Large Gas Flow Research Articles

Mixing Effect and Energy Efficiency Analysis for Different Lances in Steel Converter Process

The mixing effect in steel converter process is very important to the fluid flow and mass transfer in bath and directly affects the chemical reaction and temperature homogeneity in the industry steel process. The cold model was employed to research the relationship of mixing time, agitation power, lance type, operation parameters, bath shape et al. According to the results, the mixing time of the bath decreases with larger gas flow rate and bigger diameter of the bath. Increasing the nozzle inclination properly is benefit for decreasing the mixing time and improving the agitation of the bath. The relationship of mixing time and lance height is complicated, because the mixing time is fluctuant by the lance rising. By introduce the relative energy utilization factor, the agitation power utilization was analyzed and compared under different conditions. The energy efficiency is higher with larger nozzle inclination as well as the bigger ratio of diameter and depth of the bath.

Effect of suspension plasma spraying process parameters on YSZ coating microstructure and permeability

Suspension plasma spraying (SPS) is a modification of plasma spray processes that uses small feedstock powders suspended in a liquid to rapidly produce fully sintered, thin ceramic coatings with good microstructural control and no need for post-deposition heat treatments. This technique has been proposed as a potential next generation manufacturing method to fabricate metal supported solid oxide fuel cells (SOFC). This study produced SPS YSZ layers and characterized the effect of torch power and particle velocity on coating physical properties that are relevant to SOFC electrolyte performance such as density and permeability. The highest density (> 95% dense), lowest permeability coatings were produced from conditions with large plasma gas flow rates and small nozzles; however, these conditions resulted in low deposition efficiency. Coatings produced from conditions with slightly lower plasma gas flow rates and small nozzles were also fairly dense (93% dense) and had fairly low permeabilities, but had 70% higher deposition efficiency compared to the densest coatings.

SMA Microvalves for Very Large Gas Flow Control Manufactured Using Wafer-Level Eutectic Bonding

This paper presents a novel gas microvalve design concept, in which a flow control gate is opened by a pneumatic pressure and closed by a shape memory alloy actuator, allowing large flow control. Two different design variations were fabricated using a novel wafer-level Au–Si eutectic bonding process for TiNi to silicon integration. The resulting microvalves demonstrate a record pneumatic performance per footprint area; a microvalve with a footprint of only <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$1 \times 3.3\ \hbox{mm}^{2}$</tex></formula> successfully controls a flow difference of 3100 sccm at a pressure drop of 70 kPa using a power of 0.35 W.

Wide field polarimetry around the Perseus cluster at 350 MHz

This paper investigates the fascinating diffuse polarization structures at 350 MHz that have previously been tentatively attributed to the Perseus cluster and, more specifically, tries to find out whether the structures are located at (or near) the Perseus cluster, or in the Milky Way. A wide field, eight point Westerbork Synthesis Radio Telescope mosaic of the area around the Perseus cluster was observed in full polarization. The frequency range was 324 to 378 MHz and the resolution of the polarization maps was 2'x3'. The maps were processed using Faraday rotation measure synthesis to counter bandwidth depolarization. The RM-cube covers Faraday depths of -384 to +381 rad m^{-2} in steps of 3 rad m^{-2}. There is emission all over the field at Faraday depths between -50 and +100 rad m^{-2}. All previously observed structures were detected. However, no compelling evidence was found supporting association of those structures with either the Perseus cluster or large scale structure formation gas flows in the Perseus-Pisces super cluster. On the contrary, one of the structures is clearly associated with a Galactic depolarization canal at 1.41 GHz. Another large structure in polarized intensity, as well as Faraday depth at a Faraday depth of +30 rad m^{-2}, coincides with a dark object in WHAM H-alpha maps at a kinematic distance of 0.5 \pm 0.5 kpc. All diffuse polarized emission at 350 MHz towards the Perseus cluster is most likely located within 1 kpc from the Sun. The layers that emit the polarized radiation are less than 40 pc/B|| thick.

