Application of a scaled homogeneous nucleation-rate formalism to experimental data at T≪Tc

1986 ◽  
Vol 33 (6) ◽  
pp. 4156-4163 ◽  
Author(s):  
Barbara N. Hale
Keyword(s):  
Experimental Data ◽  
Nucleation Rate ◽  
Homogeneous Nucleation

scholarly journals Homogeneous nucleation of NAD and NAT in liquid stratospheric aerosols: insufficient to explain denitrification

2002 ◽  
Vol 2 (3) ◽  
pp. 669-687 ◽  
Author(s):  
D. A. Knopf ◽  
T. Koop ◽  
B. P. Luo ◽  
U. G. Weers ◽  
T Peter
Keyword(s):  
Experimental Data ◽  
Nitric Acid ◽  
Nucleation Rate ◽  
Homogeneous Nucleation ◽  
Particle Production ◽  
Rate Coefficients ◽  
The Arctic ◽  
Linear Extrapolation ◽  
Acid Hydrate ◽  
Stratospheric Clouds

Abstract. The nucleation of NAD and NAT from HNO3/H2O and HNO3/H2O/H2SO4 solution droplets is investigated both theoretically and experimentally with respect to the formation of polar stratospheric clouds (PSCs). Our analysis shows that homogeneous NAD and NAT nucleation from liquid aerosols is insufficient to explain the number densities of large nitric acid containing particles recently observed in the Arctic stratosphere. This conclusion is based on new droplet freezing experiments employing optical microscopy combined with Raman spectroscopy. The homogeneous nucleation rate coefficients of NAD and NAT in liquid aerosols under polar stratospheric conditions derived from the experiments are < 2 x 10-5 cm-3 s-1 and < 8 x 10-2 cm-3 s-1 , respectively. These nucleation rate coefficients are smaller by orders of magnitude than the value of ~ 103 cm-3 s-1 used in a recent denitrification modelling study that is based on a linear extrapolation of laboratory nucleation data to stratospheric conditions (Tabazadeh et al., Science, 291, 2591--2594, 2001). We show that this linear extrapolation is in disagreement with thermodynamics and experimental data and, therefore, must not be used in microphysical models of PSCs. Our analysis of the experimental data yields maximum hourly production rates of nitric acid hydrate particles per cm3 of air of about 3 x 10-10 cm-3 h-1 under polar stratospheric conditions. Assuming PSC particle production to proceed at this rate for two months we arrive at particle number densities of < 5 x 10-7 cm-3, much smaller than the value of ~ 10-4 cm-3 reported in recent field observations. This clearly shows that homogeneous nucleation of NAD and NAT from liquid supercooled ternary solution aerosols cannot explain the observed polar denitrification.

scholarly journals Homogeneous nucleation of NAD and NAT in liquid stratospheric aerosols: insufficient to explain denitrification

2002 ◽  
Vol 2 (3) ◽  
pp. 207-214 ◽  
Author(s):  
D. A. Knopf ◽  
T. Koop ◽  
B. P. Luo ◽  
U. G. Weers ◽  
T. Peter
Keyword(s):  
Experimental Data ◽  
Nitric Acid ◽  
Nucleation Rate ◽  
Homogeneous Nucleation ◽  
Particle Production ◽  
Rate Coefficients ◽  
The Arctic ◽  
Linear Extrapolation ◽  
Acid Hydrate ◽  
Modelling Study

