The Effect of Turbulence on Rates of Particle Formation by Homogeneous Nucleation

Lesniewski, T.K.; Friedlander, Sheldon K.

doi:10.1080/02786829508965302

Cited by 43 publications

(41 citation statements)

References 19 publications

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“…This agrees with Lesniewski and Friedlander (1995) where the nucleation rate was calculated using an experimentally measured PDF for vapour concentration and temperature. The changed nucleation rate due to the turbulence led to reduced particle number densities in the shear layer of the jet.…”

Section: Discussionsupporting

confidence: 70%

“…This is done for SF results using a mixing timescale for the aerosols equal to T eddy and also assuming an infinite mixing timescale. As expected assuming infinite Lesniewski (1997), which shows results found in Lesniewski and Friedlander's earlier paper (Lesniewski and Friedlander, 1995). In this they calculate reaction rate for one set of trial conditions, assuming unity Lewis number, in the shear layer using mean values and also by using measured PDF's for concentration and temperature from experimen-tal data.…”

Section: Particle Number Concentrationmentioning

confidence: 54%

“…It also implies that attempting to calculate a nucleation rate for the mean population using only mean vapour concentration and temperature can lead to large errors. This is shown by Lesniewski and Friedlander (1995) who show that for nucleation at the edge of a turbulent jet a sharp ring of nucleation is predicted, if only mean quantities are used, but when turbulence is considered the nucleation region is spread out and the peak significantly lowered.…”

Section: Introductionmentioning

confidence: 89%

“…It has been found (Lesniewski and Friedlander, 1995;Wu and Menon, 2001;Falk and Schaer, 2001) that calculating nucleation, growth and coagulation terms as functions of mean quantitites can lead to significant errors compared to correctly including the effect of turbulence-induced fluctuations. Rigopoulos (2007) performs Reynolds averaging of the governing population balance equation for the evolution of an aerosol population, in order to examine the effects of turbulent fluctuations on these processes.…”

Section: Introductionmentioning

confidence: 99%

“…The effect of turbulence on aerosol processes has been the subject of several recent studies (Lesniewski and Friedlander, 1995;Falk and Schaer, 2001;Moody and Collins, 2003;Rigopoulos, 2007). Wu and Menon (2001) investigated aerosol production in a turbulent jet engine wake.…”

Section: Introductionmentioning

confidence: 99%

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Aerosol nucleation and growth in a turbulent jet using the Stochastic Fields method

Garmory

Mastorakos

2008

Chemical Engineering Science

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The Stochastic Fields transported PDF method for turbulent reacting flows has been used to model the nucleation and growth of Dibutyl Phthalate particles in a hot, turbulent jet in a colder background for which experimental data is available.The aerosol population is modelled using an assumed log-normal size distribution.It has been found that neglecting the effect of turbulent fluctuations leads to the peak particle concentration being predicted too close to the jet and the concentration downstream underpredicted. However, this effect was small compared to that of adjusting modelled surface tension. Only by adjusting this was it possible to reproduce correctly the downstream evolution of particle number found in experiment.Particle mass mean diameter was significantly underpredicted at the centre of the jet, which may be due to the inability of log-normal size distribution to capture the distribution in detail. Taking account of turbulent fluctuations leads to increased mean particle size at the edge of the plume. The extent of this increase is strongly dependent on the choice of micromixing timescale.

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Section: Discussionsupporting

confidence: 70%

Section: Particle Number Concentrationmentioning

confidence: 54%

Section: Introductionmentioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Aerosol nucleation and growth in a turbulent jet using the Stochastic Fields method

Garmory

Mastorakos

2008

Chemical Engineering Science

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Particle nucleation in turbulent gas jets

Lesniewski

Friedlander

1997

AIChE J.

