Characteristics Of Gas-liquid Flow Research Articles

Deep deoxidation of water in a miniaturized annular rotating device: Experimental investigation and machine learning modeling

Conventional gas–liquid devices exhibit limitations, including inadequate dispersion efficiency and significant backmixing, leading to low conversion and large equipment volume. Thus, a miniaturized annular rotating device (m-ARD) was proposed based on microscale effects and rotating flow field to achieve efficient gas–liquid mass transfer and high conversion. Nitrogen-oxygenated water was selected as the experimental system to evaluate the performance of the m-ARD. The gas–liquid flow characteristics were investigated. The analysis focused on examining the impact of different factors on deoxygenation efficiency. The deoxygenation performance was optimized and compared with different devices. The study found that the m-ARD enables a continuous counter-current gas–liquid flow mode, with superior mixing performance and a narrow residence time distribution. The deoxygenated water with an oxygen concentration as low as 0.14 ppm can be produced, with a volumetric mass transfer coefficient (kLa) of 0.26 s−1, a theoretical stage value of 4.22, and a handling capacity of 30 mL/min under optimized experimental conditions. In addition, kLa was predicted using an artificial neural network model and showed good agreement with the simulated values. This work provides a promising reactor for chemical reactions that require high conversions.

Analysis of the Bubble Diameter Effect on the Gas-liquid Flow Characteristics of a Multiphase Rotodynamic Pump

Abstract In order to study the effect of bubble diameter on the gas-liquid flow in the multiphase rotodynamic pump, steady simulations with different bubble diameters were conducted using ANSYS CFX17.0. When the inlet gas content IGVF is 10%, the pump head and efficiency decrease with the increased inlet bubble diameters, and there are different downward trends at different stages of bubble diameter increase. The pump head and efficiency with small bubble diameter (d≤0.3 mm) are much higher than those of large bubble diameter(d≥0.4 mm). A small amount of gas accumulates on both the blade suction and pressure surfaces near the hub under conditions of small bubble diameters. When the bubble diameter is large, A large amount of gas accumulates on the blade suction surface, and almost no gas accumulates on the blade pressure surface. Due to the density difference between gas and liquid phases, gas accumulates near the hub. The gas content rapidly decreases when away from the hub under small bubble diameter conditions, resulting in good gas-liquid fluidity and weak gas-liquid separation.

A novel numerical approach for assessing the gas-liquid flow characteristics in pipelines utilizing a two-fluid model

The accumulation of liquid condensate in the wet gas pipelines gives negative effects on the piping efficiency and flow managements. Accurate prediction of the condensate behavior is of crucial importance in the pipeline engineering. In this study, the one-dimensional two-fluid model with the stratified modeling in its source term is used to describe the gas-liquid kinetic motion along the pipe and the flow fields obtained from the newly proposed numerical approach are utilized to analyze the flow characteristics. Firstly, four cases with varying inlet liquid fractions, outlet pressures, and different meshes are utilized to investigate the gas-liquid steady-state variations along the pipe. The numerical results indicate that the outlet pressure influences the working pressure of the inlet gas-liquid, subsequently altering the equilibrium state and momentum exchange direction near the inlet, resulting in different condensate distributions in the pipeline. In the transient analysis with initial empty pipe, the inlet gas-liquid mainly impacts the pressure wave propagations in pressure spread stage, the gas kinetic motion in gas filling stage and the motion of the dividing interface between different regions in liquid filling stage, which is validated by the proposed numerical approach through comparison with the simulation tool OLGA designed by Schlumberger. Furthermore, when the liquid condensates appear in the initial state, the transition zones have two physical forms between different flow regions, which include the sudden dividing interface due to the high liquid amount carried by the inlet gas and the transition region resulted from the liquid accumulations.

