Part I: Dynamic evolution of the particle size distribution in particulate processes undergoing combined particle growth and aggregation

2004 ◽  
Vol 59 (24) ◽  
pp. 5751-5769 ◽  
Author(s):  
A.H. Alexopoulos ◽  
A.I. Roussos ◽  
C. Kiparissides
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Particle Growth ◽  
Dynamic Evolution ◽  
Particulate Processes

scholarly journals Theoretical analysis of particle size re-distribution due to Ostwald ripening in the fuel cell catalyst layer

Open Physics ◽  
2019 ◽  
Vol 17 (1) ◽  
pp. 779-789 ◽  
Author(s):  
Ambrož Kregar ◽  
Tomaž Katrašnik
Keyword(s):  
Particle Size ◽  
Fuel Cells ◽  
Fuel Cell ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Electric Potential ◽  
Ostwald Ripening ◽  
Particle Growth ◽  
Mean Particle Size ◽  
Fuel Cell Catalyst

Abstract The limited durability of hydrogen fuel cells is one of the main obstacles in their wider adoption as a clean alternative technology for small scale electricity production. The Ostwald ripening of catalyst material is recognized as one of the main unavoidable degradation processes deteriorating the fuel cell performance and shortening its lifetime. The paper systematically studies how the modeling approach towards the electrochemically driven Ostwald ripening in the fuel cell catalyst differs from the classical diffusion driven models and highlights how these differences affect the resulting evolution of particle size distribution. At moderately low electric potential, root-law growth of mean particle size is observed with linear relation between mean particle size and standard deviation of particle size distribution, similar to Lifshitz-Slyozov-Wagner theory, but with broader and less skewed distribution. In case of high electric potential, rapid particle growth regime is observed and qualitatively described by redeposition of platinum from a highly oversaturated solution, revealing the deficiencies of the existing platinum degradation models at describing the Ostwald ripening in the fuel cells at high electric potentials. Several improvements to the established models of platinum degradation in fuel cell catalysts are proposed, aimed at better description of the diffusion processes involved in particle growth due to Ostwald ripening.

scholarly journals Insight into winter haze formation mechanisms based on aerosol hygroscopicity and effective density measurements

2017 ◽  
Author(s):  
Yuanyuan Xie ◽  
Xingnan Ye ◽  
Zhen Ma ◽  
Ye Tao ◽  
Ruyu Wang ◽  
...  
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Particle Growth ◽  
Water Soluble ◽  
Effective Density ◽  
Pollution Level ◽  
Formation Mechanisms ◽  
Haze Pollution ◽  
Haze Formation

Abstract. We characterize a representative haze event from a series of periodic particulate matter (PM) episodes that occurred in Shanghai during winter 2014. Particle size distribution, hygroscopicity, and effective density were measured online, along with analysis of water-soluble inorganic ions and single particle mass spectrometry. Regardless of pollution level, the mass ratio of SNA/PM1.0 (sulfate, nitrate, and ammonium) slightly fluctuated around 0.28 over the whole observation, suggesting that both secondary inorganic compounds and carbonaceous aerosols (including soot and organic matter) contributed substantially to the haze formation. Nitrate was the most abundant ionic species during hazy periods, indicating that NOx contributed more to haze formation in Shanghai than did SO2. The calculated PM concentration from particle size distribution displayed a variation pattern similar to that of measured PM1.0 during the representative PM episode, indicating that enhanced pollution level was attributable to the elevated number of larger particles. The number fraction of the near-hydrophobic group increased as the PM episode developed, indicating accumulation of local emissions. Three "banana-shape" particle evolutions were consistent with the rapid increase in PM1.0 mass loading, indicating rapid size growth by condensation of condensable materials was responsible for the severe haze formation. Both hygroscopicity and effective density of the particles increased considerably with growing particle size during the banana-shaped evolutions, indicating that secondary transformation of NOx and SO2 was a major contributor to the particle growth. Our results suggest that the accumulation of gas-phase and particulate pollutants under stagnant meteorological conditions and subsequent rapid particle growth by secondary processes, were primarily responsible for the haze pollution in Shanghai during wintertime.

Effect of Fluid Dynamics on Particle Size Distribution in Particulate Processes

2006 ◽  
Vol 29 (2) ◽  
pp. 191-199 ◽  
Author(s):  
D. L. Marchisio ◽  
M. Soos ◽  
J. Sefcik ◽  
M. Morbidelli ◽  
A. A. Barresi ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Particulate Processes
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