Influence Of Gas Flow Rate Research Articles

Hydrodynamics and Particle Mixing Characteristics of a Ternary Mixture in a Gas-Solid Fluidized Bed

Gas-Solid Fluidized Beds are widely used in current industrial practices for their high efficiency in producing products of very high standards. The study of bed dynamics has become an important concern for the design of fluidized beds. Various parameters like pressure, temperature, gas velocity, mean residence time and solids composition affect the bed behavior. In this view, an experimental study was carried out to determine the influence of gas flow rate, mixing time, solids composition and bed height on mixing/segregation behaviour of the bed of particles. Since fluidized beds involving more than two solids are more frequently encountered in current industrial practices, the experiments were conducted using three solid sand particles of average sizes 231 μm, 335 μm, and 510 μm. Various mixing patterns were observed for different mixing times (10, 20 and 30 minutes), different gas flow rates (7.5, 12.5, 17.5, 22.5 and 27.5 LPM), and different solids ratio. Good mixing occurred at an optimum mixing time of 30 minutes and gas flow rates of 17.5 LPM and 22.5 LPM at all solids ratio. The components exhibited relatively better mixing at intermediate bed heights.

Influence of gas flow rate on the synthesis of gas hydrate of freon 134a by the method of explosive boiling of liquefied gas in water volume

This paper is part of the work aimed at finding the optimal parameters of the method of explosive boiling of liquefied hydrate-forming gas in a volume of water during decompression. The paper presents an experimental study of the effect of gas flow during decompression on the synthesis of gas hydrate. The studies were carried out at constant operating parameters, with a change in gas flow during decompression. The studies were conducted on hydrate-forming gas Freon 134a.

Experimental Investigation on Plume Enlargement and Fountain Effect Due to Gas Blowout nn Seawater

The present paper focuses on experimental tests performed in an experimental outdoor basin with three gases (air, CO 2 and methane) in order to characterize the consequences of underwater gas release. Water elevation (fountain effect) and surface velocity where measured for various mass flow. Results for maximum water elevation clearly show a strong influence of gas flow rate with an increase of water elevation with decrease of gas density. Results obtained for current velocity with air and methane release show an increase of water velocity with gas flow rate. On the contrary, for CO 2 release water velocities are lower due to solubilization process of CO 2 in water column involving decrease of gas momentum.

Carbon dioxide chemical absorption in non-aqueous solvents by the presence of water

Abstract Present work analyzes the role of water in a gas–liquid–liquid absorber using a non-soluble amine (octylamine) in water. The presence of water causes an enhancement in carbon dioxide loading and absorption rate in comparison with the use of the organic solvent. Several issues have been analyzed in present research work: influence of gas flow-rate, water and amine concentration, type of organic solvent and solvent regeneration. The analysis of experimental data and speciation studies by using nuclear magnetic resonance allows to understand the overall behavior with the accumulation of reaction products in the organic phase by the formation of water-in-oil microemulsion. The accumulation of reaction products allows to decrease the solvent flow rate that must be regenerated and it can decrease the cost of this type of operation.

Numerical study on the influence of gas flow rates on the gas-assisted extrusion deformation of plastic micro-tubes

In this paper, the effects of flow rate of assisted gases on the gas-assisted extrusion forming of plastic micro-tube were numerically investigated by using the finite element software Polyflow. Three phases fluid model was established and same volume flow rate was imposed on the inlet face of melt, different flow rate of inner and outer assisted gases were imposed on the inlet faces of two layers of assisted gases. Giesekus constitutive model was used to describe the rheological properties of melt. Numerical results show that with the increase of inner assisted gas’s flow rate, the inner and outer diameter will exponentially increase, that is, the inner cavity becomes bigger and bigger. When excessive flow rate of inner assisted gases is imposed, the inner cavity will be blown and broken. On the other hand, with the increase of the flow rate of outer assisted gas, the inner cavity shrinkage becomes more and more serious. The inner gas-assisted extrusion will be failed at the time of excessive flow rate of outer assisted gas imposed on the inlet face of outer assisted gas layer. Therefore, the reasonable controlling flow rates of inner and outer assisted gases are very important in the practice.

