Gas-liquid Separation Research Articles

Study on Improving Liquid Carrying Performance of Horizontal Wells With Swirl Jet Composite Device

ABSTRACTIn the later stages of horizontal gas well development, due to insufficient formation energy, the stratified flow of gas and liquid in the horizontal section generates a decrease in the well's liquid‐carrying capacity, accumulating liquid in the wellbore. Since the flow pattern of gas–liquid two‐phase flow in horizontal wells is significantly different from that in vertical wells, existing vertical well liquid removal and gas production technologies cannot be directly applied to address the liquid accumulation issues in horizontal wells. This paper presents a swirl jet composite device that, through the combination of a spiral guide belt and an internal flow channel, effectively integrates the jet and vortex effects, capable of transforming the stratified flow in the horizontal section into an annular flow, thereby enhancing the gas well's liquid‐carrying capacity. This study applies a combination of theoretical, experimental, and simulation methods to conduct computational fluid dynamics analysis on the device's ability to improve the gas well's liquid‐carrying capacity. It deeply investigates the flow characteristics of the gas–liquid two‐phase flow within the device. The results indicate that the device can not only achieve gas–liquid separation by transforming the flow regime from laminar to an orderly annular flow but also increase the axial velocity to extend the effective distance of the swirling section. Compared with the case without the device installed, the liquid phase volume fraction at the bottom of the well is reduced by 85.9%, and the liquid holdup is reduced by 38%. This demonstrates that compared to traditional technologies such as gas‐lift dewatering and gas production, the device can enhance the liquid‐carrying capacity of horizontal wells and effectively address the issue of liquid accumulation in horizontal wells. It provides theoretical guidance and a practical basis for future research on applying swirl jet composite devices to improve the liquid‐carrying capacity of horizontal wells.

Numerical and Experimental Investigation of Gas/Liquid Separator with Various Tip Clearance

Summary Gas/liquid separators (GLSs) are widely used in petroleum extraction and the chemical industry, as well as aerospace and other fields. Experimental studies and numerical simulations were conducted to investigate the impact of tip clearance (TP) on the separation performance and energy characteristics of a dynamic GLS. The Reynolds stress model (RSM) was used for the numerical simulation of the gas/liquid separation process, and the reliability and accuracy of the model were confirmed through comparison and analysis of experimental findings. The results demonstrate a linear correlation between TP and device performance under specific flow rate conditions. As TP increases, there is a corresponding decrease in separation efficiency, power of the liquid-phase outlet (LPO), and differential pressure at the inlet. This trend can be attributed to reduced maximum tangential velocity and increased TP, which lead to heightened backflow. Consequently, this impedes the outflow of the liquid phase post-separation, resulting in reduced separation efficiency and energy performance. Furthermore, at particular TPs, a significant decline in device performance is observed under conditions of high flow rates. This is primarily due to the intensified turbulence between the blades, which increases flow rates. Consequently, the disorder in the internal flow field escalates, leading to considerable energy losses and impacting the gas/liquid two-phase separation process. This study offers valuable insights into designing high-performance dynamic gas/liquid separation devices (DGLSDs), providing a robust theoretical foundation for future endeavors.

Gas-Liquid Separation of Liquid Hydrogen in Microgravity: Optimization of Structural Parameters, Angles, Rotational Speeds, and Gas-Liquid Ratios

Abstract Liquid hydrogen (LH2) is a high-efficiency cryogenic propellant extensively used in the aerospace industry due to its superior specific impulse and energy density. Despite its advantages, managing LH2 in orbit presents significant challenges, particularly in microgravity, where fluid transport and gas-liquid interface stability are adversely affected. This study addresses these challenges by investigating the effects of different structural parameters, angles, rotational speeds, and gas-liquid ratios on LH2 gas-liquid separation through comprehensive numerical simulations validations. We analyze the impacts of various pore diameters and axial spacings, as well as the evolution of gas-liquid configurations at different angles and rotational speeds. Additionally, we explore the effects of different gas-liquid ratios on separation performance. Our findings identify optimal parameter combinations and elucidate key mechanisms influencing gas-liquid separation efficiency. The study employs high-precision models and microgravity simulation experiments to validate the numerical results, providing a robust foundation for optimizing LH2 management devices. This research contributes valuable insights into the management of liquid hydrogen (LH2) in microgravity environments and provides foundational knowledge that may benefit future deep-space exploration missions.

