Search

Some precise measurements of the vapor pressure of liquid water at seven temperatures in the range 25 to 100 °C were reported recently by H. F. Stimson of NBS. These measurements have an estimated standard deviation of 20 ppm or less, except at 25 °C where the estimated standard deviation is 44 ppm. We have derived a formula which yields computed values of vapor pressure agreeing with Stimson’s measurements to within 7 ppm. We integrated the Clausius-Clapeyron equation using the accurate calorimetric data of Osborne, Stimson, and Ginnings and the Goff and Gratch formulations for the virial coefficients of water vapor to obtain an equation that has a rational basis. This equation was then adjusted to bring it into closer accord with Stimson’s pressure measurements. Two tables are given of the vapor pressure, expressed in pascals, as a function of temperature at 0.1-deg intervals over the range 0 to 100 °C, one on the International Practical Temperature Scale of 1948 and the other on the International Practical Temperature Scale of 1968.

Concentration distribution is essential for the emergency disposal of cryogenic fuel leakage. In the dispersion process of cryogenic gas, its concentration is greatly influenced by the atmospheric water vapor. The authors have presented an adiabatic mixing model to derive the concentration of the cryogenic gas, in which the value of water vapor density is obtained by referring to the NIST database continuously. However, it is difficult to achieve fast system response times for real-time monitoring systems when calling NIST. Thus, a simple algebraic model of water vapor density with high calculation efficiency is necessary. Based on the detection of temperature and the solution of water vapor partial pressure, a calculation model was developed. For a given initial ambient temperature and relative humidity, the dew point could be solved by Qian’s correlation. By temperature comparisons of the mixture cloud, dew point, and triple point, the water vapor partial pressure can be calculated by the Goff–Gratch formulation. Then, the water vapor density during the temperature declining process can be derived via EOS. The results show that the model has high estimation accuracy, and has a close mean deviationof 0.08%to the IAPWS 95 of 0.03%. The increase in the computation efficiency was confirmed as +67% under nine testing points. The model facilitates the engineering utilization of the adiabatic mixing model for cryogenic fuel leakage monitoring.

The quest for a reliable means to detect cannabis intoxication with a breathalyzer is ongoing. To design such a device, it is important to understand the fundamental thermodynamics of the compounds of interest. The vapor pressures of two important cannabinoids, cannabidiol (CBD) and Δ 9 -tetrahydrocannabinol (Δ 9 -THC), are presented, as well as the predicted normal boiling temperature (NBT) and the predicted critical constants (these predictions are dependent on the vapor pressure data). The critical constants are typically necessary to develop an equation of state (EOS). EOS-based models can provide estimations of thermophysical properties for compounds to aid in designing processes and devices. An ultra-sensitive, quantitative, trace dynamic headspace analysis sampling called porous layered open tubular-cryoadsorption (PLOT-cryo) was used to measure vapor pressures of these compounds. PLOT-cryo affords short experiment durations compared to more traditional techniques for vapor pressure determination (minutes versus days). Additionally, PLOT-cryo has the inherent ability to stabilize labile solutes because collection is done at reduced temperature. The measured vapor pressures are approximately 2 orders of magnitude lower than those measured for n -eicosane, which has a similar molecular mass. Thus, the difference in polarity of these molecules must be impacting the vapor pressure dramatically. The vapor pressure measurements are presented in the form of Clausius-Clapeyron (or van’t Hoff) equation plots. The predicted vapor pressures that would be expected at near ambient conditions (25 °C) are also presented.

In this study, air accumulation in vapor condensation across a horizontal tube was investigated experimentally. A total of 16 thermistors were mounted uniformly on the horizontal tube wall along the circumference of z = 0.17 m and z = 0.63 m to measure wall temperature. Results show that vapor exists as a three-dimensional diffusion flow and air is carried by vapor toward the downstream at θ = 135°–225° and z = 0–0.6 m, and forms a saturated moist air region there, whereas another region is full of moist vapor. A vapor flowing front lies at the joint of two regions, where interdiffusion between vapor and air is in dynamic equilibrium. In the saturated moist air region, the ratio of gas film layer to overall thermal resistance is within the range of 0.92–0.97, the air mole fraction on the gas–liquid interface is within the range of 0.75–0.87, and the heat transfer coefficient at the condensation side is less than 300 W m−2 K−1. An increase in cooling water mass flux pushes the vapor flowing front forward, expanding the moist vapor region, ultimately enlarging the vapor condensation area. The present experimental results were compared with the results of the works of Zhou and Rose (1996), Sherkriladze and Gomelauri (1966), Rose (1984), Fujii et al. (1972), Memory et al. (1993), and Chen and Lin (2009). The wall temperature distribution and Nu ‾ / Re l 0.5 variation are reasonable.

