Increase In Superficial Gas Velocity Research Articles

Experimental fluid dynamics of particles in a dielectric barrier discharge plasma-enhanced spouted bed

This study proposed the fluidized particles with dielectric barrier discharge (DBD) plasma in a slot-rectangular divergent-base spouted bed and focused on the dynamics of solid particles with the plasma irradiation. Two bed materials (Polypropylene (PP) particles and Polyamide (PA) particles) with same diameter (3 mm) were fluidized in this study. Fluidization parameters included gas velocity (7.4–14.9 m/s), particle amount (100–500), and plasma parameter (apply voltage, 0 and 7 kV) as the applied voltage were investigated here. Particle velocity profiles were analyzed through the methods of particle image velocimetry (PIV) and particle tracking velocimetry (PTV). Results show that the particle velocity was increased with the plasma irradiation, mainly by the enhancement in the vertical direction. The location of the highest particle velocity area related to the fluidization behavior of particles. With the increase of superficial gas velocity, the location of the highest particle velocity area raised along the central line but not reached the top of the solid bed. While the electron temperature of Ar plasma decreased with the addition of particles. Two electric fields (external electric field and surface charge electric field) presenting in the system were assumed to give the reason for the changes of the particle fluid dynamics.

An Experimental Study of Gas Flow Regime and Pressure Drop in a Random Packed Bed with Sinter Particles

The gas flow regime and pressure drop in a gas–solid packed bed with irregularly shaped sinter particles were experimentally investigated. Using a self-made experimental facility for data measurement, the gas flow pressure drop in a sinter bed layer was determined for various experimental conditions. According to the changes in the modified coefficients, α and β, for different flow regimes, the flow transitions from one regime to another in packed beds with different particle diameters were described. Furthermore, the pressure drop correlations for different flow regimes were determined, and the reliabilities of the obtained correlations were contrastively analyzed. The results show that, when the particle diameter is constant, the modified pressure drop per unit height, ΔP/Hu, increases linearly with the increasing gas superficial velocity. When the gas superficial velocity is larger than 1.15 m/s under atmospheric conditions, the gas flow regime in the sinter bed layer is the turbulent flow. Compared with the experimental correlation of the whole flow, the pressure drop correlations obtained by the piecewise fitting method provided a better prediction of the experimental values, and the average deviations of the obtained correlations for the Forchheimer flow and the turbulent flow were 5.31% and 4.07%, respectively.

Experimental Observation of a Regression Dependence for Hydrodynamic Performance of the Regular Packing

The investigational studies of regression dependence of the new efficient regular packing bed’s flow friction on gas velocity and liquid spray rate has been carried out. The tests were made by the procedure of a complete two-factor experiment. On account of experiment design matrix, there are four tests to be made to determine the regression dependence. It is found that the packing bed’s flow friction builds up along with increase of superficial gas velocity and liquid spray rate. The regression dependence that puts packing bed’s flow friction in touch with superficial gas velocity and liquid spray rate is procured. The specific dependence is valid for air velocity 1.21-3.12 m/sec and liquid spray rate 0.0080-0.0304 m3/(m2 sec). The conclusion on significance of regression dependencies has been made in terms of Student’s t-test. The sufficiency of regression equation has been inspected via the Fisher’s criterion. The resulting regression equation can be utilized in the design and engineering process of absorbers with the shock-spray packing.

Evaluation of Velocity Impact on Sand Particles in Two-Phase Annular Flow in Horizontal Pipes

Experimental investigations on sand particles in annular flow in horizontal pipes were presented. The aim is to enhance the knowledge related to sand transportation in the oil and gas industry. More so, to add values in facilitating the optimum design of oil and gas production systems where annular flow is often encountered. The experimental investigations were conducted using a closed-loop consisting of a horizontal pipe with an internal diameter of 2-inch (0.0504m). The experimental investigations covered both: water/sand flow and water/air/sand annular flow. The water/sand flow experiments were carried out to establish sand transport regime in liquid such as sand saltation, sand streak, and sand suspension. While, water/air/sand annular flow experiments revealed that the only the only sand transport regime in annular flow are saltation and suspension. Sand concentration profile in the annular flows were also estimated by using the sampling method. It was found that the bigger the sand particle size (500microns) leads to higher concentration of sand being transported at the bottom of the pipe because of gravity effect, while the smaller the sand particle size (212microns), leads to the higher sand concentration. Also, the sand concentration increased at the gas core as the superficial gas velocity increases.

