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Showing papers on "Atmospheric pressure published in 1998"


Journal ArticleDOI
TL;DR: In this paper, the authors confirm the existence of atmospheric pressure dielectric controlled glow discharge and describe its main behavior using electrical measurements, short time exposure photographs, and numerical modeling.
Abstract: The aim of this paper is to confirm the existence of atmospheric pressure dielectric controlled glow discharge and to describe its main behavior. Electrical measurements, short time exposure photographs, and numerical modeling were used to achieve this task. Experimental observations and numerical simulation are in good agreement. Therefore, the analysis of the calculated space and time variations of the electric field together with the ion and electron densities helps to explain the discharge mechanisms involved, showing the main role played by the electron as well as helium metastable density just before the discharge is turned on.

904 citations


Journal ArticleDOI
02 Oct 1998-Science
TL;DR: Ammonia was synthesized from its elements at atmospheric pressure in a solid state proton (H+)-conducting cell-reactor and the thermodynamic requirement for a high-pressure process is eliminated.
Abstract: Ammonia was synthesized from its elements at atmospheric pressure in a solid state proton (H+)-conducting cell-reactor. Hydrogen was flowing over the anode and was converted into protons that were transported through the solid electrolyte and reached the cathode (palladium) over which nitrogen was passing. At 570 degreesC and atmospheric pressure, greater than 78 percent of the electrochemically supplied hydrogen was converted into ammonia. The thermodynamic requirement for a high-pressure process is eliminated.

540 citations


Proceedings ArticleDOI
01 Jan 1998
TL;DR: In this paper, a low speed wind tunnel data have been acquired for planar panels covered by uniform, glow-discharge surface plasma in atmospheric pressure air known as the One Atmosphere Uniform Glow Discharge Plasma (OAUGDP).
Abstract: Low speed wind tunnel data have been acquired for planar panels covered by a uniform, glow-discharge surface plasma in atmospheric pressure air known as the One Atmosphere Uniform Glow Discharge Plasma (OAUGDP). Streamwise and spanwise arrays of flush, plasma-generating surface electrodes have been studied in laminar, transitional, and fully turbulent boundary layer flow. Plasma between symmetric streamwise electrode strips caused large increases in panel drag, whereas asymmetric spanwise electrode configurations produced a significant thrust. Smoke wire flow visualization and mean velocity diagnostics show the primary cause of the phenomena to be a combination of mass transport and vortical structures induced by strong paraelectric electrohydrodynamic (EHD) body forces on the flow.

421 citations


Journal ArticleDOI
TL;DR: In this paper, three different dielectric barrier-controlled discharge regimes in helium at atmospheric pressure under sinusoidal excitation have been obtained by varying the excitation frequency or the gas chemical composition.
Abstract: Three different dielectric barrier-controlled discharge regimes in helium at atmospheric pressure under sinusoidal excitation have been obtained by varying the excitation frequency or the gas chemical composition: the filamentary discharge, which is the discharge that is usually obtained; the glow discharge, which is controlled by cathode secondary emission; and the homogeneous discharge, which is of a nature in between those of the filamentary and the glow discharges. All the characteristics that have been studied, such as the discharge current, the emission spectrum, the wettability and the chemical transformations of a polypropylene film, are related to the discharge-regime variation. The glow discharge is clearly more efficient than the others as a means of increasing the polypropylene-surface energy. Values as high as 62 mJ are obtained with this discharge whereas the maximum value after interaction with the filamentary one is 45 mJ . This improvement in wettability is due to there being more O atoms implanted at the surface as well as to the addition of N atoms. The differences among in surface transformations have been correlated to the characteristics of these different discharges and more specifically to the localization of the electrical energy transfer into the gas and to the nature of the ions created during the discharge.

