Saturated Water Vapor Pressure Research Articles

Modification of Vapor-Pressure Reference Functions to Include Parameter Covariance

The reference functions for the saturation water vapor pressure and the water vapor-pressure enhancement factor for moist air used by the humidity community are approximate, and the uncertainty contributions from their use are characterized by simple functions or tables. Many humidity calculations, such as for the determination of the dew point of moist air following a change in pressure, require two evaluations each of these functions and errors in the functions will tend to cancel. It has been shown that if the reference function uncertainty is represented using parameter covariance, the expected reduction in error is reflected in a corresponding reduction in the uncertainty of the calculation result. Here, two major vapor-pressure reference functions are modified to encapsulate the published uncertainty as parameter covariance, by refitting the equations or modified forms to “input data” generated by the original equations. It is shown that the form of the uncertainty function is influenced by the degree of correlation in the input data and that there is greater uncertainty reduction with greater input data correlation. In all cases the reduction in uncertainty is significant and indicates that conventional uncertainty analysis for many humidity calculations overestimates the uncertainty deriving from the reference functions.

2011년 강원 폭설과 GPS 가강수량의 상관성 분석

본 연구에서는 2011년 강원도 영동 지방의 폭설 기간 동안 GPS 위성 신호의 대류권 지연량 추정으로부터 대기 가강수량을 복원하였다. 폭설이 발생하는 기간 동안에 GPS 가강수량과 신적설 발생량과의 상관관계에 대한 분석을 실시하였다. 분석 결과, GPS를 이용하여 복원한 대류권에서의 가강수량 증가가 발생된 이후에 강설량이 증가하는 추세를 나타냈다. 또한 웨이블릿을 이용한 주기 분석에서는 본 연구기간에 한해서 GPS 가강수량의 주기가 포화수증기압의 주기와 유사한 것으로 검출되었다. GPS 가강수량의 감소와 이에 대응하는 신적설량의 증감은 두 연구 지역인 강릉과 울진에서 모두 다르게 증감하는 경향을 나타냈다. 폭설 기간 동안 GPS 가강수량과 포화수증기압의 상관 계수는 강설이 발생하지 않는 기간 동안의 결과와는 달리 양의 상관성을 갖는 것으로 나타났다. In this paper, the GPS precipitable water vapor was retrieved by estimating of GPS signal delay in the troposphere during the progress of heavy snowfall on the Gangwon Province, 2011. For this period, the time series analysis between GPS precipitable water vapor and fresh snow depth was accomplished. The time series and the comparison with the GPS precipitable water vapor and the fresh snow depth indicates that the temporal change of two variations is closely related to the progress of the heavy snowfall. Also, the periodicity of GPS precipitable water vapor using the wavelet transform method was showed a similar cycle of saturated water vapor pressure as the limitation of this study span. The result shows that the decrement of GPS precipitable water vapor was conflicted with the increment of fresh snow depth at two sites, Gangneung and Uljin. The correlation between the GPS precipitable water vapor and the saturated water vapor pressure for the event was showed a positive correlation, compare with the non-heavy snowfall periods.

Kinetic Study of Epoxy Resin Decomposition in Near‐Critical Water

AbstractA diglycidyl ether type epoxy resin from bisphenol A, E‐51, was cured by methylhexahydrophthalic anhydride (MeHHPA) and then decomposed in near‐critical water without any additives. The effects of the experimental parameters such as the reaction temperature, reaction time, pressure, and feedstock ratio on the percentage of decomposition were investigated to obtain optimized reaction conditions. The results revealed that the percentage of decomposition can be enhanced by increasing either temperature or reaction time. At 260 °C, it initially increased with higher pressure and then decreased dramatically when the pressure further was reduced to the saturated water vapor pressure. The kinetics study of the epoxy decomposition was also carried out by monitoring the glass transition temperature of the solid product using differential scanning calorimetry. The decomposition equation was established and the activation energy was calculated to be 123.5 kJ mol–1.