Force-sensitive Sensor Based on Single-walled Carbon Nanotube Array

Traditional silicon micro-machining technology is utilized to produce parallel micro-electrodes on silicon chips,and silicon chips are deeply etched to wear a rectangular hole between the parallel micro-electrodes.Next,ultra-long single-walled carbon nanotube(SWCNT) array is grown across micro-electrodes and rectangular hole to suspend well aligned between the parallel micro-electrodes by the method of large gas flow directional chemical vapor deposition(CVD).The Si chip attached with SWCNTs is then mounted onto a thin PVC base and the connections of Si island are cut by laser technology,so that the force acting on the PVC base can directly transfer to SWCNT array.After extraction of wires,the fabrication of micro-nano-force-sensing unit is finished.Later,the research is carried out mainly on strain sensing of suspended SWCNT array.High gauge factor and linearity are obtained.The experimental results show that this sensor unit is simple and low in cost,thus providing a new way of thinking upon the preparation for micro-nano integrated sensor unit based on carbon nanotubes.

Effect of He/CF4 DBD Operating Parameters on PET Surface Modification

AbstractIn this paper, a dielectric barrier discharge (DBD) operated at (sub)atmospheric pressure in a 95/5% He/CF4 mixture is employed to increase the hydrophobicity of a poly(ethylene terephthalate) (PET) film. This paper studies the influence of different operating parameters on the hydrophobic properties of the PET film using contact angle measurements. Results clearly show that the hydrophobicity of the PET film is only enhanced when using large gas flows. Moreover, this work demonstrates that operating pressure and discharge power have a significant influence on the rate of plasma modification as well as on the uniformity of the plasma treatment. Also important to mention is that no ageing effect is observed. As a result, one can conclude that the utilized DBD is an efficient tool to create stable, hydrophobic PET surfaces.

Inhomogeneous nanocrystallization of Joule-heated amorphous Vitroperm alloy

Crystallization of Vitroperm® alloy has been realized by means of Joule heating. The influence of the gas flow around the sample during the heat treatment is dramatic and it produces an inhomogeneous crystallization. For large enough gas flow the temperature of the sample surroundings can be considered constant and a temperature gradient appears over the sample width, which means a gradient in size and concentration of Fe–Si and Fe–B nanocrystals. For adequate gas flow values the temperature of the sample edges is below the Fe–B crystallization value whereas the centre is above that value, showing therefore completely different magnetic behaviour.

Flue gas dehydration using polymer membranes

Coal-fired power plants produce electricity and in addition to that large volume flows of flue gas. To prevent condensation of the water vapor present in this flue gas stream, water has to be removed before emission to the atmosphere. The application of membrane technology for this separation is attractive due to the additional energy savings and the possible re-use of water. In the present work, we present such a membrane system with extremely high separation factors and fluxes for the removal of water vapor from flue gasses. Process simulations indicate the importance of a membrane material with very high water vapor permeabilities combined with very low inert gas fluxes. Two potential membrane materials for flue gas dehydration (PEBAX ® 1074, a block copolymer, and sulfonated poly(ether ether ketone) (SPEEK)) are compared and the results clearly show the superior performance of SPEEK. Composite hollow fiber membranes with a top layer of SPEEK were developed and built into fiber bundles. Twenty of such fiber bundles were placed in large gas flows of artificial and real flue gas. Short- and long-term testing of the membrane bundles revealed good mass transport properties and resistance against the flue gas conditions. This study not only demonstrates the technical viability of flue gas dehydration, but also suggests that polymer membranes may be a viable option in direct removal of CO 2 from flue gas.

Magnetic fields and the dynamics of spiral galaxies

We investigate the dynamics of magnetic fields in spiral galaxies by performing 3D MHD simulations of galactic discs subject to a spiral potential. Recent hydrodynamic simulations have demonstrated the formation of inter-arm spurs as well as spiral arm molecular clouds provided the ISM model includes a cold HI phase. We find that the main effect of adding a magnetic field to these calculations is to inhibit the formation of structure in the disc. However, provided a cold phase is included, spurs and spiral arm clumps are still present if $\beta \gtrsim 0.1$ in the cold gas. A caveat to two phase calculations though is that by assuming a uniform initial distribution, $\beta \gtrsim 10$ in the warm gas, emphasizing that models with more consistent initial conditions and thermodynamics are required. Our simulations with only warm gas do not show such structure, irrespective of the magnetic field strength. Furthermore, we find that the introduction of a cold HI phase naturally produces the observed degree of disorder in the magnetic field, which is again absent from simulations using only warm gas. Whilst the global magnetic field follows the large scale gas flow, the magnetic field also contains a substantial random component that is produced by the velocity dispersion induced in the cold gas during the passage through a spiral shock. Without any cold gas, the magnetic field in the warm phase remains relatively well ordered apart from becoming compressed in the spiral shocks. Our results provide a natural explanation for the observed high proportions of disordered magnetic field in spiral galaxies and we thus predict that the relative strengths of the random and ordered components of the magnetic field observed in spiral galaxies will depend on the dynamics of spiral shocks.

