High Pressure Side Research Articles

Compact, field-portable capillary ion chromatograph

We describe a fully computer controlled, field-portable capillary scale suppressed conductometric ion chromatograph that fits in a standard briefcase (28×43×15 cm) and weighs 10 kg. The system uses an electrodialytic sodium hydroxide generator on the high-pressure side of a syringe pump. This provides isocratic or gradient operation with excellent eluent purity. A 100 nl loop-volume, electrically actuated valve is used for sample injection and allows for facile automation. Analytical columns, 50 cm×180 μm I.D., were packed in the laboratory using commercial packing and fused-silica capillaries. A novel flow-through conductivity detection cell was developed. The system provides detection limits in the sub- to low ppb range, with mass limits of detection >100 times better than standard IC systems. Sample preconcentration is demonstrated with a concentrator column, 10 cm in length.

Oxygen permeation in SrCo 0.8Fe 0.2O 3 − δ membranes with porous electrodes

Measurements of oxygen flux, in the temperature range, 770–870 °C on planar membranes of SrCo 0.8Fe 0.2O 3−δ, consisting of a dense discs ~ 0.1 cm thick modified by coating with porous layers on both sides, yielded an enhancement in the oxygen flux, η ≈ 2, compared to the uncoated membrane. When only one side of the disc was coated with the porous layer on the high pressure side of the membrane then η ≈ 1.2, while when the modified side was on the low pressure side then η ≈ 1.4. The observed values of η were explained by a model of diffusion-reaction transport in mixed ionic electronic conductor membranes with porous electrodes, extended to the case of finite thickness of the dense layer. From a fit of the model to the experimental data, values of the surface exchange coefficient, k iO , and ambipolar oxygen ion-electron hole pair diffusion coefficient, D a , were deduced. At 870 °C, k iO = 2.5 × 10 −4 cm/s and D a = 5 × 10 −6 cm 2/s.

NUMERICAL SIMULATION OF AN ETHYLENE RE-LIQUEFACTION PLANT

The present paper is concerned with the numerical simulation of an ethylene re-liquefaction plant. The plant is part of a petrochemical complex, set up in the city of Aratu, state of Bahia, Brazil. The cooling effect is obtained through a two-stage cascade cycle, involving two circuits with different working fluids: ammonia in the high pressure side, and ethylene is the low pressure. The main components of the system include: two-stage double acting reciprocating compressors, shell-and-tube heat exchanger, store and flash tanks and control valves. The simulation model was developed by considering the energy and mass conversion laws, the empirical heat transfer coefficient relations, heat exchanger and compressor theories and the thermophysical properties of the working fluids. The result was a set of nonlinear equations solved by a sequential modular technique. Predicated thermodynamic parameters (temperature, pressure and mass flow rate), at different points of the systems, were compared with the available plant operational data, with food agreement being obtained. A parametric anaylsis of the plant was also carried out. © 1997 John Wiley & Sons, Ltd.

Separation of mixed gases through porous polymeric membranes

The separation of a gas from a two component gas system was studied both theoretically and experimentally. Helium and argon as an inorganic gas pair, ethylene and butane as an organic gas pair, and air were used. The theory based on the free molecular flow could not be applied to all the combinations of the gases experimentally studied. Experiments showed that the permeability coefficient of each component in the mixture was very close to that of each single component, when the pressure in the low pressure side became zero, but those of the mixture approached one another rapidly as the pressure increased. In the case of the separation of one inorganic gas from another, there exists most suitable pressures both in the high and low pressure sides for the most efficient separation, as considered from the selectivity and permeability. In the cases of the mixed organic gases and the organic-inorganic gas combination, a rather high separation efficiency is expected for a very high pressure on the high pressure side.

Rapid diagnosis of flow separation around an axial impeller in a mixing vessel

The relative flows around a flat plate axial impeller in a mixing vessel were visualized directly using a combined image shifting and image de-rotation technique. The image shifting technique used a rotating mirror to produce a velocity bias equal to the blade velocity so that the relative flow field could be studied in a co-axial plane cutting through the 2-dimensional blade section. The technique provides a rapid means of locating local flow separation on the blade. To visualize the relative flow field in the plane of the blade span, an image de-rotation method was used. The method includes using a dove-shaped prism which, when rotated, produce a rotation of an image about the optical axis. It was observed in the relative frame of reference through the prism that a new vortex structure, not reported previously, with vorticity sign opposite to that of the rotation of the shaft, exists near the hub at the high pressure side of the blade.