353 citations


Journal ArticleDOI
TL;DR: In this paper, a plasma jet was developed for etching materials at atmospheric pressure and between 100 and C. Gas mixtures containing helium, oxygen and carbon tetrafluoride were passed between an outer, grounded electrode and a centre electrode, which was driven by 13.56 MHz radio frequency power at 50 to 500 W. At a flow rate of, a stable, arc-free discharge was produced.
Abstract: A plasma jet has been developed for etching materials at atmospheric pressure and between 100 and C. Gas mixtures containing helium, oxygen and carbon tetrafluoride were passed between an outer, grounded electrode and a centre electrode, which was driven by 13.56 MHz radio frequency power at 50 to 500 W. At a flow rate of , a stable, arc-free discharge was produced. This discharge extended out through a nozzle at the end of the electrodes, forming a plasma jet. Materials placed 0.5 cm downstream from the nozzle were etched at the following maximum rates: for Kapton ( and He only), for silicon dioxide, for tantalum and for tungsten. Optical emission spectroscopy was used to identify the electronically excited species inside the plasma and outside in the jet effluent.

291 citations


Journal ArticleDOI
TL;DR: In this article, a plasma jet was developed which deposits silica films at up to at 760 Torr and 115 to C. The jet operates by feeding oxygen and helium gas between two coaxial electrodes, driven by a 13.56 MHz radio frequency source at 40 to 500 W. Tetraethoxysilane is mixed with the effluent of the plasma jet and directed onto a substrate located 1.7 cm downstream.
Abstract: A plasma jet has been developed which deposits silica films at up to at 760 Torr and 115 to C. The jet operates by feeding oxygen and helium gas between two coaxial electrodes that are driven by a 13.56 MHz radio frequency source at 40 to 500 W. Tetraethoxysilane is mixed with the effluent of the plasma jet and directed onto a substrate located 1.7 cm downstream. The properties of the silica films, as determined by infrared spectroscopy and capacitance measurements, are comparable to those of thermally grown silicon dioxide films at C.

259 citations


Journal ArticleDOI
TL;DR: In this paper, a tube wall catalytic reactor was simulated as a model for a single pore of the monolithic catalyst using a 2-D flow field description coupled with detailed reaction mechanisms for surface and gas-phase chemistry.
Abstract: Partial oxidation of methane in monolithic catalysts at very short contact times offers a promising route to convert natural gas into syngas (H2 and CO), which can then be converted to higher alkanes or methanol. Detailed modeling is needed to understand their complex interaction of transport and kinetics in these systems and for their industrial application. In this work, the partial oxidation of methane in noble-metal (Rh and Pt)-coated monoliths was studied numerically as an example of short-contact-time reactor modeling. A tube wall catalytic reactor was simulated as a model for a single pore of the monolithic catalyst using a 2-D flow field description coupled with detailed reaction mechanisms for surface and gas-phase chemistry. The catalytic surface coverages of adsorbed species are calculated vs. position. The reactor is characterized by competition between complete and partial oxidation of methane. At atmospheric pressure, CO2 and H2O are formed on the catalytic surface at the entrance of the catalytic reactor. At higher pressure, gas-phase chemistry becomes important, forming more complete oxidation products downstream and decreasing syngas selectivity by about 2% at 10 bar. Temperature (from 300 to ∼ 1,200 K), velocity, and transport coefficients change very rapidly at the catalyst entrance. The dependence of conversion and selectivity on reactor conditions was examined.

245 citations


Journal ArticleDOI
TL;DR: In this article, the effect of pressure on the relaxation processes in poly(propylene glycol) of number-average molecular weights 400 and 4000 g mol-1 (PPG-400 and PPG-4000) has been investigated using dielectric spectroscopy as well as thermal conductivity and heat capacity measurements.
Abstract: The effect of pressure on the relaxation processes in poly(propylene glycol) of number-average molecular weights 400 and 4000 g mol-1 (PPG-400 and PPG-4000) has been investigated using dielectric spectroscopy as well as thermal conductivity and heat capacity measurements. The relaxations associated with segmental motions within the polymer chain ( relaxation) and whole chain motions ( relaxation) have been studied in the temperature range 200400 K for pressures up to 2 GPa. The two processes display slightly different sensitivities to pressure, and as a consequence, are better separated at high pressures. As a result, high-pressure data exhibit the relaxation also in PPG-400, whereas previous investigations at atmospheric pressure have detected it only in PPG of molecular weights above about 1000 g mol-1. At atmospheric pressure, the values for (T/p)=1s of the relaxation are, respectively, 140 and 192 K GPa-1 for PPG-400 and PPG-4000, where is the relaxation time. Because of the difference in (T/p), the r...

