Vapor Density Research Articles

Surface tension of binary mixtures of benzene + propionic acid and butanoic acid between 298.15 K and 318.15 K: Measurement and modeling

Experimental measurement of the surface tension of benzene + propanoic acid and benzene + butanoic acid has been carried out in the temperature range of 298.15 K to 318.15 K and atmospheric pressure. 170 new experimental points of surface tension have been obtained. Three theoretical models, i.e., Linear gradient theory (LGT), Shereshefsky model (SM), and the extended Langmuir model (LM), were used to modeling the surface tension and adsorption phenomenon of these binary mixtures. The three models correlated the surface tension of the benzene + carboxylic acid mixtures, and the average percent deviation was, 0.04% for LGT, 0.08% for SM, and 0.05% for LM. The Helmholtz density term and the liquid and vapor densities required in computing density with LGT were obtained with perturbed chain-statistical associating fluid theory equation of state (PC-SAFT EOS). Based on SM, the standard Gibbs energy of adsorption and the free energy change in the surface region were calculated. The free energy change was used to obtain the excess number of molecular layers in the surface region. The required parameters of the LM were adjusted, the standard Gibbs energy of adsorption was calculated, and negative deviations from ideality were determined. Also mole fractions of solute 0at surface were calculated by using LM. Additionally, by using surface tensions at different temperatures, specific surface enthalpy and specific surface entropy were calculated for (benzene + carboxylic acid) mixtures.

Observations of ultrafast superfluorescent beatings in a cesium atomic vapor excited by femtosecond laser pulses

Picosecond and femtosecond superfluorescent beatings are observed from a dense atomic vapor. Cesium atoms are excited by femtosecond laser pulses via two-photon processes into their coherent superpositions of the ground 6S and excited 8S states. The yoked superfluorescent blue light at lower transitions of 6S – 7P is recorded and studied. Delayed buildup time of this blue light is measured as a function of the input laser beam power using a high-resolution 2 ps streak camera. At low power and density, a beating with a period of approximately 100 picoseconds is observed as we believe that represents the ground state splitting. The autocorrelation measurements of the generated blue light exhibit a beating with a quasi-period of 200 ± 60 fs corresponding to the splitting of the 7P level. Our experimental observations may hold a promising direction for investigation of cooperative radiation in many-body systems including solid-state materials.

Shaping the equation of state to improve numerical accuracy and stability of the pseudopotential lattice Boltzmann method.

It has recently been shown that altering the shape of the metastable and unstable branches of an equation of state (EOS) can substantially improve the numerical accuracy of liquid and vapor densities in the pseudopotential lattice Boltzmann method [Peng et al., Phys. Rev. E 101, 063309 (2020)2470-004510.1103/PhysRevE.101.063309]. We found that this approach reduces stability of the method in nonequilibrium conditions and is unstable for bubbles at low reduced temperatures. Here we present an improved method for altering the shape of the metastable and unstable branches of the EOS which remains stable for both equilibrium and nonequilibrium situations and has no issues with bubbles. We also performed a detailed study of the stability of the methods for a droplet impact on a liquid film for reduced temperatures down to 0.35 with Reynolds number of 300. Our approach remained stable for a density ratio of up to 3.38×10^{4}.

Characterisation of silicon oxynitride thin films and their response to swift heavy-ion irradiation

Silicon oxynitrides (a-SiO x N y ) are materials whose composition ranges between two binary materials: a-SiO2 and a-Si3N4. In this work, we present a systematic study of the fine structure of the damaged regions produced by swift heavy-ions (SHIs), or ‘ion-tracks’ and quantify the density variation profiles with respect to composition. Thin films were deposited by plasma-enhanced chemical vapor deposition (CVD), where thickness, density, stoichiometry and bond configuration were initially determined. The fine structure and radial size of the ion tracks was determined using small angle x-ray scattering. The tracks exhibit a core–shell cylindrical geometry, with an under-dense core surrounded by an over-dense shell with a smooth transition between the two regions. We observed two trends with composition: a constant increasing ion track radius is observed when the O/Si ratio is below one (. And saturation of the radial dimensions above this value, being similar to a-SiO2. The IR spectra allowed to quantify the bond configuration and its evolution with fluence. After irradiation, the energy deposited by the SHI irradiation leads to a preferential damage of Si–N bonds. IR spectroscopy also showed the formation of new Si–H bonds with increasing fluences and resulting in a rather complex ion-induced structural modification of the a-SiO x N y network.