Capillary Ion Chromatography with On-Line High-Pressure Electrodialytic NaOH Eluent Production and Gradient Generation

A small inexpensive system is described that allows high-performance suppressed anion chromatography on a capillary scale. A fully computer-controlled stepper motor-driven syringe-type dispenser, equipped with a 500 μL-capacity glass syringe is capable of pumping at pressures up to 1000 psi when equipped with an appropriate inlet check valve. Fused-silica capillary columns ∼50 cm in length and 180 μm i.d., packed in-house with a commercial packing, provide excellent performance, significantly exceeding the efficiencies observed for the same packing in commercially available 2 mm bore format. The system operates with a pressure drop of <800 psi at a flow rate of 2 μL/min. The system utilizes a novel electrodialytic NaOH eluent generator that is deployed on the high-pressure side of the pump and thus requires no special measures for electrolytic gas removal. This device permits both isocratic and gradient operation with excellent eluent purity; the NaOH concentration is generated linearly with applied current with near-Faradaic efficiency, up to a concentration of at least 100 mM.

Oxygen permeation through thin zirconia/yttria membranes prepared by EVD

Ultra-thin dense zirconia/yttria membrane composites were fabricated by EVD technique on porous α-alumina substrates. The deposited membranes consisted primarily of cubic/tetragonal phases as determined by XRD. The EVD film growth rate estimated by SEM photographs was 3–4 μm/h. Oxygen permeation data of thin dense zirconia/yttria membranes with different thickness (2–15 μm) were measured at 900 °C and 1000 °C. From the oxygen permeation data, the surface reaction and bulk diffusion rate parameters, α and β, were calculated. At 900 °C, α = 3.0 × 10 −8 mol/cm 2 · s · atm 1 2 and β = 3.0 × 10 −8 mol/cm · s · atm 1 4 with activation energy 53 KJ/mol and 72 KJ/mol for α and β, respectively. Presence of steam in the high oxygen partial pressure side promoted electrochemical surface reaction.

Fan having blades with sound reducing material attached

An air moving device such as an axial cooling fan comprises a rotatable shaft assembly and a plurality of fan blades coupled to the rotatable shaft assembly, each of the fan blades having a trailing edge when the rotatable shaft assembly is rotated in a given direction. In accordance with one illustrative embodiment of the invention, at least one of the fan blades has a sound reducing material attached thereto alongside the trailing edge thereof. The sound reducing material reduces aeroacoustic noise by reducing the aerodynamic effect that occurs when turbulence produced by the pressure differential between the two sides of one blade comes into contact either with the trailing edge of the given blade which created it, or, more significantly, with the following blade, at or near that blade's trailing edge. In various embodiments the sound reducing material may comprise felt, loops from a hook-and-loop-type fastener such as that sold under the VELCRO trademark, or a small piece of fiberglass, cotton or wool batting. In one illustrative embodiment, the sound reducing material is advantageously attached to the fan blade on the high pressure side thereof.

Application of Electroless Deposited Thin-Film Palladium Composite Membrane in Hydrogen Separation

In recent years, there has been increased interest in developing inorganic and composite membranes for in-situ separation of hydrogen to achieve an equilibrium shift in catalytic membrane reactors. The productivity of these membrane reactors, however, is severely limited by the poor permeability and selectivity of available membranes. To develop a new class of permselective inorganic membranes, electroless plating has been used to deposit palladium thin-films on a microporous ceramic substrate. A palladium thin-film coating was deposited on a microporous ceramic disk (α-alumina, φ 39 mm × 2 mm thickness, nominal pore size 150 nm and open porosity ≈ 42%) by electroless deposition. The film was evaluated by SEM and EDX analysis. A steady-state counter-diffusion method, using gas chromatographic analysis, was used to evaluate the permeability and selectivity of the composite palladium membrane for hydrogen separation at temperatures from 373 to 573 K. The pressure on the high pressure side of the membrane ranged from 170 to 240 kPa and the low pressure side was maintained at 136 kPa. The measured hydrogen permeabilities at 573 K were found to be 1.462×10−9 mol·m/m2·s·Pa0.778, and 3.87×10−8 mol · m/m2 · s · Pa0.501 for palladium film thicknesses of 8.5 and 12 μm, respectively. The results indicate that the membrane has both high permeability and selectivity for hydrogen and may find applications in high temperature hydrogen separation and membrane reactors.