Deposition of DLC:H films by C-sputtering assisted CH4-Ar PE-CVD technique

Hydrogenated diamond-like carbon (DLC:H) films were deposited on Si substrates by a methane (CH 4 )-argon (Ar) plasma enhanced chemical vapor deposition (PE-CVD) technique assisted by carbon (C) sputtering. The deposition rates of DLC:H films increased with increasing Ar gas flow rate under a CH 4 gas flow rate, and saturated at large Ar gas flow rates. The dielectric constants varied from 2.2 e 0 on DLC:H films deposited without Ar gas flow to 6.3 e 0 on DLC:H films deposited with large Ar gas flow. The C – V curve for the sweep of bias voltages from positive to negative was positioned above that of the return sweep of bias voltages from negative to positive because electrons are injected from Si substrates to the surfaces of DLC:H films. The C – V curve on the returning bias voltage sweep approached that of the going bias voltage sweep accompanying to an increase in dielectric constant.

Experimental investigation of particle mixing behavior in a large spout–fluid bed

Experimental investigations on particle mixing in a larger spout–fluid bed with cross section of 1 m × 0.05 m and height of 4 m were carried out. The axial and radial distributions of tracer particle under different spouting gas velocities and fluidizing gas flow rates were measured. The particle mixing behaviors were studied according to the concentrations of tracer particles and flow patterns. Besides, the mechanism of particle mixing was preliminarily discussed. It is found that increase in spouting gas velocity and fluidizing gas flow rate can both promote the particle mixing in spout–fluid beds. Particle mixing in spout–fluid beds is due to three mechanisms: diffusion, transportation and circulation, and bubbles action. However, it changes significantly with increasing fluidizing gas flow rate and spouting gas velocity. Diffusion, transportation and circulation dominate the particle mixing at low fluidizing gas flow rates, while bubble actions dominant the particle mixing at large fluidizing gas flow rates. When increasing the spouting gas velocity, diffusion, transportation and circulation dominant the particle mixing.

Bubble Size Distribution near the Vessel Wall in a Gas Sparged Vessel Agitated by Pitched Blade Paddle Up-Pumping

For understanding of gas–liquid mixing characteristics in an aerated agitated vessel, knowledge of bubble size distribution is very important. In this work, bubble size distribution and interfacial area were investigated for making a comparison of a pitched blade paddle creating upward flow with the Rushton disc turbine and Scaba SRGT impeller, which are commonly recommended for gas–liquid mixing. The results indicated that the size of the bubble created by the up-pumping of the pitched blade paddle could be kept small and the enhanced interfacial area could be maintained constant until 22.2 vvm, while large bubbles increased and the interfacial area decreased with an increasing gas flow rate, 4.8–15.8 vvm, for DT and SRGT. The correlation of the Sauter mean diameter with the gas flow rate Qg was derived at large gas flow rates for three impellers.

Development of Catalyst and Gas Diffusing MEA Layers for PEFC using Taguchi's Method

Taguchi's method was applied to an MEA design, and identified the robust design conditions. The generic function was defined as the relationship between the fuel gas flow rate and the electric power. The four kinds of control factors for the catalyst layer formation and eight control factors for the geometrical and process parameters of gas diffusing layer (GDL) were selected to optimize the MEA design conditions. These parameters were allocated in the orthogonal arrays of L9 (for the catalyst layer) and L18 (for GDLs) based on the design of experiment (DOE). The robustness and performance were identified of MEA using the indexes called S/N ratio and sensitivity. The variability of the power operated at a large gas flow rate was diminished (within 20%), and the time required for optimum designing was also reduced.