Experimental investigation of gas-brine liquid flow in horizontal pipeline

Pipelines that are transporting fluids of different salinity in different pressurized conditions are met with different behaviors of flow. Flow behavior of two-phase gas–liquid system in simulated horizontal pipeline conditions are investigated experimentally with three different brine salinity concentrations comparable to the reservoir fluid properties within the Malay Basin. A test facility in total length of 80-feet was designed and configured for data acquiring of flow regimes which were observed via a 1.5-in diameter and a 7.5-feet long transparent acrylic pipe. A flow regime map where the transition of flow pattern from stratified to intermittent to mixed is proposed as the superficial gas velocity and superficial liquid velocity increase at increasing brine concentration. There is a combination flow pattern presumed to be the combination of plug flow, slug flow and thin annular. When the brine salinity increases, the pressure drop of the system increases. The lowest pressure drop in the form of percentage for brine concentration of 1000, 15,000, and 30,000 ppm at brine superficial velocity of 3.0 m/s were 57.1, 50, and 42.9% respectively. Pressure drop experimental results from this study were compared with previous mathematical correlations. Results also indicate that water holdup increases when water input fraction increases.

Investigation of bubble-particle attachment, detachment and collection efficiencies in a mechanical flotation cell

The paper presents the effect of impeller speed and superficial gas velocity on bubble-particle attachment, detachment and collection efficiencies using pure quartz particles in a mechanical flotation cell. Detachment and collection efficiencies in different parts of cell were calculated by local turbulent energy dissipation rate measurements using high speed stereoscopic particle image velocimetry technique. In addition to high detachment efficiency, low attachment efficiency is also one of the reasons for low collection efficiency for coarse particles. The flotation rate constant increased with an increase in superficial gas velocity. However, the effect of superficial gas velocity on collection efficiency was negligible. This means that any effect of superficial gas velocity on flotation rate constant was due to changes in the number of bubbles and collision frequency. The flotation rate constant, collision frequency, and the number of bubbles increased with increasing impeller speed. However, collection efficiency decreased with increasing impeller speed.

Performance comparison of swirl-venturi bubble generator and conventional venturi bubble generator

The bubble generation performance and liquid volumetric mass transfer coefficient kLa of the venturi microbubble generator and the swirl-venturi microbubble generator were evaluated through the high-speed photography and measurement of dissolved oxygen concentration. The results show that the swirl-venturi microbubble generator generates more bubbles with smaller Sauter mean diameter than the venturi microbubble generator. And the maximum stable bubble size of the swirl-venturi microbubble generator is also smaller than that of the venturi microbubble generator. Moreover, the maximum stable bubble size of the swirl-venturi microbubble generator is not sensitive to the increase of superficial gas velocity, which indicates that the swirl-venturi microbubble generator has a higher probability of breaking bubbles. Eventually, the liquid volumetric mass transfer coefficient kLa of swirl-venturi microbubble generator is measured and higher than that of the venturi microbubble generator at high superficial gas velocity. Based on all above, it can be concluded that the swirl-venturi microbubble generator is a more effective way to generate microbubbles.

Experimental and modeling study on the hydrodynamics in multiphase monolith modules with different distributors

Three commonly used distributors (i.e., nozzle, packed bed, and foam) were introduced into a multiphase monolith reactor in this work to investigate the pressure drop, liquid holdup and gas–liquid distribution performance by combining experimentation and CFD simulation. The experimental results showed that the nozzle distributor exhibited the better gas-liquid phase distribution and the lowest pressure drop. However, so far, the gas and liquid velocities at the top of the monolith bed, which are crucial for the transition from a single channel to bed scale, have not been studied. Thus, a discrete phase and continuous phase coupling 3D model using CFD simulation was established for the nozzle distributor, and the magnitude and distribution of the gas and liquid velocities at the entrance of the monolith module were investigated. The simulation results showed that the droplets’ velocity reaching the monolith module was very high and had a strong influence on the gas velocity distribution. The increase in superficial gas velocity could enhance the gas distribution to some extent.

Electrostatic Sensor for Determining the Characteristics of Particles Moving From Deposition to Suspension in Pneumatic Conveying