Study on mechanism of unsteady gas-liquid two-phase flow in liquid-ring vacuum pump

To investigate the gas-liquid two-phase flow mechanism in liquid-ring vacuum pump, the large-eddy simulation coupled with volume-of-fluid method (LES-VOF) was used to numerically simulate the unsteady gas-liquid flow characteristics in pump. The structure of gas-liquid flow within pump and its dynamic evolution characteristics were studied, and the hydraulic excitation characteristics induced by gas-liquid flow were analyzed. The result shows that the channel vortex inside the impeller on the pump suction side gradually flows out of the flow passage with the rotation of the impeller, and continuously mixes with the wake vortex at the outlet of the impeller and the separation vortex at the inner wall of the casing. The evolution and development of vortex structures with different intensities and scales near the inner wall of the suction side casing have a relatively large contribution to pressure fluctuation. The wake vortex at the impeller outlet of the exhaust side gradually enters the flow passage and dissipates gradually with time. There is an obvious high-intensity backflow vortex in the exhaust section due to the pressure difference between the flow channels near the leading edge of the exhaust port, which leads to obvious rotor-stator interaction in the exhaust section.

Influence of diffuser structure on draining and dry process of Tokamak cooling water system

The diffuser used at the pipe size changing is a common part in the Tokamak cooling water system. It is one of the factors affecting the cooling water retention in the drainage and drying process, which will reduce the dryness of the drying system. This paper focuses on the effect of diffuser structure on gas-liquid flow characteristics in drainage drying process. Further, a numerical simulation model is established to analyze the pressure field, velocity field and phase distribution in the diffuser with different expansive angle in detail. According to the research results, the reflux phenomenon in the diffuser increases with the increase of the angle of the diffuser. This work provides a reference for the design and analysis of drying system of fusion reactor in the future.

Flow Characteristics of Electrochemical Catalytic Reduction of CO2 in Microchannel

Human beings need abundant material support and energy supply in their exploration of the universe. The sustainable supply of materials is an important condition for long-term space exploration. In situ resource utilization technology (ISRU) is an important way to realize the sustainable development of space exploration, which uses the abundant raw materials in outer space to transform energy and materials. In this paper, a microfluidic reaction device based on in situ resource utilization is designed, which converts H2O and CO2 into O2 and organic matter through photoelectrocatalysis. The flow and mixing process of gas-liquid two-phase flow was studied, and both the characteristics of mass transfer and the chemical reaction of fluids in the microchannel were studied. The dynamic process of the fluid-in-microchannel chemical reaction was expounded, and a prediction model of the volumetric mass transfer coefficient was proposed. The results show that the mass transfer coefficient of the chemical reaction is affected by the gas-liquid flow characteristics, and the mass transfer affects the rate of the chemical reaction. The material conversion of in situ resources by using the microchannel device can improve efficiency and accurately control the reaction products.

Numerical investigation of gas–liquid two-phase performance in a mixed-flow pump by using a modified drag force model

As key devices to lift deep-sea oil and gas, mixed-flow pumps can transport multiphase flow with high inlet gas volume fraction (IGVF). Performance parameters of mixed-flow pumps may be disturbed by the complex flow and gas–liquid distribution under various conditions that need an accurate two-phase flow numerical methodology for prediction. In this work, the gas–liquid mixed flow performance of a mixed-flow pump is investigated based on the modified drag force model, which considers the bubble deformation at high IGVF. The effects of the IGVF on pressure increment and gas phase distribution are explored. The influences of flow rate and rotational speed are studied as well. Experiments are conducted to obtain performance parameters and gas–liquid distribution images. The results show that performance parameters and gas–liquid distribution predicted in simulations are consistent with those obtained in experiments. The pressure increment of the mixed-flow pump is decreased as the IGVF and flow rate increase. Especially when IGVF increases from 5% to 15%, the pressure increment drops sharply, which is the surging phenomenon. The increased speed may improve the performance. The evolution of gas phase distribution is deeply analyzed to improve the understanding of gas–liquid flow characteristics in mixed-flow pumps.

