Nitrogen Water Vapor Research Articles

On the Influence of Humidity on a Thermal Conductivity Sensor for the Detection of Hydrogen.

Thermal conductivity sensors face an omnipresent cross-influence through varying humidity levels in real-life applications. We present the results of investigations on the influence of humidity on a hydrogen thermal conductivity sensor and approaches for predicting the behavior of thermal conductivity towards humidity. A literature search and comparison of different mixing equations for binary gas mixtures were carried out. The theoretical results were compared with experimental results from three different thermal conductivity sensors with mixtures of water vapor in nitrogen. The mixing equations show a large discrepancy between each other. Some of the models predict a continuously decreasing thermal conductivity and some predict an increasing thermal conductivity for increasing levels of humidity. Our measurements indicate an increase in thermal conductivity followed by a decrease after reaching a peak value. It is shown that the measured behavior is reproducible with different sensors. Depending on the sensor, this corresponds to an error up to 2 vol.% in the measured hydrogen value. The measured behavior is consistent with only one of the three models. Compared to this model, our own sensor shows a maximum deviation of 1.4%. Mixing equations for gas mixtures must be chosen carefully, taking into consideration whether mixing partners include polar or non-polar molecules. Some simplified mixing equations cannot be used to calculate the thermal conductivity of water vapor in air or nitrogen.

Dual-Pump Vibrational Coherent Anti-Stokes Raman Scattering System Developed for Simultaneous Temperature and Relative Nitrogen–Water Vapor Concentration Measurements

Simultaneous gas phase temperature and water vapor concentration measurement are important to understand reacting flows such as combustion or gas reforming processes. Here, coherent anti-Stokes Raman scattering (CARS) offers the possibility for non-intrusive measurements with a high temporal and spatial resolution. Therefore, this work demonstrates the simultaneous measurement of temperature and relative water vapor–nitrogen concentrations by using dual-pump vibrational coherent anti-Stokes Raman scattering (DPVCARS). A calibration procedure is developed for a temperature range of 473 K to 673 K and a water vapor concentration of 24% to 46% at ambient pressure. This setup is tested with 500 CARS single pulse spectra taken in a gas cell at a known temperature and concentration. Based on these results, information about precision and accuracy can be delivered.

Real world evaluation and control of vehicle engine exhaust air pollution using adaptive neural fuzzy inference system

Internal combustion engines are considered primarily responsible for air pollution. Accordingly, a concentrated effort has been made to reduce these pollutants which are emitted from the exhaust system of these engines while preserving energy and fuel consumption. There are also other sources besides internal combustion engines, such as power stations and those released from industry and home consumption. Industrial and household fuel consumers are also adding pollution. The industrial development requires the establishment of effective control systems to deal with its equipment to increase its operational life and increase its productivity with lower maintenance costs. Therefore, the aim of the study in this research is exposed to be used of adaptive neural fuzzy inference system to control the components of the emission of exhaust pollutants for gasoline vehicle. Exhaust pollutants consist of unburned carbon monoxide, hydrocarbons, carbon dioxide, water vapor nitrogen oxides, and energy produced from the combustion process which emit into atmosphere through the exhaust tailpipe. Also, there are hydrocarbons produced from gasoline vaporization and from the crankcase of the vehicle. The results indicate that the adaptive neural fuzzy inference system proves to be a useful tool for simulating and controlling vehicle engine exhaust emissions.

Direct numerical simulation of sublimating ice particles

A thermodynamically consistent numerical framework for the simulation of three-dimensional sublimation processes of ice at temperatures below the triple point and low pressure is presented. To this end, a novel description of the local thermodynamic equilibrium of frozen water (ice) and a mixture of water vapour and an inert gas is derived, where anisotropic surface energy densities can be considered. A new correlation for the diffusion coefficient of water vapour in nitrogen is proposed based on equilibrium molecular dynamics simulations. The simulation results are in excellent agreement with experimentally obtained sublimation rates.