The minimum conveying velocity or the lowest point of pressure drop curve can reflect the characteristics of particles moving from deposition to suspension in pneumatic conveying. However, when the mass flow rate is low, the change of particles flow cannot be effectively reflected by the above methods. In this paper, based on a 4-arc electrode electrostatic sensor, with localised sensitivity, the detailed scale signals that represent the particle random motion are extracted by the combination of Empirical Mode Decomposition (EMD) and Hurst exponent. The differences in the particle random motion energy ratio (PRMER) of 4-channel electrode signals are used to characterize the transition of flow state. In the verification experiment by using a belt-style electrostatic velocity measured rig, the higher the velocity of rubber belt or the closer to the electrode, the higher the PRMERs of electrostatic signal. In the experiment of gas-solid two-phase flow rig, the PRMERs of 4-channel electrode signals are all increasing with the increase of superficial gas velocity, and the PRMERs of different electrodes are rather different at low superficial gas velocity ( ${V}_{g}$ ). When ${V}_{g}$ drops at the minimum pressure drop point ( ${P}_{{MPD}}$ ), the PRMERs of top/bottom and left/right electrodes begin to separate (e.g. the particle mass flow rates are 100 kg/h and 120 kg/h). Furthermore, when the solid mass flow rate is 80 kg/h, the proposed method can clearly characterize the transition of flow states in the pipeline, but the pressure drop phase diagram cannot.

Evaluation of Wave Characteristics in Annular Flow in Horizontal Pipes

Annular flow experiments in horizontal flow in pipes were conducted with emphasis on wave characteristics (wave velocity, wave frequency) and liquid film thickness. The experiments were conducted using water/air in a 0.0504m pipe diameter with a total flow loop length of 28.68m. Liquid film thickness in all the flow matrix in this study, were observed to be decreasing with increase in gas velocity while increasing with increase in liquid velocity. The decreasing tendency with superficial gas velocity was because of liquid entrainments which were accounted. Pan and Hanratty correlation for liquid entrainment was chosen because it gave the most realistic results among other correlations from the experimental data. Wave velocity and wave frequency were presented to be increasing with increase in superficial gas velocity in annular flow. For wave frequency, it was observed that both superficial liquid and gas velocities have great impact on it. In annular flow in horizontal pipe, it was also observed that the lower the superficial liquid velocity, the lower the amplitude and the higher the wave frequency. This indicates that at low liquid velocity, more ripple waves occurred and at this time more energy were dissipated which resulted to the high frequency observed in this study. However, several correlations where compared with the obtained wave frequency in this study, but [2] preferably matched better as the superficial liquid velocity increases from 0.0903m/s to 0.1851m/s.

Evaluation of Liquid Film Thickness in Gas-Liquid Annular Flow in Horizontal Pipes Using Three Methods

Experimental investigations on annular flow film thickness were conducted using a closed-loop horizontal pipe with an internal diameter of 2-inch (0.0504m). The aim is to progress the understanding of such flow and facilitate the optimum design of hydrocarbon production systems were such flow is encountered. Liquid film thickness was extensively investigated using three methods: the conductance probe sensors installed at the bottom of the pipe, conductivity ring sensors and triangular relationship model. From these methods, liquid film thickness was proven to decrease with increase in superficial gas velocity, while increases with increase in superficial liquid velocity. In comparison, the predicted triangular relationship liquid film thickness matched better with the liquid film thickness obtained from conductance probe sensors at all the flow conditions in the experiments, while the conductivity ring sensor results matched closely at superficial liquid velocity of 0.0505m/s and 0.0714m/s but overestimated at superficial liquid velocity of 0.0903m/s and 0.1851m/s. This has shown the impact of high superficial gas velocity on conductivity ring sensors in accounting for liquid film thickness.

Pola Aliran Dua Fase Gas - Fluida Non Newtonian Melalui Belokan Pipa

Two-phase flow applications can be used in chemical reactors, fuel cell and a cooler of electronic devices. Nowadays, the study on multiphase flow is concern with the gas-non Newtonian liquids flow. Since, non-Newtonian liquids commonly used in both industrial and medical applications such as blood flow, polymer and chemical solutions. The viscosity of a non-Newtonian liquid cannot be described by Newton’s law viscosity. The viscosity will affect flow behavior in pipes depends on the rheology of the fluid. The purpose of this study is to further investigate the flow pattern characteristic of gas-Newtonian/non-Newtonian liquid two-phase flows in a normal channel. Ultrapure water, polyacrylamide aqueous solutions (PAM) were used as test fluids, while argon gas as the test gas. Liquid and gas were introduced in T-junction, which placed on the upstream of the test section. In this study, the polyacrylamide concentration was variated on 0.1% wt and 0.4% wt. Moreover, the flow rate of liquids tested were variated on 0.1167 m 3 /s, 0.183 m 3 /s, 0.25 m 3 /s; and 0.283 m 3 /s. Therefore, the gas tested was variated on 0.083 m 3 /s, 0.167 m 3 /s, and 0.25 m 3 /s. The circular channel and bend pipe were used in this study, which has hydraulic diameter of 25.4 mm. The high-speed video camera was used to record the flow patterns in the bend as the test section. The flow pattern, bubble length, bubble velocity and void fraction were determined by analyzing the video image of the flows. Slug and plug flow patterns mostly appear in this study for each variation of liquids tested. Increasing gas superficial velocity induced the longer bubble. Furthermore, because of the higher viscosity of the non-Newtonian liquid, the bubble nose of gas-non Newtonian liquid two-phase flow becomes sharper than the bubble nose of gas-Newtonian liquid two-phase flow.

