Evaluation of natural gas dehydration in supersonic swirling separators applying the Discrete Particle Method

The natural gas flow fields and particles separation characteristics were numerically calculated with the RNG k ? ε turbulence model and Discrete Particle Method (DPM) in the supersonic swirling separator. An experimental system was set up for testing the separation efficiency of three new designed separators with wet air. The numerical results showed that the new annular nozzle not only expanded the natural gas to supersonic velocity with resulting in low temperature (?72 °C), but also strengthened the swirling flow with the centrifugal field of 640 000g (g is the acceleration of gravity), both of which created good conditions for natural gas dehydration. Under the strong swirling flow field, most particles collided with the walls or entered into the liquid-collection space directly, while only few particles escaped together with the gas flow. The separation efficiency reached over 95%, when the length of the cyclone separation section was about 10 times of the diameter of the wall at throat. The experimental results indicated that the water can be efficiently removed from the wet air. The numerical results were in good agreements with the experimental findings, which demonstrated that the Discrete Particle Method (DPM) was accurate and stable enough to evaluate the dehydration characteristics of the supersonic swirling separator.     

Acoustic emission waveform characterization of crack origin and mode in fractured and ASR damaged concrete

Different constituents of concrete can have cracking behavior that varies in terms of the acoustic waveform that is generated. Understanding the waveform may provide insight into the source and behavior of a crack that occurs in a cementitious composite. In this study, passive acoustic emission (AE) was used to investigate the waveform properties of the individual components of concrete (i.e., aggregate, paste, and interfacial transition zone (ITZ)). First, acoustic events produced by cracks generated using mechanical loading in a wedge splitting test were detected. It was observed that cracks that occurred through the aggregate have an AE frequency range between 300 kHz and 400 kHz, while cracks that propagated through the matrix (paste and ITZ) have a frequency range between 100 kHz and 300 kHz. Second, tests were performed using samples that were susceptible to alkali silica reaction; and AE and X-ray computed tomography were used to detect cracking. AE events with a frequency range between 300 kHz and 400 kHz were detected at early ages, suggesting the initiation of cracks within reactive aggregate. At later ages, AE events were detected with frequency ranges of 100–300 kHz, indicating crack development and propagation in the matrix.     

Development of porous plug phase separator and superfluid film flow suppression system for the Soft X-ray Spectrometer onboard ASTRO-H

ASTRO-H is the sixth Japanese astronomy satellite scheduled for launch in 2014. The Soft X-ray Spectrometer instrument is onboard ASTRO-H. This is a 6 × 6 array of X-ray microcalorimeters with an energy resolution of <7 eV at 0.5–10 keV. Superfluid liquid helium is utilized as a part of the cooling system. To retain the liquid helium in the tank under zero-gravity, a porous plug phase separator made of sintered stainless is used. Since the vapor mass flow rate is only 29 μg/s, any additional superfluid film loss influences the lifetime of the liquid helium. Therefore, a film flow suppression system consisting of an orifice, a heat exchanger, and knife edge devices is adopted based on the design used for the X-ray Spectrometer onboard Suzaku. The film flow will be suppressed to <2 μg/s, sufficiently smaller than the vapor flow rate. In the present investigation, the design and ground experiments of a helium vent system composed of the porous plug and film flow suppression system are presented. The results show that the phase separation and the film flow suppression are satisfactorily achieved.     

Poly(methyl methacrylate) monolayers at the air–water interface

Several poly(methyl methacrylate) (PMMA) molecules with various chain numbers has been synthesised using Emulsifier-free emulsion polymerisation method. Langmuir–Blodgett thin film technique is an excellent method to investigate the surface behaviours of organic monolayers at the air–water interface. In this study, PMMA molecules have been studied at the air–water interface using Langmuir–Blodgett thin film method. Area per molecule for several PMMA molecules is found to be between 0.29 ± 0.01 and 0.98 ± 0.01 nm². The surface pressure–area graphs were taken in two stages i.e. during the first compression of the monolayer and also during the second compression of the same monolayer before the collapsed stage of the monolayer. It is also found that first surface pressure–area graph for the first compressing of the monolayer at the water surface is different than the surface pressure–area graph obtained after a decompression of the monolayer. Isotherm graphs show that long alkyl chain groups of these molecules may cause aggregation behaviours on water surface and a model for the behaviour of PMMA molecules on the air–water interface due to surface interactions has been proposed.     

