Experimental investigation of the effects of turbulence intensity on frazil ice characteristics

2008 ◽  
Vol 35 (1) ◽  
pp. 67-79 ◽  
Author(s):  
Shawn Clark ◽  
John Doering
Keyword(s):  
Particle Size ◽  
Standard Deviation ◽  
Turbulence Intensity ◽  
Particle Diameter ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Frazil Ice ◽  
Rotating Flume ◽  
The Mean ◽  
Hot Film

The counter-rotating flume at the University of Manitoba was used to conduct a series of 21 laboratory experiments to investigate the effects of turbulence intensity on frazil ice formation and evolution. A detailed study of the velocity and turbulence intensity distributions within the counter-rotating flume was initially conducted using a constant-temperature anemometer equipped with a one-dimensional conical hot-film probe. Five levels of turbulence intensity were generated by five different sets of bed plates and flume wall rotation rates in order to study how turbulence affected the frazil particle size distributions and the statistics related to clear disk-shaped particles. It was found that a lognormal distribution could not be rejected when describing the frazil particle size distributions, regardless of the turbulence intensity of the water. The variation of the mean and standard deviation of particle diameter with turbulence intensity are well described by a parabolic shape. A preliminary equation to describe the variation of the mean and standard deviation of particle diameter as a function of turbulence intensity and time is presented.

Synthesis of Immiscible Alloys by the Mixalloying Process

1989 ◽  
Vol 111 (1) ◽  
pp. 70-78 ◽  
Author(s):  
S. Tu¨rker Oktay ◽  
Chong N. Chu ◽  
Nannaji Saka ◽  
Nam P. Suh
Keyword(s):  
Particle Size ◽  
Computational Simulation ◽  
Particle Diameter ◽  
Al Alloys ◽  
Size Distributions ◽  
Simulation Studies ◽  
Particle Size Distributions ◽  
The Mean ◽  
Log Normal ◽  
Mean Particle Diameter

Dispersed-phase microstructures of the immiscible Pb-Zn, Pb-Zn-Sn and Pb-Al alloys were produced by the Mixalloying Process [1]. The particle size was found to follow the log-normal statistical distribution and the mean particle diameter correlated well with the –3/5th power of the Weber number. Furthermore, computational simulation studies showed that the particle-size distributions became significantly broader due to Stokes coalescence during solidification.

The ATAL and its aerosol microphysical properties in the Asian Monsoon Anticyclone

2020 ◽  
Author(s):  
Christoph Mahnke ◽  
Stephan Borrmann ◽  
Ralf Weigel ◽  
Francesco Cairo ◽  
Armin Afchine ◽  
...  
Keyword(s):  
Particle Size ◽  
Asian Monsoon ◽  
Extreme Values ◽  
Monsoon Season ◽  
Measurement Techniques ◽  
Potential Temperature ◽  
Particle Diameter ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Microphysical Properties

<p>During the StratoClim 2017 measurement campaign in Nepal, within the Asian Monsoon Anticyclone (AMA), measurements of the aerosols’ microphysical properties up to UT/LS altitudes were successfully completed with a modified version of the commercially available (Droplet Measurement Technologies Inc.) aerosol spectrometer UHSAS-A. Technical rearrangements of parts of the UHSAS-A were developed and implemented, which improve the instrument’s measuring performance and extend its airborne application range from around 12 km altitude to the extreme ambient conditions in the stratosphere at heights of 20 km. The measurement techniques used for this purpose were characterized by laboratory experiments.</p><p>Within the AMA region, extreme values of the particle mixing ratio (PMR) ranging between 6 mg<sup>-1</sup> and about 10000 mg<sup>-1</sup> were found with the UHSAS-A (particle diameter range: 65 nm to 1000 nm). The median of the PMR for all research flights was about 1300 mg<sup>-1</sup> close to the ground. Within tropospheric altitudes, the PMR was highly variable and median values between 70 mg<sup>-1</sup> and 400 mg<sup>-1</sup> were observed.  At levels of 370 K potential temperature, the median PMR maximally reaches about 700 mg<sup>-1 </sup>while the 1 Hz resolved measurements show values up to about 10000 mg<sup>-1</sup>. Between 450 K and 475 K, median PMR between 40 mg<sup>-1</sup> and 50 mg<sup>-1</sup> were observed. The aerosol size distributions (measured by the UHSAS-A) were extended by an additional diameter size bin obtained from the 4-channel Condensation Particle counting System (COPAS), i.e. for aerosol diameter between 10 nm and 65 nm.</p><p>The UHSAS-A measured aerosol particle size distributions were compared with balloon-borne measurements (by T. Deshler et al., Dep. of Atmospheric Science, University of Wyoming, USA) at altitudes of up to 20 km. These show that the size distributions measured during the StratoClim 2017 campaign fit well within the range of the balloon-borne measurements during the Asian Monsoon season over India (Hyderabad) in 2015 and the USA (Laramie) in 2013. Further analyses of measured particle size distributions by means of backscatter ratio show remarkable consistency with CALIOP satellite observations of the ATAL during the StratoClim mission period.</p>

