Artículos de revistas: "Gas channels"

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Gruznov, Vladimir M. y Alexander B. Vorozhtsov. "Gas-Dynamic Kinetics of Vapour Sampling in the Detection of Explosives". Molecules 24, n.º 23 (3 de diciembre de 2019): 4409. http://dx.doi.org/10.3390/molecules24234409.

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The dynamic sorption concentration of explosive vapours on concentrators made of a metal mesh, and the transportation of explosive vapours through the extended metal channels are considered. The efficiency of the concentration and transportation is determined by the breakthrough of the substance’s molecules through the channels. The research methods we used were breakthrough calculation theory and experiment. When calculating the breakthrough, a mesh was presented as a set of parallel identical channels. Wire mesh and extended channels were made of stainless steel. The breakthrough is determined through the specific frequency of the collisions between the molecules and the channel’s surface. This is presented as a function of the ratio of the substance diffusion flow to the channel’s surface to the airflow through the channel. The conditions for high-speed concentration, complete capture of explosive vapours, and low vapour losses during their transportation through the extended channels were determined theoretically and experimentally. For a concentrator made of a mesh, the condition of a high concentration rate at a high breakthrough (up to 80%) was determined. The described sorption concentration is used in portable gas chromatographic detectors of explosive vapours of the EKHO series.

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Walewska, Agnieszka, Adam Szewczyk y Piotr Koprowski. "Gas Signaling Molecules and Mitochondrial Potassium Channels". International Journal of Molecular Sciences 19, n.º 10 (18 de octubre de 2018): 3227. http://dx.doi.org/10.3390/ijms19103227.

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Recently, gaseous signaling molecules, such as carbon monoxide (CO), nitric oxide (NO), and hydrogen sulfide (H2S), which were previously considered to be highly toxic, have been of increasing interest due to their beneficial effects at low concentrations. These so-called gasotransmitters affect many cellular processes, such as apoptosis, proliferation, cytoprotection, oxygen sensing, ATP synthesis, and cellular respiration. It is thought that mitochondria, specifically their respiratory complexes, constitute an important target for these gases. On the other hand, increasing evidence of a cytoprotective role for mitochondrial potassium channels provides motivation for the analysis of the role of gasotransmitters in the regulation of channel function. A number of potassium channels have been shown to exhibit activity within the inner mitochondrial membrane, including ATP-sensitive potassium channels, Ca2+-activated potassium channels, voltage-gated Kv potassium channels, and TWIK-related acid-sensitive K+ channel 3 (TASK-3). The effects of these channels include the regulation of mitochondrial respiration and membrane potential. Additionally, they may modulate the synthesis of reactive oxygen species within mitochondria. The opening of mitochondrial potassium channels is believed to induce cytoprotection, while channel inhibition may facilitate cell death. The molecular mechanisms underlying the action of gasotransmitters are complex. In this review, we focus on the molecular mechanisms underlying the action of H2S, NO, and CO on potassium channels present within mitochondria.

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Похабов, Д. А., А. Г. Погосов, Е. Ю. Жданов, А. К. Бакаров y А. А. Шкляев. "Двухканальный электронный транспорт в подвешенных квантовых точечных контактах с боковыми затворами". Физика и техника полупроводников 54, n.º 12 (2020): 1344. http://dx.doi.org/10.21883/ftp.2020.12.50235.9512.

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The conductance of a suspended quantum point contact fabricated from GaAs/AlGaAs heterostructures with a two-dimensional electron gas, equipped with the in-plane side gates separated from the constriction using lithographical trenches, is studied. The conductance as a function of the gate voltages demonstrates unusual double-channel regime with independent channel’s conductance quantization: two side gates can drive the conductance of the separate channels independently. A possible electrostatic mechanism of the double-channel structure formation inside a single constriction is connected with the lateral redistribution of the low-mobility X-valley electrons contained in superlattice layers, resulting in the emergence of the potential barrier in the middle of quantum point contact, separating the conducting electrons into two channels, symmetrically shifted towards the lithographical trenches, defining the nanostructure geometry.

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4

Offermans, Peter, Roman Vitushinsky, Mercedes Crego-Calama y Sywert H. Brongersma. "Gas Sensing with AlGaN/GaN 2DEG Channels". Procedia Engineering 25 (2011): 1417–20. http://dx.doi.org/10.1016/j.proeng.2011.12.350.

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5

Schneider, I. A., D. Kramer, A. Wokaun y G. G. Scherer. "Oscillations in Gas Channels". Journal of The Electrochemical Society 154, n.º 8 (2007): B770. http://dx.doi.org/10.1149/1.2742291.

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Schneider, I. A., S. A. Freunberger, D. Kramer, A. Wokaun y G. G. Scherer. "Oscillations in Gas Channels". Journal of The Electrochemical Society 154, n.º 4 (2007): B383. http://dx.doi.org/10.1149/1.2435706.

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7

Herrera, Marcela y Jeffrey L. Garvin. "Aquaporins as gas channels". Pflügers Archiv - European Journal of Physiology 462, n.º 4 (2 de agosto de 2011): 623–30. http://dx.doi.org/10.1007/s00424-011-1002-x.

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8

Szwast, Maciej y Zbigniew Szwast. "A Mathematical Model of Membrane Gas Separation with Energy Transfer by Molecules of Gas Flowing in a Channel to Molecules Penetrating this Channel from the Adjacent Channel". Chemical and Process Engineering 36, n.º 2 (1 de junio de 2015): 151–69. http://dx.doi.org/10.1515/cpe-2015-0012.

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Abstract The paper presents the mathematical modelling of selected isothermal separation processes of gaseous mixtures, taking place in plants using membranes, in particular nonporous polymer membranes. The modelling concerns membrane modules consisting of two channels - the feeding and the permeate channels. Different shapes of the channels cross-section were taken into account. Consideration was given to co-current and counter-current flows, for feeding and permeate streams, respectively, flowing together with the inert gas receiving permeate. In the proposed mathematical model it was considered that pressure of gas changes along the length of flow channels was the result of both - the drop of pressure connected with flow resistance, and energy transfer by molecules of gas flowing in a given channel to molecules which penetrate this channel from the adjacent channel. The literature on membrane technology takes into account only the drop of pressure connected with flow resistance. Consideration given to energy transfer by molecules of gas flowing in a given channel to molecules which penetrate this channel from the adjacent channel constitute the essential novelty in the current study. The paper also presents results of calculations obtained by means of a computer program which used equations of the derived model. Physicochemical data concerning separation of the CO2/CH4 mixture with He as the sweep gas and data concerning properties of the membrane made of PDMS were assumed for calculations.