Hydrogen isotopes separation using frontal displacement chromatography: The influences of column temperature and gas flow rate

Based on the previous study in frontal displacement chromatography (FDC) packed with Pd-Al2O3, two groups of separation experiments were conducted to derive the rules how the two most significant factors, temperature and gas flow rate, to influence the separation performance. Separations of the first group were carried out at the feed gas flow rate of 15 mL/min and temperature of 303–213 K, and the second group at 253 K and 10–100 mL/min, with the identical composition of feedstock ((5 ± 0.1)%H2-(5 ± 0.1)%D2-(90 ± 0.1)%Ar). The results indicate the derived rules are consistent with those from references: 1) the rules of temperature effects on separation efficiency lie in two aspects that the lower the temperature is, the larger the thermodynamic separation effect is, and the higher the temperature is, the quicker the hydrogen isotopes exchange dynamics becomes. As to FDC using palladium, 263–213 K will be an appropriate temperature range to have excellent separation performance achieved with the insight into these two aspects. 2) the rule of the influence of gas flow rate basically obeys the van Deemter equation, which means that it does exist an theoretically optimal gas flow rate, ūopt, at a certain temperature and for a certain composition of feedstock, and considering the theoretics and efficiency, separations conducted at the gas flow rate of an suitable range that higher than ūopt but less than 10ūopt can derive good separation performance. The results and discussion have verified the imperative impact of temperature and gas flow rate on the separation performance of this FDC method, and the derived desirable temperature and gas flow rate ranges would supply valuable supports and references for future applications of FDC in hydrogen isotopes separation and tritium recovery in fusion reactors.

Thermal Analysis of In-Service Welding Process for Pipeline

A numerical model had been developed using three dimensional finite element method to predict temperature history of pipe wall thickness by using a FORTRAN computer program. The developed numerical model concerned with the effect of power and velocity of moving heat source, temperature dependent material properties, and transient heat transfer and phase change transformation. Also the effect of heat flux and flow rate on cooling time was investigated numerically.
 An experimental setup had been designed, manufactured and instrumented to investigate the thermal history of an in-service welding process considering air as the flowing fluid inside test pipe. The burn-through was investigated experimentally under the influence of gas flow rate, heat flux and the depth of defect presented in pipeline wall. It has been concluded that the burn-through do not occur for the studied parameter range. The results showed that as the flow rate increases from (24 - 30 lpm) the cooling time decrease by a rate of (11.7 %) and when the flow rate increase from (24-60 lpm) the cooling time decrease by a rate of (41.1 %) without affecting peak temperature with pipe wall thickness of (6mm). Also it has been concluded that as the heat flux increases from (1110- 1370 kJ/mm) the peak temperature increases with a rate of (22.11 %) and cooling time increase with (25.4 %) when the heat flux increases from (1110- 1659 kJ/mm) the peak temperature increases with a rate of (46.86%) and cooling time increase with (50.7 %) with pipe thickness of (6mm).

Effect of particle size on adsorption kinetics of water vapor on porous aluminium oxide material

Influence of the grain size of aluminium oxide material, being a product of centrifugal thermal activation of hydrargillite, on adsorption kinetics of water vapors was studied. The material was characterized by the BET method and X-ray phase analysis (XRD). Influence of gas flow rate on adsorption dynamics was studied on a laboratory installation using McBain-Bakr quartz balance. It was shown that with the fraction size greater than 0.5-1.0 mm, the rate of water vapor adsorption on this adsorbent decreased, which was connected with the influence of internal diffusion resistance. On the base of the first-order kinetic equation for the water adsorption mathematical modeling was carried out. The kinetic parameters of the equation for the various grain size samples (0.25-0.5 mm and 0.5-1.0 mm and 3.7 x 6 mm granule) were determined.

A NEW APPROACH TO OBTAIN AEROGELS FOR GAS SAFETY APPLICATIONS

In this study a new approach for aerogel preparation is presented, along with the screening of obtained aerogel towards air decontamination potential. The synthesis method allows the tuning of the porosity degree of the aerogel by changing the amount of the solvent (water), which dictates the physical appearance of the obtained aerogel (compacted or expanded). Experiments have been carried out under dynamic conditions, by using isobutylene (ISB) as model pollutant and activated carbon as a reference sorbent. At low contaminant loading, the obtained aerogels exhibit comparable performance with that observed for activated carbon, otherwise the activated carbon presents the highest performance at higher loadings. The physical appearance of the aerogel appears to influence the ISB removal performance. Influence of gas flowrate and ISB concentration on the performance response is depicted. The obtained results reveal new perspectives in developing and using aerogels (ultralight materials) for the removal of air contaminants in special applications such as those related to gas safety (for example, the gas masks that should assure not only quality, but also comfort).