It has been demonstrated that water vapor consistently transports in asphalt pavements. The relative humidity differential, which exists between the subgrade below and the atmosphere above the pavement, is a major contributor to the water vapor diffusion. However, the effect of the relative humidity differential has not been quantified on the water vapor diffusion in asphalt mixtures. This paper designed a laboratory experiment to investigate the water vapor diffusion in asphalt mixtures under a number of relative humidity differentials. The designed experiment consisted of five individual water vapor diffusion tests, each of which was performed at a specific relative humidity differential in the pre-vacuumed measuring cell of the test equipment. Two diffusion models were developed based on the Fick’s second law of diffusion. It was found that the two-dimensional model provided an accurate characterization of the water vapor diffusion in both radial and axial directions of the cylindrical test specimens. A linear model was established between the relative humidity differential and the total diffused mass based on the real gas law. An inverse proportionality was identified between the relative humidity differential and the diffusivity in both radial and axial directions. The determined diffusivity values were further converted to the corresponding diffusivity values under 1 atmosphere, which were in agreement with the diffusivity data reported in the literature. A linear model was derived for the relationship between the relative humidity differential and the diffusivity under 1 atmosphere, which indicated faster water vapor diffusion in asphalt pavements when subjected to a larger relative humidity differential between the subgrade and the atmosphere. The diffusivity in the radial direction was always larger than that in the axial direction despite the variation of the relative humidity differential. This fact implied the anisotropic distributions of air voids and aggregates in the asphalt mixture specimens, which assisted water vapor in diffusing more easily in the radial direction than in the axial direction.

An accurate measurement of saturation vapor pressure of supercooled water is a strong challenge in metrology, mainly due to difficulties concerning keeping water at a liquid state at temperatures well below the melting point; thus few experimental data covering limited temperature ranges (down to about 253 K) are reported in literature. For this reason, an investigation of the water vapor – supercooled water equilibrium along the saturation line is carried out at Istituto Nazionale di Ricerca Metrologica (INRIM). Measurements cover the temperature range from 261.26 K to 273.25 K, corresponding to a saturation vapor pressure from about 244 Pa to 611 Pa. The experimental apparatus includes a borosilicate glass sample cell, kept in a liquid bath at a constant temperature with millikelvin stability and connected to a manifold where the pressure is measured using a capacitive diaphragm pressure gauge. In this work, the water sample preparation, the measuring method and measurement corrections are reported; moreover, a comparison between experimental and literature data is conducted along with the most used vapor pressure formulations. Measurement results are discussed and uncertainty sources estimated. The resulting expanded relative uncertainty (k = 2) varies from 0.085% at 261.26 K to 0.039% at 273.25 K.

Water vapor dilution has great impact on fundamental combustion processes such as ignition, flame propagation and extinction. In the literature, there are many studies on how water vapor addition affects flame propagation and extinction limit. However, the influence of water vapor addition on ignition receives little attention. In this study, numerical simulations considering detailed chemical mechanisms are conducted for the ignition of methane, n -butane and n -decane/air/water vapor mixtures. The emphasis is spent on examining the effects of water vapor dilution on the ignition of these fuels at normal and reduced pressures. The minimum ignition energies (MIE) at different dilution ratios and initial pressures are obtained. It is found that at normal and reduced pressures, the MIE is proportional to the inverse of pressure and it increases exponentially with water vapor dilution ratio. A general correlation among the MIE, pressure and dilution ratio is proposed for each fuel. Furthermore, for stoichiometric methane/air/water vapor mixtures, the chemical and radiation effects of water vapor dilution are isolated and quantified. It is found that the three-body recombination reaction greatly increases the MIE and reduces the dilution limit.

Water vapor is a key element in both the greenhouse effect and the water cycle. However, water vapor has not been well studied due to the limitations of conventional monitoring instruments. Recently, estimating rain rate by the rain-induced attenuation of commercial microwave links (MLs) has been proven to be a feasible method. Similar to rainfall, water vapor also attenuates the energy of MLs. Thus, MLs also have the potential of estimating water vapor. This study proposes a method to estimate water vapor density by using the received signal level (RSL) of MLs at 15, 18, and 23 GHz, which is the first attempt to estimate water vapor by MLs below 20 GHz. This method trains a sensing model with prior RSL data and water vapor density by the support vector machine, and the model can directly estimate the water vapor density from the RSLs without preprocessing. The results show that the measurement resolution of the proposed method is less than 1 g/m3. The correlation coefficients between automatic weather stations and MLs range from 0.72 to 0.81, and the root mean square errors range from 1.57 to 2.31 g/m3. With the large availability of signal measurements from communications operators, this method has the potential of providing refined data on water vapor density, which can contribute to research on the atmospheric boundary layer and numerical weather forecasting.

The vapor pressure of HFO-1234ze(E) (trans-1,3,3,3-tetrafluoropropene) was measured from 235 to 381 K for pressures from 40 to 3493 kPa using a Burnett apparatus. The temperature measurement uncertainty was estimated to be 2.3 mK, and the pressure uncertainty was estimated to be 600 Pa. A Wagner-type equation was used to correlate the vapor pressure of HFO-1234ze(E) based on the experimental data. This vapor equation has five coefficients and correlates the vapor pressure data of this work with a maximum relative deviation of 0.00082.

We demonstrated real-time measurement of bis-cyclopentadienyl magnesium (Cp 2 Mg) vapor concentration by using a non-dispersive infrared (NDIR) spectroscopy. The Cp 2 Mg concentration was determined by the calibration curve generated through determining the correlation between the Cp 2 Mg vapor pressure and infrared absorbance at 12.8 µm wavelength, which corresponds to the C–H bending oscillation of the molecule. We measured Cp 2 Mg vapor concentration in real time generated by a bubbling method where the carrier flow rate was varied in the range of 100–1000 sccm under fixed total pressure and bottle temperature (700 Torr and 30 °C). The overall behavior of measured concentration was almost constant throughout the bubbling time; however a slight concentration decrease of 1.6 ppm was captured due to the reduction of sublimation efficiency. In addition, the measured concentration was as low as 66.6–68.8% of the saturation concentration calculated from saturation vapor pressure of Cp 2 Mg. The validity of the measured concentration was evaluated by the comparison between the measured bottle weight losses after continuous bubblings and the mass consumptions calculated from the measured concentrations. Good agreements within 5% deviations were obtained, and it was confirmed that proper concentration was provided by the NDIR measurement.

