Gas-liquid Flow Research Articles

IMPROVING METHODS FOR PREDICTING THE STRUCTURE OF GAS-LIQUID FLOW IN HORIZONTAL PIPES

Analysis of existing research on the hydrodynamics of two-phase mixtures allows us to trace the main trends in the development of engineering calculation methods, as well as identify the most promising approaches for developing algorithms for predicting the patterns of gas-liquid flows in horizontal pipes. Predicting the patterns of two-phase flows is necessary to solve a number of applied problems related to the design of field pipeline systems, monitoring of operational parameters during the transportation of well products, calculation of hydraulic pressure drop in pipes, etc. Conventionally, in creating methods for predicting flow regimes in horizontal pipes, there are stages based on empirical approaches, mechanistic modeling and unification of hydrodynamic criteria for assessing the processes of patterns transformations of two-phase flows. Approaches based on the unification of hydrodynamic models of gas-liquid flows are noted as promising directions in the development of hydrodynamic forecasting criteria. The principles of unification consist in bringing to uniformity a mathematical apparatus capable of predicting all possible patterns of gas-liquid flow in vertical, inclined and horizontal pipes based on known volumetric flow rates of liquid and gas. The article proposes the improvement of known unification approaches in the development of criteria for predicting the annular and dispersed-bubble patterns of gas-liquid flow in field pipes. The verification of the obtained algorithms for pattern prediction of annular and dispersed-bubble modes of horizontal gas-liquid flow was carried out.

Simulation Analysis of the Annular Liquid Disturbance Induced by Gas Leakage from String Seals During Annular Pressure Relief

Due to the failure of string seals, gas can leak and result in the abnormal annulus pressure in gas wells, so it is necessary to relieve the pressure in gas wells. In the process of pressure relief, the leaked gas enters the annulus, causes a the great disturbance to the annulus flow field, and thus reduces the protection performance of the annular protection fluid in the string. In order to investigate the influence of gas leakage on the annular flow field, a VOF finite element model of the gas-liquid two-phase flow disturbed by gas leakage in a casing was established to simulate the transient flow field in the annular flow disturbed by gas leakage, and the influences of leakage pressure differences, leakage direction, and leakage time on annular flow field disturbance and wall shear force were analyzed. The analysis results showed that the larger leakage pressure difference corresponded to the faster diffusion rate of the leaked gas in the annulus, the faster the flushing rate of the leaked gas against the casing wall, and a larger shear force on the tubing wall was detrimental to the formation of the corrosion inhibitor film on the tubing wall and casing wall. Under the same conditions, the shear action on the outer wall of tubing in the leakage direction of 90° was stronger than that in the leakage directions of 135° and 45° and the diffusion range was also larger. With the increase in leakage time, leaked gas further moved upward in the annulus and the shear effect on the outer wall of tubing was gradually strengthened. The leaked acid gas flushed the outer wall of casing, thus increasing the peeling-off risk of the corrosion inhibitor film. The study results show that the disturbance law of gas leakage to annular protection fluid is clear, and it was suggested to reduce unnecessary pressure relief time in the annulus to ensure the safety and integrity of gas wells.

Examination on behavior of tip leakage flow in a three-stage gas-liquid two-phase flow pump

Examination on behavior of tip leakage flow in a three-stage gas-liquid two-phase flow pump

Determination of grout compactness in rebar grouted splice sleeves using frequency domain characteristics of the excitation process

Grouted splice sleeves are widely used in assembly building connections. However, void defects within the sleeve directly affect the load-bearing capacity of the building structure. This paper presents a new method for detecting void defects inside a grouted splice sleeve based on the frequency domain characteristics of mechanical vibration waves. This method analyses the grouted spliced casing containing void defects as a gas-liquid two-phase flow system. To confirm the validity of the method, this paper builds a test setup for testing. The results showed that the test method can effectively detect the void defects and the volume of the defects inside the grouted splice sleeves when the grout is not solidified.

