at rural location in the afternoon hours, mainly under conditions with low concentrations of pre-existing aerosol particles. The maximum in the size distribution of the "traffic contribution" seems to be shifted to about 28nm in the urban location compared to 22nm at kerbside. Assuming NOx as an inert tracer on urban scale allows to estimate that ToN at urban level is reduced by 15-30% compared to kerbside. Particle removal processes, e.g. deposition and coagulation, which are most efficient for smallest particle sizes (20nm) and condensational growth are likely mechanisms for the loss of particle number and the shift in particle size.

scholarly journals Evolution of Aerosol Particles in the Rainfall Process via Method of Moments

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Fangyang Yuan ◽  
Fujun Gan
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Method Of Moments ◽  
Particle Number ◽  
Aerosol Particles ◽  
Geometric Mean ◽  
Number Concentration ◽  
Brownian Diffusion ◽  
Particle Number Concentration

The method of moments is employed to predict the evolution of aerosol particles in the rainfall process. To describe the dynamic properties of particle size distribution, the population balance equation is converted to moment equations by the method of moments and the converted equations are solved numerically. The variations of particle number concentration, geometric mean diameter, and geometric standard deviation are given in the cases that the Brownian diffusion and inertial impaction of particles dominate, respectively. The effects of raindrop size distribution on particle size distribution are analyzed in nine cases. The results show that the particle number concentration decreases as time goes by, and particles dominated by Brownian diffusion are removed more significantly. The particle number concentration decreases much more rapidly when particle geometric mean diameter is smaller, and the particle size distribution tends to be monodisperse. For the same water content, the raindrops with small geometric mean diameters can remove particles with much higher efficiency than those with large geometric mean diameters. Particles in the “Greenfield gap” are relatively difficult to scavenge, and a new method is needed to remove it from the air.

Effect of fuel composition on properties of particles emitted from a diesel–natural gas dual fuel engine

2019 ◽  
Vol 22 (1) ◽  
pp. 77-87 ◽  
Author(s):  
Ali Momenimovahed ◽  
Fengshan Liu ◽  
Kevin A Thomson ◽  
Gregory J Smallwood ◽  
Hongsheng Guo
Keyword(s):  
Particle Size ◽  
Natural Gas ◽  
Particle Size Distribution ◽  
Photoacoustic Spectroscopy ◽  
Mass Concentration ◽  
Particle Mass ◽  
Effective Density ◽  
Dual Fuel ◽  
Mass Analyzer ◽  
Optical Analysis

The effective density and mixing state of particles emitted from a natural gas–diesel dual fuel engine are investigated. Measurements were conducted at three different fuel compositions including 100% diesel fuel (0% NG), 75% diesel–25% natural gas (25% NG) and 50% diesel–50% NG (50% NG). The particle effective density was measured using a differential mobility analyzer in series with a centrifugal particle mass analyzer. A catalytic stripper at 350 °C was employed upstream of the centrifugal particle mass analyzer in order to remove the semi-volatile material from the solid particles to measure the effective density of non-volatile particles as well as the particle mixing state. A scanning mobility particle sizer was used to measure the particle size distribution. The particle mass concentration was also measured using several techniques including cavity-attenuated phase-shift particulate matter single-scattering albedo, laser-induced incandescence, thermal-optical analysis, photoacoustic spectroscopy, and integrated particle size distribution. The semi-volatile number and mass fractions are found to be lower than 15%. The effective density functions of particles at 0% and 25% NG are within 6% of each other; however, the effective density values of particles at 50% NG are lower than those of the 0% NG by up to 35%. The mass-mobility exponent varies in the range of 2.42–2.51 and 2.38–2.54 for undenuded and denuded particles, respectively. For the mass concentration measurements, photoacoustic spectroscopy agrees with thermal-optical analysis within 5%, while all the other techniques measure up to 50% deviations relative to thermal-optical analysis.

scholarly journals Particle size distribution factor as an indicator for the impact of the Eyjafjallajökull ash plume at ground level in Augsburg, Germany

2011 ◽  
Vol 11 (6) ◽  
pp. 16417-16437 ◽  
Author(s):  
M. Pitz ◽  
J. Gu ◽  
J. Soentgen ◽  
A. Peters ◽  
J. Cyrys
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Long Range ◽  
Mass Concentration ◽  
Volcanic Ash ◽  
Size Range ◽  
Ground Level ◽  
Saharan Dust ◽  
Ash Plume ◽  
The Impact

Abstract. During the time period of the Eyjafjallajökull volcano eruption in 2010 increased mass concentration of PM10 (particulate matter, diameter <10 μm) were observed at ground level in Augsburg, Germany. In particular on 19 and 20 April 2010 the daily PM10 limit value of 50 μg m−3 was exceeded. Because ambient particles are in general a complex mixture originating from different sources, a source apportionment method (positive matrix factorization; PMF) was applied to particle size distribution data in the size range from 3 nm to 10 μm to identify and estimate the volcanic ash contribution to the overall PM10 load in the ambient air in Augsburg. A PMF factor with relevant particle mass concentration in the size range between 1 and 4 μm (maximum at 2 μm) was associated with long range transported dust. This factor increased from background concentration to high levels simultaneously with the arrival of the volcanic ash plume in the planetary boundary layer. Hence, we assume that this factor could be used as an indicator for the impact of the Eyjafjallajökull ash plume on ground level in Augsburg. From 17 to 22 April 2010 long range transported dust factor contributed on average 30.2 % (11.6 μg m−3) to PM10. On 19 April 2010 at 20:00 UTC+1 the maximum percentage of the long range transported dust factor accounted for around 65 % (35 μg m−3) to PM10 and three hours later the maximum absolute value with around 48 μg m−3 (61 %) was observed. Additional PMF analyses for a Saharan dust event occurred in May and June 2008 suggest, that the long range transported dust factor could also be used as an indicator for Saharan dust events.

Analysis of Aerosol Particle Size Distribution,Visibility and Mass Concentration of PM10 in Beijing City During Beijing 2008 Olympics

2010 ◽  
Vol 30 (7) ◽  
pp. 1931-1937
Author(s):  
王杰 Wang Jie ◽  
刘建国 Liu Jianguo ◽  
陆亦怀 Lu Yihuai ◽  
刘文清 Liu Wenqing ◽  
伍德侠 Wu Dexia ◽  
...  
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Aerosol Particle ◽  
Mass Concentration ◽  
Beijing City ◽  
Aerosol Particle Size
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