Experimental investigation and performance improvement of a new combined T-junctions gas-liquid separator

The objective of this paper is to study the gas-liquid separation performance and its improvement of a new combined T-junctions separator by experiments. This separator is constructed of large-diameter T-junctions (50 mm and 60 mm), symmetrically arranged in annulus. The test conditions include complete separation and incomplete separation. The gas-liquid flow characteristics of the combined T-junctions were visually observed and analysed during the separation process. The separation characteristic was quantified (F) and the effects of liquid level, inlet superficial velocities (JG1 and JL1) and outlet valve opening degree on the separation efficiency (F) were confirmed. The results show the connections between the parameters and separation efficiency. Based on the above, a self-regulating level controller is designed, which can significantly extend the range of inlet gas velocity (JG1) to 4.5 times and inlet liquid velocity (JL1) to two times for complete separation, but the level controller fails when the inlet gas-liquid velocities are too high (JG1 > 10.27 m/s, JL1 > 0.52 m/s). [Received: December 14, 2021; Accepted: August 7, 2022]

INFLUENCE OF LOW-FREQUENCY EXTERNAL PULSATIONS OF LIQUID FLOW RATE ON GAS-LIQUID SLUG FLOW IN A RECTANGULAR MICROCHANNEL

This paper presents the results of an experimental study of the influence of the liquid flow rate of external pulsations on the gas-liquid flow characteristics of periodic slug flow in a microchannel. The experimental data were obtained using high-speed visualization of the flow of an ethanol-nitrogen mixture in a T-junction microchannel with a 390 × 150 μm rectangular cross section. A novelty of this work was the use of pulsations of the continuous liquid phase on the gas-liquid flow. The form of external pulsations was a sine wave with different frequencies (f = 1 and 2 Hz) and amplitude values (A = 8%, 20%, and 40%). The results obtained showed that using high-amplitude and low-frequency external pulsations destroys periodic slug flow and changes the monodispersity of bubbles and liquid slugs. The statistical characteristics of the flow were obtained based on the frequency and amplitude of the pulsations.

Numerical investigation on flow and atomization characteristics of hydrated magnesium nitrate gas-liquid two-fluid nozzle

The aim of this study is to reveal the atomization process of Mg(NO3)2·2H2O generated in the nitric acid leaching process of laterite nickel ore through a nozzle into a pilot pyrolysis furnace using CFD method. Based on the Euler-Lagrange method, a mathematical model of the hydrated magnesium nitrate gas-liquid two-fluid atomization nozzle was established, which can describe the gas-liquid flow characteristics. A visualization experimental platform was built for whose reliability has been verified by using graphical analysis technique. The influence law of gas channel inclination angle (hereinafter referred to as inclination angle), channel number and gas inlet pressure on the velocity inside the nozzle, liquid volume fraction and velocity and particle diameter of the atomization field were further explored. The results show that the number of gas channels is the main influencing factor for the average velocity at nozzle outlet and Sauter Mean Diameter (SMD) of atomized particles, while the gas inlet pressure mainly affects the volume fraction of liquid. When the inclination angle increases, the average velocity of nozzle outlet increases, and the Average Mean Diameter (AMD) and SMD of the atomized particles decrease. At the same time, the average volume fraction of hydrated magnesium nitrate first increased and then decreased, with the maximum value to 27.91% when the angle is 30°. Therefore, the high nozzle outlet velocity can play an important role in promoting droplet fragmentation and the volume fraction of hydrated magnesium nitrate for the later pyrolysis, only when the inclination angle is set properly.

Research on Flow Field Characteristics in Water Jet Nozzle and Surface Damage Caused by Target Impact

As a new processing method, water jet processing technology has risen rapidly due to its wide range of applications, no pollution, and zero discharge. In this paper, the flow characteristics and failure characteristics of ultra-high-pressure gas-liquid jet in the range of 300 MPa are analyzed by numerical calculation. The research conclusion shows that the jet atomization diffusion is caused by the friction between the liquid medium and the surrounding gas, the mixed flow of broken water droplets and cavitation. The jet diffusion process is essentially the energy exchange process between the jet in the core area and the turbulent flow in the atomization area. The distribution of the turbulent kinetic energy in the atomization area can determine the degree of jet diffusion and the rate of energy decay. The water jet impacted the surface of the target to form a crater-like annular erosion pit. With the increase of the impact pressure, the deformation showed an overall increasing trend, and the increasing trend increased significantly. The central depression of the erosion area is caused by the damage of the material by the stagnation pressure in the core area. The flow characteristics of gas-liquid flow in the process of formation and diffusion in the high-pressure water jet nozzle are explored from the microscopic point of view, and it also provides a theoretical basis for equipment optimization in engineering.