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Experiments were conducted to test the theory of nucleation-controlled growth of spherical particles in a turbulent jet. Dibutyl phthalate (DBP) particles were formed in a bench-scale jet apparatus with nozzle diameters 0.235 cm and 0.375 cm. Size distributions and number concentrations of the particles were measured at different DBP vapor concentrations, jet velocities, and positions.There is evidence that the DBP particle nucleation was confined to the shear layer of the jet and that the particles grew by condensation as they moved away ffom the nozzle. Trends in the data suggest that for low rates of particle formation in jets, the final aerosol concentration can be predicted fiom simple scaling laws. IntroductionHomogeneous nucleation is a temperature-and concentration-dependent process that frequently occurs in turbulent flow. Examples of particle formation by nucleation are emissions from industrial, vehicular and aircraft sources, and process gas mixing. The complexity of turbulent flow fields has made it necessary to make simplifying assumptions, often oversimplifications, in predicting nucleation rates. Turbulent fluctuations have frequently been neglected and calculations based on mean velocity, temperature, and concentration profiles. As methods have been developed to incorporate turbulent fluctuations into models, the effects of these fluctuations have been found to be significant.A condensable vapor at high temperature may become supersaturated as it undergoes turbulent mixing with a gas at lower temperature. When the vapor attains only moderate saturation ratios such that rates of nucleation are in the range lo4 -10' particles/cm3 s, the resulting particle number concentrations are low. Particle-particle collisions are infrequent; growth is by heterogeneous condensation and the particle concentration changes only by dilution. In such cases, the growth is said to be nucleation-controlled because the final particle size and concentration are determined by the rates and duration of homogeneous nucleation in the initial mixing stage.This study focuses on a specific flow system of great practical interest, the turbulent jet. As shown in Figure 1, the flow pattern of a turbulent jet has two distinct regions, the initial and similarity regions. The initial region consists of the potential core, a cone of undisturbed nozzle fluid, surrounded by the shear layer. For aerosol formation studies, the shear layer is very important since it is where incipient turbulent mixing, supersaturation, and homogeneous nucleation occur. Hidy and Friedlander (1964) showed qualitatively that processes occurring in the shear layer of a jet strongly affect particle formation by homogeneous nucleation. Lesniewski and Friedlander (1995) hypothesized that particle formation occurs in the shear layer of the jet, but is quenched as the particles move down the axis. Quenching may occur by three mechanisms: (1) the condensable vapor is diluted by ambient fluid entrained into the jet; (2) the number concentration of newly formed partic...

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Particle deposition in natural gas pipelines using computational fluid dynamics modelling

Veluswamy

Utikar

Pareek

et al. 2011

Asia-Pacific J Chem Eng

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Solid particles within natural gas transmission and distribution pipeline systems are known to create varying operational constraints for pipeline operators—from temporary to complete stoppage of the gas flow. The solid particles can be extremely variable, both in composition and origin. The particles can consist of discrete elements or mechanically and chemically driven combinations of soils, iron oxides, iron sulfides, sulfur compounds, salts, metal oxides, hydrocarbons and other contaminants. These particles tend to get deposited along the walls of gas pipelines under different circumstances. The flow dynamics and the turbulence associated with the flow play an important role in the complex mechanism of particle deposition. In this work, we have shown how turbulence acts as a dominant mechanism in influencing particle deposition. A ball valve's downstream flow was simulated for various opening positions and varying inlet Reynolds numbers to understand turbulence and its effect on particle deposition. The percentage of number of particles getting deposited at the downstream increased on decreasing the valve opening, whereas it was not greatly affected by the change in the inlet Reynolds number. The particle deposition sites at downstream were governed indirectly by valve opening percentage. © 2011 Curtin University of Technology and John Wiley & Sons, Ltd.

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The Effect of Turbulence on Rates of Particle Formation by Homogeneous Nucleation

Cited by 43 publications

References 19 publications

Aerosol nucleation and growth in a turbulent jet using the Stochastic Fields method

Aerosol nucleation and growth in a turbulent jet using the Stochastic Fields method

Particle nucleation in turbulent gas jets

Particle deposition in natural gas pipelines using computational fluid dynamics modelling

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