Homogeneous nucleation and droplet growth in supersaturated argon vapor: The cryogenic nucleation pulse chamber

2006 ◽  
Vol 124 (16) ◽  
pp. 164710 ◽  
Author(s):  
Alexander Fladerer ◽  
Reinhard Strey
Keyword(s):  
Homogeneous Nucleation ◽  
Droplet Growth ◽  
Pulse Chamber

scholarly journals Hygroscopic properties of NaCl and NaNO<sub>3</sub> mixture particles as reacted inorganic sea-salt aerosol surrogates

2014 ◽  
Vol 14 (23) ◽  
pp. 33143-33183
Author(s):  
D. Gupta ◽  
H. Kim ◽  
G. Park ◽  
X. Li ◽  
H.-J. Eom ◽  
...  
Keyword(s):  
Heterogeneous Nucleation ◽  
Homogeneous Nucleation ◽  
Aerosol Particles ◽  
Sea Salt ◽  
Droplet Growth ◽  
Dehydration Process ◽  
Two Stage ◽  
Mixing Ratios ◽  
Sea Salt Aerosol ◽  
Wide Range

Abstract. NaCl in fresh sea-salt aerosol (SSA) particles can partially or fully react with atmospheric NOx / HNO3, so internally mixed NaCl and NaNO3 aerosol particles can co-exist over a wide range of mixing ratios. Laboratory-generated, micrometer-sized NaCl and NaNO3 mixture particles at ten mixing ratios (mole fractions of NaCl (XNaCl) = 0.1 to 0.9) were examined systematically to observe their hygroscopic behavior, derive experimental phase diagrams for deliquescence and efflorescence, and understand the efflorescence mechanism. During the humidifying process, aerosol particles with the eutonic composition (XNaCl = 0.38) showed only one phase transition at their mutual deliquescence relative humidity (MDRH) of 67.9(± 0.5)%. On the other hand, particles with other mixing ratios showed two distinct deliquescence transitions, i.e., the eutonic component dissolved at MDRH and the remainder in the solid phase dissolved completely at their DRHs depending on the mixing ratios, resulting in a phase diagram composed of four different phases, as predicted thermodynamically. During the dehydration process, NaCl-rich particles (XNaCl > 0.38) showed two-stage efflorescence transitions: the first stage was purely driven by the homogeneous nucleation of NaCl and the second stage at the mutual efflorescence RH (MERH) of the eutonic components, with values in the range of 30.0–35.5%. Interestingly, aerosol particles with the eutonic composition (XNaCl = 0.38) also showed two-stage efflorescence with NaCl crystallizing first followed by heterogeneous nucleation of the remaining NaNO3 on the NaCl seeds. NaNO3-rich particles XNaCl ≤ 0.3) underwent single-stage efflorescence transitions at ERHs progressively lower than the MERH, because of the homogeneous nucleation of NaCl and the almost simultaneous heterogeneous nucleation of NaNO3 on the NaCl seeds. SEM/EDX elemental mapping indicated that the effloresced NaCl-NaNO3 particles at all mixing ratios were composed of a homogeneously crystallized NaCl moiety in the center, surrounded either by the eutonic component (for XNaCl > 0.38) or NaNO3 (for XNaCl ≤ 0.38). During the humidifying or dehydration process, the amount of eutonic composed part drives particle/droplet growth or shrinkage at the MDRH or MERH (second ERH), respectively, and the amount of remnant pure salts (NaCl or NaNO3 in NaCl- or NaNO3-rich particles, respectively) drives the second DRHs or first ERHs, respectively. Therefore, their behavior can be a precursor to the optical properties and direct radiative forcing for these atmospherically relevant mixture particles representing the coarse, reacted inorganic SSAs. In addition, the NaCl-NaNO3 mixture aerosol particles can maintain an aqueous phase over a wider RH range than the genuine SSA surrogate (i.e., pure NaCl particles), making their heterogeneous chemistry more probable.