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9

Alexiadis, A., M. P. Dudukovic, P. Ramachandran, A. Cornell, J. Wanngård y A. Bokkers. "The Flow Pattern in Single and Multiple Submerged Channels with Gas Evolution at the Electrodes". International Journal of Chemical Engineering 2012 (2012): 1–9. http://dx.doi.org/10.1155/2012/392613.

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We show that the gas-liquid flow pattern in a single gas-evolving electrochemical channel can be remarkably different from the flow pattern in multiple submerged gas-evolving electrochemical channels. This is due to the fact that in a single channel there is a higher accumulation of small bubbles and these can considerably affect the liquid velocity pattern which in turn may affect the performance of a cell. Since experimental work is often carried out in single channels, while industrial applications almost always involve multiple channels, this study provides insight into the factors that affect the flow pattern in each situation and establishes the basis for relating the behavior of single-and multiple-channel devices.

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10

Bantel, Carsten, Mervyn Maze y Stefan Trapp. "Noble Gas Xenon Is a Novel Adenosine Triphosphate-sensitive Potassium Channel Opener". Anesthesiology 112, n.º 3 (1 de marzo de 2010): 623–30. http://dx.doi.org/10.1097/aln.0b013e3181cf894a.

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Background Adenosine triphosphate-sensitive potassium (KATP) channels in brain are involved in neuroprotective mechanisms. Pharmacologic activation of these channels is seen as beneficial, but clinical exploitation by using classic K channel openers is hampered by their inability to cross the blood-brain barrier. This is different with the inhalational anesthetic xenon, which recently has been suggested to activate KATP channels; it partitions freely into the brain. Methods To evaluate the type and mechanism of interaction of xenon with neuronal-type KATP channels, these channels, consisting of Kir6.2 pore-forming subunits and sulfonylurea receptor-1 regulatory subunits, were expressed in HEK293 cells and whole cell, and excised patch-clamp recordings were performed. Results Xenon, in contrast to classic KATP channel openers, acted directly on the Kir6.2 subunit of the channel. It had no effect on the closely related, adenosine triphosphate (ATP)-regulated Kir1.1 channel and failed to activate an ATP-insensitive mutant version of Kir6.2. Furthermore, concentration-inhibition curves for ATP obtained from inside-out patches in the absence or presence of 80% xenon revealed that xenon reduced the sensitivity of the KATP channel to ATP. This was reflected in an approximately fourfold shift of the concentration causing half-maximal inhibition (IC50) from 26 +/- 4 to 96 +/- 6 microm. Conclusions Xenon represents a novel KATP channel opener that increases KATP currents independently of the sulfonylurea receptor-1 subunit by reducing ATP inhibition of the channel. Through this action and by its ability to readily partition across the blood-brain barrier, xenon has considerable potential in clinical settings of neuronal injury, including stroke.

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11

Burmistrov, A. V., S. I. Salikeev y A. A. Raykov. "Simulation of Gas Flow in Channels with Variable Cross-Section at Different Flow Modes using Lattice Boltzmann Method (LBM)". Herald of the Bauman Moscow State Technical University. Series Mechanical Engineering, n.º 6 (129) (diciembre de 2019): 105–15. http://dx.doi.org/10.18698/0236-3941-2019-6-105-115.

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All contact-free vacuum pumps operate in a very wide pressure range. Therefore, the calculation of flows through the slot channels is associated with the need to take into account the laws of all three modes of gas flow: viscous, transitional and molecular. Most of channels of contact-free pumps are formed by curved walls, which are slits of variable cross-section in the direction of gas flow, having a minimum gap in some place. The paper considers the basic methods of calculating flows in channels of variable cross-section: the Monte Carlo method for molecular mode, the numerical solution of Navier --- Stokes equations for viscous mode and the Lattice Boltzmann method (LBM) for a wide range of pressures. The results of gas flow simulation calculated in COMSOL Multiphysics with LBM method are presented. The influence of the gas flow mode on the velocity profile in the channel is discussed. Based on the simulation results, the conductivity of channels of different geometries was calculated at various pressures at the inlet and outlet of the channel. The graphs of conductivity dependence on the Knudsen number for the method of angular coefficients, the model of lattice Boltzmann equations and experimental data are presented. It is shown that for slit channels of variable cross-section, the LBM model agrees well with the experiment under any gas flow modes.

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12

Boron, Walter F. "Sharpey-Schafer Lecture: Gas channels". Experimental Physiology 95, n.º 12 (16 de noviembre de 2010): 1107–30. http://dx.doi.org/10.1113/expphysiol.2010.055244.

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13

Harley, John C., Yufeng Huang, Haim H. Bau y Jay N. Zemel. "Gas flow in micro-channels". Journal of Fluid Mechanics 284 (10 de febrero de 1995): 257–74. http://dx.doi.org/10.1017/s0022112095000358.

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An experimental and theoretical investigation of low Reynolds number, high subsonic Mach number, compressible gas flow in channels is presented. Nitrogen, helium, and argon gases were used. The channels were microfabricated on silicon wafers and were typically 100 μm wide, 104 μm long, and ranged in depth from 0.5 to 20 μm. The Knudsen number ranged from 10-3 to 0.4. The measured friction factor was in good agreement with theoretical predictions assuming isothermal, locally fully developed, first-order, slip flow.

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14

TAUSCHWITZ, A., R. BIRKNER, R. KNOBLOCH, S. NEFF, C. NIEMANN, D. PENACHE, R. PRESURA, D. PONCE y S. YU. "Stability of gas discharge channels for final beam transport". Laser and Particle Beams 20, n.º 3 (julio de 2002): 503–9. http://dx.doi.org/10.1017/s0263034602203286.