Gas dispersion and solid suspension in a three-phase stirred tank with triple impellers

The hydrodynamics is still not fully understood in the three-phase stirred tank equipped with multi-impeller due to the intensive interaction between phases. In this work, the solid critical suspension speed ( N JSG ), relative power demand (RPD) and overall gas holdup ( ε G ) were measured in an air–water–glass beads stirred tank equipped with multi-impeller, which consists of a parabolic blade disk turbine below two down-pumping hydrofoils. Results show that either the N JSG or the specific power consumption increases when increasing the volumetric solid concentration or superficial gas velocity. RPD changes less than 10% when solid volumetric concentration ranges from 0 to 15%. ε G decreases with the increase of solid concentration, and increases with the increase of both superficial gas velocity and the total specific power consumption. The quantitative correlations of N JSG , RPD and ε G were regressed as the function of superficial gas velocity, specific power consumption, Froude number and gas flow number, in order to provide the reference in the design of such three-phase stirred tank with similar multi-impellers. • Just-suspension speed, RPD and gas holdup with triple impeller were measured. • Superficial gas velocity significantly affects the suspension speed. • Overall gas holdup is evidently affected by the solid.

A novel sieve plate hole pattern: effect on gas hold-up and flow regimes in a bubble column

The effect of an innovative sieve plate orifice layout on the hydrodynamics of a cylindrical bubble column is investigated. The classical triangular layout is compared with a novel spiraled layout, using the same number and diameter of orifices. The experiments include two different column aspect ratios and two liquid phases of different coalescing nature. According to the holdup data, if the spiraled layout is used, the flow regimes evolve from a pseudo-homogeneous regime to a heterogeneous regime going through a transition regime, as the superficial gas velocity increases. When the triangular layout is used, the homogeneous regime is not detected and pure heterogeneous regime is obtained at all superficial gas velocities. When using the spiraled layout, the gas retention increases, resulting 24% higher in the homogeneous regime and 13% higher in the heterogeneous regime with respect to the gas retention obtained with the triangular layout. If bubble coalescence is modified by the addition of NaCl, the holdup increases for both layouts, but to a lower extent in the spiraled layout (10%) compared to the triangular layout (24%). The reason behind the reduction of coalescence and higher gas holdup values is the ability of the spiraled layout to produce bubbles that do not interact with each other during a longer path along the column.

Microbubble generation with shear flow on large-area membrane for fine particle flotation

Fine particle flotation is carried out in a flotation column with a 19-channel ceramic membrane sparger. The microbubble generation is controlled by the shear flow in the membrane channels. Bubbles in the flotation column are photographed via a high speed video camera. Gas holdup and quartz recovery is investigated under different operating conditions. Gas holdup in the flotation column firstly increases and then decreases with the increase in superficial gas velocity. Similar trend in gas holdup is also found by increasing cross flow velocity. Larger particle concentration in the feed results in smaller gas holdup, while the gas holdup positively changes with collector concentration. The quartz recovery is strongly influenced by gas holdup and bubble size. Similarly, the recovery firstly increases and then decreases when increasing superficial gas velocity and cross flow velocity. The collector concentration plays a more obvious role in flotation recovery at high superficial gas velocity.

Investigation of slug-churn flow induced transient excitation forces at pipe bend

Numerical simulations of two-phase flow induced fluctuating forces at a pipe bend have been carried out to study the characteristics of multiphase flow induced vibration (FIV). The multiphase flow patterns and turbulence were modelled using the volume of fluid (VOF) method and the k−ϵ turbulence model respectively. Simulations of seventeen cases of slug and churn flows have been carried out showing the effects of superficial gas and superficial liquid velocities. The simulations results show good agreement of the volume fraction fluctuation frequencies of slug and churn flows with the reported experiment. In addition, the vibration characteristics of the excitation force have been accurately captured. The simulation results show that the predominant frequency of fluctuations of force decreases and the RMS of force fluctuation increases with the increase of superficial gas velocity. On the other hand, both predominant frequency and the RMS of force fluctuations increases with the increase of superficial liquid velocity. Increase of gas fraction narrows the range of frequency ranges, while increasing the liquid expands the frequency ranges of force fluctuations.

