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.

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.

Analytical Investigation on the Homogeneous Nucleation in a Mono-Component and Bi-Component Droplet

2019 ◽  
Author(s):  
Xi Xi ◽  
Hong Liu ◽  
Chang Cai ◽  
Ming Jia ◽  
Weilong Zhang
Keyword(s):  
Nucleation Rate ◽  
Homogeneous Nucleation ◽  
Ambient Pressure ◽  
Analytical Investigation ◽  
Bubble Nucleation ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Liquid Temperature ◽  
Wide Range ◽  
Good Agreement

Abstract The work attempts to analyze the performance of homogeneous nucleation by using the non-equilibrium thermodynamics theory and the classical nucleation theory. A nucleation rate graph was constructed under a wide range of operating temperature conditions. The results indicate that the superheat limit temperature (SLT) estimated by the modified homogeneous nucleation sub-model is in good agreement with the experimental results. The nucleation rate increases exponentially with the liquid temperature rise when the liquid temperature exceeds the SLT under atmospheric pressure. The superheated temperature needed to trigger the bubble nucleation decreases with the elevated ambient pressure.

How does a Homogeneous Nucleation Event respond to changes of Parameterizations of Water Activity and Saturation Vapor Pressure?

2021 ◽  
Author(s):  
Manuel Baumgartner ◽  
Martina Krämer ◽  
Christian Rolf
Keyword(s):  
Water Vapor ◽  
Water Activity ◽  
Nucleation Rate ◽  
Homogeneous Nucleation ◽  
Saturation Pressure ◽  
Cirrus Clouds ◽  
Ice Crystals ◽  
Nucleation Theory ◽  
Ice Microphysics ◽  
Water Vapor Saturation Pressure

&lt;p&gt;Homogeneous nucleation of ice crystals via freezing of small supercooled solution particles represents a major pathway in the formation of cirrus clouds with high ice water content at low temperatures. A reasonable physical explanation of this type of freezing is provided by Koop's nucleation theory, relating the homogeneous nucleation rate to the water activity of the solution particles. While the homogeneous nucleation rate encodes the probability of freezing of solution particles, the water activity represents the ratio of water vapor saturation pressures over the solution to that over pure water in Koop's portrayal.&lt;/p&gt;&lt;p&gt;By using the ice microphysics model &quot;CLaMS-Ice&quot;, we investigate the effect of various formulations of the water activity and the water vapor saturation pressure on the resulting cirrus clouds. Although CLaMS-Ice is a two-moment bulk model, it implements a comparatively detailed ice microphysics formulated by Spichtinger and Gierens. Such a microphysics scheme is suitable to be implemented in full three dimensional atmospheric models in contrast to even more detailed bin microphysics schemes.&lt;/p&gt;&lt;p&gt;We performed sensitivity simulations over a wide range of temperatures and vertical velocities by using two different direct parameterizations of water activity based on thermodynamic models in addition to the one used by Koop. Also, three different formulations of the water vapor saturation pressure are applied in the simulations. The results are evaluated regarding the predicted number of ice crystals and the ice onset humidities. In particular, one major finding is that the freezing thresholds are increased compared to Koop's freezing lines.&lt;/p&gt;

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