Influence of gas flow rate and surfactant concentration on SDBS foam properties

ABSTRACTFoams stabilized by surfactants are widely applied in many industrial practices; thus, the investigation of properties of these foams is of significance. The aim of this study is to examine the influence of gas flow rate and surfactant concentration on properties of foams stabilized by sodium dodecyl benzene sulfonate (SDBS). Experiments were conducted using a commercially available instrument, FoamScan, with which the foamability, foam stability, bubble size, and liquid content of foam were determined. The results showed that as an increase in gas flow rate at the same surfactant concentration the foaming time decreased while the liquid content of foam increased. On the other hand, increasing the surfactant concentration at a desired gas flow rate, the foam properties (both foamability and foam stability) of SDBS increased at concentrations c < critical micelle concentration (cmc), but this effect did not scale linearly with concentration. When c ≥ cmc, there was no evident change in both foamability and foam stability. Moreover, foam stability was controlled not only by foam drainage process but also by bubble coalescence. These findings provide guidelines for generating foams with excellent properties suitable for specific foam applications by adjusting the gas flow rate and surfactant concentration.

The effect of multi-orifice plate configuration on bubble detachment volume

Abstract The multi-orifice plate gas sparger, mainly composed of a multi-orifice plate and a gas chamber, is one of the most common sparger facilities. The aeration performance of multi-orifice plate has a close relation with the multi-orifice plate configuration. In addition, the weeping phenomenon has a considerable influence on the gas chamber condition which affects the bubble detachment volume directly. This paper conducts a set of visual experiments to study the influence of multi-orifice configuration and gas chamber condition on the aeration performance of gas sparger. For multi-orifice plate, an improved theoretical model is proposed which considers the wave effect of the previous bubbles generated from adjacent orifices and the variance of the number of active bubbling orifice. A parameter is proposed to evaluate the aeration performance in order to overcome the difficulty caused by the randomness of bubble formation process. The experimental results suggest that the gas chamber filled with water is in favor of large bubble formation. The influence of the pitch of orifice on aeration performance can only be observed in high-restricted case. According to the theoretical model and experimental results, the influences of gas flow rate and the number of open orifices on the aeration performance are analyzed and a design criterion for the number of open orifice is proposed.

Polyethylenimine-impregnated resins: The effect of support structures on selective adsorption for CO2 from simulated biogas

Adsorbents prepared by impregnating porous materials with polyethylenimine (PEI) are potential candidates for CO2 capture from biogas. The objective of current research is to investigate the effect of structures of resins on CO2 capture performance of PEI-impregnated resins from simulated biogas. Here, three commercially available resins (D101, X-5 and ADS-17) with different pore volumes or surface functional group were selected as supports. N2 adsorption-desorption, infrared spectroscopy, scanning electron microscopy and thermal gravimetric analysis were used to characterize the resins before and after impregnating PEI. Breakthrough experiments revealed that all these PEI-impregnated resins could selectively adsorb CO2 at ambient temperature. Meanwhile, PEI-impregnated ADS-17 exhibited a superior performance among the tested adsorbents, despite that it had the lowest BET surface area and total pore volume. It is mainly because that ADS-17 had uniform voids and carbonyl group, enhanced the dispersion of PEI and thus improved the CO2 adsorption performance. In addition, ADS-17-20% PEI possessed excellent regenerability. The influence of gas flow rate and temperature on the CO2 adsorption behavior upon ADS-17-20% PEI was also investigated. It was found that the adsorption capacity did not depend much on the flow rate when the gas flow rate ranging from 100 to 200 mL/min. When the temperature was increased from 25 to 45 °C, a slight increase in CO2 adsorption was observed. Furthermore, CO2 adsorption performance of ADS-17-20% PEI can be improved under humid condition.