Recognition of gas-liquid flow regimes in helically coiled tube using wire-mesh sensor and KNN algorithm

• Flow patterns in helically coiled tube are classified by visual observation. • Void fraction for entire cross-section is measured by wire-mesh sensor. • k -Nearest Neighbors algorithm is utilized to identify flow patterns objectively. • Influence of centrifugal force and secondary flow on phase distribution and flow transition is revealed. Helically coiled tube (HCT) is used extensively in compact types of heat exchangers. Complete knowledge of gas-liquid flow behavior in HCT is essential in designing the heat transfer equipment involving phase change. Although the gas-liquid flow patterns in straight tubes have been widely studied, investigations on flow pattern recognition in HCT are still scarce. In this paper, based on the backlight imaging tomography and self-designed wire-mesh sensor, air-water experiments are carried out to study the characteristics of gas-liquid flow in a transparent HCT. Bubble, plug, slug, wavy and annular flow are observed, and their void fraction at the cross-section of the tube are measured and analyzed using the statistic parameters of time-trace, PDF and CPDF. Owing to the simplicity of implementation, the void fraction data are subsequently utilized along with the k -Nearest Neighbors algorithm (KNN algorithm) to identify the flow patterns objectively. Finally, a flow regime map is proposed and compared with the previous straight flow map and HCT map in the literatures. Accordingly, the influence of curvature-induced centrifugal force and secondary flow on the phase distribution and flow-regime transition is revealed in the present study.

A novel drift eliminator enhanced by Voronoi-based porous foam applied to liquid desiccant system: Separation performance and preliminary design

A novel drift eliminator enhanced by Voronoi-based porous foam (VPF-enhanced drift eliminator) is proposed for the control of salt-spray aerosol in liquid desiccant systems. The gas-liquid flow characteristics though VPF-enhanced drift eliminator under different conditions are examined numerically and verified by the experimental results in the literature. Additionally, a new prediction model of separation efficiency is obtained based on response surface methodology. The results show that 3-D modeling of porous foam based on Voronoi technology can well characterize the structure properties of actual porous foam in terms of meso-scale (i.e. pore shape, strut orientation and cell topology) and macro-scale (i.e. strut diameter and porosity), which provides support for more accurate analysis of separation performance from the microscopic aspect of droplet. Separation performance exhibits a strong dependence on the structure properties of porous foam and operating conditions. Moreover, the interaction of thickness and porosity has a significant impact on separation efficiency. For porous foams with relatively low resistance (i.e. smaller thickness and higher porosity), separation efficiency can be simply quantified by the specific surface area of the porous foam. For relatively high resistance, it is jointly determined by the specific surface area and resistance. It is concluded that prediction model combined with multi-objective optimization can provide guidance for the structural design and selection of VPF-enhanced drift eliminator. Meanwhile, Voronoi-based porous foam can be conveniently processed by the additive manufacturing techniques, which provides engineering significance for the development of VPF-enhanced drift eliminator under specific needs.

Falling film co-current flow cyclone demister for separating high-boiling droplets: Gas-liquid flow pattern and performance

In many processes, the product gas stream contains liquid droplets that easily condense or solidify, which can deteriorate demister performance and even block equipment during gas–liquid separation. We proposed a falling film co-current flow cyclone demister (F2CFCD) to solve the above problems. The novel idea is that an additional stream of solvent fluid is added to the gas stream containing the droplets. After injecting the demister, the solvent fluid forms a film on the wall of F2CFCD. When the droplets are separated to the wall surface by centrifugal force, they are dissolved by the liquid film, thereby avoiding crust formation. In this work, the gas–liquid flow characteristics and the performance of F2CFCD are investigated numerically and experimentally. A hot-wire anemometer (HWA) is used to measure the gas velocity, and a conductivity method is used to measure the liquid film thickness. A coupled numerical model of the RSM-DPM and Eulerian wall film (EWF) model is applied to discuss the effect of the gas–liquid flow rate on the flow field in the demister. The liquid volume flow rates ranges from 0.5–10.5 m3/h, and the gas volume flow rates range from 640–894 m3/h. The gas flow pattern and the liquid film flow regimes are explored in the F2CFCD. A film thickness model is established to evaluate the average film thickness in the waterfall regime. Experimental observations illustrate that F2CFCD has a high separation efficiency for droplets under all conditions.