CFD study on Taconis thermoacoustic oscillation with cryogenic hydrogen as working gas

Taconis oscillation is a kind of typical self-excited thermoacoustic oscillation, the study of which is of great significance to reveal the thermoacoustic conversion effect and find ways to suppress self-excited oscillation in cryogenic systems. Based on computational fluid dynamics (CFD) method, the onset process of Taconis oscillation with low temperature hydrogen at atmospheric pressure as working gas is first simulated. It is shown that a standing-wave acoustic field operating at 91 Hz starts spontaneously and finally develops to a saturation state in the Taconis tube with length and inner diameter of 1 m and 0.01 m respectively. Parametric variations in both axial and radial directions of thermoacoustic field are then studied in detail. By combining the computational results with Rott’s theory, the spatial distributions of viscous dissipation, thermal relaxation dissipation, and source/sink terms of Taconis thermoacoustic oscillation are obtained quantitatively. The dissipation and source terms are found to be mainly brought forth by the traveling-wave and standing-wave components of the acoustic field, respectively.     

First-principles investigations on structural,elastic and electronic properties of SnO2 under pressure

We investigate the structural, elastic, and electronic properties of rutile-type SnO₂ by plane-wave pseudopotential density functional theory method. The lattice constants, bulk modulus and its pressure derivative are all calculated. These properties at equilibrium phase are well consistent with the available experimental and theoretical data. Especially, we study the pressure dependence of elastic properties such as the elastic constants, elastic anisotropy, aggregate acoustic velocities and elastic Debye temperature Θ. It is concluded that this structure becomes more ductile with increasing pressure up to 28 GPa. Moreover, our compressional and shear wave velocities V_P = 7.02 km/s and V_S = 3.84 km/s, as well as elastic Debye temperature Θ = 563 K at 0 GPa compare favorably with the experimental values. The pressure dependences of band structures, energy gap and density of states are also investigated.     

Thermal resistance of indium coated sapphire–copper contacts below 0.1 K

High thermal resistances exist at ultra-low temperatures for solid–solid interfaces. This is especially true for pressed metal–sapphire joints, where the heat is transferred by phonons only. For such pressed joints it is difficult to achieve good physical, i.e. thermal contacts due to surface irregularities in the microscopic or larger scale. Applying ductile indium as an intermediate layer reduces the thermal resistance of such contacts. This could be proven by measurements of several researchers. However, the majority of the measurements were performed at temperatures higher than 1 K. Consequently, it is difficult to predict the thermal resistance of pressed metal–sapphire joints at temperatures below 1 K.In this paper the thermal resistances across four different copper–sapphire–copper sandwiches are presented in a temperature range between 30 mK and 100 mK. The investigated sandwiches feature either rough or polished sapphire discs (Ø 20 mm × 1.5 mm) to investigate the phonon scattering at the boundaries. All sandwiches apply indium foils as intermediate layers on both sides of the sapphire. Additionally to the indium foils, thin indium films are vapour deposited onto both sides of one rough and one polished sapphire in order to improve the contact to the sapphire.Significantly different thermal resistances have been found amongst the investigated sandwiches. The lowest total thermal resistivity (roughly 26 cm² K⁴/W at 30 mK helium temperature) is achieved across a sandwich consisting of a polished sapphire with indium vapour deposition. The thermal boundary resistance between indium and sapphire is estimated from the total thermal resistivity by assuming the scattering at only one boundary, which is the warm sapphire boundary where phonons impinge, and taking the scattering in the sapphire bulk into account. The so derived thermal boundary resistance agrees at low temperatures very well with the acoustic mismatch theory.     