Manure on dairies is the second largest agricultural source of ammonia emissions. Ammonia (NH3) emissions were measured at a 3400-cow open-lot dairy in Texas using a backward Lagrangian Stochastic model in combination with measurements from long-path tunable diode lasers and on-site sonic anemometers. Measurements were made for multiple weeks at a time for most seasons over two years. Both 30-min and daily average emissions were influenced by air temperature consistent with a van &rsquo, t Hoff equation. Emissions were also linearly related to saturation vapor density deficit. The influence of temperature on NH3 solubility, expressed by the van &rsquo, t Hoff temperature correction function, decreased as the water vapor deficit increased. The mean annual daily NH3 emissions at the farm was estimated at 82 g NH3 d&minus, 1 per animal (105 g NH3 AU&minus, 1 d&minus, 1, 1 AU = 500 kg) with mean emission during the summer of 124 g NH3 d&minus, 1 per animal (159 g NH3 AU&minus, 1). A distinct diurnal pattern in NH3 emissions was consistent with diurnal patterns in wind speed, saturation vapor density deficit and air temperature. The mean daytime emissions were twice the mean nighttime emissions. Additional studies are needed to evaluate the frequency of high emission days during the summer.

Condensation heat transfer in the presence of non-condensable gas is a vital problem in the nuclear engineering applications, such as the gas-steam pressurizer design, and heat removing on containment in the case of postulated accident. An improved diffusion layer model of condensation heat transfer at high pressure is presented in the vapor domination region, and it shows the influence of the pressure in the film condensation in presence of non-condensable gas. All gases in this improved model are considered to be real gases as the compressibility factor of gas is utilized. New modified equations are developed to describe the relation between partial pressure and mole fraction, and an approximate analytical solution for heat transfer coefficient in the presence of non-condensable gas is obtained. The analysis result indicates that the compressibility factor of vapor has a great effect on the condensation heat transfer coefficient in the vapor domination region at high pressure, whereas the compressibility factor of the non-condensable gas does not. The gas/vapor mean concentration ratio is a ternary function of vapor compressibility factor, gas mean concentration and vapor mean concentration instead of a binary function of gas mean concentration and vapor mean concentration in the previous model based on ideal gas assumption. The deviation of these two gas/vapor mean concentration ratios is about 30% when the total pressure is about 16.0 MPa and the mole fraction of non-condensable gas is less than 2%. Compared with the experimental data, it has been proven that this improved model can get good applicability and accuracy.

We present experimental measurements of the density, speed of sound, and vapor pressure of trans-1-chloro-3,3,3-trifluoropropene, which is also known as R1233zd(E). Densities were measured over the temperature range from (215 to 444) K, with pressures from (0.3 to 24.1) MPa. Sound speed data were measured at temperatures between (290 and 420) K, with pressures from (0.07 to 2.1) MPa. Vapor pressures span the temperature range from (280 to 438) K. The experimental data cover the saturation curve, the vapor and liquid phases, and also the vicinity of the critical point. Densities and vapor pressures were measured in a two-sinker densimeter with a magnetic suspension coupling. Sound speed data were measured with a spherical acoustic resonator. An equation of state written in terms of the Helmholtz energy was developed; it represents the present experimental data with relative root-mean-square deviations of 0.020 % for densities, 0.223 % for vapor pressures, and 0.131 % for speeds of sound.

In the present paper, a Visual Basic program was developed by describing the set of equations required to determine the value of seven different psychrometric properties (partial pressure of water vapor, absolute humidity, percentage humidity, relative humidity, dew point temperature, humid heat, humid volume or adiabatic saturation temperature) for mixtures of water vapor in air given the dry bulb temperature, the total atmospheric pressure and one additional parameter. Eight different cases are studied according to the corresponding input parameters. © 2015 Wiley Periodicals, Inc. Comput. Appl. Eng. Educ. 9999:1–5, 2015; View this article online at wileyonlinelibrary.com/journal/cae; DOI 10.1002/cae.21670

The density and viscosity were measured in the temperature range of (273.15 to 333.15) K at atmospheric pressure, and the vapor pressure was measured at temperatures from (293.59 to 400.80) K for 1,1,1-trifluoro-2,3-dichloropropane. The expanded uncertainties in temperature, density, viscosity, and pressure measurements were estimated to be less than 20 mK, 0.0005 g·cm–3, 0.006 mPa·s and 1.2 kPa, respectively. A total of 31 density experimental points were obtained with 31 viscosity experimental points and 58 vapor pressure experimental points. Temperature-dependence correlation equations for the density, viscosity, and vapor pressure were proposed.