Direct measurements of the saturated vapor pressure of water confined in extended nanospaces using capillary evaporation phenomena

Download options Please wait... Supplementary files Supplementary information PDF (73K) Article information DOI https://doi.org/10.1039/C2RA01330D Article type Communication Submitted 21 Dec 2011 Accepted 15 Feb 2012 First published 15 Feb 2012 Download Citation RSC Adv., 2012,2, 3184-3186 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Direct measurements of the saturated vapor pressure of water confined in extended nanospaces using capillary evaporation phenomena T. Tsukahara, T. Maeda, A. Hibara, K. Mawatari and T. Kitamori, RSC Adv., 2012, 2, 3184 DOI: 10.1039/C2RA01330D To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author Takehiko Tsukahara Taku Maeda Akihide Hibara Kazuma Mawatari Takehiko Kitamori

NUMERICAL STUDY ON THE INHIBITION OF CAVITATION IN PIPING SYSTEMS

Abrupt closing valve in piping systems is sometimes resulted in cavitation due to the occurrence of high pressure difference. The bubbles generating by cavitation influence operating pressure and then those generate shock wave and vibration. These phenomena can consequentially cause to corrosion and erosion. So, the cavitation is the important factor to consider reliability of piping systems and mechanical lifetime. This paper investigated the various inhibition methods of cavitation in piping systems in which butterfly valves are installed. To prevent cavitation occurrence, it is desirable to analyze its characteristics between the upstream and downstream of process valve. Results show that the fluid velocity is fast when a working fluid passed through butterfly valve. The pressure of these areas was not only under saturation vapor pressure of water, but also cavitation was continuously occurred. We confirmed that the effect of existence of inserted orifice and influence to break condition under saturation vapor pressure of water. Results were graphically depicted by pressure distribution, velocity distribution, and vapor volume fraction.

Estimation methods for monthly humidity from dynamical downscaling data for quantitative assessments of climate change impacts

Methods are proposed to estimate the monthly relative humidity and wet bulb temperature based on observations from a dynamical downscaling coupled general circulation model with a regional climate model (RCM) for a quantitative assessment of climate change impacts. The water vapor pressure estimation model developed was a regression model with a monthly saturated water vapor pressure that used minimum air temperature as a variable. The monthly minimum air temperature correction model for RCM bias was developed by stepwise multiple regression analysis using the difference in monthly minimum air temperatures between observations and RCM output as a dependent variable and geographic factors as independent variables. The wet bulb temperature was estimated using the estimated water vapor pressure, air temperature, and atmospheric pressure at ground level both corrected for RCM bias. Root mean square errors of the data decreased considerably in August.

Use of a nonlinear pseudo‐relative humidity variable in a multivariate formulation of moisture analysis

AbstractWe present a reformulation of the humidity part of the HIRLAM (HIgh‐Resolution Limited‐Area Model) variational data assimilation. The purpose is to rectify some of the shortcomings of the present formulation which uses specific humidity, q, as an assimilation control variable with homogeneous and static covariances. One problem is that specific humidity forecast errors tend to have a non‐Gaussian probability distribution, in particular near saturation and near zero humidity. In addition, the variance of the distribution tends to change in space and time due to the dependency of the water vapour saturation pressure on temperature. A modified pseudo‐relative humidity variable has been adapted to the statistical balance background constraint, including the associated moisture balance formulation. Background‐error statistics for the new moisture control variable and the moisture‐related balances were derived, taking differences between forecasts valid at the same time as a proxy for background forecast errors. The background‐error statistics were compared with the corresponding statistics for specific humidity as the moisture assimilation control variable. In connection with the nonlinearity of the change of the variable, it was noted that specified background‐error standard deviations were chosen to be substantially reduced for nearly dry and saturated states, which can raise difficulties. The impact of the new moisture assimilation control variable is illustrated with simulated observation experiments as well as data assimilation experiments using real observations, for one summer month and one winter month in a 4D‐Var assimilation cycle using two outer loop iterations in the 4D‐Var minimization. The impact of the new formulation on forecast verification scores is small and essentially neutral, while using the second outer loop in the old formulation has a small positive impact. Copyright © 2011 Royal Meteorological Society

Influence of temperature and pressure on solute decomposition efficiency by microwave-excited plasma

Decomposition efficiency of organic solute by microwave underwater discharge was investigated using methylene blue (MB) as a test solute. It was found that the energy efficiency for the MB decomposition was strongly influenced by the discharge conditions, i.e., the solution temperature and the pressure. The most efficient MB decomposition was observed when the pressure was close to the saturated water vapor pressure. The result was explained by taking account for the power dissipation for the gas phase production in the liquid.