Study of interface gas-liquid flow characteristics in a rectangular microchannel for wavy-annular flow

The aim of this work is an experimental study of a gas-liquid flow in a rectangular slit microchannel with a cross-section of 200 × 2045 μm. Ethanol/water (95/5) mixture and nitrogen are used as working liquid and gas, accordingly. The external T-mixer is used for obtaining of wavy-annular flow pattern. The experimental data on interfacial waves and their characteristics in the meniscus area on the short side of the microchannel are obtained using high-speed visualization for a wide range of gas and liquid superficial velocities. Images are processed using the Python libraries to define the average liquid layer thickness and maximum amplitude of waves. An increase of gas superficial velocity causes decreasing in the average liquid layer thickness and maximal amplitude of the liquid layer thickness. The waves on the liquid layer surface (maximal amplitude) can be three times larger than the average liquid layer thickness for presented liquid and gas velocities. With increasing gas superficial velocities more liquid displace from the meniscus area to the liquid film on the wide side of the microchannel.

Critical heat flux enhancement using composite porous structure produced by selective laser melting

• Uniform porous structures (with single pore size) and Composite porous structures（with two different pore sizes) are fabricated by selective laser melting. • Composite porous structure has the best heat transfer performance. • Critical heat flux enhancement of up to 3.2 times is achieved. • Gas-liquid flow characteristics of the composite porous structure is analyzed. Cross scale composite porous structures have been proved to have a better effect on enhanced boiling heat transfer. Accurate control of composite pore size and porous structure thickness is important for the study of enhanced boiling heat transfer. In this study, composite porous structures were manufactured with selective laser melting (SLM) technique from aluminum alloy (AlSi10Mg) powder. The heat transfer characteristics of a composite porous structure with composite pores (0.6 mm small pores and 2 mm large pores) for pool boiling under atmospheric pressure were investigated. A comparative analysis was performed with the uniform porous structure (0.6 mm pores) and the composite porous structure. The results shown that the composite porous structure can significantly increase the critical heat flux (CHF) compared to the plain copper surface. The CHF of the composite porous structure was higher than that of the uniform porous structure with the same height. As the height increases, the nucleate boiling heat transfer performance with composite porous structures will decrease, due to the larger gas–liquid resistance as a result of the height increment. In the range of 1.5–4.5 mm studied in this research, the 1.5 mm high composite porous structure achieves the maximum increase in CHF. The maximum CHF was 346.6 W/cm 2 , which was 3.2 times that of the plain surface. The large pores in the composite porous structure can play a role of shunting to reduce the escape resistance of the bubbles, which can further enhance CHF.

Gas-liquid flow seal in the smooth annulus during plunger lifting process in gas wells

Liquid leakage and gas slippage through the annulus between an upward moving plunger and vertical tubing significantly reduce the uploading efficiency of the accumulated liquid during plunger lifting in gas wells. Understanding the characteristics of gas-liquid two-phase flow in the annulus during plunger lifting process is crucial to enhance the fluid seal and to improve the plunger lift technology, but investigations of this important issue in literature is extremely limited. In this paper, we employ VOF-CFD numerical approach to provide a computationally efficient flow model to account for interactions between loading liquid, producing gas and the lifting plunger in gas wells. Results from simulations are consistent with both the in-door experimental data and field observations, thus allowing us to reproduce detailed characteristics of gas-liquid flow in the annulus during plunger lifting process. The actual conditions in gas wells are simulated, in which the plunger upward velocity is ranged in 2 m/s ≤ vp ≤ 10 m/s and the gas density is ranged in 13.9 kg/m3 ≤ ρg ≤ 80.9 kg/m3. Numerical results indicate that with the plunger lifting velocity increasing, the liquid leakage flow rate increases, the gas slippage flow rate decreases, and the gas-liquid countercurrent annular flow in the annular space transforms to the co-current upward annular flow. Based on the interface instability analysis, we reveal the mechanism of gas-liquid flow seal in the annulus which is promoted by the droplet entrainment and is weakened by the droplet deposition. A simple dimensionless coefficient is proposed to evaluate the uploading efficiency of the accumulated liquids by the plunger in gas wells, the bigger value of the coefficient represents the better performance of liquid sealing during plunger lifting process. The optimal diameter ratio between the plunger and tube (0.96), as well as the optimal diameter-length ratio of the plunger (0.13) are proposed to improve the plunger lift technology.