Dynamic simulation of wind-powered alkaline water electrolysis system for hydrogen production

Alkaline water electrolysis (AWE) is a mature and cost-effective technology, especially suited for large-scale deployment, yet faces challenges in adapting to the dynamic nature of renewable energy sources. Evaluating AWE's adaptability to fluctuating renewable energy inputs is crucial. This study introduces a dynamic model to assess the influence of wind energy on a 250 kW industrial-scale AWE system for hydrogen production. This paper pioneers the utilization of Aspen Plus Dynamics for dynamic modeling, offering a comprehensive approach that incorporates all vital components and controllers of the balance of plant, such as gas-liquid separator, heat exchangers, deionized water supply, pumps, and the cooling loop. This methodology allows comprehensive simulation at the system level, revealing the real dynamic characteristics of the system under fluctuating wind energy conditions. Due to the absence of a dedicated module for AWE in Aspen Plus Dynamics, an integrated dynamic operation unit for the electrolyzer is constructed using Aspen Custom Modeler. The study analyzes the dynamic characteristics of the AWE system, specifically focusing on temperature, voltage, and liquid level. The study compares two temperature control strategies, before-stack and after-stack, with the refined after-stack method effectively addressing over-temperature issues and improving system energy efficiency by 1.44%.

Working Condition Sensitivity Analysis and Optimal Structure Parameter Determination of IVT Based on CFD and Orthogonal Experiment

To address liquid accumulation in horizontal gas wells, a specialized internal vortex tool (IVT) was developed for use in the horizontal sections, functioning as a drainage gas recovery device. This tool operates by leveraging centrifugal forces generated during fluid swirl to separate liquid from gas. The study examined the performance of IVT under various operational conditions and sought to identify optimal structural parameters. Through a controlled variable approach, the impact of inlet velocity and the water-gas volume ratio on pressure drop range, MGV (maximum gas velocity), and MVFLP (maximum liquid phase volume fraction) was analyzed. The results indicated that when the inlet velocity is between 2-4m/s and the water to gas volume ratio is between 0.5-2m3/104m3, the smaller the inlet velocity and the smaller the water to gas volume ratio, the better the gas-liquid separation effect of the IVT. An orthogonal test was subsequently employed to fine-tune the tool's structural parameters for different conditions, culminating in the creation of a comprehensive optimization chart for IVT. This study can effectively design drainage gas production tools for gas wells under different working conditions, reduce energy loss during drainage gas production, effectively utilize downhole resources, and achieve the goal of increasing natural gas well production and reducing costs.

Liquid film breakup pattern and optimization of vane-type separator

The formation of liquid film and fragmentation downstream of swirler in vane-type separators, which is the key phenomena affecting the separation efficiency, is not well understood. To reveal the film breakup mechanism and the distribution characteristics of liquid film at the outlet of swirler, a visual vane-type separator test facility has been developed. By high-speed camera from the top, serious film breakup occurs in the rear of arc-vane swirler due to liquid accumulation on the hub and vanes is captured. While both bag breakup and ligament breakup are the dominant film breakup types, bag breakup resulting in divergent secondary droplets prolongs the gas–liquid separation path and is the main threaten to achieve high separation efficiency. New swirler using tilted-flat vanes with micro-pillars are proposed to guide the liquid film to migrate towards the wall of the riser and suppress liquid film fragmentation. Visual observation verified that the liquid film and fragmentation on the hub are significantly reduced. This is consistent with the quantitative measurement of void fraction distribution by wire mesh conductivity sensor (WMS). The average void fraction at the outlet of the new swirler (1.3D above) is increased, especially in low gas flow rate and high fluid flow rate cases, and the maximum increasement is as high as 26.0% compared to the original arc-vane swirler. The results deepen our knowledge about the film structure near the outlet of swirler in vane-type separators and provide guide to the optimization of vanes.