Continuous float–sink density separation of lump iron ore using a dry sand fluidized bed dense medium

A continuous separator based on float–sink density separation using a gas–solid fluidized bed dense medium was used to upgrade iron ore. The separator has three devices for (A) conveying floaters, (B) recovering floaters, and (C) conveying and recovering sinkers. The optimum speeds of these devices were investigated using density adjusted spheres of the diameter = 30 mm in the range of 2400–3300 kg/m³ in density increments of 100 kg/m³. A mixture of zircon sand and iron powder was used as the fluidized medium to adjust the fluidized bed density to produce a separation density = 2850 kg/m³, a typical separation density for lump iron ore wet separation. The recovery of the spheres as floaters or sinkers depended on the speed of the devices, because the recovery was affected by the number density of spheres directly under the feeder, the local fluidized bed density, and flow currents in the medium derived from the movement of the devices. The optimum speeds were determined to be 3.5 cm/s for (A), 2.0 rpm for (B) and 1.0 cm/s for (C), respectively. Continuous separation experiments were conducted on lump iron ore particles in the size range of +11.1–31.5 mm in the fluidized bed with medium density of 2850 kg/m³ and feed rate of 200 kg/h. Comparison of the feed rate and the recovery rate indicated that the feed and the recovery were in equilibrium after 10 min of operation. The experiments resulted in nearly perfect separation; 98.4% of the ore with density greater than 2850 kg/m³ was recovered. The Fe, Al and Si content of the feed ore particles (before the separation) and the floaters and sinkers (after the separation) was measured using inductively coupled plasma spectrometry. The separator produced an upgrade in iron content of 3.3 wt% and reduced the Al and Si content by 44%.     

Pressure drop correlation for oil–refrigerant R134a mixture flashing flow in a small diameter tube

This paper presents an experimental investigation of the ester oil ISO VG10/refrigerant R134a mixture flashing flow in a 6.0 m long, 3.22 mm ID tube, which is one of the primary steps towards the construction of a methodology for the study of the lubrication and gas leakage in refrigeration compressors. The phase change starts with solubility reduction of the refrigerant in the oil as the pressure decreases due to the friction forces. In this flashing flow the foam pattern is observed at the end of the tube as vapor quality reaches high values, and this is a particular phenomenon of this kind of mixture flow. In order to study this pressure drop, an experimental apparatus was designed to allow the measurement of both pressure and temperature profiles along the tube as well as the visualization of the flow patterns. Pressure and temperature distribution along the flow were measured for saturation pressure ranging from 450 to 650 kPa, mass flux ranging from about 2000 to 3000 kg/(m²s), temperatures around 303 K, and inlet refrigerant concentration varying between 0.2 and 0.4 kg ref/kg mixt. An available correlation proposed to predict the frictional pressure drop for a mixture composed by the mineral oil SUNISO 1GS and refrigerant R12 flowing in small diameter tubes yielded large deviations in predicting the ester oil and refrigerant R134a mixture flow. A new correlation has been proposed that fitted the experimental data with rms deviations of 24%.     

Optimization and characterization of direct coating for ibuprofen particles using a composite fluidized bed

Ibuprofen particles (mean particle size, 27 μm and melting point, 76 °C) as core materials were directly coated with a water-soluble polymer. The primary particles were preserved using a composite fluidized bed with a dispersing mechanism at the bottom of the fluidized bed apparatus. Coated primary particles were obtained under the following 3 conditions: (1) Setting the spray air flow rate at 10 L/min from the initial to 2% coating, (2) adding the low-viscosity water-soluble polymer macrogol 6000 to the hypromellose coating solution, and (3) changing the spray air flow rate to 15 L/min from 2% coating. The particles obtained were confirmed to be coated primary particles by scanning electron microscopy of their cross sections prepared by the cryo-focused ion beam method. The dissolution test showed a marked improvement in the solubility of ibuprofen from the coated primary particles compared with that of a physical mixture. In conclusion, the optimization of the direct coating process made it possible to undertake primary particle coating of a raw material that has a low melting point and a particle size of not more than 50 μm. Primary particle coating contributes to improvements in the physicochemical properties of drugs.     