Diagnostics of adsorbed water vapor molar heat and accumulation at bubble surface during refinery waste water aeration treatment with membrane distributor was performed, on the basis of experimentally measured air temperature and pressure on input and exit and measured stationary oxygen content after saturation period. The working hypothesis is that electromotor and compressor favor the consumption of water vapor adsorption heat at bubbles surfaces and the relaxation with active centers transport work, according to II law of thermodynamic. During air overpressure relaxation, active centers enable the couple of prevented exothermic hydration and favored endothermic processes and water vapor accumulation up to catalyst final titration points in zone of condensation, precipitatation, vaporization, nitrification/denitrification and biological slime that can cause diffuser fouling and scalling. Diagnostics results for the all 15 examined systems with the same membrane diffuser and various combination of process parameters, c-h-q: without and with added motor oil, c = 0 mg/l 5 mg/l and 10 mg/l, with two heights of water column, h =1m and 2 m and with three air flows, q=2m3/h, 6m3/h and 10 m3/h verified the linear functional dependence of indicator of proper process condition, i.e. experimental determined oxygen saturation degree on water vapor accumulation (R2=0.766).

Generally the lower part of the Earth`s atmosphere, which is 20km above the ground, is called "air." The composition of this area is almost consistent consisting of nitrogen, oxygen, and other gases. Air density refers to the mass per unit volume of earth atmosphere. Though air is made of the mixed gases in a constant composition, the water vapor is one of the very changeable components. The density of moist air is lower than the dry one at the same temperature and pressure. As the density varies according to the pressure and temperature, this paper attempts to explore the main factors in the air quantity calculation by examining first the density calculation process according to the air property, and second the relation between the actual and standard air flow.

The vapor phase equilibrium analysis has been carried out for the Sb-S-O-H quarternary system using a Constrained Chemical Potential Method (CCPM). A total 24 species in vapor phase and 9 condensable constituents have been considered. The resulting data for the system have been plotted on Gibbs triangles as a function of the gas phase composition. Decreasing the partial pressure of H2O, SO2 and SbS are likely to increase the fraction of Sb in the vapor phase and get a higher partial pressure of Sb4O6. The calculation results show that the vapor phase constituents in the Sb-S-O-H system are mainly composed of Sb4O6, SO2 and H2O. Under an appropriated temperature (1023K < T < 1073K), an oxygen partial pressure of 10−12.5 to 10−11.5 kPa and a sulfur partial pressure of less than 10−6.2 kPa, it is expected to result in a higher partial pressure of Sb4O6. The condensation of Sb2O3 (s) and S2 (s) is likely to occur in suitable oxygen partial pressure. The water vapor can accelerate the volatilization of Sb from Sb-bearing ores. XRD result of roast of Sb2S3 indicates that, in the water vapor atmosphere, the condensed product obtained is composed of Sb2O3 with small quantities of S2. It is in accordance with the calculation results (main Sb-bearing species is Sb4O6).

In order to measure thermal and water vapor resistance of fabrics under non-isothermal conditions, the sweating guarded hot plate was modified. A nitrogen stream was used to sweep the water vapor away. The water vapor flux across the sample was determined by detecting the relative humidity of the outgoing nitrogen stream. The water vapor resistance was then calculated first. The dry heat loss for calculating thermal resistance was obtained by subtracting the evaporative heat loss from the total heat losses. The thermal resistance was determined accordingly. The thermal and water vapor resistance values of four fabrics were determined simultaneously by this test method. The results indicated that the total and intrinsic thermal resistance values of four fabrics measured in the presence of water vapor transfer were lower than those obtained without water vapor transfer. In addition, the total and intrinsic water vapor resistance values obtained under the non-isothermal condition were higher than those under the isothermal condition.

Laboratory experiments were conducted to investigate the effects of water vapor on the reaction of nitric oxide with ozone in a gas-phase chemiluminescence instrument used for fast response and high sensitivity detection of atmospheric ozone. Water vapor was introduced into a constant level ozone standard and both ozone and water vapor signals were recorded at 10 Hz. The presence of water vapor was found to reduce, i.e. quench, the ozone signal. A dimensionless correction factor was determined to be 4.15 ± 0.14 × 10−3, which corresponds to a 4.15% increase in the corrected ozone signal per 10 mmol mol−1 of co-sampled water vapor. An ozone-inert water vapor permeable membrane (a Nafion dryer with a counterflow of dry air from a compressed gas cylinder) was installed in the sampling line and was shown to remove the bulk of the water vapor in the sample air. At water vapor mole fractions above 25 mmol mol−1, the Nafion dryer removed over 75% of the water vapor in the sample. This reduced the required ozone signal correction from over 11% to less than 2.5%. The Nafion dryer was highly effective at reducing the fast fluctuations of the water vapor signal (more than 97%) while leaving the ozone signal unaffected, which is a crucial improvement for minimizing the quenching interference of water vapor fluxes and required density correction in the determination of ozone fluxes by the eddy covariance technique.

Louis Joseph Troost (1825-1911) carried on a large number of researches, alone or with Deville, Hautefeuille, and other colleagues, on the isolation of lithium, determination of its atomic mass, and preparation of many of its salts, on allotropic phenomena, on the use of electromotive force of a cell to determine the heat effects of a reaction, determination of the density of vapors at high temperatures, dissociation of gases, niobium and its compounds, the hydrides of palladium, sodium, and potassium, and the influence of manganese and silicon on the properties of the different varieties of iron.Resumen (Cuatro estudiantes brillantes de Henry Sainte-Claire Deville. Parte 2. Louis Joseph Troost)Louis Joseph Troost (1825-1911) llevó a cabo un gran número de investigaciones, solo o junto con Deville, Hautefeuille, y otros, acerca del aislamiento del litio, determinación de su masa atómica, y la preparación de muchas de sus sales, acerca de la alotropía, el uso de la fuerza electromotriz de una pila para determinar los efectos térmicos de reacciones químicas, la determinación de la densidad de gases a alta temperatura, disociación de gases, el niobio y sus compuestos, los hidruros de paladio, sodio y potasio, y la influencia del silicio y el manganeso en las propiedades de diversas variedades de fierro.

