Saturated Water Vapor Pressure Research Articles

Vapor Cartesian diver

The article proposes a new research object for a general physics course—the vapour Cartesian diver, designed to study the properties of saturated water vapour. Physics education puts great importance on the study of the saturated vapour state, as it is related to many fundamental laws and theories. For example, the temperature dependence of the saturated water vapour pressure allows the teacher to demonstrate the Le Chatelier’s principle: increasing the temperature of a system in a dynamic equilibrium favours the endothermic change. That means that increasing the temperature increases the amount of vapour present, and so increases the saturated vapour pressure. The experimental setup proposed in this paper can be used as an example of an auto-oscillatory system, based on the properties of saturated vapour. The article describes a mathematical model of physical processes that occur in the experiment, and proposes a numerical solution method for the acquired system of equations. It shows that the results of numerical simulation coincide with the self-oscillation parameters from the real experiment. The proposed installation can also be considered as a model of a thermal engine.

Environmental Significance of the Stable Isotopes in Precipitation at Different Altitudes in the Tuolai River Basin

Precipitation samples and meteorological data were collected simultaneously during individual precipitation events at Tuole station (3367 m a.s.l.) and Jiayuguan station (1658 m a.s.l.) in the Tuolai River Basin. A study of temporal variation, Local Meteoric Water Lines, and altitude change on precipitation stable isotopes was conducted. The relationships between precipitation stable isotopes and temperature, precipitation, average vapor pressure, and relative humidity were determined in order to explore the environmental significance of the stable isotopes at different altitudes in the middle reaches of the Qilian Mountains. The analysis indicated that the stable isotopes of the precipitation in Tuole and Jiayuguan station were characterized by pronounced seasonal variation, with Tuole having higher δ18O values in summer and autumn and lower δ18O values in spring and winter, while Jiayuguan displays higher δ18O values in spring and lower in other seasons. The d-excess was correlated negatively with δ18O, and the correlation coefficients between δ18O and d-excess decreased with increasing altitude due to weakening sub-cloud evaporation. The slope and intercept of the Local Meteoric Water Lines from Jiayuguan to Tuole rose significantly, showing an increasing trend from low altitude to high altitude. For the precipitation events above 10℃, δ18O of Tuole was positively correlated with the temperature, but the Jiayuguan results indicated the opposite. Sub-cloud evaporation weakened with high precipitation events in Jiayuguan. δ18O and d-excess were positively correlated with the average vapor pressure, which declined from Tuole to Jiayuguan. Since the water vapor pressure and saturated water vapor pressure increased, it was difficult to form precipitation with decreasing altitude. The local strong sub-cloud evaporation caused δ18O and δD was positive at low altitude, while the effect of moisture recycling is obvious, such that δ18O and δD are negative in high altitude areas. There is no significant positive correlation between the δ18O and the relative humidity of the precipitation in Jiayuguan, while Tuole displays an opposite pattern. The results of the study will provide a scientific basis for further study of precipitation isotopes in the Tuolai River basin.

A Simple Accurate Formula for Calculating Saturation Vapor Pressure of Water and Ice

AbstractIt is necessary to calculate the saturation vapor pressure of water and of ice for some purposes in many disciplines. A number of formulas are available for this calculation. These formulas either are tedious or are not very accurate. In this study, a new formula has been developed by integrating the Clausius–Clapeyron equation. This new formula is simple and easy to remember. In comparison with the International Association for the Properties of Water and Steam reference dataset, the mean relative errors from this new formula are only 0.001% and 0.006% for the saturation vapor pressure of water and of ice, respectively, within a wide range of temperatures from −100° to 100°C. In addition, this new formula yields a mean relative error of 0.0005% within the commonly occurring temperature range (10°–40°C). Therefore, this new formula has significant advantages over the improved Magnus formula and can be used to calculate the saturation vapor pressure of water and of ice in a wide variety of disciplines.