Measurement of Water Activity in the Presence of High Volatile Concentrations Using a Tunable Diode Laser-Single Laboratory Validation, First Action 2021.04.

Water activity is measured by equilibrating a test portion with a sealed head space and measuring the test portion temperature and the vapor density of the head space. The water activity is the ratio of head space vapor density to the saturation vapor density at test portion temperature. Headspace vapor density is typically measured using capacitance or chilled mirror sensors, but, when volatiles in significant concentration are present, these measurements may fail. Evaluate the accuracy of a tunable diode laser (TDL) for measuring the headspace vapor density and water activity of pharmaceutical preparations and food in the presence of non-aqueous volatiles. A commercial TDL water activity meter was calibrated against standards of known water activity and used to measure water activity of pharmaceutical preparations and food with high concentrations of non-aqueous volatiles. When no volatiles other than water vapor are present, this method is capable of measuring water activity with an accuracy of 0.005 or better. When high concentrations of volatiles such as ethanol, isopropanol, propylene glycol, tetrahydrofuran, or acetonitrile are present the uncertainty of the measurement increases. This is at least partly due to the uncertainty of the standards. Based on uncertainties in the water activity estimates of the water-organic mixtures, the uncertainties in water activity measurements with high concentrations of non-aqueous solvents is 0.02 or less up to mass fractions of the organic of 0.97. The theoretical background for TDL measurement of water activity is presented showing that the water vapor concentration is proportional to the area of the absorption line which is not affected by the presence of other volatiles.

Improvements for a fully consistent description of the new semi-empirical vapor density model for pure compounds

In chemical engineering, surrogate functions are commonly used in modeling thermodynamic properties of pure compounds because they are often more accurate than equations of state. In 2020, we presented a semi-empirical model describing the vapor density from the reduced triple point temperature to about a reduced temperature of 0.97 with only one temperature-dependent term. However, in many cases the temperature range up to critical temperature is necessary. Therefore, the existing semi-empirical model was extended by another temperature-dependent term. This allows the vapor density to be described from the triple point temperature up to the critical temperature. This model has the additional advantage that it can predict the vapor pressure data from vapor density data. Therefore, this model can also be used for thermodynamic consistency testing. This is not possible with conventionally known surrogate models for describing vapor density. The model was successfully tested using fluoromethane (R41) and difluoromethane (R32) as examples.

Физико-математическая модель переноса газообразного кремния в ходе высокотемпературного силицирования углеродных композитных материалов

We propose a new physical and mathematical model for description of silicon vapor high-temperature transfer under medium vacuum conditions from the melt mirror to the surface of an absorbing porous medium in an atmosphere of residual gas. The developed model is simplified to the greatest extent possible and is intended for further numerical implementation in the course of modeling a non-stationary three-dimensional process of high-temperature siliconization of arbitrary-shaped porous carbon products under the condition of a complex distribution of silicon sources. The physical and mathematical model of transport consists of only one non-linear partial differential equation for the silicon vapor concentration in an atmosphere of argon or any other residual gas. In the limiting case of the simplest geometry and one-dimensional formulation of the problem, we obtained a stationary analytical solution that explains the anomalously large silicon vapor flux into the porous material in full-scale experiments. The obtained analytical solution for the studied gas mixtures is expressed in terms of the known verified values of the material parameters. It shows that despite the low saturation density of silicon vapor, the vapor-liquid-phase process of high-temperature siliconization of carbon materials is physically possible in a reasonable time.