In this paper, condensation heat transfer characteristics of ethanol–water vapor mixtures on a vertical mini-vertical tube with 1.221 mm outside diameter were investigated experimentally. The experiments were performed at different velocities and pressures over a wide range of ethanol mass fractions in vapor. The test results indicated that, with respect to the change of the vapor-to-surface temperature difference, the condensation curves of the heat transfer coefficients revealed nonlinear characteristics, and had peak values. At 2 % ethanol mass fraction in vapor, the condensation heat transfer coefficient value of the ethanol–water vapor mixture was found to have a maximum heat transfer coefficient of 50 kW m−2 K−1, which was 3–4 times than that of pure steam. The condensation heat transfer coefficients decreased with increased ethanol mass fraction in vapor. The vapor pressure and vapor velocity had a positive effect on the condensation heat transfer coefficients of ethanol–water vapor mixtures.

A fundamental equation of state explicit in the Helmholtz energy is presented for trifluoromethyl methyl ether (HFE-143m). The independent variables of the equation of state are temperature and density. The equation of state is based on reliable experimental data for the vapor pressure and densities of the liquid and vapor phases. The equation covers temperatures between 240 K and 420 K for pressures up to 7.2 MPa. Comparisons to available experimental data are given that establish the accuracy of calculated properties from the equation of state. The estimated uncertainties are 0.1% in liquid density, 0.3% in pressure of the vapor phase, and 0.1% in vapor pressure. Comparisons of the vapor pressures and heats of vaporization of HFE-143m are made to those of 1,1,1,2-tetrafluoroethane (HFC-134a), 2,3,3,3-tetrafluoropropene (HFO-1234yf), and trans-1,3,3,3-tetrafluoropropene (HFO-1234ze(E)). The performance analysis of refrigeration cycles with these refrigerants is also demonstrated.

New fundamental equations of state explicit in the Helmholtz energy with a common functional form are presented for 2,3,3,3-tetrafluoropropene (R-1234yf) and trans-1,3,3,3-tetrafluoropropene (R-1234ze(E)). The independent variables of the equations of state are the temperature and density. The equations of state are based on reliable experimental data for the vapor pressure, density, heat capacities, and speed of sound. The equation for R-1234yf covers temperatures between 240 K and 400 K for pressures up to 40 MPa with uncertainties of 0.1 % in liquid density, 0.3 % in vapor density, 2 % in liquid heat capacities, 0.05 % in the vapor-phase speed of sound, and 0.1 % in vapor pressure. The equation for R-1234ze(E) is valid for temperatures from 240 K to 420 K and for pressures up to 15 MPa with uncertainties of 0.1 % in liquid density, 0.2 % in vapor density, 3 % in liquid heat capacities, 0.05 % in the vapor-phase speed of sound, and 0.1 % in vapor pressure. Both equations exhibit reasonable behavior in extrapolated regions outside the range of the experimental data.

Reference books and original studies devoted to the determination of the saturation vapor pressure of silicon in a wide range of temperatures have been analyzed. It has been established that no reliable experimental data in the range of high temperatures (above 2000 K) are available in the literature. It has been demonstrated that there is a need to perform additional theoretical and experimental investigations with the use of different methods. The total pressure and partial pressures of Si n (n = 1−6) molecules over liquid silicon are calculated in the temperature range 1700–3400 K. The calculation of the composition of the gas phase over the “Si(l)-container” systems is performed. Materials of the crucibles intended for the use in experimental investigations of the temperature dependence of the saturation vapor pressure of silicon over the liquid phase are recommended.

Methods are given of extrapolating the saturated vapor pressure of substances of “atmospheric range” to the entire liquid phase region from the triple to critical point. The extrapolation of the pT parameters from room temperature to the triple point is performed by simultaneous processing of vapor pressure and of differences between the heat capacities of ideal gas and liquid. The liquid-vapor equilibrium in the region from the normal boiling temperature to the critical point is predicted by the law of corresponding states of L.P. Filippov using the experimentally obtained pT data and values of density of liquids. Experimental facilities are described for determining the saturated vapor pressure by the comparison ebulliometric method and for determining the low-temperature heat capacity by the vacuum adiabatic calorimetry. The methods of extrapolating the vapor pressure are tested with standard substances for which reliable pT data are available for the entire liquid phase region.

A series of low-temperature (246 < T(I)(L) < 267 K) steady-state ethanol evaporation experiments have been conducted to determine the saturation vapor pressure of metastable ethanol. The measured interfacial conditions have been used with statistical rate theory (SRT) to develop an expression for the saturation vapor pressure as a function of temperature, f(srt)(eth). This expression is shown to be thermodynamically consistent because it gives predictions of both the evaporative latent heat and the liquid constant-pressure specific heat that are in agreement with independent measurements of these properties. In each experiment, the interfacial vapor temperature was measured to be greater than the interfacial liquid temperature, [triple bond]DeltaT(I)(LV). When f(srt)(eth) is used in SRT to predict DeltaT(I)(LV), the results are shown to be consistent with the measurements. Other expressions for the saturation vapor pressure that are in the literature are examined and found to be thermodynamically inconsistent and do not lead to valid predictions of DeltaT(I)(LV).