Out-of-Plane Knife-Gate Microvalves for Controlling Large Gas Flows

This paper considers design issues for microvalves for large gas flow control. It introduces out-of-plane knife-gate microvalves as a novel design concept and a proportional microvalve concept for pressure control applications. The design of three different actuator-gate configurations and first prototypes are presented. The first valve prototypes feature thermal silicon-aluminum bimorph actuators and the pressure-flow performance per chip area of the demonstrator valve presented is greatly increased using out-of-plane actuation and an out-of-plane orifice. The characterization of the actuators and of the pressure-flow performance is presented. The prototype valve allows for a flow change of DeltaQ= 3.4 standard liters per minute (SLPM) at a pressure change of DeltaP= 95 kPa (P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in</sub> = 196.3 kPa, P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">out</sub> = 101.3 kPa) on an active chip area of only 2.3times3.7 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> 1515

Axial and Radial Investigation of Hydrodynamics in a Bubble Column; Influence of Fluids Flow Rates and Sparger Type

A detailed investigation of local hydrodynamics in a pilot plant bubble column has been performed using various techniques, exploring both axial and radial variations of the gas hold-up, bubble average diameter and frequency, surface area. A wide range of operating conditions has been explored up to large gas and liquid flow rates, with two sparger types. Two main complementary techniques were used: a quasi local measurement of gas hold-up via series of differential pressure sensors to get the axial variation and a double optic probe giving radial variations of gad hold-up, bubble average size and frequency and surface area.According to axial evolutions, three zones, where radial evolutions have been detailed, have been separated: at the bottom the gas injection zone, the large central region or column bulk and the disengagement zone at the column top. It was found that significant axial and radial variations of the two phase flow characteristics do exist even in the so called homogeneous regime. The normalized profiles of bubble frequency appear sparger and gas velocity independent contrary to bubble diameter, gas hold-up and interfacial area normalized profiles. In any case bubbles are larger in the sparger zone than elsewhere.The main result of this work is the very strong effect of liquid flow on bubble column hydrodynamics at low gas flow rate. First the flow regime map observed in batch mode is dramatically modified with a drastic reduction of the homogeneous regime region, up to a complete heterogeneous regime in the working conditions (uG&gt; 0.02 m/s). On the contrary, liquid flow has limited effects at very high gas flow rates.A large data bank is provided to be used for example in detailed comparison with CFD calculations.

Critical aspects of the determination of pentafluorobenzyl derivatives of aldehydes by gas chromatography with electron-capture or mass spectrometric detection: Validation of an optimized strategy for the determination of oxygen-related odor-active aldehydes in wine

This work presents a thorough study of some aspects critical to the quantitative performance of methods for the determination of volatile aldehydes previously derivatized to pentafluorobenzyl hydroxylamine oximes. The conclusions of the study are further applied to the validation of an optimized procedure for the determination of oxidation-related aldehydes from wine. Aspects studied include the chromatographic injection, the analytical performance of electron-capture detection (ECD) or MS detection, and the way in which the derivatization is carried out. Different injection techniques have been optimized and compared (classical splitless-hot injection; cold splitless; and large volume solvent split injection). All of them were carried out in a programmed temperature vaporization (PTV) injector, with a 350 μL internal volume liner (3.4 mm internal diameter). Classical splitless injection of hexane extracts is troublesome and requires large carrier gas flows (>10 mL min −1). Cold splitless injection was clearly superior. Large volume solvent split injection has been also optimized. ECD has been found to lack the necessary selectivity for the determination of unsaturated aldehydes in wine, although the quantitation of several minor aldehydes is possible. MS detection has proven to be superior for the determination of these compounds in wine. The way in which the reagent is applied is also critical and for the case of wine is important to ensure that the reagent is applied after some of the major wine aldehydes have been eliminated. The finally proposed method is extremely sensitive. Method detection limits ranged from 0.002 μg L −1 (for unsaturated aldehydes) to 0.73 μg L −1 (for phenylacetaldehyde) and precision (measured as relative standard deviation) is ≤6% in all cases. The method makes it possible to determine quantitatively in a single run the wine aldehydes with sensory significance (isobutyraldehyde, 2-methylbutanal, isovaleraldehyde, ( E)-2-hexenal, ( E)-2-heptenal, ( E)-2-octenal, ( E)-2-nonenal, methional and phenylacetaldehyde).