Gas-phase particle size distributions and lead loss during spray pyrolysis of (Bi,Pb)–Sr–Ca–Cu–O

1995 ◽  
Vol 10 (7) ◽  
pp. 1644-1652 ◽  
Author(s):  
Abhijit S. Gurav ◽  
Toivo T. Kodas ◽  
Jorma Joutsensaari ◽  
Esko I. Kauppincn ◽  
Riitta Zilliacus
Keyword(s):  
Particle Size ◽  
Spray Pyrolysis ◽  
Gas Phase ◽  
Phase Particle ◽  
Average Particle Size ◽  
Particle Diameter ◽  
Processing Temperature ◽  
Average Particle ◽  
Size Distributions ◽  
Particle Size Distributions

Gas-phase particle size distributions and lead loss were measured during formation of (Bi,Pb)-Sr-Ca-Cu-O and pure PbO particles by spray pyrolysis at different temperatures. A differential mobility analyzer (DMA) in conjunction with a condensation particle counter (CPC) was used to monitor the gas-phase particle size distributions, and a Berner-type low-pressure impactor was used to obtain mass size distributions and size-classified samples for chemical analysis. For (Bi,Pb)-Sr-Ca-Cu-O, as the processing temperature was raised from 200 to 700 °C, the number average particle size decreased due to metal nitrate decomposition, intraparticle reactions forming mixed-metal oxides and particle densification. The geometric number mean particle diameter was 0.12 μm at 200 °C and reduced to 0.08 and 0.07 μm, respectively, at 700 and 900 °C. When the reactor temperature was raised from 700 and 800 °C to 900 °C, a large number (∼107 no./cm3) of new ultrafine particles were formed from PbO vapor released from the particles and the reactor walls. Particles made at temperatures up to 700 °C maintained their initial stoichiometry over the whole range of particle sizes monitorcd; however, those made at 800 °C and above were heavily depleted in lead in the size range 0.5–5.0 μm. The evaporative losses of lead oxide from (Bi,Pb)-Sr-Ca-Cu-O particles were compared with the losses from PbO particles to gain insight into the pathways involved in lead loss and the role of intraparticle processes in controlling it.

scholarly journals The Influence of Wildfires on Aerosol Size Distributions in Rural Areas

2012 ◽  
Vol 2012 ◽  
pp. 1-13 ◽  
Author(s):  
E. Alonso-Blanco ◽  
A. I. Calvo ◽  
R. Fraile ◽  
A. Castro
Keyword(s):  
Particle Size ◽  
Rural Areas ◽  
Size Distributions ◽  
Average Increase ◽  
Particle Size Distributions ◽  
Before And After ◽  
Fine Mode ◽  
The Mean ◽  
The One ◽  
Number Of Particles

The number of particles and their size distributions were measured in a rural area, during the summer, using a PCASP-X. The aim was to study the influence of wildfires on particle size distributions. The comparative studies carried out reveal an average increase of around ten times in the number of particles in the fine mode, especially in sizes between 0.10 and 0.14 μm, where the increase is of nearly 20 times. An analysis carried out at three different points in time—before, during, and after the passing of the smoke plume from the wildfires—shows that the mean geometric diameter of the fine mode in the measurements affected by the fire is smaller than the one obtained in the measurements carried out immediately before and after (0.14 μm) and presents average values of 0.11 μm.