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Discharge plasma channels have been investigated in recent years at Gesellschaft für Schwerionenforschung–Darmstadt (GSI) and at the Lawrence Berkeley National Laboratory in Berkeley, California, in a number of experiments. A short summary of the experimental work at Berkeley and GSI is given. Different initiation mechanisms for gas discharges of up to 60 kA were studied and compared. In the Berkeley experiments, laser ionization of organic vapors in a buffer gas was used to initiate and direct the discharge while at GSI, laser gas heating and ion-beam-induced gas ionization were tested as initiation mechanisms. These three initiation techniques are compared and the stability of the resulting discharge channels is discussed. A discharge current of 50 kA, a channel diameter well below 1 cm, a pointing stability better than 200 μm, and MHD stability of more than 10 μs have been demonstrated simultaneously in the recent experiments. These parameters are sufficient or close to the requirements of a reactor application depending on the details of the target design. The experimental results show that transport channels work with sufficient stability, reproducibility, and ion optical properties for a wide pressure range of discharge gases and pressures.

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15

Bisht, Kamal S. y Michael E. Dreyer. "Phase Separation in Porous Media Integrated Capillary Channels". Microgravity Science and Technology 32, n.º 6 (9 de noviembre de 2020): 1001–18. http://dx.doi.org/10.1007/s12217-020-09828-6.

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Abstract Phase separation in space is critical for gas-free propellant supply, life support systems, refueling of spacecraft in low earth orbit (LEO), and for deep space exploration missions. In the absence of gravity, the stability of the liquid-gas interface depends on capillary forces. High liquid flow rates, sudden accelerations, and vibrational disturbances can cause the free surface of the liquid to collapse, which results in the ingestion of gas. Propellant tanks may have screen channel liquid acquisition devices (SCLADs) to position and maintain a gas-free propellant supply to the outlet. A saturated porous screen permits liquid to pass through but acts as a barrier to the gas. We investigated phase separation in porous media integrated capillary channels during parabolic flights (33rd DLR parabolic flight campaign in March 2019). An open side of a rectangular channel was covered with a dutch twill weave 200×1400. The liquid was ingested into the channel from its surroundings by establishing a differential pressure across the screen section. The gas-phase was blocked during the liquid withdrawal. We could show that the gas breakthrough occurs when the pressure difference across the screen exceeds the bubble point pressure. The experimental results showed good agreement with correlations from literature.

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16

Jazaeri, Mohammad Javad y John Andrews. "Design and Testing of a Modified Parallel Flow Field for Uniform Flow Distribution in PEMFuel Cells". Applied Mechanics and Materials 330 (junio de 2013): 693–97. http://dx.doi.org/10.4028/www.scientific.net/amm.330.693.

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The focus of this paper is to develop and test a modified design of the conventional parallel flow channel configuration in a proton exchange membrane (PEM) fuel cell. One of the main objectives in designing flow channel configurations is to achieve a uniform distribution of reactants across the catalyst layer of the membrane electrode assembly of the fuel cell. Uniform reactant distribution promotes an even current density distribution, and enhances power output and overall cell performance. A simple method for visualizing the flow distribution is used to study the flow distribution in the flow channels of a PEM fuel cell. In the experiment the principle of dimensional analysis and similitude was employed to study gas distribution by using water instead of gas. The results demonstrate that providing storage volumes before the channels creates a better flow distribution. The results also reveal that channels with the shortest distance between inlet and outlet manifold are reactant rich and are filled prior to the channels with longer such distances.

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17

Zamashchikov, V. V., Ya V. Kozlov, A. A. Korzhavin y V. S. Babkin. "Gas combustion in narrow single channels". Combustion, Explosion, and Shock Waves 46, n.º 2 (marzo de 2010): 154–61. http://dx.doi.org/10.1007/s10573-010-0024-6.

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18

Chen, C. K., L. Wang, J. T. Yang y L. T. Chen. "Experimental and Computational Analysis of Periodic Flow Structure in Oscillatory Gas Flow Meters". Journal of Mechanics 22, n.º 2 (junio de 2006): 137–44. http://dx.doi.org/10.1017/s1727719100004433.

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AbstractThe oscillatory characteristics and dynamic structure of periodic flow in an oscillatory gas flow meter were studied experimentally and numerically. The flow oscillations were triggered by the Coanda effect and an universal correlation between Strouhal number and Reynolds number, Str = 1.09 × 10−3 for ReHD >800, was deduced based on spectral analysis of the pressure fluctuations in the flow channel. Numerical simulation indicated that the evolution of the flow patterns was classified into stages of induction and sustainable periodic oscillation. The transformation between the two stages was noticeably affected by the design of the feedback channels. The results further revealed that the development of the main vortex in the oscillating chamber and the small vortices at the entrance of the feedback channels concurrently modulate the mechanism of oscillation. The small vortices located at both entrances of the feedback channels play the role of a pair of modulating valves, which alternatively switch on and off the bypass flow through each feedback channel, thus reinforcing the periodic oscillation.

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Munte, Annes y Hendra Jonathan Sibarani. "Pengaruh saluran distribusi, keunggulan produk, dan persediaan produk, melalui keputusan pembelian pada PT. Tasya Gasindo Medan". Jurnal Paradigma Ekonomika 16, n.º 1 (14 de febrero de 2021): 109–22. http://dx.doi.org/10.22437/jpe.v16i1.12084.