207 citations


Journal ArticleDOI
TL;DR: In this paper, the effects of entrapped air on water infiltration into a loamy sand were quantified using transparent three-dimensional (3-D) and 2-D columns.
Abstract: Experiments were conducted to quantify the effects of entrapped air on water infiltration into a loamy sand. Transparent three-dimensional (3-D) and 2-D columns were used for experiments carried out for two infiltration conditions: (1) when air was free to move ahead of the wetting front and leave the bottom of the column (air draining) and (2) when air was confined ahead of the wetting front and hence could escape only through the soil surface (air confining). The measurement setup was composed of a tension- pressure infiltrometer, an air flowmeter, water manometers, and video-picture cameras. We applied both positive and negative water pressures at the soil surface and measured the simultaneous changes in the rates of water inflow and air outflow, the air pressure ahead of the wetting front, and the dynamic behavior and advance of the wetting front. The air pressure ahead of the wetting front for the air-confining condition was generally found to increase with time rather than reaching a constant level, as observed in other studies by other researchers. The air pressure fluctuated locally because of air escaping from the soil surface. On the basis of an analysis of the results we present two empirical equations to predict the maximum air pressure at which air begins to erupt from the soil surface and to predict the minimum air pressure at which air eruption stops. We found that the infiltration rate was always equal to, and controlled by, the rate of air outflow. The infiltration rate varied inversely with the air pressure ahead of the wetting front and with the ponding depth at the soil surface. The infiltration rate fluctuated with time rather than undergoing changes in a three-stage process, as is often characterized in the literature. The volume of residual entrapped air in the air-confining condition increased 7% on average, and the infiltration rate decreased threefold to tenfold as compared to the air-draining condition. Finally, it was shown that the air-confining infiltration flow is fingered and unstable, consistent with the predictions of an existing theory.

176 citations


Journal ArticleDOI
TL;DR: In this paper, prepared fruits and vegetables were subjected to high pressure processing at 100-400 MPa for 5-60 min in an isostatic press and their influence on product texture was evaluated.
Abstract: Prepared fruits and vegetables were subjected to high pressure processing at 100–400 MPa for 5–60 min in an isostatic press and their influence on product texture was evaluated Pressure had a dual effect on product texture characterized by an initial loss in texture, ascribed to the instantaneous pulse action of pressure, followed by a more gradual change as a result of pressure-hold The extent of the initial loss and the subsequent partial recovery were pressure dependent with the former more prominent at higher pressures and the latter at lower pressures The pressure treated samples were generally brighter in color somewhat resembling the appearance of mildly heat treated samples For all vegetables pressure treated at 100 MPa for 60 min, the initial loss in texture was totally recovered during the pressure hold yielding an overall texture firmer than that of the raw product There was no recovery of texture during the standing period at atmospheric pressure after the pressure treatment

160 citations


Patent
11 Sep 1998
TL;DR: In this paper, the mass spectra containing internal calibration peaks can be achieved by spraying different solutions simultaneously from the multiple inlet probes (3, 4, 6, 7, 7).
Abstract: A multiple sample introduction mass spectrometer apparatus (1) having atmospheric pressure ion sources (3, 4, 6, 7) interfaced to mass analyzers (21) for introducing samples through multiple electrospray (ES) and atmospheric pressure chemical ionization (APCI) probes (3, 4, 6, 7). The mass spectra containing internal calibration peaks can be achieved by spraying different solutions simultaneously from the multiple inlet probes (3, 4, 6, 7). The electrospray (ES) and atmospheric pressure chemical ionization (APCI) probes (3, 4, 6, 7) are arranged in one atmospheric pressure ionization chamber (20) and can be switched on or off during an analytical run.