Solubility of MoO3 in Aqueous Acid Chloride-Bearing Solutions at 573 K

This study reports the measurements of the solubility of crystalline molybdenum trioxide, MoO3, in aqueous solutions of the mixture HCl–HClO4–NaCl (up to 1 m of chloride ion) at 573.2 K and pressures close to the saturation water vapor pressure by the autoclave method with the chemical analysis of quenched solutions. In total, there are 75 data points. The data treatment shows that the most probable chloride species of Mo(VI) in the studied solutions is MoO2(OH)2Cl– (the coordinated water is omitted), which agrees with the literature extended X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge structure (XANES) spectra studies of speciation of Mo(VI) in chloride solutions at elevated temperatures. For the solubility reaction MoO3(cr) + H2O(l) + Cl– = MoO2(OH)2Cl–, log10 K° = −(0.87 ± 0.2).

Corrosion of SiC layers on coated zirconia particles in wet atmosphere

Properties of SiC coating layer in the postulated accident condition of air and water ingress is crucial to the in-pile safety of tristructural-isotropic (TRISO) coated fuel particles of high temperature gas-cooled reactors (HTR). Particles of ZrO2 kernels coated with low-density pyrolytic carbon buffer layer, high-density pyrolytic carbon layer and SiC layer fabricated by fluidized-bed chemical vapour deposition (FBCVD) were used to simulate real fuel particles in this research. The coated particles were tested at 1673 K in a certain flowing air with different water content between 0 and 100 g/m3 for 10 h. Analysis results show that the corrosion reaction took place mainly on the outer surface of SiC layer with changing infiltration depth according to the flowing gas compositions. Steam content was controlled according to the relationship between saturated water vapour pressure and environment temperature. SiO2 layer was the main product formed on the surface with thickness increase from 1.5 µm to 3 µm along with the content of water vapour in air. Formation of two types of micro-cracks after oxidation are observed: micro-cracks on spherulitic SiO2 and penetrating micro-cracks on flat SiO2. Micro-stress generation mechanism is illustrated. Three are also some bubbles are observed either in SiO2 layer or between SiO2 and SiC layers. Results showed that no fracture occurred in the SiC layer after wet oxidation.

A Review on Water Vapor Pressure Model for Moisture Permeable Materials Subjected to Rapid Heating

This paper presents a comprehensive review and comparison of different theories and models for water vapor pressure under rapid heating in moisture permeable materials, such as polymers or polymer composites. Numerous studies have been conducted, predominately in microelectronics packaging community, to obtain the understanding of vapor pressure evolution during soldering reflow for encapsulated moisture. Henry's law-based models are introduced first. We have shown that various models can be unified to a general form of solution. Two key parameters are identified for determining vapor pressure: the initial relative humidity and the net heat of solution. For materials with nonlinear sorption isotherm, the analytical solutions for maximum vapor pressure are presented. The predicted vapor pressure, using either linear sorption isotherm (Henry's law) or nonlinear sorption isotherm, can be greater than the saturated water vapor pressure. Such an “unphysical” pressure solution needs to be further studied. The predicted maximum vapor pressure is proportional to the initial relative humidity, implying the history dependence. Furthermore, a micromechanics-based vapor pressure model is introduced, in which the vapor pressure depends on the state of moisture in voids. It is found that the maximum vapor pressure stays at the saturated vapor pressure provided that the moisture is in the mixed liquid/vapor phase in voids. And, the vapor pressure depends only on the current state of moisture condition. These results are contradictory to the model predictions with sorption isotherm theories. The capillary effects are taken into consideration for the vapor pressure model using micromechanics approach.

Modeling Water Vapor and Clouds as Passive Tracers in an Idealized GCM

This paper introduces an idealized general circulation model (GCM) in which water vapor and clouds are tracked as tracers, but are not allowed to affect circulation through either latent heat release or cloud radiative effects. The cloud scheme includes an explicit treatment of cloud microphysics and diagnoses cloud fraction from a prescribed subgrid distribution of total water. The model is capable of qualitatively capturing many large-scale features of water vapor and cloud distributions outside of the boundary layer and deep tropics. The subtropical dry zones, midlatitude storm tracks, and upper-tropospheric cirrus are simulated reasonably well. The inclusion of cloud microphysics (namely rain re-evaporation) has a modest but significant effect of moistening the lower troposphere in this model. When being subjected to a uniform fractional increase of saturated water vapor pressure, the model produces little change in cloud fraction. A more realistic perturbation, which considers the nonlinearity of the Clausius–Clapeyron relation and spatial structure of CO2-induced warming, results in a substantial reduction in the free-tropospheric cloud fraction. This is reconciled with an increase of relative humidity by analyzing the probability distributions of both quantities, and may help explain partly similar decreases in cloud fraction in full GCMs. The model provides a means to isolate individual processes or model components for studying their influences on cloud simulation in the extratropical free troposphere.

