Saturated Water Vapor Research Articles

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.

Humidity affects the morphology of particles emitted from beclomethasone dipropionate pressurized metered dose inhalers

The effects of propellant type, cosolvent content, and air humidity on the morphology and solid phase of the particles produced from solution pressurized metered dose inhalers containing the corticosteroid beclomethasone dipropionate were investigated. The active ingredient was dissolved in the HFA propellants 134a and 227ea with varying levels of the cosolvent ethanol and filled into pressurized metered dose inhalers. Inhalers were actuated into an evaporation chamber under controlled temperature and humidity conditions and sampled using a single nozzle, single stage inertial impactor. Particle morphology was assessed qualitatively using field emission scanning electron microscopy and focused ion beam-helium ion microscopy. Drug solid phase was assessed using Raman microscopy. The relative humidity of the air during inhaler actuation was found to have a strong effect on the particle morphology, with solid spheroidal particles produced in dry air and highly porous particles produced at higher humidity levels. Air humidification was found to have no effect on the solid phase of the drug particles, which was predominantly amorphous for all tested formulations. A critical level of air relative humidity was required to generate porous particles for each tested formulation. This critical relative humidity was found to depend on the amount of ethanol used in the inhaler, but not on the type of propellant utilized. The results indicate that under the right circumstances water vapor saturation followed by nucleated water condensation or ice deposition occurs during particle formation from evaporating propellant-cosolvent-BDP droplets. This finding reveals the importance of condensed water or ice as a templating agent for porosity when particle formation occurs at saturated conditions, with possible implications on the pharmacokinetics of solution pMDIs and potential applications in particle engineering for drug delivery.

Investigation of moisture uptake into printed circuit board laminate and solder mask materials

Presence of moisture in a printed circuit board (PCB) laminate, typically made of glass fibres reinforced epoxy polymer, significantly influences the electrical functionality in various ways and causes problems during soldering process. This paper investigates the water uptake of laminates coated with different solder mask materials and exposed to saturated water vapour and liquid water. The solder masks are characterised for their microstructure and constituent phases using scanning electron microscopy and X-ray diffraction. The observations are correlated with the moisture absorption characteristic such as diffusivity, permeability, and solubility. In addition, the effect of a reflow soldering simulation on microstructural changes and on increase of water uptake of the materials has been analysed.

Numerical Approximation of a Variational Inequality Related to the Humid Atmosphere

We investigate the numerical approximation of solutions to some variational inequalities modeling the humid atmosphere when the saturation of water vapor in the air is taken into account. In order to overcome the difficulties caused by the constraints on the humidity $q$ ($0 \leq q \leq 1$) and the discontinuity in the variational inequalities, we construct a penalized and regularized implicit Euler method. We manage to show that the approximation functions associated with the numerical scheme converge to the solutions of the variational inequalities through deriving various delicate a priori estimates and by using compactness arguments.

Sea Water-mineral Substance-living Matter System

Formation of hydrocarbons in the seawater - mineral substance - living matter system is modeled. Some systems of various living matter compositions and stoichiometry and also at several sets of T,P parameters are simulated. During diagenesis kerogens and hydrocarbons are formed. The equilibrium constant of the reaction between oily kerogen and oxidized one, methane and CO2 is evaluated: Φ1C292H288O12(kerogen, H/C 0.99, O/C 0.041) → Φ2C128H68O7(kerogen, H/C 0.53, O/C 0.055)+xСH4+yCO2+zH2O, where Φ1 and Φ2 moles of kerogens; x, y, z – stoichiometry coefficients. In thermodynamically closed system the aqueous natural hydrocarbons are stable up to 300оС (at pressure above water saturated vapor) due to reductive environment formation (lg f H2 ≈ 10-4 бар). Equilibrium mineral assemblages of the system include quartz, kaolinite, muscovite, ankerite, siderite, pyrite, (Ca,Mg)CO3, (Ca,Sr)CO3 and paragonite. High salinity Cl-HCO3-Na aqueous solution also contains CO2 of tens g/l and ammonium nitrogen.