Modeling of Phase Coexistence via Thermodynamic Potentials

Thermodynamic potentials can be used to study various phase phenomena. In particular, they can be used to determine the phase coexistence of a liquid and vapor for a simple van der Waals fluid, which relates the interactions and size of particles (molecules/atoms) represented by spheres as simple constants a and b, respectively. Phase coexistence at a given temperature for a simple fluid is determined using Newton’s method, thermodynamic potentials, and the conditions of phase coexistence. From this information, we are able to construct a phase diagram of the vapor and liquid densities versus the temperature. The constructed phase diagram shows how the simple van der Waals fluid predicts the occurrence of a critical point (point at which the fluid is no longer simply characterized as a gas or liquid but rather a liquid and gaseous fluid or critical fluid) as opposed to the ideal gas law. This phase diagram can then be further used to study homogeneous (a pure solution or solution containing a single molecule/atoms) and inhomogeneous (mixture or solution containing multiple molecules/atoms or a substrate/wall) nucleation by classical density functional theory in statistical mechanics.

CHARACTERISTICS OF HEAT TRANSFER DURING COOLING DOWN PROCESS IN A SINGLE CARGO TANK OF LNG CARRIER

A deep understanding of heat transfer characteristics is essential in evaluating risk and putting forward any option for the Liquefied Natural Gas (LNG) tank cooling down process. A novel Computational Fluid Dynamics (CFD) model was built to perform the flow and heat transfer simulation of the process. The predicted results agreed well with the test data from a prototype LNG tank. Then the heat transfer characteristics of the process were analysed. It was found that the vapour temperature and density were linearly varying and became stable after 2.3 hours. A sudden pressure drop risk was identified during the process, which will cause the inwards collapse risk of the invar membrane. Then the proposals to prevent the risks of the inwards collapsing membrane are presented. The heat transfer characteristics of the vapour and different membrane layers were analysed in detail, and if the suggested option was to be implemented this could save about 39% of LNG consumed.

Monitoring the Characteristics of Ecological Cumulative Effect Due to Mining Disturbance Utilizing Remote Sensing

This study conducted land cover classification and inversion analysis to estimate land surface temperature, soil moisture, specific humidity, atmospheric water vapor density, and relative humidity using remote sensing and multi-source mining data. Using 1990–2020 data from the Shendong mining area in Inner Mongolia, China, the eco-environmental evolution and the ecological cumulative effects (ECE) of mining operations were characterized and analyzed at a long-term scale. The results show that while the eco-environment was generally stable, mining activities affected the eco-environment at the initial stage (1990–2000) to a certain degree. During the rapid development stage of coal mining, the eco-environment was severely damaged, and the ECE were significant at the temporal scale. The absolute value of the change rate of ecological parameters was increasing. Due to an increased focus on ecological restoration, starting in 2010, the environmental indicators gradually stabilized and the eco-environment improved considerably, ushering in a period of stability for coal mining activities. The absolute value of the change rate of ecological parameters became stable. Analysis of the change in eco-environmental indicators with distance and comparison to the contrast area showed the ECE characteristics from mining disturbance at the spatial scale. This study shows that remote sensing technology can be used to characterize the ECE from mining operations and analyze eco-environmental indicators, providing crucial information in support of ecological protection and restoration, particularly in coal mining areas.

Experimental measurements and correlations of the vapor phase pvTx behavior of binary mixtures of 1,1,1,2-tetrafluoroethane (R134a) + 2,3,3,3-tetrafluoroprop-1-ene (R1234yf)

In the present study, the accurate determination of the vapor phase pvTx behavior of binary mixtures of 1,1,1,2-Tetrafluoroethane (R134a) + 2,3,3,3-Tetrafluoroprop-1-ene (R1234yf) by using a Burnett apparatus was demonstrated. Measurements have been performed over the temperature range from (303 to 388) K and at pressures up to 5023 kPa covering the mole fractions of xR134a = (0.000, 0.099, 0.328, 0.523, 0.726, 0.919, 1.000). The combined expanded uncertainties of temperature, pressure, mole fraction and vapor density with a level of confidence of 0.95 (k = 2) were estimated to be 24 mK, 1.6 kPa, 0.01 and within 0.2% over the entire temperature, pressure and mole fraction ranges, respectively. In order to facilitate practical industrial applications and explore the thermophysical behavior of the second and third virial coefficients, the experimental vapor density data of this work were used to develop the virial equation of state with the average absolute deviation of compressibility factor lower than 0.52% for each composition. Furthermore, the obtained gaseous pvTx properties of R134a/R1234yf mixtures were compared with the multi-parameter equation of state of REFPROP 10.0 (Lemmon et al., 2018) and the relative deviations were less than 1.2%.