Study on the Spatio-temporal Evolutionary Properties of Gas-liquid Two-phase Flow in Centrifugal Pump as Turbine (PAT)

With the increasing complexity of the industrial production process, the transmission medium of the hydraulic turbine is no longer satisfied, and the gas-liquid two-phase mixed medium has to be considered. The presence of gas in the transmission medium will alters the internal flow structure of the hydraulic turbine and affect its operational stability. Therefore, for the purpose of clarifying the influence of inlet gas content on the internal flow of PAT, the unsteady flow of the PAT is simulated in this paper using numerical simulation. Based on the numerical simulation results, the influence of inlet gas content on the internal flow characteristics, characteristics of pressure fluctuation in impeller and volute, and vortex evolution of flow field are analyzed. The accumulation of gas phase leads to the emergence of vortices, and regions with low pressure values appear at the vortex generation. The major factor of the periodic variation of pressure fluctuation between volute and cut-water is the dynamic and static interference of impeller. The increase of gas content causes more flow disorder in the cut-water region and the volute contraction section. Since the gas in the flow channel is predominantly on the suction side of blades, the flow field on the suction side is more complex than that on the pressure side, and the amplitude of pressure fluctuation increases appropriately. The vortex structure is mainly distributed on balance hole, inlet area of impeller and suction side of blade. As the blade rotates, there are new shedding and growth of vortices, and finally attached to the volute wall. Increasing gas content enhances the influence of blade rotation on the vortex evolution characteristics in the volute and impeller.

VOF-based modeling study of surface oscillation behavior and gas–liquid stirring dynamics in the bottom-blown reactors

Gas bottom-blown reactors are widely employed in the chemical, metallurgical, and biochemical industries due to their superior mixing capabilities. This study numerically investigates the gas–liquid flow hydrodynamics and bubble dynamics in a bottom-blown system with a circular boundary using the volume of fluid approach. Following the experimental validation of the mathematical model, the study evaluates the effects of gas flow rates, liquid heights, and fluid medium properties on both the dynamics of the bubble swarm and the mixing characteristics of the flow field. The results indicate that: (1) Rising bubbles disturb the fluid, generating numerous vortices that facilitate momentum transfer for effective gas stirring; (2) The height of the liquid surface oscillation during the bottom-blown process exhibits significant temporal variation, with the peak showing clear lateral swings; (3) Due to the nonlinear interactions involving bubble coalescence and breakup during their ascent, along with constructive and destructive interference between liquid surface waves, the liquid surface can exhibit violent fluctuations at certain moments; (4) Bubble size and aspect ratio significantly influence liquid surface oscillations; (5) The bubble rising path displays instability due to vortex shedding, with some vortices forming at locations where the bubble shape changes abruptly. A bubble velocity prediction equation is proposed: uc=σ5.2737Lcρc4.2737/16156μl9.5475.

On hydromagnetic two-phase gas-liquid flow in ciliary channel: An application of a metachronal rhythm

On hydromagnetic two-phase gas-liquid flow in ciliary channel: An application of a metachronal rhythm

Numerical simulation of hydrate particle behavior in vertical pipeline gas-liquid flow

During the extraction of deep terrestrial and deep-sea natural gas reservoirs, changes in temperature and pressure in the production well can lead to the formation of natural gas hydrates in the wellbore, blocking the flow channel and posing significant challenges to gas well production and management. To address this, we have established a mathematical model to describe the flow characteristics of hydrate multiphase flow systems in vertical pipelines. We employ Computational Fluid Dynamics simulations coupled with a Population Balance Model to predict the formation and breakage of hydrate particles, taking into account mechanisms such as particle collision, aggregation, and breakage. We have analyzed the impact of gas flow rate, slurry flow rate, and hydrate volume fraction on hydrate particle size in the pipeline. The results indicate that hydrate particles tend to aggregate at the bottom of the pipeline. The larger the hydrate slurry flow rate, the faster the hydrate particle size increases. As the gas phase flow rate increases, the increase in particle size slows down. High gas phase flow rates help form turbulence to suppress particle aggregation, velocity fluctuations contribute to particle aggregation growth, and stable velocities facilitate particle decomposition. The increase in hydrate volume fraction significantly increases the diameter of hydrates in the center of the pipeline. The research results can provide suggestions for wellbore blockage caused by hydrate particle aggregation on the wall and a decline in gas well production during actual natural gas well production.