Numerical Simulation of Heat and Mass Transfer in a Liquid Film Moving Over a Heated Horizontal Surface Under the Action of a Gas Flow

Heat and mass transfer during desorption on a horizontal film of lithium bromide water solution flowing on a heated wall under the action of shear stress is numerically investigated in this paper. The shear stress on the film surface is set by the motion of surrounding saturated water vapor. It is shown that at low values of heat flux the film temperature and vapor concentration in the solution downstream decreases due to desorption. However, with an increase in heat flux, general film heating and desorption slowing down are observed.

Flue gas moisture capacity calculation at the outlet of the condensation heat recovery unit

As a result, study equation has been obtained which determine the flue gas moisture capacity at the outlet of the condensation heat recovery unit with an error of less than 1%. It possible to at the temperature of the flue gas below the dew point and the known air-fuel ratio efficient. The equation can be used to calculate plants operating on products of gas combustion without Use of tables and programs for calculating the water-vapor saturation pressure.

Water thickness effect on the fin efficiency and heat transfer for partially wet-surface heat exchanger

Heat and mass transfer, in this paper, is considered in one-row heat exchanger, that fins are hotter than air flow and water is added to fins. Related governing equations are derived by analyzing a two-dimension model in a unique cell of a heat exchange. These equations are numerically solved by finite difference method. Heat transfer and efficiency under partially wet surface are calculated by changes in thickness of water layer on the fins and wet percentage region of fin with constant airflow characteristics. In this study, Lewis Number as unity and water vapor saturation as parabolic are assumed. Obtained results show that increasing in thickness of fin leads to increasing thermal resistance; therefore, efficiency of fin decreases. But thickness of water layer dose not play a significant role in fin efficiency when water layer covering the surface of fins is thin or it covers a small region of fins because thermal resistance of water is not comparable with thermal conductivity of fin material. But where thickness of water layer is comparable with fin pitch or more surface of fins is wetted, fin efficiency and heat transfer change obviously because of increasing thermal resistance and changing in air flow velocity that cause more decreasing in efficiency of fins.

Influence of Dispersivity of Micron-Sized Aluminum Powders on their Resistance to Water Vapor

The influence of dispersivity of micron-sized industrial Al powders with interval of the particles diameter of 0.18-11.0 μm on their resistance to oxidation in the saturated water vapor atmosphere at its different partial pressures has been studied. It was experimentally shown the effect of increasing the stability of powders with a higher proportion of submicron particles to oxidation when exposed to water vapor, which consists in reducing the degree of oxidation with increasing dispersivity of Al powders under the same exposure conditions to water vapor. Enhancing the stability of submicron and nanoparticles of Alto oxidation with water vapor was explained by the formation on the particle surface a special charge state of the oxide film (double electric layer) which slows the diffusion of oxidant to the metal core of particles.

Influence of Corrosion Product on Corrosion Behavior of Carbon Steel in Atmospheric Environment

