scholarly journals Determination of the Critical Supersaturation Ratio in Heterogeneous Nucleation of Benzene Vapor on a Cold Substrate.

1992 ◽  
Vol 25 (2) ◽  
pp. 139-146 ◽  
Author(s):  
Hideo Shinagawa ◽  
Kenichiro Sotowa ◽  
Yuji Kawamura ◽  
Kikuo Okuyama
Keyword(s):  
Heterogeneous Nucleation ◽  
Benzene Vapor ◽  
Supersaturation Ratio ◽  
Critical Supersaturation

Determination of Critical Supersaturation from Microdroplet Evaporation Experiments

2006 ◽  
Vol 6 (5) ◽  
pp. 1175-1180 ◽  
Author(s):  
Guangwen He ◽  
Venkateswarlu Bhamidi ◽  
Reginald B. H. Tan ◽  
Paul J. A. Kenis ◽  
Charles F. Zukoski
Keyword(s):  
Critical Supersaturation

Molecular Dynamics Simulation of Nano Cluster-Seed Effects on Heterogeneous Nucleation

2009 ◽  
Author(s):  
Donguk Suh ◽  
Seung-chai Jung ◽  
Woong-sup Yoon
Keyword(s):  
Molecular Dynamics ◽  
Heterogeneous Nucleation ◽  
Three Dimensional ◽  
Seed Mass ◽  
Nucleation Theory ◽  
Dynamics Simulation ◽  
Classical Nucleation Theory ◽  
Supersaturation Ratio ◽  
Order Of Magnitude ◽  
Nano Cluster

A three-dimensional heterogeneous nucleation is simulated by classical molecular dynamics, where the Lennard-Jones gas and solid nano cluster-seed molecules have argon and aluminum properties, respectively. All dimensions of the wall are periodic and a soft core carrier gas within the system controls the temperature rise induced by latent heat of condensation. There are three shapes of cluster-seeds being cube, rod, and sphere, three classes of masses, and the simulation took place under nine supersaturation ratios, making a total of 81 calculations. An analysis of variance was performed under a three-way layout to analyze the cluster-seed and supersaturation ratio effects on the system. For supersaturation ratios above the critical value nucleation rates were evaluated, below growth rates, and overall liquefaction rates were each defined and calculated. Results show that the supersaturation ratio dominantly controls all rates, but seed characteristics are important for the growth of the largest cluster under the critical supersaturation ratio. Overall liquefaction increases subject to an escalation of supersaturation ratio and seed mass. However, the significance of the supersaturation ratio for overall liquefaction suggests that thermal diffusion is more dominant than mass interactions for this system. Homogeneous characteristics are also compared with the heterogeneous system to find that though nucleation may occur for an insufficient supersaturation ratio when a seed is within the system, the addition of a seed does not in fact facilitate the increase in rates of the phenomena at high supersaturation ratios. Finally a comparison with the classical nucleation theory asserts a 3 to 4 order of magnitude difference, which is within the lines of deviation when it comes to theory and molecular simulations.

Nucleations of pressure induced phase transitions in mercury selenide

1977 ◽  
Vol 55 (3) ◽  
pp. 222-226
Author(s):  
B. A. Lombos ◽  
H. M. Mahdaly ◽  
B. C. Pant
Keyword(s):  
Phase Transitions ◽  
Heterogeneous Nucleation ◽  
Direct Relationship ◽  
Activation Volume ◽  
Three Dimensional ◽  
Direct Determination ◽  
Nucleation Theory ◽  
Kinetic Transition ◽  
Mercury Selenide

The resistance discontinuity technique combined with a three-dimensional heterogeneous nucleation theory permitted the direct determination of the rate of pressure induced phase transitions in mercury selenide. A direct relationship between the activation volumes and kinetic transition pressures was found which facilitated the determination of the thermodynamical transition pressure by extrapolating to zero activation volume. At low nucleation concentration, a faster rate of transition is observed.

Distribution of Vapor Inside a Cylindrical Minichannel With Evaporative Walls and Its Effect on Droplet Growth by Heterogeneous Nucleation

2011 ◽  
Vol 3 (1) ◽  
Author(s):  
Sushant Anand ◽  
Jae Yong Lee ◽  
Deepak Veettil ◽  
Sang Young Son ◽  
Milind A. Jog
Keyword(s):  
Heterogeneous Nucleation ◽  
Accurate Determination ◽  
Species Conservation ◽  
Particle Growth ◽  
Droplet Growth ◽  
Inlet Temperature ◽  
Inlet Flow Rate ◽  
Flow Heat ◽  
Micrometer Size

The present study aims to understand the dynamics of particle growth inside a minichannel where evaporation from heated wet wall column generates supersaturated conditions. Such multiphase flow with phase-change is encountered in condensation particle sensors where nanoscale particles grow to micrometer size and can be measured optically. To develop condensation particle sensors that are miniscale and highly portable, we have computationally modeled the flow, heat, and mass transfer in a minichannel and determined parameters that facilitate particle growth. The mass, momentum, energy, and species conservation equations are solved, and particles are tracked and their growth through condensation is determined. Variation of thermophysical properties as a function of temperature and species concentration is incorporated for accurate determination of particle growth. The results show that the size of condensation sensors can be decreased by employing minichannels where conditions can be created, which enhance supersaturation region inside the channel where condensation occurs on the nanoparticles by heterogeneous nucleation and cause them to grow to micron sizes. The effects of inlet humidity, inlet temperature, inlet flow rate, and wall temperature on the operation of the miniscale sensor are investigated. The numerical framework provides solution to optimal working of the sensor.

scholarly journals Application of osmolality for the determination of water activity and the modelling of cloud formation

2004 ◽  
Vol 4 (6) ◽  
pp. 7667-7689 ◽  
Author(s):  
G. Kiss ◽  
H.-C. Hansson
Keyword(s):  
Water Activity ◽  
Droplet Diameter ◽  
Cloud Formation ◽  
Activity Data ◽  
Fog Water ◽  
Molecular Weights ◽  
Critical Supersaturation ◽  
20 Nm ◽  
Complete Dissociation

Abstract. A simple approach is suggested here to give reliable estimates on the Raoult term of the Köhler equation when calculating critical supersaturation (Sc) for real atmospheric samples. Water activity is calculated from osmolality and thus the original Köhler equation can be applied avoiding the difficulties with unknown molecular weights, solubilities, van't Hoff factors of aerosol constituents and also the interactions in the growing droplet. First, water activity calculated from osmolality data was compared to literature values both for electrolytes and a non-electrolyte. Then the applicability of the approach was demonstrated by generating Köhler curves from osmolality derived and literature activity data as well as by using the simplified Köhler equation. Sc values calculated with the osmolality approach fitted those obtained by using literature water activity data within a relative deviation of less than 0.3%, 0.8%, 1.1% and 3.4% for sucrose, CaCl2, NaCl and H2SO4, respectively, while the corresponding errors with the simplified Köhler equation were 11%, 8.5%, 4.5% and 19% in the dry nucleus size range of 20 nm to 100 nm. Finally, the osmolality method was used to show how considerably Sc is underestimated for organic acids if complete dissociation is assumed. The method described in this paper can be applied to real atmospheric samples (aerosol extracts, fog water or cloud water) thus improving the reliability of estimates on critical supersaturation and critical droplet diameter in atmospheric modelling.

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