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Natural gas is used by the public because it is more efficient and cheaper than others. but the 3 kg gas cylinder often leaks, the weight of the gas cylinder is not as expected, then the 3kg gas cylinder is often empty of stock. this study aims to determine the effect of distribution channels, product advantages, and product supplies through purchasing decisions. This type of research uses descriptive research. The research aims to determine the effect of distribution channels, product advantages, and product supplies through purchasing decisions. The population in the company as many as 70 and taken 30 populations from similar companies so that the population amounted to 100, the number of samples studied in this study were 100 samples. The study used multiple linear analysis shows distribution channels, product advantages, and product suppliesseffect spositive sand ssignificant sto purchasing sdecisions. The t-test of the distribution channel obtained tcount < ttable the sig value Fcount> Ftable means that the distribution channel has no effect and is not significant towards purchasing decisions, product excellence is obtained tcount > ttable then the sig value Fcount<Ftable means that product excellence has a significant effect on purchasing decisions, and value product inventory obtained tcount> ttable then the sig value Fcount < Ftable means that product inventory has a significant effect on purchasing decisions. Keywords: Distribution channels, Product advantages, Product inventory, Buying decision

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Bao, Fubing, Zhihong Mao y Limin Qiu. "Study of gaseous velocity slip in nano-channel using molecular dynamics simulation". International Journal of Numerical Methods for Heat & Fluid Flow 24, n.º 6 (29 de julio de 2014): 1338–47. http://dx.doi.org/10.1108/hff-04-2013-0145.

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Purpose – The purpose of this paper is to investigate the gas flow characteristics in near wall region and the velocity slip phenomenon on the wall in nano-channels based on the molecular dynamics simulation. Design/methodology/approach – An external gravity force was employed to drive the flow. The density and velocity profiles across the channel, and the velocity slip on the wall were studied, considering different gas temperatures and gas-solid interaction strengths. Findings – The simulation results demonstrate that a single layer of gas molecules is adsorbed on wall surface. The density of adsorption layer increases with the decrease of gas temperature and with increase of interaction strength. The near wall region extents several molecular diameters away from the wall. The density profile is flatter at higher temperature and the velocity profile has the traditional parabolic shape. The velocity slip on the wall increases with the increase of temperature and with decrease of interaction strength linearly. The average velocity decreases with the increase of gas-solid interaction strength. Originality/value – This research presents gas flow characteristics in near wall region and the velocity slip phenomenon on the wall in nano-channels. Some interesting results in nano-scale channels are obtained.

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21

Milanovic, Sasa, Milos Jovanovic, Boban Nikolic y Vladislav Blagojevic. "The influence of secondary flow in a two-phase gas-solid system in straight channels with a non-circular cross-section". Thermal Science 20, suppl. 5 (2016): 1419–34. http://dx.doi.org/10.2298/tsci16s5419m.

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The paper considers two-phase gas-solid turbulent flow of pneumatic transport in straight horizontal channels with a non-circular cross-section. During turbulent flow, a specific flow phenomenon, known as secondary flow, occurs in these channels in the cross-sectional plane. The existence of strong temperature gradients in the cross-sectional plane of the channel or the cases of curved channels result in the appearance of the secondary flow of the first kind. However, in straight channels with a non-circular cross-section, in the developed turbulent flow mode, a secondary flow, known as Prandtl?s secondary flow of the second kind, is induced. The paper presents a numerical simulation of a developed two-phase turbulent flow by using the PHOENICS 3.3.1 software package. Reynolds stress model was used to model the turbulence. The paper provides the data on the changes in turbulent stresses in the channel cross-section as well as the velocities of solid particles transported along the channel.

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22

Wu, Zisen, Pingchuan Dong, Gang Lei, Nai Cao, Yudan Li, Yifan Wang y Xuejiao Zhang. "Study on the micro-scale effect in the micro–nano organic pores of a shale reservoir". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 232, n.º 3 (16 de octubre de 2017): 491–501. http://dx.doi.org/10.1177/0954406217729718.

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The micro-scale effect occurs because of the gas flows in shale reservoirs containing small organic pores. In this study, based on a lattice Boltzmann model incorporating the bounce-back and specular-reflection boundary conditions, the gas flow through two parallel plates driven by differential pressures is simulated, which in turn verifies the model. Considering the effects of the slippage, surface diffusion, and adsorption, the gas flow in the organic channels is simulated based on the proposed lattice Boltzmann model. It is shown that the micro-scale effect is significant in the gas flows in the micro-scale channels. The compression effect leads to a nonlinear distribution of pressures along the centreline of the flow channels, and the nonlinearity increases with an increase in the pressure difference between the two sides of the flow channel. In case of gas flows in organic pores, the adsorption effect decreases the free-gas velocities, and with a decrease in pore sizes, the average free-gas velocity is reduced owing to the increased adsorption effect. The slippage effect and surface diffusion have a significant impact on the free-gas velocity of the mass flow. Compared to the slippage effect, surface diffusion contributes more to the mass flow of gas in organic pores. An increase in the Knudsen number intensifies the slippage effect and surface diffusion and enhances the mass flow.

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23

Chlebnikovas, Aleksandras y Pranas Baltrėnas. "Research of the Aerodynamic Parameters in a Special Cyclone with Secondary Inlets". Mokslas - Lietuvos ateitis 9, n.º 4 (11 de septiembre de 2017): 400–405. http://dx.doi.org/10.3846/mla.2017.1065.

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Special cyclone – gas treatment device which can be applied to remove the fine particulate matter bigger than 2 micrometres from aggressive gas flow at a temperature of 50–145 °C and a relative humidity of more than 95% and can be achieved the cleaning efficiency over 90%. Cyclone work is based on centrifugal forces and the resulting additional filtration process operation. Cyclone structure equipped with primary and secondary gas flow inflows through which gas dispersed flow is supplied parallel to all channels of the cyclone. Analysed modified multi-channel cyclone can be effectively treated from fine particulate matter, during the cleaning of aggressive gas flow an adhesion/cohesion phenomena could be reduced. Research of aerodynamic parameters it’s the first step of studies to determine the optimal case, at the average gas flow velocity in cyclone channels were 8, 12 and 16 m/s, the gas flow dynamics dependencies into cyclone were determined.

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Bella, G. y V. Rocco. "Regeneration Analysis Under Different Exhaust Gas Thermal Conditions". Journal of Engineering for Gas Turbines and Power 112, n.º 3 (1 de julio de 1990): 431–37. http://dx.doi.org/10.1115/1.2906514.