scholarly journals Results of the International Wet Steam Modeling Project

2018 ◽  
Vol 232 (5) ◽  
pp. 550-570 ◽  
Author(s):  
Jörg Starzmann ◽  
Fiona R Hughes ◽  
Sebastian Schuster ◽  
Alexander J White ◽  
Jan Halama ◽  
...  
Keyword(s):  
Homogeneous Nucleation ◽  
Three Dimensional ◽  
Nucleation Theory ◽  
Nozzle Geometry ◽  
Droplet Growth ◽  
Test Cases ◽  
Wet Steam ◽  
One Dimensional ◽  
Homogeneous Nucleation Theory ◽  
Design Deficiencies

The purpose of the “International Wet Steam Modeling Project” is to review the ability of computational methods to predict condensing steam flows. The results of numerous wet-steam methods are compared with each other and with experimental data for several nozzle test cases. The spread of computed results is quite noticeable and the present paper endeavours to explain some of the reasons for this. Generally, however, the results confirm that reasonable agreement with experiment is obtained by using classical homogeneous nucleation theory corrected for non-isothermal effects, combined with Young’s droplet growth model. Some calibration of the latter is however required. The equation of state is also shown to have a significant impact on the location of the Wilson point, thus adding to the uncertainty surrounding the condensation theory. With respect to the validation of wet-steam models it is shown that some of the commonly used nozzle test cases have design deficiencies which are particularly apparent in the context of two- and three-dimensional computations. In particular, it is difficult to separate out condensation phenomena from boundary layer effects unless the nozzle geometry is carefully designed to provide near-one-dimensional flow.

scholarly journals Computational analysis of homogeneous nucleation and droplet growth applied to natural gas separators

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Natalia Prieto-Jiménez ◽  
José Fuentes ◽  
Germán González-Silva
Keyword(s):  
High Pressure ◽  
Natural Gas ◽  
Homogeneous Nucleation ◽  
Drop Size ◽  
Droplet Growth ◽  
Thermodynamic Conditions ◽  
Initial Drop ◽  
Phase Nucleation ◽  
Three Stages ◽  
Different Shapes

A natural gas droplet is generated at certain thermodynamic conditions through three stages: supersaturation, where the gas has more molecules than it should have in equilibrium, forming “embryos” of liquid phase; nucleation, where embryos form groups of different shapes and sizes of nanometer order; and the droplet growth, where the number of molecules increases until equilibrium is reached. In this paper, the homogeneous nucleation and droplet growth of natural gas applied to gravitational separators operating at high pressure conditions (7MPa) are analyzed. The results showed that at a high pressure, the initial drop size reached was 8.024 nanometers and the final diameter of the drop was 4.18 micrometers.

scholarly journals Hygroscopic properties of NaCl and NaNO<sub>3</sub> mixture particles as reacted inorganic sea-salt aerosol surrogates

2015 ◽  
Vol 15 (6) ◽  
pp. 3379-3393 ◽  
Author(s):  
D. Gupta ◽  
H. Kim ◽  
G. Park ◽  
X. Li ◽  
H.-J. Eom ◽  
...  
Keyword(s):  
Heterogeneous Nucleation ◽  
Homogeneous Nucleation ◽  
Aerosol Particles ◽  
Sea Salt ◽  
Droplet Growth ◽  
Dehydration Process ◽  
Two Stage ◽  
Mixing Ratios ◽  
Sea Salt Aerosol ◽  
Wide Range