Water-vapor foreign-continuum absorption in the 8–12 and 3–5 μm atmospheric windows

The frequency and temperature dependence of the water vapor–nitrogen continuum in the 8–12 and 3–5μm spectral regions obtained experimentally by CAVIAR and NIST is described with the use of the line contour constructed on the basis of asymptotic line shape theory. The parameters of the theory found from fitting the calculated values of the absorption coefficient to the pertinent experimental data enter into the expression for the classical potential describing the center-of-mass motion of interacting molecules and into the expression for the quantum potential of two interacting molecules. The frequency behavior of the line wing contours appears to depend on the band the lines of which make a major contribution to the absorption in a given spectral interval. The absorption coefficients in the wings of the band in question calculated with the line contours obtained for other bands are outside of experimental errors. The distinction in the line wing behavior may be explained by the difference in the quantum energies of molecules interacting in different vibrational states.

Effect of fluid medium in source rock porosity on oil primary migration

Abstract With the self-designed simulation instrument for hydrocarbon generation and expulsion in formation porosity under controlled heating and pressuring conditions, a series of experiments was made with different systems such as nitrogen-water vapor, water vapor-liquid water, liquid water, and anhydrous. Oil discharge efficiency was compared to study the effect of the fluid medium in source rock porosity on oil primary migration. In the oil and gas generation phase, pore space in the source rock was charged by fluids (hydrocarbon gas, non-hydrocarbon gas, oil, formation water) with certain temperature and pressure. Liquid water was an indispensable transport carrier in oil primary migration process. Water might adsorb onto the surface of minerals, preventeding the adsorption of hydrocarbon and was favorable for hydrocarbon migration. CO2 associated with hydrocarbon generation easily dissolved in oil, which reduced the interfacial tension between the oil and water, oil viscosity and oil migration resistance, and promoted oil primary migration.

Photoelectrochemical investigations on individual ferritic and austenitic grains of a duplex stainless steel oxidized in water vapour

This work presents a multiscale photoelectrochemical characterization of oxide layers, and aims mainly at introducing the mesoscopic scale (ca 30 µm). For the first time, photocurrent energy spectra could be recorded on individual ferritic and austenitic grains of a unique 2205 duplex stainless steel sample oxidized for 5 minutes at 650°C under 20% water vapour in nitrogen. These results allowed us to explain contrasting issues in the photoelectrochemical images obtained from the oxidized sample. Moreover, the bandgap energies obtained by fitting these individual mesoscopic photocurrent energy spectra with a novel approach developed in our laboratory, showed that all oxide scales were constituted of Fe2O3 and Cr2O3 and of an Fe2-xCrxO3 solid solutions, but that the x-value of the latter was different depending on the metallurgic phase of the oxidized substrate. The latter results were shown to be in agreement with those of additional Raman analyses of the oxidized austenitic and ferritic grains.

Photoelectrochemical investigations on individual ferritic and austenitic grains of a duplex stainless steel oxidized in water vapour

This work presents a multiscale photoelectrochemical characterization of oxide layers, and aims mainly at introducing the mesoscopic scale (ca 30 µm). For the first time, photocurrent energy spectra could be recorded on individual ferritic and austenitic grains of a unique 2205 duplex stainless steel sample oxidized for 5 minutes at 650°C under 20% water vapour in nitrogen. These results allowed us to explain contrasting issues in the photoelectrochemical images obtained from the oxidized sample. Moreover, the bandgap energies obtained by fitting these individual mesoscopic photocurrent energy spectra with a novel approach developed in our laboratory, showed that all oxide scales were constituted of Fe2O3 and Cr2O3 and of an Fe2-xCrxO3 solid solutions, but that the x-value of the latter was different depending on the metallurgic phase of the oxidized substrate. The latter results were shown to be in agreement with those of additional Raman analyses of the oxidized austenitic and ferritic grains.