The vapor pressures of three important fluorinated propanes, 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea), 1,1,1,3,3,3-hexafluoropropane (HFC-236fa) and 1,1,1,3,3-pentafluoropropane (HFC-245fa) were measured precisely with an improved experimental system in the temperature range of 234–371, 239–398 and 235–427 K, respectively. The uncertainty of the vapor pressures was estimated to be ±300 Pa. The experimental samples were prepared carefully and analyzed with a gas chromatographic (GC) system and a gas chromatographic coupled with a mass spectrum (GC/MS) system. The effects of impurities on the vapor pressure were also considered to explain the discrepancies between the experimental results and other literature data. Wagner-type vapor pressure equations were correlated from the experimental results for the three fluids. The critical pressure, normal boiling point, triple-point pressure and acentric factor for the three substances were also obtained from the vapor pressure equations.

The output concentration pressure dependences of the water vapor passed in portions through a layer of MN-200 adsorbent whose delay and shape drastically depend on the parameters of introduced portions are determined using diode-laser spectroscopy. A model describing the experimental data and demonstrating the important role of interphase mass-exchange lag in the process of water vapor propagation in a porous-granular medium is proposed.

Based on the existing theory such as soil mechanics and fluid mechanics, the transfer mechanism of water vapor inside unsaturated soil is investigated in this paper. A formula that depends on matric suction and temperature is obtained for calculating the saturated water vapor pressure inside the voids of soil. The equation by which the water content changing with time in unsaturated soil resulting from water vapor transfer was also derived. The equation reveals that water vapor transfer is attributed to temperature gradient and water content gradient. The nonuniform distribution of temperature and water content may separately or jointly result in water vapor transfer, which confirms the results demonstrated in experiments. A case history is analyzed using the equation in this paper. The reliability of the equation is verified by analyzing the measured and calculated data. It has to be pointed out that water transfer in unsaturated soil normally occurs simultaneously in both liquid and vapor phases. As a r...

Two different definitions of the vapor quality during a diabatic two-phase flow with and without the presence of oil are presented in this paper: the well-known vapor flow quality and the thermodynamic vapor quality. The vapor flow quality is based on the mass flow rates whereas the thermodynamic vapor quality is based on the mass. Two-phase thermodynamic diagrams for pure R-134a and R-134a/oil mixture are plotted for different slip ratios. It is shown that the iso-flow quality lines are moved to lower enthalpies for larger slip ratios. In addition, the maximum vapor flow quality of a fluid/oil mixture is shown to increase when increasing the slip ratio whereas the maximum thermodynamic vapor quality remains constant. In addition, the correct expression of the elementary derivative of the vapor quality is also proposed, highlighting the role of the heat capacity at constant vapor quality.

It has been proved that water vapor in moist air contributes to slider air-bearing pressure in a totally different way from dry air. It is a very good first order approximation to take a constant water vapor pressure inside and outside the interface. The simulated slider flying height and attitude in moist air are different from that in dry air and the higher the relative humidity the bigger the difference. This work is a further study of the effect of water vapor on slider air bearing. In this paper, the effect of slider air-bearing pressure on the saturated water vapor pressure is explained. The adsorbed water film thickness on slider and disk surfaces as a function of relative humidity at different temperatures is calculated. The effects of slider air-bearing pressure, temperature, slider-disk spacing, and relative humidity on the water vapor pressure in slider-disk interface are studied. An empirical equation is developed for the calculation of accurate water vapor pressure distribution in slider-disk interface.

The primary environmental variables which influence the water vapor transmission rate of fabrics include air temperature, relative humidity, and wind speed. The combined quantitative effects of air temperature, relative humidity, and wind speed have been explored. The air temperature varied from 10 °C to 30 °C in 5 °C-intervals. The relative humidity ranged from 0% to 50%. The wind speed was from 0.1 m/s to 0.4 m/s. A new test method was employed to measure the water vapor transmission rate of four typical fabrics exposed under 120 conditions of combinations of relative humidity and wind speed with air temperature. The results showed that high air temperature, low relative humidity, and high wind speed led to high water vapor transmission rate. The exponential equations were obtained from the whole database based on the multiple nonlinear regression analysis, resulting in a generalized quantitative description of various effects on the water vapor permeability of fabrics. The prediction quality was good, as the regression equations provided high correlation coefficients and low standard errors of the estimate. The prediction values from the regression equations agreed well with the experimental results.

A gas saturation apparatus capable of simultaneous measurements on 18 samples was used for this work. The vapor pressures of 2-nitrotoluene (2-NT), 3-nitrotoluene (3-NT), 4-nitrotoluene (4-NT), and tetradecane (a control compound) were measured with this apparatus over the temperature range (283.15 to 313.15) K. Over this temperature range, the vapor pressure of 2-NT ranged from (5.53 to 61.1) Pa; the vapor pressure of 3-NT ranged from (3.39 to 37.8) Pa; and the vapor pressure of 4-NT ranged from (1.25 to 26.4) Pa. The enthalpies of vaporization or sublimation were determined using the Clausius−Clapeyron equation.