Journal ArticleDOI
TL;DR: In this article, the authors measured the temperature-dependent lifetime of BrNO2 in a quartz cell and obtained the activation energy EA = 89 ± 9 kJ/mol for the unimolecular decay at atmospheric pressure.
Abstract: The heterogeneous reactions leading to formation and loss of BrNO2 on salt solutions as a model substrate for atmospheric sea salt aerosol are investigated. Further to the reaction of ClNO2 with bromide solutions, the reaction of Br2 with nitrite solution was found to be a convenient method for the synthesis of BrNO2. We measured the temperature-dependent lifetime of BrNO2 in a quartz cell and obtained the activation energy EA = 89 ± 9 kJ/mol for the unimolecular decay at atmospheric pressure. The reactive uptake of BrNO2 and ClNO2 on water and aqueous solutions was determined using a wetted-wall flow tube technique. We observed the reactions Br2 + NO2- ↔ BrNO2 + Br-, Cl2 + NO2- → ClNO2 + Cl-, and the net reaction ClNO2 + Br- ↔ BrNO2 + Cl-. BrNO2 and ClNO2 both react with NO2- to release NO2 into the gas phase. Observed concentration profiles in the gas phase and in solution can be described qualitatively by a numerical model of the diffusion and reaction processes in the experimental setup.

Journal ArticleDOI
TL;DR: In this article, temperature and species mole fraction profiles have been measured in laminar premixed n-heptane/O2/N2 and iso-octane/N 2 flames.
Abstract: Temperature and species mole fraction profiles have been measured in laminar premixed n-heptane/O2/N2 and iso-octane/O2/N2 flames. Both flames have been stabilized on a flat-flame burner, at atmospheric pressure. Species identification and concentration measurements have been performed by gas chromatography and GC-MS analysis of samples withdrawn locally by a quartz microprobe. Temperature profiles were measured by Pt-Pt 10%Rh thermocouples with radiative heat losses suppressed by the electrical compensation method. For both flames, the equivalence ratio was equal to 1.9 and a faint yellow luminosity due to soot particles was observed.|The main objective of this work was to provide detailed experimental data on the nature and concentration of the intermediate species formed by consumption of a linear or highly branched fuel molecule. In addition to reactants and major products (CO, CO2, H2, H2O), the mole fraction profiles of C1(CH4), C2(C2H2, C2H4, C2H6), C3(allene, propyne, propene, propane), C4(C4H2, C...

Journal ArticleDOI
TL;DR: In this article, experiments on the combustion of n-heptane droplets in helium-oxygen environments conducted in spacelab onboard the Space Shuttle Columbia during the first launch (STS-83) of the Microgravity Science Laboratory mission in April 1997 were presented.
Abstract: Results are presented from experiments on the combustion of freely floated n-heptane droplets in helium-oxygen environments conducted in Spacelab onboard the Space Shuttle Columbia during the first launch (STS-83) of the Microgravity Science Laboratory mission in April 1997. During this shortened flight, a total of eight droplets were burned successfully in nominally 300 K oxygen-helium atmospheres having oxygen mole fractions of 25, 30, and 35% at a total pressure of 1 atm. Initial droplet sizes ranged from about 2 to 4 mm. The results demonstrated both radiative and diffusive flame extinction during burning, whereas droplet surface regression followed the d-square law. The full range of possible droplet-burning behaviors was thus observed. The results provide information for testing future theoretical and computational predictions of burning rates, soot and flame characteristics, and extinction conditions.