Partial molar volumes of organic solutes in water. XXIII. Cyclic ketones at T = (298 to 573) K and pressures up to 30 MPa

Density data for dilute aqueous solutions of four cyclic ketones (cyclopentanone, cyclohexanone, cycloheptanone, and cyclohexane-1,4-dione) are presented together with standard molar volumes (partial molar volumes at infinite dilution) calculated from the experimental data. The measurements were performed at temperatures from T = 298 K up to T = 573 K. Experimental pressures were close to the saturated vapor pressure of water, and (15 and 30) MPa. The data were obtained using a high-temperature high-pressure flow vibrating-tube densimeter. Experimental standard molar volumes were correlated as a function of temperature and pressure using an empirical polynomial function. Contributions of the molecular structural segments (methylene and carbonyl groups) to the standard molar volume were also evaluated and analyzed.

Collapse transition in thin films of poly(methoxydiethylenglycol acrylate)

The thermal behavior of poly(methoxydiethylenglycol acrylate) (PMDEGA) is studied in thin hydrogel films on solid supports and is compared with the behavior in aqueous solution. The PMDEGA hydrogel film thickness is varied from 2 to 422 nm. Initially, these films are homogenous, as measured with optical microscopy, atomic force microscopy, X-ray reflectivity, and grazing-incidence small-angle X-ray scattering (GISAXS). However, they tend to de-wet when stored under ambient conditions. Along the surface normal, no long-ranged correlations between substrate and film surface are detected with GISAXS, due to the high mobility of the polymer at room temperature. The swelling of the hydrogel films as a function of the water vapor pressure and the temperature are probed for saturated water vapor pressures between 2,380 and 3,170 Pa. While the swelling capability is found to increase with water vapor pressure, swelling in dependence on the temperature revealed a collapse phase transition of a lower critical solution temperature type. The transition temperature decreases from 40.6 °C to 36.6 °C with increasing film thickness, but is independent of the thickness for very thin films below a thickness of 40 nm. The observed transition temperature range compares well with the cloud points observed in dilute (0.1 wt.%) and semi-dilute (5 wt.%) solution which decrease from 45 °C to 39 °C with increasing concentration.

Proton Conduction in Composite Membranes of Sulfonated Hydrocarbon Electrolyte and Layered Tin Phosphate Hydrates

The characteristics and mechanism of proton conduction in organic/inorganic composite membranes composed of sulfonated poly(ether sulfone) (SPES) and layered tin phosphate hydrates Sn(HPO4)2·nH2O (SnP) were examined. SPES/SnP membranes were prepared by mixing 0–50 vol% of SnP with SPES solution and casting the mixture. Fourier-transform infrared, Raman, and solid-state 1H NMR spectroscopy and thermogravimetric analysis showed that hydrogen-bond networks are formed between SPES and SnP in the composite membranes. At intermediate temperatures up to 150°C, the membranes showed good proton-conducting properties, high chemical stability (low water solubility), and high thermal stability as a result of the formation of hydrogen bonds between SPES and SnP. The membrane containing 35 vol% SnP showed the highest conductivity of 8.1 × 10−2 S cm−1 at 130°C under saturated water vapor pressure. The membrane containing 25 vol% SnP showed a conductivity of 5.3 × 10−2 S cm−1 at 130°C under saturated water vapor pressure, despite its low water uptake. This membrane retained a high conductivity of 2.6 × 10−3 S cm−1 at 130°C at a low relative humidity of 40%, indicating that SPES/SnP membrane is a promising proton conductor at intermediate temperatures.

J091013 弁下流に発生するキャビテーションのモニタリング手法の検討([J09101]流体関連の騒音と振動(1))

In this study, monitoring method of cavitation generated at the downstream of the flow control valve was examined. On the occurrence of cavitation, piping vibration was measured at the low-frequency range of less than 1 kHz. The frequency components like white noise was measured when cavitation was generated. Therefore, it was found that cavitation could be monitored by measuring the frequency component like white noise. However, the generation location of cavitation couldn't be identified by measuring the frequency component like white noise, because the frequency components like white noise wasn't damped in the piping. To identify the generation location of cavitation in the piping system, the method by numerical analysis was examined. Pressure in the piping was calculated by the numerical analysis using the method of characteristics. The generation location of cavitation generation was examined by detecting the pressure which was lower than saturated vapor pressure of water. The results of the numerical analysis and the experiment agree. Therefore it was demonstrated that the generation location of cavitation could be identified by numerical analysis.