Numerical Modeling of Water Transport in a Microporous Layer-Coated Porous Transport Layer for a Polymer Electrolyte Membrane Water Electrolyzer with an Interdigitated Flow Field for Internal Gas-Liquid Separation

We have developed a novel interdigitated flow field for polymer electrolyte membrane electrolyzers (proton exchange membrane water electrolysis cells) for ground and space applications1),2), which are supposed to work in a hybrid system with a low temperature Sabatier reactor for effective use of heat3),4). This design separates the oxygen and liquid water inside the anode of the cell. It dispenses with water circulators and external separators that use natural or centrifugal buoyancy. To date, we have developed a numerical model for optimizing cell structures. Finite element modeling (COMSOL Multiphysics) of water transport is three-dimensionally conducted for the anode porous transport layer coated with a hydrophobic microporous layer (MPL) (SIGRACET 29BC, SGL Carbon Inc.) assembled with the interdigitated flow field. The MPL can separate the evolved oxygen gas and pressurized liquid water owing to capillary pressure5). The electrochemical kinetic parameters for the model are determined using electrochemical impedance spectra. We model the current densities and the current ratio between the reactant liquid water and water vapor at the interface between the MPL and catalyst layer (CL)6). The model involves the fractional bubble coverage of the produced oxygen gas at the CL, as well as liquid water saturation and liquid water permeability in the MPL7). The vapor evaporating from the liquid water in the MPL is assumed to be mixed with the evolved oxygen for diffusive water transport. The volumetric evaporation rate was estimated from experimental data8). Acknowledgement This study is based on results obtained from a project, JPNP21014, commissioned by the New Energy and Industrial Technology Development (NEDO).References1) Y. SONE, O.S. HERNANDEZ-MENDOZA, A. SHIMA, M. SATO, H. NAKAJIMA, and H. MATSUMOTO, Water Electrolysis by the Direct Water Supply to the Solid Polymer Electrolyte through the Interdigitated Structure of the Electrode, Electrochemistry, 89 (2021) 138–140. https://doi.org/10.5796/electrochemistry.20-00145.2) H. NAKAJIMA, V. VEDIYAPPAN, H. MATSUMOTO, M. SATO, O.S. MENDOZA-HERNANDEZ, A. SHIMA, and Y. SONE, Water Transport Analysis in a Polymer Electrolyte Electrolysis Cell Comprised of Gas/Liquid Separating Interdigitated Flow Fields, Electrochemistry, 90 (2022) 017002. https://doi.org/10.5796/electrochemistry.21-000973) H. NAKAJIMA, A. SHIMA, M. INOUE, T. ABE, H. MATSUMOTO, O.S. MENDOZA-HERNANDEZ, and Y. SONE, Three-Dimensional Numerical Modeling of a Low-Temperature Sabatier Reactor for a Tandem System of CO2 Methanation and Polymer Electrolyte Membrane Water Electrolysis, Electrochemistry, 90 (2022) 22–00035. https://doi.org/10.5796/electrochemistry.22-000354) A. Shima, M. Sakurai, Y. Sone, H. Nakajima, M. Inoue, and T. Abe, Development of CO2 Reduction-Water Electrolysis Tandem Device as a Full-Scale Model, in: 52nd Int. Conf. Environ. Syst., 2023: ICES-2023-196. https://hdl.handle.net/2346/896225) H. Nakajima, S. Iwasaki, and T. Kitahara, Pore network modeling of a microporous layer for polymer electrolyte fuel cells under wet conditions, J. Power Sources, 560 (2023) 232677. https://doi.org/10.1016/j.jpowsour.2023.2326776) H. Nakajima, H. Ekström, A. Shima, Y. Sone, and G. Lindbergh, Water Transport Modeling in a Microporous Layer for a Polymer Electrolyte Membrane Water Electrolyzer Having a Gas-Liquid Separating Interdigitated Flow Field, ECS Transactions, 112 (4) (2023) 273–281. https://doi.org/10.1149/11204.0273ecst7) S. Kubota, H. Nakajima, M. Sato, A. Shima, M. Sakurai, and Y. Sone, Liquid Water Permeability in a Hydrophobic Microporous Layer for the Anode Interdigitated Flow Field of a Gas-Liquid Separating Polymer Electrolyte Membrane Water Electrolyzer, ECS Transactions, 112 (4) (2023) 207-214. https://doi.org/10.1149/11204.0207ecst8) P. Wang, H. Nakajima, and T. Kitahara, Effect of Hydrophilic Layer in Double Microporous Layer Coated Gas Diffusion Layer on Performance of a Polymer Electrolyte Fuel Cell, J. Electrochem. Soc., 170 (2023) 124514. https://doi.org/10.1149/1945-7111/ad13da