Journal ArticleDOI
TL;DR: This article showed that the structural transformations which occur in silica glass under high pressure do not require thermal activation, and arise from localized mechanical instabilities associated with disappearances of local minima on the potential energy surface.
Abstract: Molecular simulations show that the structural transformations which occur in silica glass under high pressure do not require thermal activation, and arise from localized mechanical instabilities associated with disappearances of local minima on the potential energy surface. This result leads to the prediction that the kinetic stability of silica glass structures differs from that of silica crystal structures: The glass will undergo a pressure-induced transformation to a structure with high average silicon coordination at any arbitrarily low temperature, but this glass structure with high average coordination can never be quenched to atmospheric pressure.

Journal ArticleDOI
TL;DR: In this article, the soot surface growth rate was correlated successfully with predictions based on the hydrogenabstraction/carbon addition (HACA) mechanisms of both Frenklach and co-workers and Colket and Hall, extending an earlier assessment of these mechanisms for premixed ethylene/air flames to conditions having larger H/C ratios and acetylene concentrations.

Journal ArticleDOI
TL;DR: In this article, reference spectra of the Herzberg bands of oxygen are presented, that allow to eliminate this oxygen interference for practical purposes, and are used to correct DOAS measurements of monocyclic aromatic hydrocarbons.

Journal ArticleDOI
TL;DR: In this paper, the authors studied the electrical properties of Mg-doped Al x Ga 1− x N grown by atmospheric pressure MOCVD, using Cp 2 Mg.

Journal ArticleDOI
TL;DR: In this paper, a comparison of a filamentary discharge in air with a glow discharge in helium was performed. And the results showed that the helium GDBD is better than air FDBD to increase polypropylene wettability without decreasing the bulk electrical properties below a certain level.
Abstract: Recently, a glow like dielectric controlled barrier discharge (GDBD) working at atmospheric pressure has been observed. Such a discharge could replace a filamentary dielectric controlled barrier discharge (FDBD) used in corona treatment systems to improve the wettability or the adhesion of polymers. So it is of interest to compare these two types of discharges and their respective effect on a polymer surface. This is the aim of an extensive study we have undertaken. The first step presented here is the comparison of a filamentary discharge in air with a glow discharge in helium. Helium is the most appropriate gas to realize a glow discharge at atmospheric pressure. Air is the usual atmosphere for a corona treatment. The plasma was characterized by emission spectroscopy and current measurements. The surface transformations were indicated by the water contact angle, the leakage current measurement and the X-ray photoelectron spectroscopy. Results show that the helium GDBD is better than air FDBD to increase polypropylene wettability without decreasing the bulk electrical properties below a certain level. Contact angle scattering as well as leakage current measurements confirm that the GDBD clearly results in more reproducible and homogeneous treatment than the FDBD.

Journal ArticleDOI
TL;DR: In this article, the emission of various low-pressure microwave-induced plasmas created and sustained by a surfatron or by a Beenakker cavity has been studied after the introduction of molecular species (i.e. N2, CO2, SF6 and SO2).

Journal ArticleDOI
TL;DR: In this paper, a field study was carried out in a glacial aquifer with a 10-12 m thick sandy unsaturated zone to explore gas exchange between the atmosphere and the unsaturated zones.
Abstract: Gas transport induced by temporal pressure fluctuations in the atmosphere can be an important mechanism for transport of atmospheric oxygen within the unsaturated zone. Moreover, the presence of oxygen in the unsaturated zone may be a factor controlling oxidation of sulphide minerals and other redox processes. A field study was carried out in a glacial aquifer with a 10–12 m thick sandy unsaturated zone to explore gas exchange between the atmosphere and the unsaturated zone. The exchange occurs through a “geological window” in a till layer which covers the sandy unsaturated zone. Observed pressure distribution and oxygen concentrations within the unsaturated zone were compared to numerical simulations with SUTRA, a finite element and fluid density dependent groundwater flow model. The simulations were carried out by modeling the gas pressure distribution within the unsaturated zone based on atmospheric pressure time series. The spatial variation in permeability observed from borehole logging was implemented in the model. The analysis demonstrated a good match between the field observations and the numerical simulations. During an atmospheric pressure cycle, atmospheric oxygen migrated more than 10 md−1 horizontally in the capped unsaturated zone. The analysis shows that both the amplitude and the length of the period of pressure variations are important for the transport of oxygen, and it shows that the combined effects determine the extent of a subsurface zone where atmospheric oxygen can reach.