Thermoplastic starch wastes are converted and stored into acetone through butanol in a depressurised digester

A biofilm containing both hydrolytic fermentative bacteria and acidogenic bacteria (including acetogenic and acetoclastic bacteria) was developed for the treatment of plastic wastes in a two-phase, batch digester. The biotransformation and further degradation were electrochemically observed. It was found that the organic wastes were initially fermented in a single-phase (i.e. liquid phase) digester, where it entirely obeyed microbial growth kinetics in accumulating acetate. As the carbonates produced were vaporised, the single-phase became a two-phase fermentation (gas and liquid) accumulating volatile fatty acids (VFAs), where it obeyed a proton driving force based on Le Chatelier’s principle. Interestingly, as the digester was depressurised to the saturated vapour pressure of water, the accumulated VFAs were rapidly transformed into acetone via butanol, so that the VFAs forms were not observable. It was found that in extreme conditions, the organic feeds were converted and stored into acetone, via butanol.

Solubility of calcium molybdate in aqueous solutions at 573 K and thermodynamics of monomer hydrolysis of Mo(VI) at elevated temperatures

This study presents new experimental results on solubility of synthetic crystalline calcium molybdate, CaMoO4(cr), at 573 K and pressure ~ 10 MPa in aqueous solutions of HCl (10−4–0.02 m), HClO4 (10−4–0.03 m), NaCl (0–3.82 m) and NaClO4 (0.10–1.61 m). In addition, the thermodynamic analysis of literature and own data allowed recommendations of the equilibrium constants, $$\log_{10} {{K}}^{\text {o}}$$ , of the reactions H+ + MoO4 2− = HMoO4 −, MoO3(cr) + OH− = HMoO4 −, MoO3(cr) + H2O(l) = H2MoO4(aq), and 2H+ + MoO4 2− = H2MoO4(aq) at temperatures 273–623 K and the saturated water vapor pressure, P s. Knowledge of the thermodynamic properties of the molybdate ion, MoO4 2− (this work), Ca2+, and of calcium molybdate CaMoO4(cr) allowed calculating the values of the solubility product of this phase at temperatures 273–623 K and P s. The thermodynamic modeling of solubility of CaMoO4(cr) at 573 K and P s in studied aqueous solutions (HCl, HClO4, NaCl, and NaClO4) showed that all our experimental data can be reproduced using the same set of species, which includes only the molybdate ion, MoO4 2−, and products of its hydrolysis, HMoO4 − and H2MoO4(aq). Although the formation of ion pairs involving Na+ and the molybdate and hydrogenmolybdate ions at high temperatures appears likely due to the fall of the dielectric constant of water, the current data do not support the formation of such forms of Mo(VI), at least they are never the dominating species at conditions of presented experiments. The increase of temperature leads to the expansion of the predominance field of the hydrogenmolybdate ion HMoO4 − and of H2MoO4(aq) and the decrease of the relative share of MoO4 2−.

Application of a Relative Humidity Sensor for Monitoring Water Vapor Concentration inside Enclosures