Physical properties evolution of sputtered zirconium oxynitride films: effects of the growth temperature

Zirconium oxynitride (ZrNO) films were deposited by RF reactive magnetron sputtering in water vapour–nitrogen atmosphere varying the deposition temperature from RT to 600 °C. Optical analysis, x-ray diffraction, x-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) are the employed characterization techniques to investigate the influence of the substrate temperature on the films physical properties. It was found that the variation of the substrate temperature from RT to 600 °C caused a structural transition from cubic phase of Zr2ON2 to ZrN one, as confirmed by TEM observations too. In particular, Forouhi–Bloomer dispersion equations for optical parameters (n and k) and deconvolution of XPS spectra allowed further chemical properties be elucidated. They also permitted identification of two oxynitride phases, γ phase (Eg = 1.94 eV) and β phase (Eg = 1.7 eV), and an over-stoichiometric nitride one. The use of [Ec − Ev] values helped to confirm further the distinction between (γ, β)-phases and N-rich zirconium nitride compound, which is unachievable by using only Eg values.

Nano-crystalline Zr 2ON 2 thin films deposited by reactive magnetron sputtering

Zirconium oxynitride films were deposited by RF reactive magnetron sputtering in water vapor–nitrogen atmosphere varying the deposition temperature from RT to 600 °C. The influence of the substrate temperature on the films physical properties was investigated. The obtained films quality was evaluated using optical analysis, X-ray diffraction, X-photoelectron spectroscopy, and Secondary Ion mass spectroscopy. It was found that the variation of the substrate temperature from RT to 600 °C caused the transition from cubic phase of Zr 2ON 2 to ZrN one, as confirmed by TEM observations. In particular, a co-presence of Zr 3N 4–ZrN was detected when the deposition was performed at 400 °C. Moreover, Forouhi–Bloomer dispersion equations for extinction coefficient ( k) and deconvolution of XPS spectra are utilized to further elucidate chemical structure.

Effect of the substrate temperature on zirconium oxynitride thin films deposited by water vapour–nitrogen radiofrequency magnetron sputtering

ZrN x films were deposited by radiofrequency reactive magnetron sputtering technique in nitrogen and water vapour atmosphere varying the working temperature from room temperature to 600 °C. The films' physical properties were investigated using X-ray diffraction, Secondary Ion Mass Spectroscopy, Atomic Force Microscopy and Transmission Electron Microscopy. It was found that the increase of temperature caused a decrease in the oxygen incorporation and a transition from cubic phase of Zr 2ON 2 to ZrN one. The formation of nanosized crystalline particles dispersed in the amorphous matrix was observed.

Measurement of the continuum absorption coefficient of water vapor near 14400 cm−1 (0.694 μm)

The continuum absorption coefficient (CAC) of water vapor (k cont) in the visible region is determined for the first time from the data of laboratory measurements. For this purpose, the absorption spectra of water vapor in the region 14395–14402 cm−1 are recorded with the aid of a high-sensitivity photoacoustic spectrometer with a frequency-tunable single-pulse ruby laser, and the absorption measured in this transparency microwindow is compared with that calculated based on the HITRAN 2004 data bank. In the spectral region under study, k cont = (0.53 ± 0.18) × 10−9 cm−1 mbar−1 at a total pressure of a water vapor-nitrogen mixture of 1000 mbar and a temperature of 295 K. This value of the CAC is roughly 23% higher than the CAC value in the IO-CKD model of the continuum.

Phénix Steam Generator Module Repair: Sodium Removal Process, Ultrasonic Controls, and Repair Method

As part of the renovation project of the Phénix plant, the modular-type steam generators were the subject of an expert evaluation program in order to verify their condition after ~100 000 h of power operation and demonstrate their ability to continue operation for the planned lifetime extension (30 000 h).This evaluation, based on the destructive examination of several modules, showed that some parts of the superheater and reheater were affected by some delayed reheat cracking of 321 H stainless steel. Thus, the extension of the operation of the units for the prolonged lifetime of the plant could not be justified.A major repair operation was undertaken. Every superheater and reheater module was disassembled. A cleaning process was developed for removal of residual sodium inside the modules, based on the water vapor nitrogen method, and adapted to the special geometry of the component. The potentially defective parts were replaced by new ones. A specific procedure was used for welding of aged to new materials. The nonreplaced parts were controlled by a specially developed ultrasonic technique; 47 modules were successfully repaired within 1 yr.