Enhanced Impeller Gas-Liquid Flow Using Ribs for High Performance of Centrifugal Pump

Transporting two-phase fluids presents a challenge due to their negative effects on centrifugal pump performance. The accumulation of gas bubbles in the pump impeller forms large gas pockets, reducing efficiency. This work aims to improve the performance of a two-phase flow centrifugal pump by modifying the pump impeller through the addition of ribs. These ribs are positioned near gas bubble accumulation. The modified impeller helps to disperse this accumulation, thereby enhancing pump performance. A study was conducted to evaluate the effect of ribs on the pump efficiency. The results showed a negative effect in low (GVF) and single-phase flows. However, at high GVF, the ribs significantly improved head up to 9%. Moreover, rib characteristics, such as diameter and radial position, were key parameters affecting the pump's efficiency. The ribs with a diameter of 1 mm and a radial position of 33 mm showed the best performance.

Inclusion Transfer Phenomenon under Unsteady Multiphase Flow during Rheinstahl–Heraeus Vacuum Treatment Process

Inclusion particles are extremely harmful to the quality of steel products, and Rheinstahl–Heraeus (RH) vacuum treatment is the key process to remove the inclusions from molten steel. By coupling analyzing the unsteady gas–liquid flow and decarbonization reaction, the inclusion mass/population conservation model is developed to explore the inclusion particles transfer phenomenon during RH vacuum treatment process. The coupling mathematical models are validated by the metallurgical experimental data. The results show that the predicted inclusion mass concentration in unsteady CO–Ar–molten steel multiphase system has significantly smaller relative error than that in steady Ar–molten steel flow. CO bubble plays a key role in the inclusion transfer phenomenon, which prompts the inclusion transport, the collision‐aggregation, and the removal process. At the 4th minute of vacuum treatment, the average inclusion volume concentration and the average inclusion number density in CO–Ar–molten steel are 72.75% and 64.62% of those in Ar–molten steel, respectively. The average inclusion characteristic radius in CO–Ar–molten steel is 7.33% larger than that in Ar–molten steel.

Experimental Investigation and Calculation of Convective Heat Transfer in Two-Component Gas–Liquid Flow Through Channels Packed with Metal Foams

This paper presents a study on heat transfer in two-phase mixtures (air–water and air–oil) flowing through heated horizontal channels filled with open-cell aluminum foams characterized by porosities of 92.9–94.3% and pore densities of 20, 30, and 40 PPI. The research included mass flux densities ranging from 2.82 to 284.7 kg/(m2·s) and heat flux densities from 5.3 to 35.7 kW/m2. The analysis examined the effects of flow conditions, fluid properties, and foam geometry on the intensity of heat transfer from the heated walls of the channel to the fluid. Results indicate that the heat transfer coefficient in two-component non-boiling flow exceeds that of single-phase flow, primarily due to fluid properties and velocities, with minimal impact from flow structures or foam geometry. An assessment of existing methods for predicting heat transfer coefficients in gas–liquid and boiling flows revealed significant discrepancies—up to several hundred percent—between measured and predicted values. To address these issues, a novel computational method was developed to accurately predict heat transfer coefficients for two-component non-boiling flow through metal foams.

Bubble deformation characteristics and the effect on particle removal efficiency in wet scrubbers

Single-bubble formation and rise are fundamental to the prediction of decontamination factors (DF) under the complex hydrodynamics of bubble flow and the gas–liquid flow pattern. However, bubbles in the water for particle control are not always perfectly spherical or ellipsoidal. To date, studies of bubble washing for particle removal have mainly focused on models with simple spherical and ellipsoidal shapes or the impact of operating parameters on removal efficiency. No attempt has been reported in the literature to determine the effect of bubble shape on particle removal efficiency. An investigation of the influence of bubble deformation during the bubble rising period was carried out using a high-speed camera and image analysis techniques to study the bubble shape. The experimental results show that the deformation of a bubble is directly correlated with its rising velocity, rising tail, equivalent radius and residence time. These parameters are generally estimated using ideal values, which are crucial for the accuracy of efficiency calculation model results. SPARC-90 code is an important scrubbing modelling tool developed for prediction of bubble hydrodynamics and the corresponding aerosol retention behavior. The potential for particle removal with a single rising deformed bubble was recently determined using a prototype of the SPARC-90 code with the experimental results. The results of SPARC-90 calculations with various equivalent diameters obtained in this experiment have provided more accurate decontamination factors compared to those obtained with a round bubble and a default bubble diameter.