Gas-Liquid Mass Transfer Coefficient of a Pitched Bladed Paddle Up-Pumping at Extraordinary Large Gas Flow Rates

The gas–liquid mass transfer coefficient at extraordinarily large gas flow rates was investigated for a pitched bladed paddle creating upward flow in comparison with those of the Rushton disc turbine and the Scaba SRGT impeller, which are commonly recommended for gas–liquid mixing. The results indicated that the pitched bladed paddle up-pumping gave the enhanced mass transfer coefficient kLa at large gas flow rates compared to Rushton disc turbine and Scaba SRGT. In this study, it was confirmed that the kLa of DT and SRGT depend only on the aerated energy dissipation rate (eT)g at the gas flow rates of 4.8–15.8 vvm. In contrast, the kLa of PPU was shown to be functions of both (eT)g and supercritical gas velocity vs until 22.2 vvm.

LINER‐like Extended Nebulae in ULIRGs: Shocks Generated by Merger‐Induced Flows

In this work we studied the two-dimensional ionization structure of the circumnuclear and extranuclear regions in a sample of six low-z Ultraluminous Infrared Galaxies using Integral Field Spectroscopy. The ionization conditions in the extranuclear regions of these galaxies (~5-15 kpc) are typical of LINERs as obtained from the Veilleux-Osterbrock line ratio diagnostic diagrams. The range of observed line ratios is best explained by the presence of fast shocks with velocities of 150 to 500 km s^{-1}, while the ionization by an AGN or nuclear starburst is in general less likely. The comparison of the two-dimensional ionization level and velocity dispersion in the extranuclear regions of these galaxies shows a positive correlation, further supporting the idea that shocks are indeed the main cause of ionization. The origin of these shocks is also investigated. Despite the likely presence of superwinds in the circumnuclear regions of these systems, no evidence for signatures of superwinds such as double velocity components are found in the extended extranuclear regions. We consider a more likely explanation for the presence of shocks, the existence of tidally induced large scale gas flows caused by the merging process itself, as evidenced by the observed velocity fields characterized by peak-to-peak velocities of 400 km s^{-1}, and velocity dispersions of up to 200 km s^{-1}.

Pressure Drop in a Packed Bed under Nonadsorbing and Adsorbing Conditions

Simulation of cyclic adsorption processes for gas separations relies on accurate models of the bed pressure drop during dynamic pressurization, depressurization, and breakthrough steps. This is especially true for rapid pressure swing adsorption (RPSA), where large gas flows can cause significant changes in the axial pressure gradient through the bed, influencing process performance. Under these conditions, there is some question as to the validity of conventional steady-state models used to represent the dynamic, rapidly changing pressures. In this study, the ability of the steady-state Ergun equation to represent pressure drop under dynamic adsorbing and nonadsorbing conditions was tested. The Ergun equation accurately reproduced dynamic depressurization and breakthrough pressure profiles using values of κviscous and κkinetic (the two Ergun parameters) determined experimentally from the steady-state flow of a variety of gases through a packed bed of LiLSX pellets. The full momentum equation was also tested, and errors of <0.1% were observed between the Ergun equation and the full momentum balance under dynamic conditions for a nonadsorbing packed bed. These observations and simulations suggest the Ergun equation can be reliably used to reproduce experimental profiles under dynamic adsorbing conditions where high gas flows result.

A seat microvalve nozzle for optimal gas-flow capacity at large-controlled pressure

Seat microvalves are the most common microvalve type for gas-flow control. This paper presents a general method for optimizing the flow capacity of a seat valve nozzle and diminishing the requirements on the valve actuator's stroke length. Geometrical analysis and finite element (FE) simulations show that for controlling large gas flow at elevated pressure, the optimal nozzle design in terms of flow capacity for a given actuator performance is a multiple-orifice arrangement with miniaturized circular nozzles. Experimental results support the design introduced in this paper.