Journal ArticleDOI
TL;DR: The recent development of infrared-visible sum frequency generation (SFG), a surface-specific vibrational spectroscopy, has helped bridge the pressure gap between studies of heterogeneous catalysis under high vacuum and atmospheric pressure as discussed by the authors.
Abstract: The recent development of infrared-visible sum frequency generation (SFG), a surface-specific vibrational spectroscopy, has helped bridge the pressure gap between studies of heterogeneous catalysis under high vacuum and atmospheric pressure. This is achieved by in situ monitoring of surface species at high pressure via their SFG vibrational spectra and correlating the results with the simultaneously measured reaction rate using gas chromatography. Examples of systems studied include olefin hydrogenation and carbon monoxide oxidation over the (111) crystalline face of platinum. In these examples, the studies succeed in revealing the molecular details of the surface reactions. Identification of key intermediates and their concentrations has made it possible for the first time to calculate turn over rates per active surface species rather than just per exposed surface metal atom. In all cases, the key intermediate of the reaction is not detectable on the surface in UHV under similar temperatures.

Journal ArticleDOI
TL;DR: In this article, rotational and vibrational temperatures are measured by optical emission spectroscopy in a discharge with liquid non-metallic electrodes (DLNME) in air at atmospheric pressure.
Abstract: Rotational and vibrational temperatures are measured by optical emission spectroscopy in a discharge with liquid non-metallic electrodes (DLNME) in air at atmospheric pressure. We used the transition of the second positive system of to determine the two parameters of this discharge. In this paper we describe first the experimental set-up and then the method of determination of rotational and vibrational temperatures by comparison with calculated spectra. We present the results obtained along the discharge's axis.

Journal ArticleDOI
TL;DR: By reducing the diameter of the cathode opening in a hollow cathode discharge geometry to values on the order of 100 μm, the authors of as mentioned in this paper were able to operate these discharges in noble gases in a direct current mode up to atmospheric pressure.
Abstract: By reducing the diameter of the cathode opening in a hollow cathode discharge geometry to values on the order of 100 μm, we were able to operate these discharges in noble gases in a direct current mode up to atmospheric pressure. High-pressure discharges in xenon were found to be strong sources of excimer radiation. Highest intensities at a wavelength of 172 nm were obtained at a pressure of 400 Torr. At this pressure, the vacuum ultraviolet (VUV) radiant power of a single discharge operating at a forward voltage of 220 V and currents exceeding 2 mA reaches values between 6% and 9% of the input electrical power. The possibility to form arrays of these discharges allows the generation of flat panel VUV lamps with radiant emittances exceeding 50 W/cm2.