Influence of Tourmaline on Saturation Vapor Pressure of Water

Elbaite powders were roasted for 2 h at different temperatures from 300 to 950°C, and the effect on saturation vapor pressure of water was studied. The tourmaline’s phase structure and infrared radiation property were investigated by X-ray diffraction and Fourier transform infrared spectrometry, and the influence mechanism of tourmaline on the saturated vapor pressure of water was discussed. The results showed that the saturation vapor pressure of treated water increased 6.55, 5.04, 1.19 and 5.14% after tourmaline was roasted at 300°C , 350°C, 650°C and 950°C, respectively. The pressure decreased 3.50% after roasted at 800°C, suggesting that the infrared radiation property of tourmaline was an important factor influencing the saturated vapor pressure of water.

Pathways of Amino Acid Transformation and Decomposition in Saturated Subcritical Water Conditions

The reactions of amino acids under subcritical water conditions were investigated. All reactions were carried out under a pressure value corresponds to the saturated vapor pressure of water at the employed reaction temperature (hereafter called the saturated subcritical water condition). The reaction temperatures were in the range of 503-563 K. As reactants, seventeen different amino acids were investigated including, glycine, alanine, valine, leucine, isoleucine, methionine, phenylalanine, tyrosine, serine, threonine, cysteine, proline, lysine, histidine, arginine, aspartic, and glutamic. The obtained data revealed that the major decomposition pathway were the deamination and decarboxylation. It was found that glycine, alanine, valine, and proline were synthesized as intermediate decomposition products of other amino acids. Glutamic acid is the only amino acid that decomposed through lactamization process to pyroglutamic acid. Based on the experimental data a general decomposition pathway of all tested amino acids was developed by considering that the decomposition reactions extended to produce final decomposition products, carbon monoxide, water, and ammonia.

High ionic conductivity of Mg–Al layered double hydroxides at intermediate temperature (100–200 °C) under saturated humidity condition (100% RH)

Ionic conduction properties of layered double hydroxides (LDHs), [Mg (1 − x) Al ( x) (OH) 2](CO 3) x/2 · nH 2O (═CO 3-type) and [Mg (1 − x) Al ( x) (OH) 2](OH) x · nH 2O (═OH-type), have been investigated in the temperature range of 25–200 °C under saturated water vapor pressure (100% RH). Conductivity was measured by the complex impedance method using pressed pellet samples. The conductivity of an OH-type sample ( x = 0.25) is as high as 4 × 10 − 3 S cm − 1 already at room temperature. On heating, it increases as slowly (the activation energy E a ∼ 55 meV) as those of liquid electrolyte solutions, suggesting that ions are transported via exchange of protons between OH − and H 2O species in the interlayer space of the LDH (a kind of the Grotthus mechanism). The conductivity at 200 °C reaches 3 × 10 − 2 S cm − 1 . Although the conductivity of the CO 3-type counterpart is considerably low (∼ 10 − 6 S cm − 1 ) at room temperature, it increases with increasing temperature with showing a jump by about four orders of magnitude around 80 °C, after which the compound is turned into an almost the same liquid-like conductor as the OH-type sample; the conductivity jump is probably due to the interlayer reaction CO 3 2− + H 2O = 2OH − + CO 2 (g). Thus those Mg–Al LDH materials show the potential application as solid electrolyte materials for intermediate temperature fuel cells, not only because they have high conductivity but also they should not suffer from the degradation by CO 2 which is a serious problem for conventional anion exchange membranes.