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A refinement of the honeycomb trap model developed by the authors for analyzing the temperature history of the trap channels during the regeneration period is presented. The first results obtained, shown in previous papers [1, 2], encouraged the authors to improve the model in order to account for the heat transfer not only along the channel length, but also in the radial direction. In order to achieve this objective, a control volume approach was used to simulate the soot regeneration in all contiguous channels along the axial and radial directions of the monolith, and to determine the wall temperature and soot oxidation as a function of time. Different thermodynamic conditions of the exhaust gas at the trap inlet were considered in order to examine the effects of cold regeneration. For the same soot amount accumulated in the trap, the soot burnup time and temperature history depend on the inlet temperature. In addition to varying the gas initial conditions, the effects of the amount of soot collected and its radial distribution in the channels, before the regeneration process takes place, were also considered in order to predict the wall temperature rise and the soot oxidation rate. The results show the temperature peak values and their location inside the trap, and permit estimation of the conditions under which the trap temperature can reach unbearable values.

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Duy, Vinh Nguyen, Jung Koo Lee, Ki Won Park y Hyung Man Kim. "Enhancement of PEM Fuel Cell Performance by Flow Control". Materials Science Forum 804 (octubre de 2014): 75–78. http://dx.doi.org/10.4028/www.scientific.net/msf.804.75.

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Flow-field design affects directly to the PEM fuel cell performance. This study aims to stimulate the under-rib convection by adding sub-channels and by-passes to the conventional-advanced serpentine flow-field to improve the PEM fuel cell performance. The experimental results show that if reacting gases flow in the same direction as the neighboring main channels, the under-rib convection shows a flow from the main channels to the sub-channels makes progress in reducing pressure drop and enhancing uniform gas supply and water diffusion. Alternatively, if in the direction opposite to that of the neighboring main channels, the under-rib convection shows a flow from the inlet side towards the outlet side across the sub-channel as in the conventional serpentine channels. Analyses of the local transport phenomena in the cell suggest that the inlet by-pass supplies the reacting gases uniformly from the entrance into the sub-channels and the outlet by-pass enhances water removal. Novel serpentine flow-field pattern employing sub-channels and by-passes shows uniform current density and temperature distribution by uniformly supplying the reacting gas. Furthermore, performance improvement of around 20% is observed from the experimental performance evaluation. As a result, longer battery life is expected by reducing the mechanical stress of membrane electrode assembly.

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Krasnov, Andrey, Gennadiy Kolovertnov, Marina Prakhova y Elena Khoroshavina. "Improving data transfer efficiency in a gas field wireless telemetry system". Arctic Environmental Research 18, n.º 1 (30 de marzo de 2018): 14–20. http://dx.doi.org/10.17238/issn2541-8416.2018.18.1.14.

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Effective organisation of communication channels in autonomous information and measurement systems (AIMS) is a burning issue. It is particularly challenging for areas where, for a number of reasons (primarily unprofitability or immaturity of the wired infrastructure), telecommunications can rely only on wireless technologies, i.e., radio channels. Arctic regions of the Russian Federation, where most of Russia’s gas and gas condensate deposits are located, constitute a typical example of such areas. The key challenges during construction of wireless communication channels are associated with the fixed range of frequencies that can be used without a licence. For the purposes of radio traffic, the frequency used by AIMS transmitters and receivers depends on the frequency of the quartz crystal resonators used in such devices. The stability of this frequency determines both the number of radio channels that can be used and the efficiency of data transfer. Key factors affecting the quartz frequency include temperature and “ageing” of quartz crystals. Known methods for increasing the frequency stability generally allow compensation for the temperature drift of the quartz frequency. In addition, such methods are increasingly energy-consuming, which is unacceptable in the Extreme North. This article suggests using GPS receiver data for frequency adjustment. With a minor increase in energy consumption, this technique enables full compensation for quartz crystal resonator frequency drift, no matter what the cause of such drift, eventually allowing operation of more radio channels within the authorised bandwidth with preserved channel separation. In general, it helps increase the efficiency of data transfer in the telemetry systems of gas field operations.

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Bilynsky, Yosyp, Oksana Horodetska, Svitlana Sirenko y Dmytro Novytskyi. "EXPERIMENTAL STUDY OF NATURAL GAS HUMIDITY CONTROL DEVICE". Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska 10, n.º 3 (30 de septiembre de 2020): 86–90. http://dx.doi.org/10.35784/iapgos.2079.

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The means of measuring humidity based on the use of the ultrahigh frequency method have been recently gaining widespread use, because of its simple, robust construction and high measuring accuracy. We used the advanced waveguide ultrahigh frequency method of measuring the moisture content of natural gas which, in contrast to the known the use of a traveling wave in a waveguide, is proposed. In this case, the interaction with waves of the ultrahigh frequency range changes the dielectric properties of the gas, and this change is registered. On the basis of an improved ultrahigh frequency method of humidity measurement, a device for natural gas humidity control using a traveling wave in a waveguide is proposed. The investigations have shown that a comparative channel increased the measurement accuracy, as a two-channel system – in contrast to a single-channel – eliminates the instability of the value of the input signal supplied to the generator. The principle of operation of a natural gas humidity control device that contains an ultrahigh frequency generator, attenuators, waveguide tees, a waveguide section for comparison, temperature sensor and pressure switches for the comparative and measuring channels, a measuring cuvette, amplifier, microprocessor, and display unit is described. A mathematical model of a natural gas humidity control device, which takes into account the values of the dielectric permittivity of the measuring gas and reference channels and contains correction factors for temperature, the use of which increases the accuracy of humidity measurement, is proposed. The lower and upper calibration points of the natural gas humidity control device are defined. The influence of correction factors for the temperature at the measurement error of the humidity is analyzed.

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28

Chen, Shi Zhong, Yu Hou Wu, Hong Sun y Hong Tan Liu. "An Improved Two-Phase Flow and Transport Model for the PEM Fuel Cell". Advanced Materials Research 105-106 (abril de 2010): 691–94. http://dx.doi.org/10.4028/www.scientific.net/amr.105-106.691.