Peculiar aspects related to the hydrogen permeation flux through a martensitic steel membrane before and after ion implantation

We have observed peculiar hydrogen transient fluxes through stainless steel membranes which cannot be explained in terms of the linear permeation laws. In particular, before attaining the steady-state regime, the hydrogen flux may show a maximum, depending on the membrane temperature. Moreover, by repeating the measurement without changing the relevant parameters, the steady-state permeation rate may strongly differ from the first measurement. To clarify whether the observed anomalous behaviour is due to surface or bulk effects we have modified the membrane surface layers by implantation of a reactive (N +) or a non-reactive species (Ar +). The subsequent H-permeation experiments show that the implanted surface, when facing the high-pressure side, does not permit the flux peaks (independently of the implanted species). Moreover, permeation processes are reproducible in the sense that there is no difference between the steady rates of the first and second measurements, except at high temperature.

Performance and pore characterization of nanoporous carbon membranes for gas separation

The performance of a novel nanoporous carbon membrane for separation of hydrogen-hydrocarbon gas mixtures is described. The membrane selectively adsorbs hydrocarbons from hydrogen at the high pressure side and the adsorbed molecules then diffuse along the pore walls to the low pressure side. Pressure levels at thigh gh and low pressure sides of the membrane and the type and flow rate of the sweep gas at the low pressure side of the membrane were varied. The effects of these variables on the hydrogen recovery and hydrocarbon rejection by the membrane were investigated. Atomic force microscopy and scanning tunnelling microscopy scans of the membrane surface suggested that the membrane pore diameters were approximately 5 Å in diameter. Comparison between pure methane diffusivity through the membrane and those through nanoporous zeolites of various pore opening alsoo suggested that the membrane pores diameters were in the range of 5–6 Å. A sensitivity analysis indicated that the membranes contained a very narrow distribution of pore sizes.

The Three-dimensional Structure of the Cassiopeia A Supernova Remnant. I. The Spherical Shell

view Abstract Citations (351) References (42) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Three-dimensional Structure of the Cassiopeia A Supernova Remnant. I. The Spherical Shell Reed, Jeri E. ; Hester, J. Jeff ; Fabian, A. C. ; Winkler, P. F. Abstract The three-dimensional structure of the Cassiopeia A supernova remnant is explored via 73 long-slit optical spectra (spanning 6250-7600 Å) which cross the face and "jet" region of the nebula. We extracted position, radial velocity, and line intensity information from nearly 25,000 cross sections of these original data, resulting in a library of 3663 fast-moving knots (FMKs) and 450 quasi-stationary flocculi (QSFs) detections. We performed an iterative least-squares spherical fit to the data, using this to convert radial velocities to line-of-sight distances. We have built up a picture of the remnant as a spherical circumstellar shell of 104"5±0"7 radius, corresponding to 5.3 × 1018 cm (1.7 pc). The center on the sky is displaced by 8".7 west and 12".6 north of the proper motion center. The velocity center of our fitted sphere has been redshifted by 770±40 km s-1 from the presumed expansion center at zero velocity. This expansion of the ejecta from a displaced center accounts for the observed radial velocity difference at the front and back faces. The average rate of expansion of the FMKs is 5290±90 km s-1, while the asymmetric values are 4520 km s-1 at the blueshifted face, and 6060 km s-1 at the redshifted face. Based on a comparison of our suite of radial velocities with all the available proper-motion and age data, we find the distance to Cas A to be 3.4+0.3-0.1 kpc. Our kinematic analysis shows the optically emitting ejecta of Cas A have been slowed certainly by less than 7%, and probably by less than 4% and that the velocity of the reverse shock driven into the knots is about 200 km s-1. We conclude that the center of expansion of the supernova is displaced by about 0.36 pc (1.1 × 1018 cm) to the northwest and front of the geometric center of the bubble. The geometry suggests that the density of the surrounding medium is greater in the direction of displacement. The asymmetrically distributed radial velocities of the QSFs, of which 76% are blueshifted, also support this interpretation. Line ratios suggest that the pressure is higher on the front side of the remnant than on the back. There is a global trend of increasing electron density with radial velocity in this direction, and a stronger trend of increasing [O II]/[S II] from back to front. We suggest that this is due to collisional deexcitation of [S II] on the high-pressure side of the remnant, rather than a real composition trend. We also see evidence for density variations in both the shell and ejecta, concluding that the front face of the composite shell is of higher density than the far face, and that the blueshifted ejecta may be of higher density than that at the far face. However, in this study we see no evidence for any ordered change in abundances of the ejecta across Cas A. The weight of observational evidence suggests that the general form of the Cas A supernova remnant is due to the expansion of ejecta from a displaced center within an approximately spherical shell. We have concluded that there is no optical evidence for a dual-hemisphere model in the velocity structure of Cas A. In particular, we find that the outer radio emission must truly lie outside the inner radio and optical shell. The inner shell is made up of decelerated circumstellar material and the SN material which was ejected at highest velocity. The optical FMKs consist of newly interacting knots of ejecta which are just undergoing deceleration and are distributed in rings on the surface of the sphere. Publication: The Astrophysical Journal Pub Date: February 1995 DOI: 10.1086/175308 Bibcode: 1995ApJ...440..706R Keywords: ISM: STRUCTURE; ISM: INDIVIDUAL NAME: CASSIOPEIA A; ISM: KINEMATICS AND DYNAMICS; ISM: SUPERNOVA REMNANTS full text sources ADS | data products SIMBAD (4)

