High Pressure Side Research Articles

Mass transport mechanism on the high-pressure side in reverse osmosis: an analysis

The mass transfer coefficient in use so far, for the solute transport on the high-pressure side in reverse osmosis, is for the black-flow due to concentration polarisation from the wall (membrane interface) towards the center of the high-pressure channel. The correlations for it are borrowed from studies with non-porous ducts. However, the real net solute transport in reverse osmosis is in the same direction as permeation. A simple rate equation for this real solute transport has been derived, based on a new concept of mass transfer coefficient. It can be combined with rate equations for transport through the membrane to' yield overall mass transfer coefficients for reverse osmosis. Correlations for the new mass transfer coefficient based on dimensionless numbers have been theoretically derived and verified against experimental data. It has also been illustrated how, with this new concept, permeate salinity and flux can be computed in a simple and straightforward manner.

Measuring the ratio of aqueous diffusion coefficients between 6Li +Cl − and 7Li +Cr − by osmometry

Osmotic equilibrium is a singular occurrence in the evolution of an osmotic cell because at this event the net solution flux is zero such that −J w · V ̄ w = J s · V ̄ s . At this juncture, the diffusion coefficient of the solute through the membrane (ω) equals the solute flux ( J s ) divided by the osmotic pressure (ΔΠ). Because the solute permeability coefficient (ω) is related to the Fickian diffusion coefficient ( D) through the gas constant, temperature, and the membrane's thickness and tortuosity, the ratio of ω values for individual isotopic species equals the ratio of D values for the same isotopic components. A 0.9450 molal LiCl solution was placed within sealed dialysis tubing and osmoted against a kilogram of deionized water at 22°C. Osmotic equilibrium occurred at 164 ± 10 min. The ratio of ω6Li +Cl − ω7Li +Cl − was measured to be 1.011 ± 0.003—a value close to the square root of the mass ratio between 7LiCl and 6LiCl (= 1.012) as calculated by Graham's Law. The measured diffusion coefficient ratio was used to predict the degree of hyperfiltration-induced fractionation of Li isotopes as a function of membrane ideality. When a membrane's σ exceeds 0.95 (as is likely for low-porosity shales) the 6Li 7Li ratio on the high-pressure side of the membrane can theoretically vary by more than 0.0017.

Soft x-ray transmission of thin film diamond: Applications to detectors and high pressure gas cells

Thin film diamond windows are emerging as a high technology answer for a variety of soft x-ray window applications for detectors and high pressure gas cells. This innovation provides a soft x-ray window with no measurable diffusion of gas between the high pressure (≳1 atm) and vacuum sides of the thin film diamond. Applications are discussed for soft x-ray fluorescence detectors as well as a high pressure in situ catalytic reactor for soft x-ray materials characterization at a synchrotron radiation source. We have measured the soft x-ray absolute transmission function of a thin film (0.3 to 0.5 μm) diamond window for the energy range between 275 and 750 eV using a gold photodiode at the National Synchrotron Light Source. The photodiode will be illustrated and the quantitative measurement technique fully outlined. X-ray transmission is found to be superior to other window technologies such as polymers or thin film beryllium and because of the inate high strength and thermal conductivity of diamond it has become the material of choice.

Theoretical and experimental analysis of diffusion and polarization phenomena in sugar solutions in spiral-wound modules

Reverse osmosis experiments have been carried out in a pilot plant equipped with a commercial high rejection spiral-wound module for glucose-water and sucrose-water systems at different feed concentrations in the range 0–14% and 0–25%, respectively, at pressures between 0 and 60 atm and at a temperature of 30°C. Rejections higher than 99% and fluxes of 30–40 l/m 2 h have been obtained at operating conditions of industrial interest. The data collected have been used to derive the characteristic parameters of the membrane and module, with special emphasis on polarization on the high pressure side and on diffusion through the membrane. Comparison of theoretical calculations with the experimental data indicates that a single set of parameters can be used over the whole range of concentrations and pressures for the two systems.