Atmospheric corrosion proceeds under thin water film, and it is affected by many environmental factors such as temperature, relative humidity, rainfall, deposition of airborne sea salt. Most of the previous study of atmospheric corrosion of carbon steel has been focused on the corrosion behavior in initial corrosion process. However, corrosion products are formed on the surface at an early stage in case of carbon steels. Thus it is important to clarify the influence of corrosion products on atmospheric corrosion behavior.. While corrosion products may easily lead to wet condition with absorption of moisture, it is reported that corrosion products inhibit the corrosion physically or chemically. In this study, we focus on dew condensation which occurs on the surface of carbon steels with rust layer. The electrodes with corrosion products were prepared by wet/dry cyclic corrosion test. The remodeled concentric corrosion sensor was used as the electrodes. The temperature of electrode materials can be controlled from the backside of electrode because the backside of the remodeled sensor is exposed to atmosphere. The corrosion test was carried out in a chamber at 25℃ and 60％RH by adding the droplet of 0.1M NaCl solution or distilled water. During the corrosion test, the corrosion rate of the electrode was monitored by electrochemical impedance method. The electrode covered with corrosion products was cooled with a cooling equipment in the chamber at 25 ℃ and 60 ％ RH in order to measure the dew point. The dew point was evaluated by measuring solution resistance using electrochemical impedance method. The dew point of the electrode before corrosion test was measured. The solution resistance dropped sharply to a low value at around 17 ℃. The dew point was calculated at 17℃ under the 25℃ and 60％RH from the curve of saturation water vapor pressure and Tetens’s equation, indicating that the experimental and calculated values are in good agreement. The amount of corrosion products increased with an increase of the cycle number. The solution resistance of the electrode after corrosion test went down at the temperature higher than the calculated value. In addition, the deposition of corrosion products occurred an increase of the dew point of the electrode. This is attributed to the diameter of pore in rust layer. It is known that equilibrium water vapor pressure in the crevice increases with a decrease of the crevice size. This means that the humidity in crevice increases in comparison with relative humidity of atmosphere. It is predicted the deposition of corrosion products leads to the formation of smaller size of pores. The chloride ion is included in the rust layer, and thus the water absorption of chloride ion occurs even at higher surface temperature.

Short-range and long-range cross-linking effects of polygenipin on gelatin-based composite materials.

Genipin is an ideal cross-linking agent in biomedical applications, which can undergo ring-opening polymerization in alkaline condition. The polygenipin can create short-range and long-range intermolecular cross-linking between protein chains. In this article, the polygenipin with different degree of polymerization was successfully prepared and used to fix gelatin composite materials. The short-range and long-range cross-linking effects of polygenipin were systematically studied. The results show that the composite materials present porous structure with tunable pore sizes in the gel state, which can be easily controlled by adjusting the degree of polymerization of polygenipin. Long-range cross-linking can increase the pore size of the gel. However, during the drying process, the composite films cross-linked by polygenipin with higher degree of polymerization shrank to smaller size to create more compact structure, resulting in the improvement of water resistance properties, thermal stability, tensile strength, and darker color for the composite films. It is interesting that the composite films can partly swell to the original gel structure when in contact with water and saturated water vapor. All the composite films have excellent barrier properties against UV light. However, the compatibility of gelatin and polygenipin is reduced when the degree of polymerization of polygenipin increases to a certain extent, which will result in the formation of phase separation structure. The obtained composite films are ideal candidates for food and pharmaceutical packaging materials. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2712-2722, 2016.

Wood moisture content during the thermal modification process affects the improvement in hygroscopicity of Scots pine sapwood

Elevated wood moisture contents during the thermal modification process have been shown to adversely affect the improvement in dimensional stability and hygroscopicity. This study tested the hypothesis that the effect of elevated wood moisture content is based on the impact of water on chemical reactions which determine the cell wall matrix stiffness. Samples of Scots pine sapwood (Pinus sylvestris L.) were thermally modified in saturated water vapor at different peak temperatures and durations starting either in oven-dry or in water-saturated state. For a given mass loss caused by the modification process, the improvement in maximum swelling and equilibrium moisture content was stronger for oven-dry samples. After removal of water-soluble degradation products, which caused a cell wall bulking effect, the maximum swelling even increased after modification in water-saturated state. Based on dynamic vapor sorption measurements, it was evidenced that the modification in oven-dry state increased the cell wall matrix stiffness which improved dimensional stability and hygroscopicity. Enhanced bond formation in the polymeric network, i.e., via condensation and cross-linking reactions during the treatment of oven-dry wood, is suggested as a cause for this increase in matrix stiffness. In contrast, the modification in water-saturated state enhanced the flexibility of the cell wall matrix, which increased the cell wall swelling and limited the improvement of hygroscopicity to the reduction in OH groups by removal of hemicelluloses. This enhanced matrix flexibility was potentially caused by predominant hydrolytic cleavage of bonds in case of water-saturated samples, evident from the chemical analysis of soluble degradation products, which increased the free volume between adjacent matrix polymers.