Abstract. NaCl in fresh sea-salt aerosol (SSA) particles can partially or fully react with atmospheric NOx/HNO3, so internally mixed NaCl and NaNO3 aerosol particles can co-exist over a wide range of mixing ratios. Laboratory-generated, micrometer-sized NaCl and NaNO3 mixture particles at 10 mixing ratios (mole fractions of NaCl (XNaCl) = 0.1 to 0.9) were examined systematically to observe their hygroscopic behavior, derive experimental phase diagrams for deliquescence and efflorescence, and understand the efflorescence mechanism. During the humidifying process, aerosol particles with the eutonic composition (XNaCl = 0.38) showed only one phase transition at their mutual deliquescence relative humidity (MDRH) of 67.9 (±0.5)% On the other hand, particles with other mixing ratios showed two distinct deliquescence transitions; i.e., the eutonic component dissolved at MDRH, and the remainder in the solid phase dissolved completely at their DRHs depending on the mixing ratios, resulting in a phase diagram composed of four different phases, as predicted thermodynamically. During the dehydration process, NaCl-rich particles (XNaCl > 0.38) showed a two stage efflorescence transition: the first stage was purely driven by the homogeneous nucleation of NaCl and the second stage at the mutual efflorescence RH (MERH) of the eutonic components, with values in the range of 30.0–35.5%. Interestingly, aerosol particles with the eutonic composition (XNaCl = 0.38) also showed two-stage efflorescence, with NaCl crystallizing first followed by heterogeneous nucleation of the remaining NaNO3 on the NaCl seeds. NaNO3-rich particles (XNaCl ≤ 0.3) underwent single-stage efflorescence transitions at ERHs progressively lower than the MERH because of the homogeneous nucleation of NaCl and the almost simultaneous heterogeneous nucleation of NaNO3 on the NaCl seeds. SEM/EDX elemental mapping indicated that the effloresced NaCl–NaNO3 particles at all mixing ratios were composed of a homogeneously crystallized NaCl moiety in the center, surrounded either by the eutonic component (for XNaCl > 0.38) or NaNO3 (for XNaCl ≤ 0.38). During the humidifying or dehydration process, the amount of eutonic composed part drives particle/droplet growth or shrinkage at the MDRH or MERH (second ERH), respectively, and the amount of pure salts (NaCl or NaNO3 in NaCl- or NaNO3-rich particles, respectively) drives the second DRHs or first ERHs, respectively. Therefore, their behavior can be a precursor to the optical properties and direct radiative forcing for these atmospherically relevant mixture particles representing the coarse, reacted inorganic SSAs. In addition, the NaCl–NaNO3 mixture aerosol particles can maintain an aqueous phase over a wider RH range than pure NaCl particles as SSA surrogate, making their heterogeneous chemistry more probable.

The effect of flow unsteadiness on the homogeneous nucleation of water droplets in steam turbines

1994 ◽  
Vol 349 (1691) ◽  
pp. 445-472 ◽  
Keyword(s):  
Steady Flow ◽  
Homogeneous Nucleation ◽  
Flow Direction ◽  
Previous History ◽  
Fluid Particle ◽  
Droplet Growth ◽  
Steam Turbines ◽  
Water Droplets ◽  
Blade Row ◽  
Fluid Particles

The paper describes a new theory of the formation and growth of water droplets in multistage steam turbines. The essence of the theory is that large-scale static temperature fluctuations caused by the segmentation of blade wakes by successive blade rows have a dominating influence on nucleation and droplet growth in turbines. ‘True’ turbulent fluctuations (due to shear-layer unsteadiness, etc.) are probably less important and are ignored. A Lagrangian frame of reference is adopted and attention is focused on a large number of individual fluid particles during their passage through the turbine. Homogeneous nucleation and growth of droplets in each fluid particle is assumed to be governed by classical theories. All fluid particles are assumed to experience the same pressure variation, but those particles passing close to the blade surfaces suffer greater entropy production and, therefore, have higher static temperatures than those that pursue nearly isentropic paths through the central portions of the blade passages. Particles which suffer high loss therefore nucleate later in the turbine than those that experience little dissipation. Condensation is thus viewed as an essentially random and unsteady phenomenon because the dissipation experienced by a fluid particle in one blade row is assumed to be uncorrelated with its previous history. On a time-averaged basis, the condensation zone is spread over a much greater distance in the flow direction than a simple steady-flow analysis would indicate and may encompass several blade rows, depending on the number of stages in the machine. Predicted droplet size spectra show broad, highly skewed distributions with large mean diameters and sometimes slight bimodality. These are all characteristics of experimentally measured spectra in real turbines. Conventional, steady-flow calculation methods, which predict a fixed Wilson point in a specific blade row and a nearly monodispersed droplet population, cannot reproduce any of these characteristics.