反応性スパッタリングによるＰｂ‐Ｏ，Ｌａ‐Ｏ，Ｚｒ‐Ｏ，Ｔｉ‐Ｏ薄膜の作成

Pb-O, La-O, Zr-O, Ti-O thin films were prepared by reactive rf-magnetron sputtering of metallic Pb, La, Zr and Ti target in an atmosphere of mixed gas of argon and oxygen. The deposition rate, crystal structure and optical properties of sputtered films were studied as a function of the partial pressure of oxygen (Po2). Total pressure was controlled to maintain a constant value of I Pa. The deposition rate of the films decreased remarkably when the partial pressure of oxygen exceeded a certain value. Generally, with the increase of the input power, the critical Po2 shifted to high pressure side. When films were deposited in higher Po2 than the critical, oxide thin films were prepared. From the measurement of optical emission spectra during sputtering, the formation of oxide on the surface of target was confirmed, resulting in the decrease of the deposition rate.

Demixing of (Ni, Co)O Under an Oxygen Potential Gradient Using a YSZ‐Based Galvanic Cell

Diffusion in a multicomponent system with different diffusivities of the constituent components leads to demixing, which can be a source of material deterioration. A new experimental technique has been investigated to study demixing in oxides under an oxygen potential gradient. The oxygen potential gradient across initially homogeneous polycrystalline (Ni, Co)O was established by applying an electric potential across a yttria‐stabilized‐zirconia (YSZ) tablet in the galvanic cell: Air/Pt/YSZ/Pt/(Ni, Co)O/Air. A low oxygen partial pressure was established at the left side of (Ni, Co)O, while the right side was exposed to flowing air (0.21 atm ). Steady‐state demixing profiles were observed after annealing for 10 days. Discrepancies were sometimes noticed between runs because of possible leakage problems. Growth of the sample toward the high oxygen pressure side was observed, and was used to estimate the steady‐state velocity. An attempt is made to show how demixing experiments combined with atomistic calculations can be used as a possible means to estimate the microscopic properties of materials.

Hydraulic free piston internal combustion engine. Theoretical investigation of the opposed piston type.

Depending on the previously reported experimental results of the free piston internal combustion engine of opposed piston type, a mathematical model, which describes the behavior of a free piston, is derived and numerically calculated in this paper. In the first part of this paper, the design method to determine the cross-sectional areas of the hydraulic piston and piston rod is discussed. In the latter part of this paper, control methods of the gas compression ratio and the free piston position at the end of the cycle are discussed. Even if the friction loss changes during the operation of the free piston engine, it is possible to maintain a fixed value of the compression ratio by changing the hydraulic pressure at the high-pressure side. The free piston position at the end of the cycle can be controlled by the hydraulic pressure at the low-pressure side. Its controllable range, however, is relatively narrow.

Cardiovascular and arginine vasopressin (AVP) responses to haemorrhage and nitroprusside infusion in conscious newborn calves

The effects of normotensive and hypotensive hypovolaemia (haemorrhage) as well as isovolaemic hypotension (nitroprusside administration) on diastolic, systolic and mean arterial blood pressure, heart rate and plasma concentrations of arginine vasopressin were studied in two sets of experiments on 8-10 days old conscious newborn calves bearing an indwelling aortic catheter for continuous recording of arterial blood pressure. Removal of 20% of the estimated blood volume resulted in an average maximum decrease of systolic, diastolic and mean arterial blood pressure from 132 +/- 2 to 118 +/- 8 mm Hg (P less than 0.05), from 72 +/- 2 to 67 +/- 2 mmHg (P less than 0.05) and from 92 +/- 3 to 82 +/- 6 mmHg (P less than 0.05) respectively. In the same time heart rate increased from 124 +/- 3 to 143 +/- 5 beats.min-1. Plasma concentrations of arginine vasopressin increased before blood loss had induced any change in arterial blood pressure (from 5.7 +/- 0.7 pg/ml-1 at time 0 to 25.2 +/- 3 pg/ml-1 at time 20 min; P less than 0.01). The significant fall in blood pressure was accompanied by a further prompt increase in plasma concentration of arginine vasopressin which reached maximum values (90.1 +/- 9.7 pg/ml-1) at completion of haemorrhage. The conscious newborn calf responded to i.v. nitroprusside infusion (10 micrograms/kg-1/min-1 for 10 min) with a prompt fall in diastolic (-71%, P less than 0.01), systolic (-70%, P less than 0.01) and mean (-56%, P less than 0.01) arterial blood pressure within 3 min of the infusion. Time course changes in heart rate were opposite to those in arterial blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Development of ceramic turbomolecular pumps for fusion devices