Study on the Impact of Porous Media on Condensate Gas Depletion: A Case Study of Reservoir in Xihu Sag.

During the depletion and pressure reduction process in condensate gas reservoirs, the precipitation of condensate oil transforms the single-phase gas flow into a two-phase gas-liquid flow, significantly reducing the permeability. Currently, microscopic studies of the phase behavior of condensate gas in porous media mainly focus on observing and describing the occurrence of condensate oil, lacking quantitative calculations and direct observations of condensate oil throughout the entire depletion cycle. This paper uses a microvisualization method to simulate the depletion process of condensate gas reservoirs. Condensate gases with oil contents of 175.3 and 505.5 g/cm3 were prepared by mixing methane, ethane, hexane, and decane in specific proportions. Pore structures were extracted from thin sections of real core casts, and microfluidic chips with a minimum pore diameter of 20 μm and an areal porosity of 20.75% were fabricated by using a chemical wet etching method. Subsequently, microfluidic condensate gas depletion experiments were conducted with chip images recorded during the depletion process. Grayscale analysis of the depletion images was performed using ImageJ software to quantitatively calculate condensate oil saturation and recovery rates, analyzing the effects of different condensate oil contents on condensate gas depletion, and comparing the differences between depletion in porous media and in a PVT cell. The conclusions drawn are as follows: the dew points of high and low in the porous media are 3.15% and 1.85% higher than those in the PVT cell, respectively. In the early stages of depletion, condensate oil saturation in porous media is higher than that in the PVT cell, while in the middle to late stages, condensate oil saturation in porous media is lower than that in the PVT cell. The condensate oil recovery rate in porous media is significantly higher than the depletion recovery rate in the PVT cell. Condensate oil tends to precipitate and disperse at blind ends and corners, while it easily forms patches in mainstream large pores.

Identification of gas-liquid two-phase flow patterns based on flexible ultrasound array and machine learning

Ultrasound technology has been recognized as the mainstream approach for the identification of gas-liquid two-phase flow patterns, which holds great value in engineering domain. However, commercial rigid probes are bulky, limiting their adaptability to curved surfaces. Here, we propose a strategy for autonomous identification of flow patterns based on flexible ultrasound array and machine learning. The array features high-performance 1–3 piezoelectric composite material, stretchable serpentine wires, soft Eco-flex layers and a polydimethylsiloxane (PDMS) adhesive layer. The resulting ultrasound array exhibits excellent electromechanical characteristics and offers a large stretchability for an intimate interfacial contact to curved surface without the need of ultrasound coupling agents. We demonstrated that the flexible ultrasound array combined with machine learning can accurately identify gas-liquid two-phase flow patterns, in a circular pipeline. This work presents an effective tool for recognizing gas-liquid two-phase flow patterns, offering engineering opportunities in petroleum extraction and natural gas transportation.

Two-group drift-flux model in tight lattice subchannel

Tight lattice rod bundles can increase equipment compactness and improve heat exchange efficiency, and they are widely adopted in heat exchange engineering. Understanding the flow characteristics of gas-liquid two-phase flow in tight lattice subchannels is essential for developing heat exchangers and fuel assemblies with these tight bundles. The drift-flux model (DFM) is a crucial two-phase flow model extensively used in subchannel analysis codes. Investigating the DFM in tight lattice subchannels benefits the advancement of these codes. For two-phase flow interfacial structures, significant two-group characteristics exist, with bubbles divided into small (group-one) and large (group-two) bubbles. The substantial differences in flow characteristics between these two groups provide a solid foundation for developing a two-group DFM. This study examined the two-group characteristics of two-phase flow in a tight lattice interior subchannel and developed a corresponding two-group DFM. The two-group correlations for the distribution parameters and drift velocities at the tight lattice interior subchannel level were proposed and verified using experimental data. The accuracy of the developed two-group DFM in predicting group-wise void fraction and gas velocity was also verified. The standard relative deviation between the model predictions and experimental data was 8.11 % and 13.1 % for group-one and group-two void fractions and 8.33 % and 11.7 % for group-one and group-two gas velocities, respectively. This indicates satisfactory accuracy for the newly developed two-group DFM in a tight lattice interior subchannel.