Nominal condensing capacity and performance evaluation of evaporative condenser

Heat transfer performance of an evaporative condenser is closely related to the type of refrigerants used and its operating conditions. Thus establishing a method to measure the condensing capacity of a modular product is necessary. This paper proposes saturated water vapor under a pressure of 20kPa as the benchmark working fluid to evaluate the thermal performance of the evaporative condenser. When the same evaporative condenser is used for condensing other refrigerants, the corresponding condensation ability could be obtained according to the change of the thermal property parameters in working conditions. The verification was conducted according to experimental data obtained when the water vapor and ammonia vapor were condensed respectively in the same evaporative condenser. Results showed that the calculation of the heat transfer area deviation is less than 8% when the ratio of the superheated and sub-cooling sections is less than 8%. According to the current procedural verification method, a contrast test-bed is designed to verify the design of an unknown refrigerant condensation.

Corrosion of Engineering Alloys in Supercritical CO2

Introduction: The properties of supercritical carbon dioxide (scCO2) have made it attractive in numerous industries and in a variety of applications [1-3]. The need for compatibility of materials with scCO2 has been identified as a stumbling block for even wider application in industry [4-6]. An expanded understanding of the corrosion characteristics of engineering alloys in scCO2 with various impurities will provide necessary information for increased utilization. Experimental: Experiments were conducted in an autoclave, lined with Teflon. The autoclave is capable of maintaining a temperature of up to 423K (150˚C). Materials studied include austenitic steels as well as nickel based alloys. Environment included scCO2, as well as scCO2 with impurities. The surface of the samples were characterized after exposure to scCO2 using scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy. Results: Figure 1 shows Raman spectra obtained from Inconel 625 and stainless steel 316 exposed to scCO2. Only Inconel 625 has detectable Raman modes after exposure to scCO2 with saturated water vapor at 80°C. The corrosion performance of Inconel 625 and stainless steel 316 are observed with respect to their surface chemistry. Figure 1: Raman spectra for both the austenitic steel SS316 and nickel based alloy I625 exposed to 80°C SCO2 with saturated water vapor. Spectra collected with 532nm laser. Acknowledgements: This study was supported by the Department of Energy, under Contract DE-NE0008236, and Nuclear Regulatory Commission (NRC) under award NRC-HQ-11-G-38-0039.

Stability of ettringite in CSA cement at elevated temperatures

Calcium sulfoaluminate cements are promising low carbon dioxide alternatives to Portland cement. Their main hydration products are ettringite and aluminium hydroxide. Ettringite has recently been identified as a potential heat storage material. The reversible dehydration of ettringite to metaettringite at elevated temperatures and under dry conditions involves a relatively high enthalpy, which can be used for (seasonal) heat storage. In this context, the effect of elevated temperatures (up to 110°C) and humidity conditions (steam curing and dry curing) on the stability of ettringite in calcium sulfoaluminate was studied experimentally using thermogravimetric analysis, X-ray diffraction and thermodynamic modelling. The experimental results show that ettringite decomposes under steam curing conditions at temperatures far below 100°C to monosulfate. This may lead to delayed ettringite formation when the temperature is lowered again under humid or wet conditions. Under dry conditions at low water vapour saturation, the expected dehydration of ettringite to metaettringite is found. A thermodynamic model for the stability of hydrated calcium sulfoaluminate cements based on cement composition and calculations of thermodynamic equilibria has been established. The modelled phase development under different hygro-thermal conditions agrees well with the experimental findings. Stable heating and drying conditions for calcium sulfoaluminate based heat storage materials could be identified.