Analysis of Selection of the Best Refrigerant Using the WASPAS Method

Every nation is working to stop ozone depletion and global warming as climate changes have just become apparent on a global scale. According to the prevailing theory behind ozone depletion, free chlorine radicals first eliminate ozone from the atmosphere before chlorine atoms continue to turn more ozone into oxygen. The migration of substances containing chlorine is what causes chlorine to be present in the stratosphere. This behaviour is common across a wide class of compounds called hydro chloro fluoro carbons (HCFCs) and chlorofluorocarbons (CFCs). The world's consumers and industries employ these substances in a variety of applications, particularly as refrigerants in air conditioning and refrigeration systems. The optimal refrigerant was chosen in this study using the WASPAS approach. In this paper R152a, R1234yf, R1234ze (E), R1233zd (E), R290, R600a, R744 and R1270 are used as an alternative for refrigerants. Vapour density, Latent heat of vaporization, Thermal conductivity of liquid, Critical Pressure and Saturated pressure are used to evaluate the performance of refrigerants. Rank of refrigerants R152a is third-ranked, R1234yf is ranked fifth, R1234ze (E) is ranked first, R1233zd (E) is fourth ranked, R290 is fourth-ranked, R600a is ranked eighth, R744 is second and R1270 is seventh-ranked. The result of the analysis shows that the best refrigerant is R1234ze (E) with a coefficient value of 0.634741 followed by R744 with a coefficient value of 0.517734.

The upper-thermal stability of an iron-rich smectite: Implications for smectite formation on Mars

Fe-rich smectite is a clay mineral commonly found on Mars, particularly in the lowest stratigraphic sequences. The presence of smectite is of interest because of its implications for the former presence of water in the near-surface environment. What is unclear are the range of bulk compositions and physical conditions under which this smectite formed. Here we investigated (i) the experimental synthesis of iron-rich tri-octahedral smectite (Fe-smectite) from a variety of bulk chemical compositions, primarily along the Fe-talc—Na-Fe-eastonite join, and (ii) the upper-thermal stability of Fe-smectite made from one of the investigated bulk compositions. It was found that Fe-smectite could be synthesized at 500 °C and 2 kbars in 7–10 days from all of the bulk compositions investigated, demonstrating some flexibility in the compositions of rock and soil on Mars that would yield Fe-smectite. The upper-thermal stability of the Fe-smectite synthesized from the bulk composition consisting of 87 mol% Fe-talc was investigated in the range of 1–3 kbar and 530–620 °C. Breakdown of this smectite (without interlayer water) was modeled thermodynamically by a dehydration reaction involving albite, fayalite, hercynite, quartz, magnetite, and water to permit extrapolation to lower pressures and temperatures. Results from this modeling indicate first that Fe-smectite is stable to depths of 30 km, for a geothermal gradient of 20 °C/km during the Noachian period, indicating that, even without any interlayer water, Fe-smectite has potential for storing considerable amounts of water in the crust of Mars. Second, there is no overlap in the upper-thermal stability of Fe-smectite and the water-saturated solidus of basalt, ruling out direct formation from a basaltic magma for this Mg-free smectite. Third, the upper-thermal stability of Fe-smectite is calculated to be 336 ± 25 °C at 100 bars, which is above the liquid-vapor boundary for H2O, suggesting that formation in the presence of a primordial dense vapor phase in the earliest history of Mars is possible.