Correction to “Absorption cross sections for water vapor from 183 to 193 nm”

Figure 1. Absorbance versus water vapor column amount. The different symbols represent data acquired under various experimental conditions: olid symbols, flowing source of water vapor in nitrogen; open symbols, .pure water vapor measured by pressure transducer. For the flowing experiments, the water vapor concentration was determined by three methods: filled circles, based on the assumption of 100% saturation and flow dilution; filled squares, measurement of the dew point upon exiting the absorption cell;_ fill ed up-triangles, weight loss of water bubbler. For the static experiments, several tests were performed: open circles, de-lonized water; open squares, bottled water; open up-triangles, detector and source masked with 1/4 diameter irises; open hexagons, with 10 cm of ambient air between light source and absorption cell; open down-triangles, using a 100 cm long absorption cell; open diamonds, comparison of three different mercury lamps. The line is a least squares fit to all the data with equal weighting. -18

The Effect of Water Vapor on the AC Impedance of Thin Films of Hectorite

Hectorite clay films deposited on interdigitated arrays undergo a change in AC impedance on exposure to water vapor in nitrogen. This impedance change appears to saturate at relative humidities of slightly greater than 10%. For this range of relative humidities, the clay film can act as a humidity sensor. The films do not respond to ethanol vapor; thus, the films may be used to detect the presence of water in ethanol. The response of the films to water vapor is rapid and reversible.

Laser schlieren study of vibrational relaxation of N 2 by H 2O

The vibrational relaxation of N 2 by H 2O has been studied in the temperature range 1300–3100 K behind incident shock waves. The laser schlieren technique is employed for observing the density gradient profile in the vibrational relaxation zone. Data from experiments with measured quantities of water vapour in nitrogen were reduced to relaxation times using the blackman technique. Results of this investigation are compared with few such studies available in the literature using other diagnostics. In the temperature range of our experiments, the N 2-H 2O relaxation time (in atm μs were found to be best described by 1n Pτ N 2-H 2O = −1.7325 + 11.3267 T − 1 3 , where T is the temperature in kelvin.

Molecular diffusivities of H2 16O, HD16O, and H2 18O in gases

Isotopic effects on the molecular diffusion coefficients of H2 16O, HD16O, and H2 18O have been determined by two independent methods. In the first one, the evaporation of liquid water under controlled laminar flow conditions was investigated. In the second one, the transport of water vapor through a diffusion tube was measured. The molecular diffusion coefficient of natural water vapor in nitrogen was redetermined. At 21 °C and P=760 Hg mm, D=0.244±0.004 cm2/sec. For the isotopic molecules we have DHD16O/DH216O=0.9757±0.0009 and DH218O/DH216O=0.9727±0.0007. Agreement between the data obtained in the pure gas phase experiment and the two-phase experiment shows that the condensation coefficients of the isotopically substituted molecules are identical. Interpretation of the isotopic effects on molecule diffusivities indicates that the relative mass differences between H2 16O, HD16O, and H2 18O alone cannot account for the experimental results. This is more important for the D–H substitution in which the asymetric molecule HD16O is formed. Qualitatively, the displacement of the center of gravity of the molecules H2 16O and HD16O in this substitution can explain the observed effect. Interpretation of these isotopic effects in terms of simple kinetic theory of gases indicates that for rigid spherical molecule models with diameters Γ we have the relation ΓH218O<ΓH216O<ΓHD16O. We calculate from the experimental data ratio of the coefficients of diffusion of the three isotopic molecules in air DHD16O/DH216O=0.9757±0.0009 and DH218O/DH216O=0.9727±0.0007.

Determination of Water Vapor in Nitrogen. Thermal Conductivity Measurement of Hydrogen Liberated from Calcium Hydride

Determination of Water Vapor in Nitrogen. Thermal Conductivity Measurement of Hydrogen Liberated from Calcium Hydride