Effect of Synthesis Parameter on Properties of Heat-Sensitive Nanocapsules

2013 ◽  
Vol 675 ◽  
pp. 302-305
Author(s):  
Pu Ying An ◽  
Zhao Yun Yu ◽  
Hai Song Zhang ◽  
Xin Wu Ba
Keyword(s):  
Particle Size ◽  
Glass Transition ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Glass Transition Temperatures ◽  
Hyperbranched Poly ◽  
Crosslinker Content ◽  
Mean Size ◽  
The Mean ◽  
Triton X

The crosslinked poly(methylmethacrylate) (PMMA) heat-sensitive nanocapsules were prepared by emulsion polymerization, in which Triton X-100 was used as an emulsifier and unsaturated hyperbranched poly(amide-ester) (UHBP) as a crosslinker. The effects of three determinative process parameters on the particle size distributions, glass transition temperatures(Tgs) and heat sensitive color-developing properties of nanocapsules were investigated in detail. As a result, the mean size of nanocapsules became smaller and their particle size distribution became narrower with the increase in emulsifying rate. The Tg of nanocapsules was 123.8°C with the emulsifier content being 0.6%. The color-developing absorbency was the highest with the crosslinker content being 6.0 %.

scholarly journals Physical and chemical properties of the regional mixed layer of Mexico's Megapolis Part II: evaluation of measured and modeled trace gases and particle size distributions

2012 ◽  
Vol 12 (21) ◽  
pp. 10161-10179 ◽  
Author(s):  
C. Ochoa ◽  
D. Baumgardner ◽  
M. Grutter ◽  
J. Allan ◽  
J. Fast ◽  
...  
Keyword(s):  
Particle Size ◽  
Standard Deviation ◽  
Transport Model ◽  
Trace Gases ◽  
Research Station ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Air Masses ◽  
Accumulation Mode ◽  
Mountain Site

Abstract. This study extends the work of Baumgardner et al. (2009) in which measurements of trace gases and particles, at a remote, high altitude mountain site, 60 km from Mexico City were analyzed with respect to the origin of the air masses. In the current evaluation, the temperature, water vapor mixing ratio (WMR), ozone (O3), carbon monoxide (CO), sulfur dioxide (SO2) and acyl peroxy nitrate (APN) are simulated with the WRF-Chem chemical transport model and compared with the measurements at the mountain site. Comparisons between the model and measurements are also evaluated for particle size distributions (PSDs) of the mass concentrations of sulfate, nitrate, ammonium and organic mass (OM). The model predictions of the diurnal trends in temperature, WMR and trace gases were generally well correlated; 13 of the 18 correlations were significant at a confidence level of <0.01. Less satisfactory were the average hourly differences between model and measurements that showed predicted values within expected, natural variation for only 10 of the 18 comparisons. The model performed best when comparing with the measurements during periods when the air originated from the east. In that case all six of the parameters being compared had average differences between the model and measurements less than the expected standard deviation. For the cases when the air masses are from the southwest or west northwest, only two of the comparisons from each case showed differences less than the expected standard deviation. The differences appear to be a result of an overly rapid growth of the boundary layer predicted by the model and too much dilution. There also is more O3 being produced, most likely by photochemical production, downwind of the emission sources than is predicted by the model. The measured and modeled PSD compare very well with respect to their general shape and the diameter of the peak concentrations. The spectra are log normally distributed with most of the mass in the accumulation mode centered at 200 ± 20 nm and little observed or predicted changes with respect to the time when the RML is above the Altzomoni research station. Only the total mass changes with time and air mass origin. The invariability of average diameter of the accumulation mode suggests that there is very little growth of the particles by condensation or coagulation after six hours of aging downwind of the major sources of anthropogenic emissions in Mexico's Megapolis. This could greatly simplify parameterization in climate models although it is not known at this time if this invariance can be extended to other megacity regions.