Effect of hydrocarbons on the efficiency of catalytic reactor of detritiation system in an event of fire

ABSTRACTDetritiation system of a nuclear fusion plant is mandatory to be designed and qualified taking carefully into consideration all the possible extraordinary situations in addition to that in a normal condition. We focused on the change in the efficiency of tritium oxidation of a catalytic reactor in an event of fire where the air accompanied with hydrocarbons, water vapor, and tritium is fed into a catalytic reactor at the same time. Our test results on the effect of these gases on the efficiency of tritium oxidation of the catalytic reactor indicated; (1) tritiated hydrocarbon produces significantly by reaction between tritium and hydrocarbons in a catalytic reactor; (2) there is little possibility of degradation in the detritiation performance because the tritiated hydrocarbons produced in the catalyst reactor are combusted; (3) there is no possibility of uncontrollable rise in the temperature of the catalytic reactor by heat of reactions; and (4) saturated water vapor could temporarily poison the catalyst and degrades the detritiation performance. Our investigation indicated a saturated water vapor condition without hydrocarbons would be the dominant scenario to determine the amount of catalyst for the design of catalytic reactor of the detritiation system.

Explosion behaviors of mixtures of methane and air with saturated water vapor

The explosion and combustion parameters of mixtures of methane and air with saturated water vapor were experimentally measured in a standard 20-L spherical explosion vessel at room temperature and atmospheric pressure. The experimental data were carefully scrutinized and compared to elucidate the effect of saturated water vapor in air. When the methane content is below 10%, the maximum explosion pressure, maximum rate of pressure rise and laminar flame speed during explosion are slightly affected, which is attributed to the dual role of water vapor: on one hand, the water vapor suppresses the explosion by thermal and chemical effects; on the other hand, the addition of water vapor makes the equivalence ratio higher than that at dry condition with the same methane content. Then when the methane content is relatively higher, the discrepancies between parameters are quite pronounced for the same reason. The flammability limits of methane in the mixture become narrower (6–14%) compared to dry methane/air mixtures (5–15%). Additionally, the measured laminar flame speeds and computed ones by HP-Mech agree well with each other in this work.

Generation of aerosol and droplets in binary mixtures of saturated water vapor with air and molecular gases

Results of observation of the generation of aerosol particles and droplets in mixtures of saturated water vapor with air and molecular gases are described. The kinetics of generation of aerosol and droplets was studied in the absence of a monokinetic electron beam and under its influence on a gas mixed with supersaturated water vapor formed in the process of a controllable pressure discharge from a spherical chamber of 1.4 m diameter with the gas mixture into a vacuum reservoir ~40 m3 in volume. The generation kinetics was recorded by the low-angle laser beam scattering method (for droplets) and with an aerosol spectrometer (for particles). Experimental results show a significant dependence of droplet and particle generation on the ionizing radiation effect. The 3D computer simulation of the process of super-saturated water vapor condensation on ions by the lattice Boltzmann method (LBM) and molecular dynamics (MD) describes qualitatively the experimental results.

Impact of moisture divergence on systematic errors in precipitation around the Tibetan Plateau in a general circulation model

Current state-of-the-art atmospheric general circulation models tend to strongly overestimate the amount of precipitation around steep mountains, which constitutes a stubborn systematic error that causes the climate drift and hinders the model performance. In this study, two contrasting model tests are performed to investigate the sensitivity of precipitation around steep slopes. The first model solves a true moisture advection equation, whereas the second solves an artificial advection equation with an additional moisture divergence term. It is shown that the orographic precipitation can be largely impacted by this term. Excessive (insufficient) precipitation amounts at the high (low) parts of the steep slopes decrease (increase) when the moisture divergence term is added. The precipitation changes between the two models are primarily attributed to large-scale precipitation, which is directly associated with water vapor saturation and condensation. Numerical weather prediction experiments using these two models suggest that precipitation differences between the models emerge shortly after the model startup. The implications of the results are also discussed.