Simulation Study on Gas Holdup of Large and Small Bubbles in a High Pressure Gas–Liquid Bubble Column

The computational fluid dynamics-population balance model (CFD-PBM) has been presented and used to evaluate the bubble behavior in a large-scale high pressure bubble column with an inner diameter of 300 mm and a height of 6600 mm. In the heterogeneous flow regime, bubbles can be divided into “large bubbles” and “small bubbles” by a critical bubble diameter dc. In this study, large and small bubbles were classified according to different slopes in the experiment only by the method of dynamic gas disengagement, the critical bubble diameter was determined to be 7 mm by the experimental results and the simulation values. In addition, the effects of superficial gas velocity, operating pressure, surface tension and viscosity on gas holdup of large and small bubbles in gas–liquid two-phase flow were investigated using a CFD-PBM coupling model. The results show that the gas holdup of small and large bubbles increases rapidly with the increase of superficial gas velocity. With the increase of pressure, the gas holdup of small bubbles increases significantly, and the gas holdup of large bubbles increase slightly. Under the same superficial gas velocity, the gas holdup of large bubbles increases with the decrease of viscosity and the decrease of surface tension, but the gas holdup of small bubbles increases significantly. The simulated values of the coupled model have a good agreement with the experimental values, which can be applied to the parameter estimation of the high pressure bubble column system.

Friction pressure drop model of gas-liquid two-phase flow in an inclined pipe with high gas and liquid velocities

The calculations of friction pressure drop is the most complicated in multiphase flow. Understanding of the friction pressure drop in pipes are of great importance for many industry problems. The existing friction pressure drop models are generally based on low gas and liquid velocities in horizontal and vertical pipes. In this paper, a two-phase flow experiment in inclined pipe was performed. We report the effect of superficial gas and liquid velocities on friction pressure drop, the results indicate that the pressure drop increases with the increase in superficial gas velocity and superficial liquid velocity. According to the experimental analysis and assuming that the fluid in contact with the pipe wall at high velocity is in a liquid phase, we developed a new friction pressure drop model of different flow pattern. This model based on the correlation between the fraction factor and the superficial gas and superficial liquid Reynold numbers. Compared with the previous models, the predictive performance of the present model is good and remains basically stable.

Analysis of Changes on Mean Particle Size in a Fluidized Bed using Vibration Signature

Vibration signals were measured in a lab-scale fluidized bed to investigate the changes in particle sizes. Experiments were carried out in the bed with a different mass fraction of coarser particles at different superficial gas velocities, and probe heights. The S-statistic test evaluates the dimensionless squared distance between two attractors reconstructed from time series of vibration signals. Values of parameters needed for the attractor reconstruction were derived from time series. These parameters consist of time delay, embedding dimension, bandwidth, and segment length with the values of 1, 35, (0.4-0.8), and (300-400), respectively. To reduce the sensitivity of the S-statistic to small changes in superficial gas velocities, the vibration signals were normalized in order to apply the attractor comparison test. The results showed that the attractor comparison can be a reliable technique for detecting particles size changes in fluidized beds even with small changes in the amount of coarser particles. The sensitivity of the method to particle size changes was decreased with an increase in superficial gas velocity. The results also show that the S-statistic test was almost independent of the measurement position of the vibration signals.

Investigation on the relationship between slurry droplet entrainment and fine particle emission in the limestone-gypsum WFGD system

ABSTRACTThe entrainment of desulfurization slurry droplets out of the scrubber had a significant influence on the properties of fine particle emissions in the limestone-gypsum desulfurization system. Investigations on the relationship between entrainment of slurry droplets and generation of fine particles during the desulfurization process were carried out with an experimental system. The results showed that a large number of fine droplets and submicron particles existed in the flue gas out of the scrubber, which was attributed to the entrainment of slurry droplets during the desulfurization process. The entrained droplet sizes were closely connected with the slurry atomization characteristics, and majority of them were with sizes less than 20 μm. The mass ratio of solid contents in entrained and sprayed droplets ranged from 15% to 40%, and particles in the entrained droplets were much smaller. With the increase of superficial gas velocity, liquid–gas ratio, and desulfurization slurry concentration, the proportion of entrained micron droplets was significantly higher. Correspondingly, more fine particles were emitted with increased rates of number concentrations ranging from 20% to 50%. The optimizations of spray scrubber were beneficial for the reduction of entrained droplets and fine particles such as the adjustment of nozzle arrangement and the addition of spray layer. The decrease rate of emitted fine particle concentrations ranged from 10% to 30%.