The diffusion of water vapor through construction materials is driven by the gradient of partial water vapor pressure. Traditionally, water vapor transmission tests (WVT), the `dry cup', and the `wet cup' tests have been conducted with 0 to 50% RH, and from 50% to 100% RH, respectively. Often, desiccants, saturated salt solutions or distilled water are used to generate the required RH. The stability of vapor pressure in WVT tests is of paramount significance because these values are used in calculating permeance. Dry cup tests performed with high permeance materials (>25 Perms) indicated a transient behavior for the two types of adsorbing desiccants; calcium sulfate and silica gel. Monitoring RH inside the dry cup was performed to examine the effect of low and high WVT on the performance of moisture sinks. The results indicate that for highly permeable construction materials, the use of vapor pressures corresponding to 0% RH in calculation of permeance is not appropriate.

Over about 30% of problems in construction is related to water-leaking, and the loss from this problem can incur as much as three times the cost of initial construction. Thus, water vapor pressure is known to be the primary cause of defective waterproofing. Accordingly, the theories on the relationship between water pressure and temperature as well as damp-proofing volume of concrete and the change in vapor pressure volume were reviewed and analyzed in this study by making test samples after spraying a dampness remover and applying waterproofing materials to the prepared test specimens. The result of measuring water vapor pressure with the surface temperature of the waterproofing (fluid-applied membrane) layer at the experimental temperature setting of about 10℃, which is the annual average temperature of Seoul, indicated that (1) the temperature of the fluid-applied membrane elevated to about 40℃, and the water vapor pressure generated from the fluid-applied membrane was about 0.03 N/㎟ when the surface temperature of the waterproofing layer was raised to about 80℃. (2) when the temperature of the fluid-applied membrane of the waterproofing layer was raised from 30℃ to 35℃, water vapor pressure of about 0.01 N/mm2was generated, and (3) when a thermal source was applied to the fluid-applied membrane (waterproofing) layer, the temperature increased from 35℃ to 40℃, and approximately 0.005 N/㎟ of water vapor pressure was generated.

The dependence of diffusion coefficient of O2-N2 mixture in the presence of water vapor was experimentally determined as a function of relative humidity (RH) with different temperatures using an in-house made Loschmidt diffusion cell. The experimental results showed that O2-N2 diffusion coefficient increased more than 17% when RH increased from 0% to 80% at 79 °C. In the experiments, the RH in both top and bottom chambers of the diffusion cell were the same, and the pressure inside the diffusion cell was kept as ambient pressure (1 atm.). Maxwell-Stefan theory was employed to analyze the mass transport in the diffusion cell, and found that there was no effective water vapor diffusion taking place, indicating that the gas diffusion in this ternary (O2-N2-water vapor) system could be considered binary gas (O2-N2) diffusion. The Fuller, Schettler, and Giddings (FSG) empirical equation of the kinetic theory of gases was generalized to accommodate the dependence of the binary diffusion coefficient on the RH. The prediction of the generalized equation was found to be consistent with experimental results with the difference of less than 1.5%, showing that the generalized equation could be applied to calculate the diffusion coefficients of the binary gaseous mixture with different temperature and RH values. The effect of water vapor on the increase of O2-N2 diffusion coefficient was discussed using molecule theory., available, unlimited, public

The diffusion of warm, humid air into an initially cold, dry, sandy column was analyzed to study the movement of water vapor and liquid water under nonisothermal and low water content conditions. The analysis was performed using the HYDRUS-1D code. While the water retention curve of sand was measured experimentally, the unsaturated hydraulic conductivity function was inversely estimated from the observed water content profiles in the column. The estimated unsaturated hydraulic conductivity function displayed a shape that reflected distinct processes of capillary pore water flow and film flow at high and low water contents, respectively. Four components of the total water flux, including thermal and isothermal liquid water and water vapor fluxes, were evaluated using the calibrated soil hydraulic properties. Evaporation and condensation rates were calculated based on water mass balance. Water vapor entered the soil column at the hot surface and condensed at the cold bottom. Subsequently, liquid water moved upward and evaporated at the moisture front in the middle of the column where the relative humidity decreased below unity. Liquid water and water vapor then circulated between the bottom and the moisture front, accompanied by condensation and evaporation processes. The impact of the enhancement factor in the thermal vapor diffusion term could not be clearly identified from available experimental water content profiles. Increases in liquid water flow and the evaporation rate could be compensated for by increases in vapor flow and the condensation rate. Additional data would be needed to fully evaluate the effect of the enhancement factor.

A generalized equation for calculating the saturation vapor pressure of individual substances at temperatures from the triple to the critical point is derived. The error of the calculation is close to the error of experimental data.

The tangents to the evaporation path curves in the W/O microemulsion base of water, (W), pentanol, (P), and sodium dodecyl sulfate, (S), were extended to the W/P axis to establish the relative composition, (WV, PV), of the vapor leaving the liquid. The composition of the vapor, with which the microemulsion is in contact includes also the contribution from the relative humidity of the surrounding atmosphere. The difference between the composition of these gases is clarified using the algebraic expressions from the phase diagram, but the quantitative composition of the equilibrium vapor is not available without further numerical information. The limits of the vapor for evaporation direction under different relative humidities were clarified.