The Design, Selection, and Application of Oil-Injected Screw Compressors for Fuel Gas Service

Fuel gas compressors installed in cogeneration systems must be highly reliable and efficient machines, like the other main components, such as gas turbines, gas engines, etc. In the range of gas flow rate and pressure conditions generally required for such systems, the oil-injected screw compressor is often the most suitable compressor type for these requirements. Advantages of oil injected screw compressors are: improved compression efficiency; low discharge gas temperature; high reliability; simple mechanical construction; which all result from injection of lubricant into the compressor. Injected lubricant is discharged together with compressed gas on the high-pressure side but the oil is separated by a fine oil separation system down to a level that causes no problems for the downstream combustion equipment. The oil-injected screw compressor is equipped with an integral stepless capacity control by means of a slide valve, which makes part-load operation possible with reduced power consumption and improves overall system efficiency. As cogeneration systems, which are energy efficient and environmentally sound, are now increasing in number, so oil-injected screw compressors are expected to be used more widely.

Temperature relaxation of argon and helium after injection into a vacuum vessel

When gas is transferred from a vessel with high pressure to a vessel with much lower pressure or a vacuum, considerable flow velocities larger than sonic speed or average thermal speed may occur. Since the transfer is adiabatic for a short period, the gas injected into a vessel is getting much warmer than the surrounding walls, while the gas remaining on the high pressure side, which is performing accelarating work, cools down considerably below ambient temperature; this happens even if the gas is ideal. We have investigated this effect experimentally and determined the relaxation time of the temperature for Ar and He. The measured temperature differences of the gas to the surrounding walls were as much as 20 K, when gas was transferred from a volume 1 l / with 300 kPa to high vacuum. The relaxation could be fitted with the sum of three exponential functions, with the time constants ranging from a few seconds up to 10 min. These different time constants can be related to the physical processes involved.

Isotopic fractionation and overall permeation of lithium by a thin-film composite polyamide reverse osmosis membrane

A small, but significant fractionation of lithium isotopes was observed during reverse osmosis experiments performed with a thin-film composite polyamide membrane (FilmTec FT-30 membrane). Relative to the feed solution, the heavier lithium isotope 7Li was depleted in the permeate from 4.3 to 10.6 per mil (±3.3 per mil) during six experimental runs. The observed isotopic fractionation might be the result of the slightly different permeabilities of 6Li and 7Li across the FT-30 membrane. The heavier of two solute isotopes has a slightly lower mobility due to its slightly greater mass. Therefore, the heavy isotope permeates slightly more slowly inside the membrane than its isotopically lighter counterpart. As a result, more of the heavier isotope is retained on the high-pressure side of the membrane during each run. The magnitude of isotopic fractionation generally increased with increasing water permeation rates. Additionally, experimental evidence shows that the FT-30 membrane exhibits essentially identical solute rejection with NaCl and LiCl under the same operating conditions.

Oxygen permeation modelling of La 1−yCa yCrO 3−δ

The oxygen permeation current density through La 0.75Ca 0.25CrO 3− δ was calculated as a function of the oxygen partial pressure gradient using a random point defect model. The oxygen permeation current density depends on the oxygen partial pressure at the low oxygen partial pressure side as J o 2− ∝ P −0.5 o 2 when the nonstoichiometry of the perovskite at that side is small. The oxygen permeation current density is independent of the oxygen partial pressure at the high oxygen partial pressure side when the nonstoichiometry of the perovskite at that side is small in comparison with the nonstoichiometry at the low oxygen partial pressure side. The result of this calculation describes also the Electrochemical Vapor Deposition process of this type of perovskite material.