Assessing JUICE's ability of in situ plume detection in Europa's atmosphere

ESA's upcoming JUpiter Icy moons Explorer (JUICE) is scheduled to perform two flybys of Jupiter's moon Europa. Here, we present the results of our investigation into JUICE's capability to detect plumes and to separate them from the background water in the atmosphere as a function of their source's location and mass flux on the Europan surface using the neutral mass spectrometer NIM. For both of the currently planned flybys we evaluate different scenarios to estimate how feasible such a detection is, using a Monte Carlo particle tracing model of a plume. We also incorporate the putative plume candidates reported by Roth et al. (2014b), Sparks et al. (2016), Sparks et al. (2017), Jia et al. (2018), Arnold et al. (2019) and Sparks et al. (2019) into this investigation. We come to the conclusion that the first flyby trajectory is better suited to detect the potential plume candidates listed above as they are detectable down to mass fluxes of approx. 100 ​kg/s. The second flyby requires mass fluxes between 100 ​kg/s and 500 ​kg/s for all suggested plume candidates to be detectable. This discrepancy is caused by the first flyby's closer proximity to the locations of the suggested plume sources which lie mainly on the southern hemisphere. Separation of water plumes from the atmospheric water vapour density is dependent on the mass flux of the respective plume source. The only plume separable from the background water in the atmosphere at the lowest investigated plume source mass flux of 1 ​kg/s is the one suggested by Roth et al. (2014b). It is therefore the most likely plume to be detected by JUICE. Furthermore, we investigate the detectability of trace gas contents in a plume and analyse how these impact upon plume detection. The spacecraft will be able to detect whether lighter-than-water trace gas species are present within the plume down to trace gas source mass fluxes of 0.1 ​kg/s. Provided this is the case, such species constitute a means to identifying plumes in the Europan atmosphere. Finally, the effects of lowering the flyby altitude are examined. We find that lowering the altitude of the CA does not increase the region of separability. Therefore, lowering the second flyby trajectory will not suffice for the spacecraft to be able to identify plumes that originate from the locations of the candidates mentioned above. Considering that the second flyby is the most likely to be lowered, this case study provides an example of the importance of arranging the second trajectory in a manner such that its ground track lies in close proximity to the locations of the suggested plume candidates listed above. This approach to the mission planning maximises the chance of separating the presumptive plumes from the atmospheric background water even at the lowest plume source mass fluxes.

Liquid nucleation around charged particles in the vapor phase.

We theoretically investigate the nucleation of liquid droplets from vapor in the presence of a charged spherical particle. Due to field gradients, sufficiently close to the critical pointof the vapor-gas system, the charge destabilizes the vapor phase and initiates a phase transition. The fluid's free energy is described by the van der Waals expression augmented by electrostatic energy and a square-gradient term. We calculate the equilibrium density profile at arbitrary temperatures, particle charges, and vapor densities. In contrast to classical nucleation theory, here, both liquid and vapor phases are different from the bulk phases because they are spatially nonuniform. In addition, the theory applies to both sharp and diffuse interfaces and calculates the surface tension self-consistently. We find the composition profiles and integrate them to get the adsorption near the particle. We find that the adsorption changes discontinuously at a first-order phase transition line. This line becomes a second-order phase transition at high enough temperatures. We describe the transition pointnumerically and provide approximate analytical expressions for it. Similarly to prewetting, the adsorption diverges at the binodal phase boundary. We construct a phase diagram indicating changes in the binodal, spinodal, and critical temperature. It is shown that the field gradient enlarges the range of temperature and vapor density where liquid can nucleate.

Retrieving Water Vapor From an E‐Band Microwave Link With an Empirical Model Not Requiring In Situ Calibration

AbstractAn empirical model estimating water vapor density from the attenuation of electromagnetic waves at E‐band frequencies is proposed and tested on seven months of 5‐min attenuation observations from a 4.87‐km‐long full‐duplex E‐band commercial microwave link (CML) operating at 73.5 and 83.5 GHz. The model does not require in situ calibration. Estimated water vapor density is compared to the observations from two meteorological stations located nearby the CML end nodes. Best performance is achieved for the 83.5 GHz sublink (RMSE = 1.46 g m−3, R2 = 0.85) when the actual temperature is used as a model input, in addition to the attenuation data. Use of temperature averaged over the whole evaluation period resulted in significantly worse performance. The study demonstrates the potential of E‐band CMLs for measuring near‐surface air humidity and the need for careful quality control when upscaling the water vapor monitoring to the entire network of E‐band CMLs.