Preparation of novel carbon microfiber/carbon nanofiber-dispersed polyvinyl alcohol-based nanocomposite material for lithium-ion electrolyte battery separator

A novel nanocomposite polyvinyl alcohol precursor-based material dispersed with the web of carbon microfibers and carbon nanofibers is developed as lithium (Li)-ion electrolyte battery separator. The primary synthesis steps of the separator material consist of esterification of polyvinyl acetate to produce polyvinyl alcohol gel, ball-milling of the surfactant dispersed carbon micro-nanofibers, mixing of the milled micron size (~ 500 nm) fibers to the reactant mixture at the incipience of the polyvinyl alcohol gel formation, and the mixing of hydrophobic reagents along with polyethylene glycol as a plasticizer, to produce a thin film of ~ 25 μm. The produced film, uniformly dispersed with carbon micro-nanofibers, has dramatically improved performance as a battery separator, with the ion conductivity of the electrolytes (LiPF₆) saturated film measured as 0.119 S-cm^? 1, approximately two orders of magnitude higher than that of polyvinyl alcohol. The other primary characteristics of the produced film, such as tensile strength, contact angle, and thermal stability, are also found to be superior to the materials made of other precursors, including polypropylene and polyethylene, discussed in the literature. The method of producing the films in this study is novel, simple, environmentally benign, and economically viable.     

EDU liquid acquisition device outflow tests in liquid hydrogen: Experiments and analytical modeling

This paper presents experiments and modeling of the most recent set of liquid acquisition device (LAD) vertical outflow tests conducted in liquid hydrogen. The Engineering Development Unit (EDU) was a relatively large tank (4.25 m³) used to mimic a storage tank for a cryogenic storage and transfer flight demonstration test. Six 1-g propellant tank outflow tests were conducted with a standard 325 × 2300 rectangular cross-section curved LAD channel conformal to the tank walls over a range of tank pressure (158–221 kPa), ullage temperature (22–39 K), and mass flow rate (0.0103–0.0187 kg/s) per arm. An analytical LAD channel solver, an exact solution to the Navier-Stokes equations, is used to model propellant outflow for the LAD channel. Results shows that the breakdown height of the LAD is dominated by liquid and ullage gas temperatures, with a secondary effect of flow rate. The best performance is always obtained by exposing the channel to cold pressurant gas and low flow rates, consistent with the cryogenic bubble point model. The model tracks the trends in the data and shows that the contribution of flow-through-screen pressure drop is minimized for bottom outflow in 1-g, versus the standard inverted outflow.     

Pressure drop and heat transfer during two-phase flow vaporization of propane in horizontal smooth minichannels

This study examined the two-phase flow boiling pressure drop and heat transfer for propane, as a long term alternative refrigerant, in horizontal minichannels. The pressure drop and local heat transfer coefficients were obtained for heat fluxes ranging from 5–20 kW m^?2, mass fluxes ranging from 50–400 kg m^?2 s^?1, saturation temperatures of 10, 5 and 0 °C, and quality up to 1.0. The test section was made of stainless steel tubes with inner diameters of 1.5 mm and 3.0 mm, and lengths of 1000 mm and 2000 mm, respectively. The present study showed the effect of mass flux, heat flux, inner tube diameter and saturation temperature on pressure drop and heat transfer coefficient. The experimental results were compared against several existing pressure drop and heat transfer coefficient prediction methods. Because the study on evaporation with propane in minichannels was limited, new correlations of pressure drop and boiling heat transfer coefficient were developed in this present study.     