“Heavy” Particle Dispersion Measurements With Mono- and Polydisperse Particle Size Distributions

1993 ◽  
Vol 115 (3) ◽  
pp. 523-526 ◽  
Author(s):  
J. R. Ferguson ◽  
D. E. Stock
Keyword(s):  
Particle Size ◽  
Standard Deviation ◽  
Size Distribution ◽  
Heavy Particle ◽  
Particle Dispersion ◽  
Turbulent Dispersion ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Monodisperse Particles ◽  
Polydisperse Particle

A method is presented to estimate the effects of a polydisperse particle size distribution on the measured turbulent dispersion of particles. In addition, the analysis provides a means to estimate the standard deviation of the size distribution for which a class of particles may be considered monodisperse. If monodisperse particles are unavailable because of practical considerations (e.g., the required standard deviation of particle size is too small to obtain a sufficient quantity) then the method provides a means to correct the data of near monodisperse size distributions to reflect the dispersion of monodisperse particles.

Advances in the Characterization of Particle Size Distributions of Abrasive Particles used in CMP

2007 ◽  
Vol 991 ◽  
Author(s):  
Mungai Kamiti ◽  
Stacey Popadowski ◽  
Edward E. Remsen
Keyword(s):  
Particle Size ◽  
Colloidal Silica ◽  
Particle Diameter ◽  
Water Soluble ◽  
Size Distributions ◽  
Organic Additives ◽  
Particle Size Distributions ◽  
Abrasive Particles ◽  
Theoretical Simulations

ABSTRACTThe use of density gradient stabilized centrifugal sedimentation (disc centrifugation) for the characterization of abrasive particles in CMP slurries is reported. For slurries prepared with ceria and colloidal silica abrasives, the technique is demonstrated as capable of providing highly repeatable analyses of the abrasive's apparent particle size distribution (PSD). The addition of water soluble organic additives to the slurries is shown to produce large shifts in the apparent PSD relative to the PSD of the pure abrasive particles. Particle-additive interactions driving the shift in apparent PSD could not be interpreted with confidence due to the lack of accurate densities for particle-abrasive complexes formed in the slurry. To address this problem, sucrose density gradients prepared using H2O and D2O were tested as spin fluids of different densities to analyze a colloidal silica standard with a narrow PSD. Preliminary results comparing experimental disc centrifuge data with theoretical simulations of the disc sedimentation pattern suggest that this technique can potentially characterize both the particle diameter and density of abrasive particles in a CMP slurry.

Numerical study on key issues in the Eulerian-Eulerian simulation of fluidization with wide particle size distributions

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Yang Liu ◽  
Haigang Wang ◽  
Yinqiang Song ◽  
Haiying Qi
Keyword(s):  
Particle Size ◽  
Numerical Study ◽  
Particle Diameter ◽  
Flow Characteristics ◽  
Average Particle ◽  
Size Distributions ◽  
Particle Phase ◽  
Particle Size Distributions ◽  
Particle Volume ◽  
Eulerian Approach

Abstract Gas-particle flows in circulating fluidized beds (CFB) with wide particle size distributions were simulated using the Eulerian-Eulerian approach to analyze the effects of the particle phase division and the applicability of the particle-particle drag model. The results indicate that the simulation is not accurate by just using a single average particle diameter when the particle size distribution includes a critical particle diameter. A binary particle phase division criterion was then developed to establish two particle phases representing two types of particles with different flow patterns. Coupling the Eulerian-Eulerian approach with the new criterion enabled accurate predictions of the pressures, particle volume fractions, and particle mass circulation rates that were in agreement with experimental data. The influences of different particle-particle drag models were also investigated to show that the simulation using the Syamlal model was not accurate due to the overestimated particle-particle drag, while the results without particle-particle drag and with the Manger model were similar and much more accurate. Moreover, the flow mechanism for the non-uniformity of particle circulation rates in the parallel circulating loops of the CFB boiler was revealed. This study improves the Eulerian-Eulerian simulations of fluidization with wide particle size distributions and further deepens the understanding of flow characteristics in CFB.

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