Exsolution and inversion in pigeonite from the Whin Sill, Northern England

1978 ◽  
Vol 36 (1) ◽  
pp. 474-475
Author(s):  
P.P.K. Smith
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Homogeneous Nucleation ◽  
Silicate Mineral ◽  
Antiphase Boundaries ◽  
Two Phase ◽  
Primitive Form ◽  
The Core ◽  
Nucleation Mechanisms ◽  
And Inversion

Grains of pigeonite, a calcium-poor silicate mineral of the pyroxene group, from the Whin Sill dolerite have been ion-thinned and examined by TEM. The pigeonite is strongly zoned chemically from the composition Wo8En64FS28 in the core to Wo13En34FS53 at the rim. Two phase transformations have occurred during the cooling of this pigeonite:- exsolution of augite, a more calcic pyroxene, and inversion of the pigeonite from the high- temperature C face-centred form to the low-temperature primitive form, with the formation of antiphase boundaries (APB's). Different sequences of these exsolution and inversion reactions, together with different nucleation mechanisms of the augite, have created three distinct microstructures depending on the position in the grain.In the core of the grains small platelets of augite about 0.02μm thick have farmed parallel to the (001) plane (Fig. 1). These are thought to have exsolved by homogeneous nucleation. Subsequently the inversion of the pigeonite has led to the creation of APB's.

Lattice imaging of precipitates in Al-Zn-Mg alloy

1986 ◽  
Vol 44 ◽  
pp. 412-413
Author(s):  
C. K. Wu
Keyword(s):  
Grain Boundaries ◽  
Homogeneous Nucleation ◽  
Alloy System ◽  
Mg Alloy ◽  
List Type ◽  
Lattice Structures ◽  
Type Number ◽  
Orientation Relationships ◽  
Lattice Imaging ◽  
The Matrix

The precipitation phenomenon in Al-Zn-Mg alloy is quite interesting and complicated and can be described in the following categories:(i) heterogeneous nucleation at grain boundaries;(ii) precipitate-free-zones (PFZ) adjacent to the grain boundaries;(iii) homogeneous nucleation of snherical G.P. zones, n' and n phases inside the grains. The spherical G.P. zones are coherent with the matrix, whereas the n' and n phases are incoherent. It is noticed that n' and n phases exhibit plate-like morpholoay with several orientation relationship with the matrix. The high resolution lattice imaging techninue of TEM is then applied to study precipitates in this alloy system. It reveals the characteristics of lattice structures of each phase and the orientation relationships with the matrix.

Amorphous silica coating on α-alumina particles

1995 ◽  
Vol 53 ◽  
pp. 210-211
Author(s):  
J. W. Mellowes ◽  
C. M. Chun ◽  
I. A. Aksay
Keyword(s):  
Amorphous Silica ◽  
Heterogeneous Nucleation ◽  
Homogeneous Nucleation ◽  
Silica Coating ◽  
Full Density ◽  
Optimal Conditions ◽  
Fine Grained ◽  
Alumina Particles ◽  
Complete Mullitization ◽  
Powder Compacts

Mullite (3Al2O32SiO2) can be fabricated by transient viscous sintering using composite particles which consist of inner cores of a-alumina and outer coatings of amorphous silica. Powder compacts prepared with these particles are sintered to almost full density at relatively low temperatures (~1300°C) and converted to dense, fine-grained mullite at higher temperatures (>1500°C) by reaction between the alumina core and the silica coating. In order to achieve complete mullitization, optimal conditions for coating alumina particles with amorphous silica must be achieved. Formation of amorphous silica can occur in solution (homogeneous nucleation) or on the surface of alumina (heterogeneous nucleation) depending on the degree of supersaturation of the solvent in which the particles are immersed. Successful coating of silica on alumina occurs when heterogeneous nucleation is promoted and homogeneous nucleation is suppressed. Therefore, one key to successful coating is an understanding of the factors such as pH and concentration that control silica nucleation in aqueous solutions. In the current work, we use TEM to determine the optimal conditions of this processing.

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