The influence of gas flow rate on the structural, mechanical, optical and wettability of diamond-like carbon thin films

In this research, diamond-like carbon (DLC) thin films were deposited on silicon substrates by radio-frequency plasma enhanced chemical vapor deposition method using gas mixture of CH4 and Ar. The effect of different CH4/Ar gas ratio on the structure, refractive index, transmission and hardness of the DLC thin films were investigated by means of Raman spectroscopy, ellipsometry, Fourier transform Infrared Spectroscopy and nano-indentation methods, respectively. Nuclear resonant reaction analysis was used to measure the amount of hydrogen and carbon in the thin films. Furthermore, wettability of the thin films was achieved by measuring of water contact angle (WCA). The results indicated that the structural properties of the diamond-like carbon thin films are strongly dependent on the composition of gas mixture. Based on ellipsometry results, refractive index of the thin films varied in the range of 1.89–2.06 at 550 nm. FTIR results determined that deposition of DLC thin films on silicon substrate led to an increase of the light transmission in IR region and these films have the potential to be used in silicon optics as the antireflective coatings in this region. Nano-indentation analysis showed that the thin films hardness changed in the range of 7.5–11 GPa. On the other hand hydrogen content and fraction of C‒H bonds in the samples increased by an increase in the gas ratio of CH4/Ar. Also, WCA measurements indicated that WCA for thin films with gas ratio of 3/7 is the most and equal to 79°.

Schlieren flow visualization of helium atmospheric plasma jet and influence of the gas flow rate and applied voltage frequency

We used schlieren photography to visualize the influence of gas flow rates of 1, 2.5, 5, 10 L/min and of the applied voltage frequency on a helium atmospheric plasma jet induced at the nozzle of a capillary tube. The expansion of the gas in the surrounding medium (air) was analyzed in the two different modes – plasma on/plasma off. Changes in the above parameters affect the gas flow regime and the hydrodynamics of the jet.

Rate dependency of permeability in tight rocks

Matrix permeability of tight rocks is a challenging parameter to measure. The gas permeability measurements of low-permeability rocks are sensitive to pressure, effective stress, temperature, and testing technique. However, the influence of gas flow rate on permeability measurements of tight rocks is unknown.In this work, steady-state gas permeability experiments are conducted on four shale and siltstone samples using methane and nitrogen as flowing fluid. The gas permeability is measured at several flow rates, while mean pressure and mean effective stress are held constant. The measurements are repeated at several mean pressure values. The tests are designed to study the influence of mean pressure as well as flow rate on gas permeability. After the gas permeability measurements, the samples are saturated with water to measure water permeability. Subsequently, the samples are sheared in a triaxial cell and similar gas and water permeability tests are repeated to compare the permeability behavior before and after failure. The results indicate strong rate sensitivity in permeability of tight rocks. Measured permeability is observed to rise as flow rate increases and reaches a constant value at higher rates. Permeability of the failed samples shows a similar behavior, although with higher permeability values. The rate dependency of gas permeability seems to follow a trend, similar to what is reported in the literature as the transition between pre-laminar and laminar flow regimes. Based on the experimental results, a discussion is provided on the rate at which the transition between pre-laminar and laminar flow occurs. Finally, by combining the theories on rate dependent flow regimes and pressure dependent (Knudsen number) flow regimes, a more complete picture of gas permeability in porous media is proposed.

Experimentally validated numerical study of gas-solid vortex unit hydrodynamics

A three-dimensional numerical analysis of the flow in a Gas-Solid Vortex Unit (GSVU) is carried out. The numerical model is first validated by comparing the bed pressure drop and solids velocity with experimental data. Next, the influence of gas flow rate, solids density, and particle diameter on the pressure drop, solids velocity, bed void fraction and slip velocity between the two phases is studied. A stable, solids bed is achieved for the entire range of gas flow rates tested (0.1–0.6Nm3/s). No particle entrainment is observed when varying the solid density (1800–450kg/m3) or the particle diameter (2–0.5mm). A shift to bubbling fluidization regime is observed for small particle diameters (0.5mm). The observed changes in the GSVU flow patterns are discussed by analyzing the changes in the cumulative centrifugal to drag force ratio over the bed.