A method is proposed for determining saturation pressure as a function of saturation temperature without using computers and handbooks, which is of particular interest for checking pump efficiency, appraising saturation pressure variation in the system, and designing complicated high-vacuum systems. A table is provided for construction of saturation curves, upon use of which the error in the determination of saturated vapor pressure as a function of temperature does not exceed one-half order of magnitude for all the investigated gases. An ordered relationship of critical points of noble gases is presented in saturation pressure-temperature coordinates.

From the vapor pressure equation of a metalorganic precursor, its partial pressure is calculated. The accuracy of that vapor pressure equation is therefore important when calculating the deposition efficiency of a precursor. Knowing the exact value of the vapor pressure is even more important to accurately plot the solid composition versus gas phase composition in the case of an alloy. For indium-containing Organo-Metallic Vapor Phase Epitaxy (OMVPE), trimethylindium (TMI) has been the preferred precursor. However, the four established vapor pressure equations reported in the literature for TMI have been found to differ significantly. These equations offer overestimated vapor pressure of TMI, often by as much as 20–40%. Not knowing the accurate vapor pressure has been a concern to growers. In this study, we report the comparative evaluation of these four established equations by using accurate measurements of actual consumptions of TMI from its depletion studies, coupled with gas phase concentration studies with Epison III ultrasonic monitor. Our studies conclude that the vapor pressure equation, log P (Torr)=10.98–3204/T (K), provides the most accurate vapor pressures of TMI within a wide range of growth conditions currently used in OMVPE. Also reported are the cylinder design aspects and Uni-Flo™ II cylinder design that lead to stable depletion of TMI under high throughput conditions of temperature, flow and pressure employed industrially.

The density (300–363 K, up to 3.5 MPa) and speed of sound (293–373 K, 7.5–480 kPa) in gaseous R-404a have been studied by an isochoric piezometer method and an ultrasonic interferometer, respectively. The pressures of the saturated vapor along the dew line were measured from 298 to 330 K. The experimental uncertainties of the temperature, pressure, density, and speed-of-sound measurements were estimated to be within ±20 mK, ±1.5 kPa, ±0.15%, and ±(0.1–0.2)%, respectively. On the basis of the obtained data, the isobaric molar heat capacity of R-404a was calculated for the ideal-gas state. An eight-coefficient Benedict–Webb–Rubin equation of state has been developed for the gaseous phase of R-404a.

Based on the ideal gas state equation and the saturated vapor pressure equation of helium-3, a saturated vapor density equation is proposed, which can be applied for calculating the saturated vapor density of helium-3 from 0.01 K to the critical temperature. Above 1.4 K, the average deviation between the results by this equation and experimental data is about 0.66% and the maximum is 2%. Below 1.4 K, the results of this work show a comfortable agreement with those by virial state equation (the deviations are generally within 0.1%). Based on this new vapor density equation, the compressibility factor of saturated vapor is determined and the vaporization heat is calculated.

A self-similar solution is obtained for a one-dimensional problem of diffusion mixing of vapor and gas, which is followed by condensation process. Two limiting cases of mixing are considered: in the first one, the vapor and gas occupy in their initial states the volumes of semi-infinite extension, in the second case, the vapor has a semi-infinite extension, and constant values of temperature and gas concentration are maintained at its boundary. The peculiarities of the temperature and concentration fields are analysed versus the vapor and gas temperatures, and the temperature values are found, at which the mixing occurs with the condensate formation.

The pressure distribution in a squeeze film air bearing depends on the water vapor pressure and the saturation vapor pressure of water at ambient temperature. When the water vapor pressure is compressed beyond the saturation vapor pressure, a portion of the water vapor condenses, thus reducing the total gas pressure in the air bearing. This condensation mechanism thus reduces the flying height of the slider. Using a magnetic recording system for experiments, we quantified the effect of condensation on flying height by measuring the dependence of magnetic spacing on relative humidity. We developed a numerical model based on the proposed mechanism that matches the experimental data and provides a detailed view of the air-bearing response to humidity.

This paper presents D/H isotopic fractionation factor measurements of water adsorbed on porous silica tubes in isotopic equilibrium with water vapor. The fractionation factor is measured as a function of vapor pressure ranging from 10% to 80% RH (relative humidity) at room temperature. It is shown that the fractionation factor between the adsorption film or nanometrically confined water and vapor is smaller than that between bulk liquid water and vapor. A qualitative analysis relates this deuterium depletion to a modification of the zero-point energy of the water isomers in the adsorbed/confined state. Furthermore, the behavior of the fractionation factor with RH shows two different linear trends. The transition between the two (at 60% RH) may indicate the transition from a two-dimensional adsorbed water to a three-dimensional water network.

When a steam–ethanol vapor mixture condenses on a vertical flat plate, the form of the condensate film changes and many drops are created. This non-film condensation is called pseudo-dropwise or Marangoni condensation. This paper aims to study the main influencing factors on the Marangoni condensation of steam–ethanol vapor.The factors include the ethanol concentration, vapor pressure, vapor velocity and vapor-to-surface temperature difference. The experiments show that the heat transfer coefficient has a maximum value of approximately 42 kW/m2 K when the ethanol concentration is 1%. At the low concentrations of 0.5, 1, 5.1 and 9.8%, the condensation heat transfer is greater than for pure steam. In addition, the heat transfer for all vapor mixtures increases with both the rise of vapor pressure and vapor velocity.