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A two-phase flow, multi-component model has been optimized for a PEM (Proton Exchange Membrane) Fuel Cell. The modeling domain consists of the membrane, two catalyst layers, two diffusion layers, and two channels. Both liquid and gas phases are considered in the entire cathode and anode, including the channel, the diffusion layer and the catalyst layer. The Gravity effect on liquid water was considered in channels. Typical two-phase flow distributions in the cathode gas channel, gas diffuser and catalyst layer are presented. Source term and porosity term were optimized. Based on the simulation results, it is found that two-phase flow characteristics in the cathode depend on the current density, operating temperature, and cathode and anode humidification temperatures. Water mass fraction for the fuel cell with anode upward is higher than that the case with cathode-upward. Liquid water with the case of cathode-upward blocks pores in the gas diffuser layer leading to increasing the concentration polarization. Gravity of liquid water exerts the effect on the water mass fraction in the cathode.

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29

Wang, Xuefang, Xianshan Dong, Junfeng Xiao, YuYu Zhang, Jianfeng Xu, Sheng Liu y Liang Gao. "Quantum effects of gas flow in nanochannels". Nanotechnology Reviews 10, n.º 1 (1 de enero de 2021): 254–63. http://dx.doi.org/10.1515/ntrev-2021-0022.

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Abstract Based on the thermal theory of Newtonian mechanics, the pressure difference in the macro channels will drive the gas flow until the pressure difference inside is zero. However, the 12-year vacuum packaging experiments in our laboratory showed that when the macroscopic channel is reduced to a critical size and reaches the nanometer level, the gas flow inside the channel is hindered, that is, the differential pressure cannot become zero. To explain this paradoxical phenomenon, this study analyzes the flow of air molecules in the channel by using the De Broglie’s matter waves and Heisenberg’s uncertainty principle. Based on the law of quantum mechanics, when the diameter of the nanochannel is reduced to a certain size, it has a localized high pressure in the channel, which impedes the gas flow. This article introduces quantum mechanics into nanochannel’s gas fluid dynamics for the first time, expanding the new direction of fluid mechanics.

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30

Chen, Yuan Long, H. B. Zhan, Shuo Jen Lee y S. M. Zhu. "Micro-ECM of Maze Flow Channel on Bipolar Plates of Fuel Cell". Key Engineering Materials 458 (diciembre de 2010): 125–30. http://dx.doi.org/10.4028/www.scientific.net/kem.458.125.

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A lot of flow channels should be processed on stainless steel bipolar plates of fuel cell. In order to increase contact area of gas with electrode and ensure the gas flowing smoothly, the flow channels will be multichannel maze. It is difficult to be machined by conventional methods, because the width and depth of the flow channels are very small (about 300μm). When using micro electrochemical machining, flow channels with low surface roughness and good machining accuracy could be produced efficiently. The machining cathode tool, fixture, μ-second grade pulse power supply and machining parameters are introduced. Using microsecond pulse current processing, the maze-shaped flow channel on bipolar plates of fuel cell can be processed seccessfully, with high efficiency and good quality. Thus graphite bipolar plates may be replaced by metal bipolar plates. It may promote the technology advancing for fuel cell, and reducing its cost. Key factors for influencing electrochemical machining process of flow Channels on bipolar plates include the design of cathode and fixture , microsecond pulse current, and suited technical parameters

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31

Dyga, Roman y Małgorzata Płaczek. "Influence of Hydrodynamic Conditions on the Type and Area of Occurrence of Gas–Liquid Flow Patterns in the Flow through Open–Cell Foams". Materials 13, n.º 15 (22 de julio de 2020): 3254. http://dx.doi.org/10.3390/ma13153254.

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This paper reports the results of a study concerned with air−water and air−oil two–phase flow pattern analysis in the channels with open–cell metal foams. The research was conducted in a horizontal channel with an internal diameter of 0.02 m and length of 2.61 m. The analysis applied three foams with pore density equal to 20, 30 and 40 PPI (pore per inch) with porosity, typical for industrial applications, changing in the range of 92%–94%. Plug flow, slug flow, stratified flow and annular flow were observed over the ranges of gas and liquid superficial velocities of 0.031–8.840 m/s and 0.006–0.119 m/s, respectively. Churn flow, which has not yet been observed in the flow through the open–cell foams, was also recorded. The type of flow patterns is primarily affected by the hydrodynamic characteristics of the flow, including fluid properties, but not by the geometric parameters of foams. Flow patterns in the channels packed with metal foams occur in different conditions from the ones recorded for empty channels so gas−liquid flow maps developed for empty channels cannot be used to predict analyzed flows. A new gas−liquid flow pattern map for a channel packed with metal foams with the porosity of 0.92–0.94 was developed. The map is valid for liquids with a density equal to or lower than the density of water and a viscosity several times greater than that of water.

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32

GAT, A., I. FRANKEL y D. WEIHS. "Gas flows through constricted shallow micro-channels". Journal of Fluid Mechanics 602 (25 de abril de 2008): 427–42. http://dx.doi.org/10.1017/s0022112008001055.

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We study the viscous compressible flow through micro-channels of non-uniform cross-section. A lubrication approximation is applied to analyse the flow through shallow configurations whose gap width is small in comparison with the other characteristic dimensions. Focusing on channels with a symmetric constriction (or cavity) we obtain the solution to the problem by means of a Schwarz–Christoffel transformation. This analytic solution is verified by examining the convergence of numerical simulations with diminishing Reynolds number and gap width. Explicit closed-form expressions for the pressure-head and mass-flow-rate losses in terms of the geometrical parameters characterizing the constriction are presented and discussed in the context of experimental data existing in the literature.

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33

Crawford, M. "Heat transfer in gas-cooled annular channels". International Journal of Heat and Fluid Flow 9, n.º 4 (diciembre de 1988): 434–35. http://dx.doi.org/10.1016/0142-727x(88)90015-x.

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34

MURASE, Michio, Hiroaki SUZUKI, Tomoyuki MATSUMOTO y Masanori NAITOH. "Countercurrent Gas-Liquid Flow in Boiling Channels". Journal of Nuclear Science and Technology 23, n.º 6 (junio de 1986): 487–502. http://dx.doi.org/10.1080/18811248.1986.9735012.

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35

Gulliver, John S. y Martin J. Halverson. "Air-water gas transfer in open channels". Water Resources Research 25, n.º 8 (agosto de 1989): 1783–93. http://dx.doi.org/10.1029/wr025i008p01783.