Cloud-Resolving Simulation of Low-Cloud Feedback to an Increase in Sea Surface Temperature

Abstract This study investigates the physical mechanisms of the low cloud feedback through cloud-resolving simulations of cloud-radiative equilibrium response to an increase in sea surface temperature (SST). Six pairs of perturbed and control simulations are performed to represent different regimes of low clouds in the subtropical region by specifying SST differences (ΔSST) in the range of 4 and 14 K between the warm tropical and cool subtropical regions. The SST is uniformly increased by 2 K in the perturbed set of simulations. Equilibrium states are characterized by cumulus and stratocumulus cloud regimes with variable thicknesses and vertical extents for the range of specified ΔSSTs, with the perturbed set of simulations having higher cloud bases and tops and larger geometric thicknesses. The cloud feedback effect is negative for this ΔSST range (−0.68 to −5.22 W m−2 K−1) while the clear-sky feedback effect is mostly negative (−1.45 to 0.35 W m−2 K−1). The clear-sky feedback effect contributes greatly to the climate sensitivity parameter for the cumulus cloud regime whereas the cloud feedback effect dominates for the stratocumulus regime. The increase of liquid water path (LWP) and cloud optical depth is related to the increase of cloud thickness and liquid water content with SST. The rates of change in surface latent heat flux are much higher than those of saturation water vapor pressure in the cumulus simulations. The increase in surface latent heat flux is the primary mechanism for the large change of cloud physical properties with +2 K SST, which leads to the negative cloud feedback effects. The changes in cloud fraction also contribute to the negative cloud feedback effects in the cumulus regime. Comparison of these results with prior modeling studies is also discussed.

Proton conducting membranes composed of sulfonated poly(etheretherketone) and zirconium phosphate nanosheets for fuel cell applications

The composite membranes were prepared by dispersing particles (ZrP) or nanosheets (ZrP-NS) of layered zirconium phosphate hydrate (Zr(HPO 4) 2· nH 2O) in sulfonated poly(etheretherketone) (SPEEK) with various ZrP or ZrP-NS contents (0–50 vol.%). Their chemical stability and proton conductivities at 40–150 °C were investigated, and compared for ZrP- and ZrP-NS-composite membranes. The enhanced chemical stability was confirmed in both composite membranes. The results of thermogravimetry (TG)–differential thermal analysis (DTA) and diffuse reflectance Fourier transform infra-red (FT-IR) spectroscopy suggests that hydrogen-bonds were formed at both the SPEEK/ZrP and the SPEEK/ZrP-NS interface and that enhanced stability is attributed to these bonds. The membrane with 50 vol.% ZrP-NS showed a high conductivity of 7.9 × 10 − 2 S cm − 1 at 150 °C under saturated water vapor pressure, and a smaller relative humidity dependence of conductivity at 130 °C than the SPEEK membrane with 50 vol.% ZrP. The SPEEK/ZrP-NS composites were shown to have promising potential as membranes usable at 150 °C.

Partial molar volumes of organic solutes in water. XXII. Cyclic ethers at temperatures (298 to 573) K and pressures up to 30 MPa

Density values for dilute aqueous solutions of five cyclic ethers (oxolane, 1,3-dioxolane, oxane, 1,4-dioxane, and 1,3,5-trioxane) are presented together with partial molar volumes at infinite dilution calculated from the experimental results. The measurements were performed at temperatures from (298 up to 573) K. Due to thermal decomposition, the upper temperature limit was lower for 1,3-dioxolane (448 K) and 1,3,5-trioxane (498 K). Experimental pressures were close to the saturated vapour pressure of water, and (15 and 30) MPa. The results were obtained using a high-temperature high-pressure flow vibrating-tube densimeter. Experimental standard partial molar volumes were correlated as a function of temperature and pressure using an empirical polynomial function and the semi-theoretical SOCW equation of state. Contributions of the group contribution method proposed previously were also evaluated and analyzed.

On the evaporation of ammonium sulfate solution

Aqueous evaporation and condensation kinetics are poorly understood, and uncertainties in their rates affect predictions of cloud behavior and therefore climate. We measured the cooling rate of 3 M ammonium sulfate droplets undergoing free evaporation via Raman thermometry. Analysis of the measurements yields a value of 0.58 +/- 0.05 for the evaporation coefficient, identical to that previously determined for pure water. These results imply that subsaturated aqueous ammonium sulfate, which is the most abundant inorganic component of atmospheric aerosol, does not affect the vapor-liquid exchange mechanism for cloud droplets, despite reducing the saturation vapor pressure of water significantly.

Further Study of the Effect of Water Vapor on Slider Air Bearing

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.