The presence of water can have adverse effects on the performance of mechanical and electrical hardware. Standing or condensed water can cause shorting or grounding issues in the short term and can accelerate corrosion in the long term. High humidity can also accelerate corrosion as well as cause swelling of electrical components, seals, or composite materials. Water exposure data can be used to actively intervene prior to degradation(e.g. to fix a water leak) or to calculate the remaining life of a system that has been exposed to water or high humidity. The U.S. Army has recognized the importance of environmental monitoring and failure prediction in weapon systems to ensure readiness, to enhance safety, and toimprove weapon performance. Since 2000, Picatinny Arsenal has sponsored the development of specialized environmental monitoring sensors with on-board diagnostics in various new weapon/ammunition systems. In this article we present an effort at the Pacific Northwest National Laboratory to develop an asset health monitor to assess water concentration inside the storage container of an artillery shell. Desiccant is used in the container to maintain the water vapor concentration below 5000 parts per million; a higher water concentration would indicate container leakage or the need to replace the desiccant. Various types of water sensors, including standing water indicators, corrosion indicators, and humidity sensors, were identified and categorized according to type of water exposure, accuracy, and response time. A commercially available relative humidity sensor was identified as a cost effective approach to measuring water vapor concentration inside the container. Relative humidity can be converted to waterconcentration using the water vapor saturation pressure at ambient temperature. Using diurnal temperature simulations, it was determined that the accuracy of the relative humidity sensor would be unsatisfactory in high temperature/low humidity situations where a small change in relative humidity results is a large change in water vapor concentration. To overcome this obstacle, a strategic sampling technique was developed to increase the accuracy of the water concentration measurement that is based on relative humidity sensor data. The relative humidity sensorwas integrated into the Remote Readiness Asset Prognostic/Diagnostic System (RRAPDS), which is an asset health monitor developed by PNNL to measure environmental conditions in munition containers. RRAPDS will be secured to the container with a probe that extends into the container to monitor internal temperature and humidity. RRAPDS includes a microcontroller to process environmental data and execute diagnostic routines. Thispaper will describe the approach that was developed to estimate water concentration using relative humidity sensor data and describe the sampling technique used to maximize the accuracy of the water vapor concentration assessment.

Densities and Molar Volumes of Aqueous Solutions of Li2SO4 at Temperatures from 343 to 573 K

Densities of aqueous solutions of lithium sulfate (Li2SO4) at solute molalities ranging from 0.05 to 2.7 mol·kg–1 have been measured by vibrating-tube densimetry over the temperature range 373.15 ≤ T/K ≤ 573.15 at pressures close to the saturated vapor pressure of pure water. The apparent molar volumes (Vϕ) of Li2SO4(aq) calculated from these data together with previously published data at 323.15 and 343.15 K were fitted using a modified Redlich–Rosenfeld–Meyer equation, which in turn was used to extrapolate the experimental data to infinite dilution to obtain the standard partial molar volumes. A comparison of the present and literature data revealed the latter are inaccurate at low concentrations and are increasingly unreliable at higher temperatures. The combination of the present results with selected literature data produced a reliable equation of state for Li2SO4(aq) covering the temperature and pressure ranges 323.15 ≤ T/K ≤ 573.15 and 0.1 ≤ p/MPa ≤ 40. The volumetric behavior of Li2SO4(aq) was fou...

A simple method for environmental cell depressurization for use with an electron microscope.

With the aid of the environmental cell (EC) in electron microscopy, hydrated specimens have been observed at high resolutions that optical microscopy cannot attain. Due to the ultra-high vacuum conditions of the inner column of the electron microscope, the EC requires sealing films that are sufficiently thin to allow electron transmission and that are sufficiently tough to withstand the pressure difference between the inside and outside of the EC. However, most hydrated specimens can be observed at low vacuum because the saturated vapor pressure of water is known to be 0.02 atm at room temperature. These concepts have been used in the differential pumping system, but it is complicated and relatively expensive. In this work, we propose a simple method for depressurization of the EC using a 'balloon structure' and demonstrate the theoretical benefits and practical improvement for specimen observations in low-vacuum conditions.

Thermodynamic constraint on the depth of the global tropospheric circulation

The troposphere is the region of the atmosphere characterized by low static stability, vigorous diabatic mixing, and widespread condensational heating in clouds. Previous research has argued that in the tropics, the upper bound on tropospheric mixing and clouds is constrained by the rapid decrease with height of the saturation water vapor pressure and hence radiative cooling by water vapor in clear-sky regions. Here the authors contend that the same basic physics play a key role in constraining the vertical structure of tropospheric mixing, tropopause temperature, and cloud-top temperature throughout the globe. It is argued that radiative cooling by water vapor plays an important role in governing the depth and amplitude of large-scale dynamics at extratropical latitudes.