In order to establish a transfer pumping system which is suitable for a fusion magnetic/nuclear environment, new turbomolecular pumps have been developed. The rotor assembly of the pumps is composed of ceramic (Si 3N 4) disks for gas compression, a ceramic shaft with turbine blades and a ceramic thrust disk. The rotor assembly is supported by gas bearings and is driven by an impulse gas turbine. A non-contact spiral-groove seal isolates the vacuum side from the high pressure side. After preliminary experiments with an 80 l/s ceramic turbomolecular pump, a medium-size ceramic pump was designed, manufactured and tested in 1988. The main specifications and a few of the vacuum characteristics of the pumps are given.

Pumping of condensable vapours and exhaust vapour condensation

The use of chemically resistant oil-free diaphragm pumps to pump condensable vapours allows the recovery of these vapours on the high pressure side. Due to their limited ultimate pressure they mainly replace water jet pumps and thus drastically reduce water consumption and pollution. In addition they raise the efficiency of evaporators and, as a consequence, diminish the pollution of air. The combination of this type of diaphragm pump with an oil-sealed rotary vane pump (“HYBRID” pump) combines the advantages of both pumps, i.e. low ultimate pressure and high resistivity to chemicals. Thermodynamic considerations lead to this set-up, in which the dry pump evacuates the oil reservoir of the rotary vane pump and thus the oil is permanently distilled. Due to the elevated temperatures of the oil (50–70°C) and the reduced pressure (≈ 50 mbar) condensation is avoided or significantly reduced, thus enhancing oil lifetime and maintenance intervals.

Leak detection in a nitric acid plant using argon-41

In order to find out whether either of two heat exchangers in a nitric acid plant was leaking, the radioactive tracer 41Ar was injected at the inlet of the high pressure side of the exchangers and detectors were placed at the outlet of the low pressure side. In an attempt to eliminate radiation scattering effects and to lower the detection limit, a measuring procedure according to the two-detector method was followed. However, the detection limit was not lowered as much as expected. Virtually the same detection limit could be achieved using a single detector optimally shielded from scattered radiation with lead. The measuring procedure allowed the use of an internal calibration factor, which means that it was not necessary to know the exact amount of radioactivity injected.

Pressure fluctuations in the tip region of a blunt-tipped airfoil

The characteristics of turbulence generated in the tip region of a blunt-tipped airfoil were studied using surface pressure measurements. The model was a NACA 0012; tests were performed at flow speeds of 75, 55, and 35 m/s and angles of attack of 6, 12, and 16 deg. Reynolds numbers based on the wing chord were 1.9, 3.0, and 4.1 million. Pressure fluctuations measured near the primary tip-vortex on the upper, low pressure side of the wing tip were uncorrelated with those on the blunt tip. Fluctuations on the high pressure side of the wing were strongly correlated with those on the flat tip, but 10-20 dB less intense. Spectra measured on the flat tip displayed pronounced peaks at dimensionless frequencies of 0.8 to 1.3. Cross correlations between some of the flat-tip pressures displayed two echolike groupings. A model is proposed that explains these correlations.

Formation of a fluid film between a valve plate and a cylinder block of piston pumps and motors. 3rd report. Fluid film sluctuation and loss power.

As already pointed out, a valve plate with hydrostatic pads is able to form a fluid film between the valve plate and the cylinder block over a wide range of operating conditions. In this report, the fluctuation of the fluid film and the loss power on the sliding plane are analyzed, including both the change in the number of pistons on the high-pressure side and the trapping phenomenon. The parameters treated numerically are as follows: ratio of the hydrostatic-load-carrying capacity to the pushing force, shaft spring effect on the behavior of the cylinder block, number of pistons and the solid friction between the shaft and the cylinder block.