Evolution of the microstructure and nanohardness of Ti–48 at.%Al alloy solidified under high pressure

In this work the microstructure and nanohardness of Ti–48 at.%Al alloy solidified under different pressures (normal pressure, 2 GPa, 4 GPa) were experimental investigated by using a tungsten-carbide six-anvil apparatus. The results indicate that high pressure does not change the phase constitution of Ti–48 at.%Al alloy. However, the microstructure changes under high pressure. With increasing pressure, the volume fraction of interdendritic γ (γ_s) phase decreases and Al concentration in lamellae increases. When the pressure is 4 GPa, there is only a little γ_s embedded in lamellar structure. The volume fraction of γ_s phase is approximately 17.0% for normal pressure, 8.73% for 2 GPa, 0.69% for 4 GPa. The lamellar spacings also decrease with pressure, which are 495 nm, 345 nm, 227 nm under normal pressure, 2 GPa, 4 GPa, respectively. The change in nanohardness was discussed based on the microstructural observations. It shows a certain increase of the nanohardness as the pressure increases from normal pressure to 4 GPa. When the pressure is 4 GPa, the nanohardness increases by 50.2% compared with that of normal pressure.     

Numerical investigation on a 300 Hz pulse tube cryocooler driven by a three-stage traveling-wave thermoacoustic heat engine

A 300 Hz pulse tube cryocooler (PTC) driven by a three-stage traveling-wave thermoacoustic heat engine (TSTHE) has been proposed and studied in this paper. In the configuration, three identical thermoacoustic heat engine units are evenly incorporated in a closed traveling-wave loop, in which three pulse tube cryocoolers are connected to the branch of each thermoacoustic heat engine. Compared with the conventional thermoacoustic heat engine which involves a traveling-wave loop and a long resonator, it has advantages of compact size and potentially high thermal efficiency. A TSTHE–PTC system was designed, optimized and studied in detail based on the thermoacoustic theory. Firstly, numerical simulation was conducted to design the system thus the optimum structure parameters of the system were obtained. With the operating condition of 4 MPa mean pressure and high working frequency, a cooling power of 7.75 W at 77 K and an overall relative Carnot efficiency of 11.78% were achieved. In order to better understand the energy conversion characteristics of the system, distributions of key parameters such as acoustic work, phase difference, dynamic pressure, volume flow rate and exergy loss were presented and discussed. Then, the coupling mechanism of the system was investigated. In addition, influence of coupling position on the system performance was further studied.     

Bi1.5Y0.3Sm0.2O3–La0.8Sr0.2MnO3 − δ dual-phase composite hollow fiber membrane for oxygen separation

Dense Bi_1.5Y_0.3Sm_0.2O₃–La_0.8Sr_0.2MnO_3 ? δ hollow fiber membrane was fabricated by the combined phase inversion/sintering technique. The hollow fiber possessed an asymmetric structure. The oxygen permeability of the hollow fiber was measured by exposing its shell side to ambient air and sweeping the core side with helium to carry away the permeated oxygen. An oxygen permeation flux 3.9 × 10^? 7 mol cm^? 2 s^? 1 was obtained at 850 °C under a gradient of air/helium. The oxygen permeation flux was related to the helium sweeping rate, the length of the hollow fiber and the oxygen partial pressure on the feed side, and can be further increased by modifying the membrane surfaces.     

Relating damage evolution of concrete cooled to cryogenic temperatures to permeability