Journal ArticleDOI
10 Oct 1998-BMJ
TL;DR: For example, at sea level atmospheric pressure is 1 bar absolute (1 standard atmosphere =101 kPa=1.013 bars) and the pressure on a diver is 200 kPa; at 20 m pressure is 300 kPa absolute and the gas is compressed into one third the volume.
Abstract: All organisms require oxygen for metabolism, but the oxygen in water is unavailable to mammals. Divers (and diving mammals such as whales and seals) are entirely dependent on the oxygen carried in the air in their lungs or their gas supply. Divers also have a paradoxical problem with oxygen. At higher partial pressures oxygen causes acute toxicity leading to convulsions. To understand the diver's narrow knife edge between fatal hypoxia and fatal hyperoxia we need to recall some of the physical properties of gases. A dive to 30 m for 20 minutes puts the scuba diver at risk of nitrogen narcosis and decompression illness. The elephant seal can dive to 1 km for 1 hour without risk of either condition At sea level atmospheric pressure is 1 bar absolute (1 standard atmosphere =101 kPa=1.013 bars). The weight of the atmosphere exerts a pressure which will support a column of water 10 m high; 10 m under water the pressure on a diver is 200 kPa. The volume of gas in an early diving bell full of air at sea level is halved at 10 m according to Boyle's law; at 20 m pressure is 300 kPa absolute and the gas is compressed into one third the volume. The pressure on a diver increases by 100 kPa for every 10 m he or she descends Dry air is composed of roughly 21% oxygen, 78% nitrogen, and 1% other gases. According to Dalton's law the partial pressure of oxygen at any depth will be 21% of the total pressure exerted by the air and the partial pressure of nitrogen will be 78% of total pressure. Effect of depth on partial pressures of nitrogen and oxygen Gases dissolve in the liquid with which they are in contact. Nitrogen is fat soluble and at …


01 Oct 1998
TL;DR: By reducing the diameter of the cathode opening in a hollow cathode discharge geometry to values on the order of 100 μm, the authors of as discussed by the authors were able to operate these discharges in noble gases in a direct current mode up to atmospheric pressure.
Abstract: By reducing the diameter of the cathode opening in a hollow cathode discharge geometry to values on the order of 100 μm, we were able to operate these discharges in noble gases in a direct current mode up to atmospheric pressure. High-pressure discharges in xenon were found to be strong sources of excimer radiation. Highest intensities at a wavelength of 172 nm were obtained at a pressure of 400 Torr. At this pressure, the vacuum ultraviolet (VUV) radiant power of a single discharge operating at a forward voltage of 220 V and currents exceeding 2 mA reaches values between 6% and 9% of the input electrical power. The possibility to form arrays of these discharges allows the generation of flat panel VUV lamps with radiant emittances exceeding 50 W/cm2.

Journal ArticleDOI
TL;DR: In this article, the Holub et al. model has been extended to account for the interaction between the gas and liquid phases by incorporating the velocity and the shear slip factors between the phases.
Abstract: The Holub et al. (1992, 1993) phenomenological model for pressure drop and liquid holdup in trickle flow regime at atmospheric pressure was noted by Al-Dahhan and Dudukovic (1994) to systematically underpredict pressure drop at high pressure and high gas flow rates. In this study, the Holub et al. (1992, 1993) model has been extended to account for the interaction between the gas and liquid phases by incorporating the velocity and the shear slip factors between the phases. As a result, the prediction of pressure drop at the operating conditions of industrial interest (high pressure) has been improved noticeably without any significant loss in predictability of liquid holdup. The extended model and the comparison between its prediction and experimental high pressure and high gas flow rate data are presented and discussed.

Journal ArticleDOI
TL;DR: In this paper, the pyrochlores synthesized at high pressure and atmospheric pressure are classified into four groups which depend on their oxygen nonstoichiometry, and the change from the metallic to semiconducting state is discussed from the viewpoint of structure changes.

Journal ArticleDOI
TL;DR: In this article, the plasma assisted decomposition of dilute concentrations of chlorobenzene in air/oxygen and argon-oxygen gas mixtures at atmospheric pressure using a coaxial geometry single dielectric barrier discharge for different oxygen concentrations and energy densities was investigated.
Abstract: Experiments were performed on the plasma-assisted decomposition of dilute concentrations of chlorobenzene in air/oxygen and argon/oxygen gas mixtures at atmospheric pressure using a coaxial geometry single dielectric barrier discharge for different oxygen concentrations and energy densities. The results show that the decomposition process requires higher energy densities using air mixtures compared to argon/oxygen mixtures and is not linearly dependent on the oxygen content for a given energy density. The main decomposition products detected in the offgas were carbon dioxide and carbon monoxide.