Kinetics of hydrofracturing and metamorphic veining

Veins in metamorphic rocks result from the interplay of two processes: deformation and mineral reactions. Two kinds of veins have been recognized: segregation and hydrofracturing. This paper examines quantitatively the conditions for hydrofracturing and associated vein formation due to devolatilization reactions. The inflection point of the reaction curve defines a boundary between the reaction-enhanced ductility regime (high-pressure side) and the hydrofracturing regime in a pressure-temperature diagram. Low strain rates and low permeability of rocks, together with the irreversible reaction, are important factors for hydrofracturing. Combination of reaction kinetics and percolation theory enables us to estimate the time required for macroscopic hydrofracturing. Model calculations are carried out at 1 kbar for the reaction serpentine + brucite = forsterite + water. It takes several tens of years for macroscopic hydrofracturing to develop. The result depends on rock texture (the lattice type in percolation theory) and superheating degrees; however, hydrofracturing will generally not exceed 200 yr.

Improved Procedures for Injecting Radioisotopes During Fracturing Operations

The injection of sand-entrained radioisotopes at the latest time before fracturing fluid enters the wellbore minimizes personnel exposure to radiation, contamination of surface equipment, and hazards of transporting radioactive material. This paper presents design and operational details of the devices used for wellhead injection of radioisotopes, transportation considerations, disposal of leftover radioactive sand, closed-loop control of injection, and a comparison of the injection plan with the actual injection.

Direct correlation between calcium content and blood pressure: a study of aortic coarctation in rats.

The calcium content of aorta was measured by atomic absorption after coarctation in the rat. At 7 and 14 days, the calcium content was elevated on the proximal side of the coarctation, where pressure was increased significantly. On the distal, low pressure side of the aortic coarctation, calcium was reduced significantly. There is a direct correlation between the blood pressure and the content of calcium (r = 0.69, P less than 0.001). The width of the aortic media on the high pressure side was increased significantly at 7 and 14 days after coarctation, whereas no significant changes in width were present on the low pressure side of the constriction. We conclude that pressure regulates the aortic calcium content, likely acting through a local effect.

A parametric study of recycle membrane separators

The performances of recycle membrane permeators with feed introduced to the high-pressure side (recycle stripper) and to the low-pressure side (enricher recycle) were compared by numerical simulation over a range of membrane area to feed flow rate ratios. The effect of permselectivity on the performance of the recycle permeator for either feed arrangement was also examined. The results showed that an enricher recycle always performed inferior to a recycle stripper both in terms of Rony's separation index and compressor requirements.

Tricritical point in the p-T phase diagram of Ag2HgI4

It is proven by differential scanning calorimetry that silver mercury iodide has a tricritical point at 0.474 GPa and 382 K. The phase transition is of second order on the low-pressure side, while both the transition enthalpy Δ H and the transition volume Δ V reduce gradually to nil when the tricritical point is approached from the high-pressure side. Furthermore, both Δ H and the inverse of the heat capacity anomaly, 1/Δ C p , are proportional to the pressure difference p-p cr and to the temperature difference T-T cr which is in accordance with a theory by Landau from 1935. It is essential for the existence of the tricritical point that the phase transition occurs between two disordered phases. The probability of tricritical points in other salts with a high ionic conductivity is discussed.

A Face Seal With Circumferential Pumping Grooves and Rayleigh-Steps

This paper presents an analysis of a new noncontacting pumping seal. A hydrodynamic lubricating film is maintained due to Rayleigh-steps. If the low pressure side of the seal is filled with a fluid, the fluid can be pumped into the high pressure side by pumping grooves until the shaft speed reaches a limit value. The experimental results confirm the theoretical predictions for lubrication and sealing performance. Due to the high pumping ability in addition to the high stiffness of its hydrodynamic film, the seal can operate without wear and leakage for a high pressure fluid.

Modeling reverse osmosis separations with strong solute‐membrane affinity at different temperatures using the finely porous model

AbstractThe reverse osmosis separation of toluene from water has been studied using an asymmetric cellulose acetate membrane at different temperatures, pressures, and feed concentrations. The finely porous transport model is used to describe the performance of the membrane as a function of the operating conditions. Based on experimental data, the transport parameters for the membrane are estimated. These parameters include the pore size of the membrane, the frictional parameter for the solute in the membrane pore, the relative porosity of the membrane surface, and the partition coefficients on the high and low pressure sides of the membrane. The influence of operating temperature on some of these parameters is presented and discussed. A modified form of the finely porous model which includes the effect of temperature is presented.