Sorbent Properties of Halide-Free Ionic Liquids for Water and CO2 Perfusion

Aqueous solutions of lithium halides are state-of-the-art sorbents in sorption-based heat pump and heat storage devices, with the drawbacks of high corrosivity and limited natural resources of lithium. Halide-free ILs could be well-suited alternative sorbents and have been explored with isothermal titration calorimetry showing superior thermochemical performance. Here, we have explored the performance of selected halide-free ILs in perfusion measurements monitoring the uptake of water vapor and CO2 from an air stream with well-defined flow and humidity as a model for open sorption processes. We have determined the saturation vapor pressure of water in the corresponding water–IL mixtures and moreover determined the diffusion coefficients of molecular species in binary [EMIM][Ac]–water mixtures via pulsed-field-gradient nuclear magnetic resonance (PFG NMR) measurements. These, together with variation of the absorption rates with calorimetric monitoring, indicate that diffusion is approximately 3 orders of m...

Calculation of thermodynamic properties of water by the CPA equation of state

An appreciable amount of formation water exists inevitably in the porous media of reservoirs, but the existence of water is often neglected in the usual calculation of phase equilibrium. The commonly used equation of state is simple, but may have large deviations in estimating some thermodynamic properties. The existing equation of state, which has been modified, is not very suitable for the system containing polar substances (e.g. hydrocarbons, water, and alcohols). In this paper, the CPA (Cubic-Plus-Association) equation of state which considers both physical and association interactions between molecules was used to calculate the thermodynamic properties of water under the saturated and unsaturated states. Moreover, the disadvantages of the commonly used equation of state in the calculation were analyzed. The following results were obtained. First, the commonly used equation of state can be used to effectively calculate the saturated vapor pressure of water, but it presents certain differences in calculating water density and enthalpy, and the enthalpy calculation is not affected by volume modification. Second, the average absolute/relative deviations between the thermodynamic properties of water calculated by the CPA equation of state and the experimental data are approximately 1%. For the system containing polar substances, the CPA equation of state is preferred in calculating the thermodynamic properties. The accurate estimation of the thermodynamic properties of water is fundamental in identifying the fluid state in the water-bearing gas reservoirs, and it is of great significance in the development and production of such gas reservoirs.

Intercalated water in multi-layered graphene oxide paper: an X-ray scattering study

X-ray scattering (XRS) experiments have been performed on multi-layered graphene oxide (GO) paper. GO can be easily hydrated as water naturally intercalates in the hydrophilic nanostructure. The effect of the intercalated water on the XRS signals is measured during dehydration under thermal treatment in the temperature range 298–473 K as well as during hydration under saturated water vapour pressure. A simple modelling of the XRS signals by taking into account the presence and the type of intercalated water (bound water or physisorbed water) is introduced. It allows an explanation of the variations of intensity and position of XRS reflections observed experimentally.

A freeze-drying microscopy study of the kinetics of sublimation in a model lactose system

Freeze drying microscopy has been used to probe the lyophilisation kinetics of lactose solutions of various concentrations, at temperatures ranging from −50°C to −30°C and under a constant pressure of 1Pa. Sublimation front velocities were determined by recording a sequence of video images of the sublimation and analysing the frontal progression using MATLAB. Initial experiments showed poor reproducibility. To combat this, silver iodide (AgI) was added as an ice nucleator, which raised nucleation temperatures and improved reproducibility when compared to non-AgI experiments. The lower supercooling on nucleation when AgI was used also produced larger ice crystals, which enabled the crystal microstructure of the more dilute samples to be more clearly observed. This showed long thin crystals, and the orientation of these crystals with respect to the direction of the frontal movement strongly affected frontal progression rates, which explained the earlier reproducibility problems. A twin resistance mass transfer model, comprising a fixed edge resistance and a resistance which increased with frontal depth, was able to describe the sublimation kinetics. The edge resistance first increased and then decreased with solids content. The resistance per unit depth increased exponentially with solids content, so much so that there is an optimal solids content in relation to the rate of production of dried material. Resistances were also much higher when crystals were oriented with their major axis perpendicular to the direction of frontal movement. Freeze drying rates were approximately proportional to the saturation vapour pressure of water, however the long-held belief that water vapour pressure is the main driving force for mass transfer in freeze-drying systems may be an oversimplification as this only reflects driving forces in the vapour phase (pores) rather than within the solid.