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36

Inoue, Takayoshi, Satoshi Nakada y Yuji Suzuki. "C143 Gas Flow Characteristics in Nanoscale Channels". Proceedings of the Thermal Engineering Conference 2009 (2009): 87–88. http://dx.doi.org/10.1299/jsmeted.2009.87.

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37

HWANG, Young-Kyu, Joong-Sik HEO y Myoung-Keun KWON. "Rarefied Gas Flows in Rotating Helical Channels." JSME International Journal Series B 43, n.º 4 (2000): 700–705. http://dx.doi.org/10.1299/jsmeb.43.700.

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38

Kays, W. M. "Heat Transfer in Gas-cooled Annular Channels". International Journal of Heat and Mass Transfer 32, n.º 1 (enero de 1989): 197. http://dx.doi.org/10.1016/0017-9310(89)90104-x.

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39

Ozhgibesov, M. S., T. S. Leu y C. H. Cheng. "Rarefied gas flow through nanoscale tungsten channels". Journal of Molecular Graphics and Modelling 42 (mayo de 2013): 32–38. http://dx.doi.org/10.1016/j.jmgm.2013.02.013.

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40

Carlotti, P. "Stratified Poiseuille gas flows in horizontal channels". International Journal of Heat and Mass Transfer 50, n.º 17-18 (agosto de 2007): 3690–94. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2007.01.054.

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41

Tolstopyatov, E. M. "Thickness uniformity of gas-phase coatings in narrow channels: I. Long channels". Journal of Physics D: Applied Physics 35, n.º 13 (18 de junio de 2002): 1516–25. http://dx.doi.org/10.1088/0022-3727/35/13/311.

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42

Cheng, Shan Jen, Jr Ming Miao y Chang Hsien Tai. "Numerical Simulation Applied to Study the Effects of Fractal Tree-Liked Network Channel Designs on PEMFC Performance". Advanced Materials Research 488-489 (marzo de 2012): 1219–23. http://dx.doi.org/10.4028/www.scientific.net/amr.488-489.1219.

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The effect of pressure drop and the flow-field of inhomogeneous transport of reactions gas are two important issues for bipolar flow channel design in proton exchange membrane fuel cell (PEMFC). A novel design through the imitation of biological development of the topology distribution of fractal tree-liked network channel is the main topic of this research. The effects of different Reynolds numbers and stoichiometric mass flow rate of reaction gas on the flow field distribution of tree-like channels were investigated by three-dimensional computational fluid dynamic analysis. According to numerical simulations, the fractal tree-liked network channel would have an excellent performance on the uniformity of multi-branching flow distribution and lower pressure drop along channels. The new type of fractal tree-liked bionic flow channel network design will be applied to assist in the experimental reference for improving the performance of fuel cell stack system in PEMFC for future.

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43

Kuzevanov, Vyacheslav S. y Sergey K. Podgorny. "Gas-cooled nuclear reactor core shaping using heat exchange intensifiers". Nuclear Energy and Technology 5, n.º 1 (11 de abril de 2019): 75–80. http://dx.doi.org/10.3897/nucet.5.34294.

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The need to shape reactor cores in terms of coolant flow distributions arises due to the requirements for temperature fields in the core elements (Safety guide No. NS-G-1.12. 2005, IAEA nuclear energy series No. NP-T-2.9. 2014, Specific safety requirements No. SSR-2/1 (Rev.1) 2014). However, any reactor core shaping inevitably leads to an increase in the core pressure drop and power consumption to ensure the primary coolant circulation. This naturally makes it necessary to select a shaping principle (condition) and install heat exchange intensifiers to meet the safety requirements at the lowest power consumption for the coolant pumping. The result of shaping a nuclear reactor core with identical cooling channels can be predicted at a quality level without detailed calculations. Therefore, it is not normally difficult to select a shaping principle in this case, and detailed calculations are required only where local heat exchange intensifiers are installed. The situation is different if a core has cooling channels of different geometries. In this case, it will be unavoidable to make a detailed calculation of the effects of shaping and heat transfer intensifiers on changes in temperature fields. The aim of this paper is to determine changes in the maximum wall temperatures in cooling channels of high-temperature gas-cooled reactors using the combined effects of shaped coolant mass flows and heat exchange intensifiers installed into the channels. Various shaping conditions have been considered. The authors present the calculated dependences and the procedure for determining the thermal coolant parameters and maximum temperatures of heat exchange surface walls in a system of parallel cooling channels. Variant calculations of the GT-MHR core (NRC project No. 716 2002, Vasyaev et al. 2001, Neylan et al. 1994) with cooling channels of different diameters were carried out. Distributions of coolant flows and temperatures in cooling channels under various shaping conditions were determined using local resistances and heat exchange intensifiers. Preferred options were identified that provide the lowest maximum wall temperature of the most heat-stressed channel at the lowest core pressure drop. The calculation procedure was verified by direct comparison of the results calculated by the proposed algorithm with the CFD simulation results (ANSYS Fluent User’s Guide 2016, ANSYS Fluent. Customization Manual 2016, ANSYS Fluent. Theory Guide 2016, Shaw1992, Anderson et al. 2009, Petrila and Trif 2005, Mohammadi and Pironneau 1994).

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44

Pantazis, S., S. Varoutis, V. Hauer, C. Day y D. Valougeorgis. "Gas-surface scattering effect on vacuum gas flows through rectangular channels". Vacuum 85, n.º 12 (junio de 2011): 1161–64. http://dx.doi.org/10.1016/j.vacuum.2010.12.019.

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45

Ghafarinia, Vahid, Amir Amini y Mohammad Paknahad. "Gas Identification by a Single Gas Sensor Equipped with Microfluidic Channels". Sensor Letters 10, n.º 3 (1 de marzo de 2012): 845–49. http://dx.doi.org/10.1166/sl.2012.2590.