Development and validation of a 1D gas–liquid model for dissolved Mn(II) removal by oxidation process in a square bubble column

Modeling multiphase reactors requires an in-depth multidisciplinary analysis of various phenomena including the chemical kinetics, oxygen mass transfer, as well as the simulation of flows within these contactors. In this study, a 1D model of two-phase flow for Mn(II) removal from drinking water by aeration process is developed and validated. This model is based on the Eulerian description of two-phase gas–liquid flow with the comparison between a one-medium bubble size and a two-bubble class description to represent the bubble population in the heterogeneous flow regime. All the relevant chemical species are simulated by coupling hydrodynamics, gas–liquid mass transfer, and reaction kinetic. A pseudo-first-order model accounting for homogeneous and heterogeneous kinetics is considered for Mn(II) oxidation. The performance of the developed 1D model is compared and validated with experimental data. The 1D model was able to predict quantitatively Mn oxidation as a function of pH, initial Mn(II) and initial Mn(IV) concentrations.

Gas liquid flow pattern prediction in horizontal and slightly inclined pipes: From mechanistic modelling to machine learning

This paper investigates the prediction of two-phase gas-liquid flow regimes in both horizontal and slightly inclined pipes. For this purpose, the mechanistic model of Taitel et al. (1976) and the machine learning approach have been adopted. First, the mechanistic model was implemented, tested and optimised by introducing factors in the transition equations to determine the configuration that gives the highest prediction accuracy for a specific two-phase system for which experimental data points are available. Second, several machine learning models are trained, tested and additionally validated. This is done by splitting the experimental data set corresponding to the pipe inclination range (−10∘ to 10∘) into training, test and validation sets. The best classifier achieved an accuracy of 95.5% after the test step and up to 98.9% after the validation step. Finally, the Taitel et al. model with the optimal configuration and the best machine learning classifier (XGB classifier) are used to generate the two-dimensional flow regime map.

Investigating of vibration and noise characteristics in two-phase gas-liquid flow through a spiral capillary tube

The vaporization of refrigerant in the liquid-phase in spiral capillary tube induces complex two-phase flow that causes vibrations and noise, which affect the performance and stability of refrigeration systems. Therefore, the flow patterns, vibrations, flow-borne and structure-borne noises in spiral capillary tube are explored, and the effects of coil diameters, pitches and temperatures are analyzed. The results showed that the flow upstream the vaporization point was dominant by liquid-phase, then changed to bubbly flow downstream the vaporization point under various structures, and further changed to mist flow near the outlet, while it changed to gas-phase flow near the outlet under high temperature. The flow-borne noise was mainly affected by the flow turbulence, and the total sound pressure level (TSPL) increased by 17.1 % on average as the temperature increased from 309.6 to 317.6 K, and rose with the increase in pitch. As the coil diameter increased, the TSPL first increased and then decreased. Moreover, the maximum deformation of structure increased by 58.33 % as the diameter increased from 35 to 50 mm, but changed little with various pitches. The changing trends of vibration intensity caused the similar variations of structure-borne noise. The TSPL of structure-borne noise increased by 9.14 % with the diameter increasing from 35 to 50 mm, but it changed little at various pitches. The TSPL of structure-borne noise was much higher than flow-borne noise, which meant that improving the structural vibration can control the noise of refrigerant flow in spiral capillary tube.

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.

Process Intensification of Gas–Liquid Separations Using Packed Beds: A Review

The gas–liquid multiphase process plays a crucial role in the chemical industry, and the utilization of packed beds enhances separation efficiency by increasing the contact area and promoting effective gas–liquid interaction during the separation process. This paper primarily reviews the progress from fundamental research to practical application of gas–liquid multiphase processes in packed bed reactors, focusing on advancements in fluid mechanics (flow patterns, liquid holdup, and pressure drop) and the mechanisms governing gas–liquid interactions within these reactors. Firstly, we present an overview of recent developments in understanding gas–liquid flow patterns; subsequently we summarize liquid holdup and pressure drop characteristics within packed beds. Furthermore, we analyze the underlying mechanisms involved in bubble breakup and coalescence phenomena occurring during continuous flow of gas–liquid dispersions, providing insights for reactor design and operation strategies. Finally, we summarize applications of packed bed reactors in carbon dioxide absorption, chemical reactions, and wastewater treatment while offering future perspectives. These findings serve as valuable references for optimizing gas–liquid separation processes.