A numerical investigation in characteristics of flow force under cavitation state inside the water hydraulic poppet valves

Compared with the oil hydraulic systems, cavitation is more serious in water hydraulic systems due to the higher saturated vapor pressure of water. Poppet valve is one of important hydraulic components and cavitation is easy to happen due to the sharp pressure drop caused by throttling. This paper presents a numerical investigation into the flow force and cavitation characteristics inside water hydraulic poppet valves. Three kinds of typical structures of poppet valves are selected in the research. The effects of geometric parameters and backpressure of the poppet valves on flow characteristics, cavitation and flow force have been analyzed. Considering the axisymmetric structure of the valves, a half of 2D mixture model is selected and a two-phase mixture model is adopted in the calculation. The accuracy of the numerical models has been validated by comparing the simulation results with the experiment data. The results reveal that two-stage throttle valve (TS valve) can effectively suppress the occurrence of cavitation while the flow force of TS valve is much bigger than that of other valves. By comparing the simulation results under two different boundary conditions (including with backpressure and without backpressure), it seems that cavitation could slightly decrease the flow force.

Solubility of MoO3 in acid solutions and vapor-liquid distribution of molybdic acid

This study reports the measurements of the solubility of crystalline molybdenum trioxide, MoO3, in acid (HClO4, HCl) aqueous solutions at 563, 573, 593, and 623 K, mostly at pressures close to the saturated water vapor pressure. The solubility data can be explained by the two dissolution reactions: a). MoO3(cr) + OH− = HMoO4−, with log10Ko values equal to (7.08 ± 0.20), (7.09 ± 0.20), (7.43 ± 0.20) at 563, 573, and 593 K, and b). MoO3(cr) + H2O(l) = H2MoO4(aq), with log10Ko equal to –(2.40 ± 0.20), –(2.22 ± 0.20), –(2.41 ± 0.20), –(1.95 ± 0.20) at 563, 573, 593, and 623 K, respectively. Combining these results with the literature data on the thermodynamics of H2MoO4 in the ideal gas state, we evaluated Henry's constants of this form at investigated temperatures, which turned out to be close to those of Si(OH)4, just as one would expect on the basis of chemical similarity. Reasonable estimates of the fugacity coefficients of H2MoO4 in steam allowed the calculation of the vapor-liquid distribution constant, KD=limx→0y/x, for this species, where y and x stand for the mole fractions of a solute in coexisting vapor and liquid phases, respectively. The value of the Krichevskii parameter, which governs the variation of KD in the investigated range of temperatures, is equal to –(228 ± 33) MPa for H2MoO4, being close to that of Si(OH)4, –(190 ± 10) MPa.

Estimation of grass reference evaporation and sensible heat flux using surface renewal and Monin-Obukhov similarity theory: A simple implementation of an iterative method

An iterative method was applied to daily crop reference evaporation ETo. The method correctly evaluated the slope of the saturation water vapour pressure vs temperature relationship between surface temperature and air temperature. Using daily meterological data spanning several decades from four selected locations in Australia, South Africa and USA, differences in ETo estimates were noted with and without the iteration method applied. The largest difference, which occurred under high water vapour pressure deficit conditions, ranged from 1.65mm/day for Griffith, Australia to 0.51mm/day for Pretoria, South Africa. The aerodynamic component of the ETo equation was more affected by not applying the spreadsheet iterative procedure compared to the radiative component. Other spreadsheet examples of the iterative method employed included obtaining the roots of a depressed cubic polynomial in the air temperature surface renewal (SR) ramp. This value was used for the measurement of sensible heat flux using surface renewal. An iterative method, together with Monin-Obukhov similarity theory (MOST) and surface-layer scintillometer (SLS) measurements in a mesic grassland, was also used to calculate the sensible heat flux. The simple iterative method is quick, accurate and convenient, easy to repeat following changes to equations or data, allows easy manipulation and allows convenient visual inspection of data and graphics. Sub-hourly measurements of sensible heat flux for the mesic grassland using SR and SLS MOST iterative methods compared favourably with Bowen ratio and eddy covariance measurements.