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46

Plotnikov, L. V., B. P. Zhilkin, Yu M. Brodov, N. I. Grigoriev y L. E. Osipov. "Physical simulation of thermomechanics of gas flows in the output channels of turbocharger centrifugal compressor". Power engineering: research, equipment, technology 22, n.º 3 (8 de septiembre de 2020): 44–50. http://dx.doi.org/10.30724/1998-9903-2020-3-44-50.

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It is known that the thermal and mechanical characteristics of the air flow in the output channel of the turbocharger compressor largely determine the efficiency and quality of the gas exchange processes of the piston engine. The research was carried out on an experimental installation containing a turbocharger, output channels of different configurations, a measurement database and a data collection system. It was found that the stabilization of the flow in the output channel of the compressor leads to a significant increase in the heat transfer intensity (up to 25 %) compared to the base pipeline, while reducing the degree of turbulence by up to 30 %. In the output channel of the compressor with grooves, there is an even more significant increase in the heat transfer intensity (up to 30 %) with an increase in the degree of turbulence by up to 12% compared to the base channel. The proposed configurations of the compressor output channels can be used to intensify heat exchange in order to naturally cool the air during the intake process, as well as to stabilize the gas dynamic parameters of the flow in order to reduce the hydraulic resistance of the intake system of the turbocharged engine.

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47

Said, Ibrahim, Shaoib Usman, Muthanna Al-Dahhan, Mahmoud Moharam y Vineet Alexander. "Axial dispersion and mixing of coolant gas within a separate-effect prismatic modular reactor". Nuclear Energy and Technology 4, n.º 3 (7 de diciembre de 2018): 167–78. http://dx.doi.org/10.3897/nucet.4.27346.

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Multiphase Reactors Engineering and Applications Laboratory performed gas phase dispersion experiments in a separate-effect cold-flow experimental setup for coolant flow within heated channels of the prismatic modular reactor under accident scenario using gaseous tracer technique. The separate-effect experimental setup was designed on light of local velocity measurements obtained by using hot wire anemometry. The measurements consist of pulse-response of gas tracer that is flowing through the mimicked riser channel using air as a carrier. The dispersion of the gas phase within the separate-effect riser channel was described using one-dimensional axial dispersion model. The axial dispersion coefficient and Peclet number of the coolant gas phase and their residence time distribution within were measured. Effect of heating intensities in terms of heat fluxes on the coolant gas dispersion along riser channels were mimicked in the current study by a certain range of volumetric air flow rate ranging from 0.0015 to 0.0034 m3/s which corresponding to heating intensity range from 200 to 1400 W/m2. Results confirm a reduction in the response curve spreads is achieved by increasing the volumetric air velocity (representing heating intensity). Also, the results reveal a reduction in values of axial dispersion coefficient with increasing the air volumetric flow rate.

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48

Kosov, V. N., S. A. Krasikov, O. V. Fedorenko y A. B. Kalimov. "CONVECTIVE MIXING IN AN INCLINED CHANNEL CAUSED BY TERNARY DIFFUSION UNDER CONDITION OF INCREASING DENSITY OF THE MIXTURE WITH HEIGHT". BULLETIN Series of Physics & Mathematical Sciences 69, n.º 1 (10 de marzo de 2020): 224–30. http://dx.doi.org/10.51889/2020-1.1728-7901.39.

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Using methods of numerical simulation, we studied the quasi-stationary mass transfer of isothermal ternary gas mixtures in the vertical and inclined channels for the zone of flow exit from a given channel into the lower flask of a diffusion cell. Convective mixing is considered under conditions involving an increase in the density of the mixture with the height of the channel. The characteristic features of structured flows were studied at a certain content of the component with the highest molecular weight in the mixture. The convective formations in the vertical and inclined channels are compared. The dynamics of structured convective flows at various inclination angles is analysed. Estimates of the lifetime of a structural formation consisting mainly of the component with the highest molecular weight moving in a gas mixture with a lower density value are given.

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49

Levato, Tadzio, Michal Nevrkla, Muhammad Fahad Nawaz, Lorenzo Giuffrida, Filip Grepl, Haris Zulic, Jan Pilar et al. "Experimental Study of Nanosecond Laser-Generated Plasma Channels". Applied Sciences 10, n.º 12 (13 de junio de 2020): 4082. http://dx.doi.org/10.3390/app10124082.

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Generation of plasma-channels by interaction of gas targets with nanosecond laser beams was investigated experimentally. Such laser-generated plasma channels are very promising for subsequent guiding of high peak power femtosecond laser pulses, over several tens of centimeters, as required in laser wake field electron-acceleration (LWFA). The experimental setup was based on the use of a cylindrical lens (100 mm of focal length) with the aim of proposing a technical solution easy to be integrated into a compact experimental setup for acceleration of multi-GeV electron beams using high peak-power laser systems. A pilot experiment, showing production of asymmetric plasma channels over a length of several millimeters in N and Ar targets with initial neutral-gas atomic density around 5 × 1019 cm−3, is reported. Plasma effective threshold formation was estimated, along with future optimization of the optical setup for a symmetrization of such plasma channel. Scalability of this concept to several tens of centimeters is preliminarily discussed, along with the corresponding critical requirements for an optimal LWFA scheme.

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50

Tachikawa, Hiroto. "SN2 and SN2′ reaction dynamics of cyclopropenyl chloride with halide ion A direct ab initio molecular dynamics (MD) study". Canadian Journal of Chemistry 83, n.º 9 (1 de septiembre de 2005): 1597–605. http://dx.doi.org/10.1139/v05-176.

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Direct ab initio molecular dynamics (MD) calculations have been carried out for the reaction of cyclopropenyl chloride with halide ion (F) (F + (CH)3Cl → F(CH)3 + Cl) in gas phase. Both SN2 and SN2′ channels were found as product channels. These channels are strongly dependent on the collision angle of F to the target (CH)3Cl molecule. The collision at one of the carbon atoms of the C=C double bond leads to the SN2′ reaction channel; whereas the collision at the methylene carbon atom leads to the SN2 reaction channel. The reactions proceed via a direct mechanism without long-lived complexes. The reaction mechanism is discussed on the basis of the theoretical results.Key words: SN2 reaction, direct ab initio molecular dynamics, halogen exchange, reaction mechanism.

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