Typically, 9% Ni steel is used for primary containment of liquefied natural gas (LNG). Utilization of concrete in place of 9% Ni steel for primary containment would lead to significant cost savings. Hence, this study investigates changes in the microstructure of concrete due to cryogenic freezing that would affect its relevant engineering properties for containment. The study also evaluates the effect of aggregate type on the damage potential of concrete subjected to cryogenic freezing. The aim is to investigate design methodologies to produce damage-resistant cryogenic concrete. The study employed four concrete mixture designs involving river sand as fine aggregate, and coarse aggregates with different coefficient of thermal expansion (CTE) values. Specifically, the coarse aggregates were limestone, sandstone, trap rock and lightweight aggregate. Concrete cubes were cured under water for at least 28 days and thereafter frozen from ambient (20 °C) to cryogenic temperature (−165 °C). Acoustic emission (AE) sensors were placed on the concrete cubes during freezing. X-ray computed tomography (XRCT) was employed to study the microstructure of concrete cores, before and after cryogenic freezing. The impact of the microstructural evolution thus obtained from AE and XRCT on relevant engineering properties was determined via water and chloride permeability tests. Microcrack propagation determined from AE correlated with changes in permeability. There were no observable cracks in majority of the concrete mixtures after freezing. This implies that microcracks detected via AE and increased permeability was very well distributed and smaller than the XRCT’s resolution. Damage (microcracking) resistance of the concrete with different aggregates was in the order limestone ⩾ trap rock ≫ lightweight aggregate ⩾ sandstone.     

Effect of twisted tape insert on heat transfer and pressure drop in horizontal evaporators for the flow of R-134a

An experimental study has been carried out on the heat transfer enhancement and pressure drop characteristics in presence of twisted tape inserts, during flow boiling of R-134a, inside a horizontal evaporator. The test-evaporator was an electrically heated 1260 mm long copper tube with 7.5 mm inside diameter. The experiments were performed for plain flow and four tubes with twisted tapes of 6, 9, 12 and 15 twist ratios and four refrigerant mass velocities of 54, 85, 114 and 136 kg/s m² for each tape. It has been found that the twisted tape inserts enhance the heat transfer coefficient on relatively higher pressure drop penalty, in comparison to that for the plain flow.     

Cryogenic design and test results of 30-m flexible hybrid energy transfer line with liquid hydrogen and superconducting MgB2 cable

In this paper we present the development of a new hybrid energy transfer line with 30 m length. The line is essentially a flexible 30 m hydrogen cryostat that has three sections with different types of thermal insulation in each section: simple vacuum superinsulation, vacuum superinsulation with liquid nitrogen precooling and active evaporating cryostatting (AEC) system. We performed thermo-hydraulic tests of the cryostat to compare three thermo-insulating methods. The tests were made at temperatures from 20 to 26 K, hydrogen flow from 70 to 450 g/s and pressure from 0.25 to 0.5 MPa. It was found that AEC thermal insulation was the most effective in reducing heat transfer from room temperature to liquid hydrogen in ∼10 m section of the cryostat, indicating that it can be used for long superconducting power cables. High voltage current leads were developed as well. The current leads and superconducting MgB₂ cable passed high voltage DC test up to 50 kV DC. Critical current of the cable at ∼21 K was 3500 A. It means that the 30 m hybrid energy system developed is able to deliver ∼50–60 MW of chemical power and ∼50–75 MW of electrical power, i.e. up to ∼135 MW in total.     

Decrease of Cl contents in waste plastics using a gas–solid fluidized bed separator

In order to decrease Cl content in waste plastics, dry density float-sink separation of Cl-contained and Cl-free plastics was explored using a semi-continuous rotating-type gas–solid fluidized bed separator with silica sand. The separator has two distinctive features: (1) the plastics can be fed at a middle height of the sand bed, and (2) when the plastics are recovered with the sand from a container after the float-sink, the recovery height of the sand bed can be changed to designate the plastics as floaters or sinkers. The waste plastics of Cl content = 5.4 wt% were used in this study. The separation was investigated by changing the experimental conditions. As a result, the float-sink of the plastics was affected by the air velocity for fluidization, the float-sink time and the feed amount of plastics. The possible causes of the effects were discussed by focusing on the apparent density of fluidized bed, the fluidization intensity, the size segregation of fluidized particle, the shape of the plastics, and the interactions between the plastics during the float-sink. When the recovery height was changed at the adjusted conditions, the Cl content in the floaters was successfully decreased to be 0.4–0.85 wt%, at which the recovery of the Cl-free plastics was 40–60%.