Abstract. The nucleation of NAD and NAT from HNO3/H2O and HNO3/H2SO4/H2O solution droplets is investigated both theoretically and experimentally with respect to the formation of polar stratospheric clouds (PSCs). Our analysis shows that homogeneous NAD and NAT nucleation from liquid aerosols is insufficient to explain the number densities of large nitric acid containing particles recently observed in the Arctic stratosphere. This conclusion is based on new droplet freezing experiments employing optical microscopy combined with Raman spectroscopy. The homogeneous nucleation rate coefficients of NAD and NAT in liquid aerosols under polar stratospheric conditions derived from the experiments are < 2 x 10-5 cm-3 s-1 and < 8 x 10-2 cm-3 s-1, respectively. These nucleation rate coefficients are smaller by orders of magnitude than the value of ~103 cm-3 s-1 used in a recent denitrification modelling study that is based on a linear extrapolation of laboratory nucleation data to stratospheric conditions (Tabazadeh et al., Science, 291, 2591--2594, 2001). We show that this linear extrapolation is in disagreement with thermodynamics and with experimental data and, therefore, must not be used in microphysical models of PSCs. Our analysis of the experimental data yields maximum hourly production rates of nitric acid hydrate particles per cm3 of air of about 3 x 10-10 cm-3 (air) h-1 under polar stratospheric conditions. Assuming PSC particle production to proceed at this rate for two months we arrive at particle number densities of < 5 x 10-7 cm-3, much smaller than the value of ~10-4 cm-3 reported in recent field observations. In addition, the nitric acid hydrate production rate inferred from our data is much smaller than that required to reproduce the observed denitrification in the modelling study mentioned above. This clearly shows that homogeneous nucleation of NAD and NAT from liquid supercooled ternary solution aerosols cannot explain the observed polar denitrification.

scholarly journals Atmospheric homogeneous nucleation of H<sub>2</sub>SO<sub>4</sub> and H<sub>2</sub>O

2010 ◽  
Vol 10 (11) ◽  
pp. 29051-29073 ◽  
Author(s):  
D. R. Benson ◽  
M. E. Erupe ◽  
J. H. Yu ◽  
A. Markovich ◽  
S.-H. Lee
Keyword(s):  
Experimental Data ◽  
Nucleation Rate ◽  
Homogeneous Nucleation ◽  
Laboratory Observation ◽  
Experimental Parameters ◽  
Observation Results ◽  
Atmospherically Relevant

Abstract. We report laboratory observations of H2SO4 and H2O homogeneous nucleation made under atmospherically relevant conditions ([H2SO4] of 106 – 107 cm−3 and 287 K). Our observations show that nucleation takes place at [H2SO4] of 106 – 107 cm−3, as observed in the atmosphere. The slope of nucleation rate (J) vs. [H2SO4] ranges between 4–6, consistent with thermodynamic predictions of neutral H2SO4 clusters, but is higher than those observed in the atmosphere. These results indicate that ternary aerosol precursors are needed to reduce the slope to 1–2 in the atmosphere. This study also discusses the effects of experimental parameters on laboratory observation results, in order to properly interpret the experimental data.

Homogeneous nucleation of water in argon. Nucleation rate computation from molecular simulations of TIP4P and TIP4P/2005 water model

2017 ◽  
Vol 146 (8) ◽  
pp. 084309 ◽  
Author(s):  
Lucia R. Dumitrescu ◽  
David M. J. Smeulders ◽  
Jacques A. M. Dam ◽  
Silvia V. Gaastra-Nedea
Keyword(s):  
Nucleation Rate ◽  
Homogeneous Nucleation ◽  
Molecular Simulations ◽  
Water Model

Characteristics of the Initial Stage of CaCO3 Crystallization Fouling on Straight Oblique Fin Tube

2013 ◽  
Vol 671-674 ◽  
pp. 2535-2541
Author(s):  
Ping Zhao ◽  
Jian Sheng ◽  
Hua Zhang
Keyword(s):  
Growth Rate ◽  
Induction Period ◽  
Nucleation Rate ◽  
Homogeneous Nucleation ◽  
Particle Concentration ◽  
Concentration Increase ◽  
Fouling Resistance ◽  
Initial Stage ◽  
Fin Tube ◽  
Resistance Decrease

To investigate the effect of CaCO3 concentration and velocity on scaling fouling process on plain and SOFT, experiments have been done at different CaCO3 concentration and velocity on the two kind tubes. The results are that the homogeneous nucleation rate and the growth rate are both increase when CaCO3 concentration increases. This make the scaling particle concentration and foulant ions concentration increase, the former gets more scaling on tubes and the later enlarges the heterogeneous nucleation rate and growth rate. Higher velocity decreases the nucleation of scaling, scaling crystal and fouling resistance, but it can prolong the induction period. Higher velocity increases nucleation rate on SOFT first, but the induction period extends and the mass of scaling and fouling resistance decrease. SOFT has a bigger heat transfer coefficient than PT at both clean and fouling conditions and it has smaller fouling resistance even a little more scaling.

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