Surface segregation of PdAg membranes upon hydrogen permeation

PdAg membranes are permeable to hydrogen. Hydrogen treatment results in a small chemical shift (±0.1–0.2 eV) of Pd 3d core level but no change in the Ag3d level. A new valence band in the binding energy region of 7–9 eV corresponding to the interaction between H 1s and Pd4d appears on a hydrogen permeated membrane surface. Quantitative XPS analysis reveals that Pd segregates at the membrane surface toward the high hydrogen pressure side while Ag segregation occurs at the surface on the low hydrogen pressure side after hydrogen permeation. Both surface segregations are explained based on an MTCIP-1A (modern thermodynamic calculation of interface properties — first approximation) approach. It is concluded that hydrogen chemisorption induces palladium segregation on the PdAg membrane surface.

Pulsed-electric-field crossflow ultrafiltration of bovine serum albumin

A conventional crossflow ultrafiltration (CUF) apparatus was modified by the inclusion of electrodes which permitted a pulsed electric field to be produced across the ultrafiltration membrane (PEF-UF process). Using this apparatus, a discontinuous electrophoretic velocity was imposed upon the proteins being concentrated, opposing their convective movement toward the CUF membrane. This resulted in a lower concentration of rejected solute protein in the fluid boundary layer adjacent to the high-pressure side of the membrane and, hence, in a lower solute-related filtration resistance than in the case of conventional ultrafiltration (zero electric field). Studies of the PEF-UF process with bovine serum albumin (BSA) in the range of 0.5–5% w/v demonstrated a 25–40% decrease in the solute-related resistance to the permeate flux compared to the case of a zero electric field. Accordingly, higher permeate fluxes and, therefore, higher rates of concentration of the protein solution were obtained than for conventional crossflow ultrafiltration. When the electric field was reimposed following a period of operation under conventional CUF conditions, the permeate flux could be restored to nearly the same higher value observed initially for the PEF-UF process.

REVERSE OSMOSIS TRANSPORT and MODULE ANALYSIS FOR GREEN TEA JUICE CONCENTRATION

ABSTRACTReverse osmosis experiments were performed to concentrate the green tea juice, and the experimental data was analyzed by using a set of transport equations together with osmotic pressure and density data of the green tea juice. the transport parameters obtained numerically by the above analytical procedure were then used to calculate several dimensionless quantities that can characterize a reverse osmosis module. an example of module design calculation was attempted using the dimensionless parameters so obtained. It has been found that an increase in operating pressure reduces the module length significantly when the feed tea juice concentration is high. an increase of the mass transfer coefficient on the high pressure side of the membrane has the same effect.

地下空間での高圧ガスの解放による衡撃波の挙動の数値解析 支保柱がある場合の衡撃波の挙動

This paper is concerned with a numerical experiment on the effect of shock waves on a square pillar in an underground space, as encountered in an explosion of high-pressure gas in a mining shaft or tunnel. A duct with a uniform sectional area is initially divided into two parts by a diaphragm, on the closed end side of which ther e is high-pressure stagnant gas, and on the open end side of which there is low-pressure stagnant gas. A square pillar stands as a support at the width center in the duct.In such a situation the numerical experiment has been carried out, and various phenomena have been analysed as follows: As soon as the diaphragm is broken, a strong travelling shock wave propagates into the low-pressure gas region and then interacts with the pillar. Instantaneously the shock wave is separated into the wave reflected from the frontal pillar wall and the ones passing through the both sides of pillar. The former repeats the reflection on the closed end side and frontal pillar one, and weakens and disappears some time later. The latter two waves coalesce with each other downstream from the pillar, and then the wave with triple crossing point is formed, but goes away out of the duct.In addition, it has been demonstrated that the force acting on the pillar reaches the peak state when the first shock wave from the high pressure side comes to the frontal pillar side and the reflected shock wave is formed. The force drops down a little and increases instantaneously by interaction between the reflected shock wave and the contact surface. Thereafter, the force continues to decrease by the strong flow around the pillar as well as the expansion wave, and disappears in a short time.