Influence of gas flow rate and sodium carboxymethylcellulose on foam properties of fatty alcohol sodium polyoxyethylene ether sulfate solution

ABSTRACTFoamability, foam initial liquid volume, and bubble size of fatty alcohol sodium polyoxyethylene ether sulfate (AES) surfactant solution were studied with and without the addition of sodium carboxymethylcellulose (CMC) at different gas flow rates, using a sparging method. The generation time decreased with increasing gas flow rate. At low gas flow rates, the added CMC greatly enhanced the foamability by preventing bubble collapse. The initial liquid volume of the foam first increased rapidly, and then gradually decreased. Increasing the CMC concentration increased the initial liquid volume of the foam. The mean bubble diameter first clearly decreased, then increased slowly with increasing gas flow rate. CMC showed different effects on bubble size at high and low gas flow rates. Adsorption of CMC on AES molecules forms a network structure and improves bubble film stability, which can explain the above results. These findings provide guidelines for generating foam with excellent properties suitable for coal mine dust control by adjusting the gas flow rate and the concentration of the added water-soluble polymer.

Deposition of Antimicrobial Copper-Rich Coatings on Polymers by Atmospheric Pressure Jet Plasmas.

Inanimate surfaces serve as a permanent reservoir for infectious microorganisms, which is a growing problem in areas in everyday life. Coating of surfaces with inorganic antimicrobials, such as copper, can contribute to reduce the adherence and growth of microorganisms. The use of a DC operated air plasma jet for the deposition of copper thin films on acrylonitrile butadiene styrene (ABS) substrates is reported. ABS is a widespread material used in consumer applications, including hospitals. The influence of gas flow rate and input current on thin film characteristics and its bactericidal effect have been studied. Results from X-ray photoelectron spectroscopy (XPS) and atomic force microscopy confirmed the presence of thin copper layers on plasma-exposed ABS and the formation of copper particles with a size in the range from 20 to 100 nm, respectively. The bactericidal properties of the copper-coated surfaces were tested against Staphylococcus aureus. A reduction in growth by 93% compared with the attachment of bacteria on untreated samples was observed for coverage of the surface with 7 at. % copper.

Impact of gas flow rate on breakdown of filamentary dielectric barrier discharges

The influence of gas flow rate on breakdown properties and stability of pulsed dielectric barrier discharges (DBDs) in a single filament arrangement using a gas mixture of 0.1 vol. % O2 in N2 at atmospheric pressure was investigated by means of electrical and optical diagnostics, accompanied by fluid dynamics and electrostatics simulations. A higher flow rate perpendicular to the electrode symmetry axis resulted in an increased breakdown voltage and DBD current maximum, a higher discharge inception jitter, and a larger emission diameter of the discharge channel. In addition, a shift of the filament position for low gas flow rates with respect to the electrode symmetry axis was observed. These effects can be explained by the change of the residence time of charge carriers in the discharge region—i.e., the volume pre-ionization—for changed flow conditions due to the convective transport of particles out of the center of the gap.

Performance of iodide vapour absorption in the venturi scrubber working in self-priming mode

The self-priming venturi scrubber is the key component of filtered containment venting systems for the removal of radioactive products during severe accidents in nuclear power plants. This paper is focused on the absorption performance of iodide vapour in the venturi scrubber, based on experiment and mathematical calculation. The results indicate that the absorption efficiency is closely related to solution flow rate, gas flow rate and temperature, but is not sensitive to iodide inlet concentration. When solution flow rate is low, the absorption efficiency increases rapidly with increasing the solution flow rate, and when the solution is excessive, the absorption efficiency remains around 99% stably; the influence of gas flow rate on absorption efficiency is mainly reflected in the variation of gas and liquid contacting time; when the solution flow rate is low, the increase of gas flow rate will led to an obvious decrease in absorption efficiency; temperature is not important when gas flow rate in constant but becomes effective for improving the absorption efficiency when gas velocity is constant. The proposed mathematical model can predict the iodide absorption process well in the range of experimental conditions. Especially, in the condition of lower gas flow rate and higher solution flow rate, the prediction accuracy is more satisfactory; however the accuracy of prediction will decrease at higher gas flow rates and lower solution flow rates because of neglecting the transverse exchange between gas and liquid phase.