Mechanism and fundamental models of gas–liquid surging for valve columns

AbstractThe gas–liquid streams in valve columns are likely to surge at low gas velocities, which degrades tray performances and threatens production safety. Therefore, the gas–liquid surging mechanism and vibration properties were investigated in this article. First, the theory of gas–liquid unstable flow at the seal point was proposed based on the principle of lowest energy. Then, the evolution mechanism, gas–liquid flow characteristics, and essential condition of surging are proposed. Meanwhile, experiments were carried out in a Φ580 mm valve column; the frequency spectral and hydraulic characteristics of surging were in accordance with the expected surging mechanism. Moreover, the surging vanish point criterion and safe operating superficial gas velocity for valve columns were advanced. Finally, fundamental models for surging frequency and amplitude were established. The models are in close accordance with the experimental data, which suggests that they could accurately describe the surging behavior.

Drag coefficient modification for turbulent gas-liquid two-phase flow in a rotodynamic pump

An appropriate drag coefficient model is necessary for the simulation to better predict gas–liquid flow characteristics in a multiphase rotodynamic pump. However, most of the drag coefficient models are derived based on bubbles rising through a stagnant or laminar liquid, which are not applicable for turbulent flow in pumps. In this study, the drag coefficient in the quiescent flow is correlated with the drag coefficient in the turbulent flow through the Stokes number, and the drag coefficient model proposed by Ishii and Zuber (1979) is modified. By comparing the simulation results with experimental data of a rotodynamic pump, it is found that the pump performance predicted by the simulation with the modification is larger than without it, and has better accuracy. After the correction, the bubble accumulation near the suction side of the impeller blade is reduced, the gas volume fraction in the diffuser also decreases. When the rotational speed of the pump is 2350 r/min, the drag coefficient after the correction near the suction side of the impeller blade is much larger than before the correction. At the highest turbulent kinetic energy, the drag coefficient with the modification is more than 20 times greater than the corresponding ones without it. When the rotational speed increases to 2650 r/min or 2950 r/min, the frequency of the eddies are too high to affect the bubble motion, which makes the increasing degree of the drag coefficient decreases.

Study on the effect of cetyltrimethylammonium bromide on gas-liquid flow characteristics at low gas flow rates and gas pressure

Cenomanian gas deposits account for about 80% of natural gas production in Russia. Today, mature Cenomanian gas fields are depleted by more than 75% on average, the reservoir pressure in the productive formation zone has decreased by almost 90% compared to the initial pressure and in some places reaches 1.0-1.5 MPa. Reduction of pressure in the pay zone leads to active intrusion of water from the aquifer. The liquid is loading the well, and gas production decreases. The technology of gas well operation with foaming agent is widespread in the world, which is characterized by a high level of efficiency, including economic. The use of technology leads to a solution to the liquid loading and requires a preliminary selection of the optimal concentration of surfactants. The optimal concentration should ensure the creation of a relatively stable foam and provide a minimum pressure gradient in the production tubing. The article presents the results of studies of CTAB foaming agent influence on the process of liquid removal and pressure gradient in production tubing. Sequential studies to determine CMC, foamability, foam stability, and pressure gradient under foam flow were conducted on small-scale and large-scale facilities. These results can be reliable when using CTAB foaming agent, foaming agents based on it, or other cationic foaming agents in Cenomanian gas wells under the condition of reservoir water inflow. Besides, the effect of pressure on the optimal concentration of the foaming agent was also studied in this work.