Conventional and neural network-based water vapor density model for GNSS troposphere tomography

Conventional and neural network-based water vapor density model for GNSS troposphere tomography

Finite size effect on the existence of the liquid–vapour spinodal curve

Fluids interacting with Lennard-Jones and Square Well potentials reach thermodynamic equilibrium forming two coexisting phases when simulated within the liquid–vapour spinodal region. If molecular dynamics simulations in the NVT ensemble are performed on a fluid kept in a cubic cell with periodic boundary conditions, liquid and vapour phases at equilibrium are separated by a process of spinodal decomposition. In the vapour side of the spinodal curve, spherical, cylindrical, and slab type liquid structures are formed, depending on the total density. Under the mentioned conditions, in the liquid side of the spinodal, vapour bubbles with the same shapes, surrounded by liquid, are formed. Results from this work suggest that as the simulation system size increases, the spinodal curve approaches the orthobaric, but it converges to a position closer to the coexistence curve but separated from it. The same thing happens for both potential models simulated. This is in sharp contrast with previous findings by Errington, McDowell, Binder and coworkers, where they conclude that ‘Only for infinitely large systems does the effective spinodal density converge to the macroscopic coexistence vapor density.’

Theoretical and numerical study of nanoporous evaporation with receded liquid surface: effect of Knudsen number

The liquid evaporation from nanoscale pores has attracted much attention from researchers due to its importance in water treatment and device cooling related applications. It is crucial to investigate the receded liquid case as the vapour flow resistance in a nanopore has high impacts on the evaporation rate. This paper proposed a semi-empirical analysis on nanoporous evaporation with a receded liquid surface under the influence of the Knudsen number. The vapour flow dynamics in a nanopore was examined considering the multiple reflections of vapour molecules. We calculated the value of pore transmissivity based on transitional gas flow correlation which incorporated the effect of the Knudsen number. Direct simulation Monte Carlo method was employed to provide validation for the present model. The vapour density jump near the liquid surface and the pressure ratio between the far field and saturation value were predicted by our model with good precision. It was shown that the vapour flow resistance in the nanopore accounted for more than 90 % of the total resistance in present cases. With increasing Knudsen number, the pressure ratio gradually drops and reaches an asymptotic level. This suggested a relatively higher evaporation resistance in free molecular regimes. The present work revealed the importance of the Knudsen number in nanoporous evaporation with receded liquids, providing insights into the governing factors under various Knudsen regimes.

Nonlinear wave propagation in dense vapor of Bethe–Zel'dovich–Thompson fluids subjected to temperature gradients

Flows of fluids made of complex organic molecules exhibit unconventional fluid dynamic behavior in the vapor phase if their thermodynamic state is close to that of the vapor–liquid critical point. If the molecule is sufficiently complex, this thermodynamic domain is characterized by negative values of the fundamental derivative of gasdynamics Γ, the fluid is called Bethe–Zel'dovich–Thompson (BZT) fluid, and atypical phenomena, such as rarefaction shockwaves, are theoretically admissible. The nature of the steepening of nonlinear waves in dense vapor flows of organic fluids evolving in this thermodynamic region can be significantly affected by the presence of temperature gradients in the flow. This study investigates the evolution of finite-amplitude acoustic waves in these conditions. The steepening of the wavefront is analyzed using the wavefront expansion technique, and the deformation of the wavefront is simulated numerically by solving the Westervelt equation. The results of simulations of wave propagation in dense vapors indicate that, though Γ governs the nature of steepening waves, local gradients in sound speed and density can alter the rate of steepening and can enhance or delay shock formation in the medium, a result relevant also to the envisaged experiments aimed at proving the existence of nonclassical gasdynamics phenomena in BZT vapors.