Dynamic Simulation of a Hybrid PV/Awe/SOFC Stand-Alone System for Heat and Power Generation

Global energy demand increased from 528 EJ in 2012 to 604 EJ in 2022, with CO2 emissions rising from 34 Gt to 36.8 Gt during the same period. According to the IEA, global energy demand is projected to reach 670 EJ by 2030. To meet this energy demand and simultaneously reduce greenhouse gas emissions, the capacity for renewable energy installations is expanding. However, renewable energy faces the issue of lacking flexibility to balance supply and demand due to its intermittency and variability. Sector coupling, which converts power to heat (P2H), gas (P2G), and liquid fuels (P2L), can overcome the flexibility challenges of renewable energy by integrating energy across sectors (power, transportation, industry, agriculture, and residential). As an energy storage medium, hydrogen serves as a key component in P2G and P2L and holds potential as a future energy carrier.The residential sector requires both heat and electricity, yet the power supply through photovoltaics (PV) leads to an imbalance between energy demand during day and night. To alleviate this energy imbalance while flexibly meeting heat and electricity demands, a hydrogen-based 'PV-AWE-Batt-SOFC' hybrid system was proposed. Numerous previous studies have performed capacity optimization of hybrid systems with cost as the objective function. However, research on Energy Management Strategies (EMS) for stable operation of each system in conjunction with renewable energy is limited. Therefore, a stable hybrid system EMS based on the analysis of the dynamic behavior of AWE and SOFC needs to be established.In this study, a dynamic model of the PV-AWE-Batt-SOFC hybrid system was developed using AMESim®. The AWE system consists of a stack, pump, heat exchanger, gas-liquid separator, cooling system, condenser, oxygen catalytic combustor, and dryer. The SOFC system comprises a stack, blower, heat exchanger, and after-burner. The stack was modeled with an in-house code to accurately resolve the electrochemical reactions. To establish a stable EMS for the hybrid system integrated with renewable energy, the dynamic behavior of both the AWE and SOFC systems was analyzed, and EMS scenarios were proposed. The scenarios were evaluated by comparing the state of charge of the battery and the state of charge of the hydrogen tank. Analyzed parameters in the AWE system include stack temperature/voltage, condenser temperature/hydrogen purity, oxygen catalytic combustor temperature/conversion rate, and dryer temperature/hydrogen purity. In the SOFC system, analyzed parameters are stack temperature/voltage/fuel utilization, and after-burner temperature/conversion rate. Figure 1

Numerical and experimental study of dynamic gas–liquid separator with various viscosities

The gas–liquid separation process is important in various industries, such as electric power, aerospace, and petroleum. This study introduces an innovative, dynamic gas–liquid separator (DGLS) in which a cyclonic flow pattern is induced by blade rotation. This cyclonic flow enhances the efficiency of gas and liquid phase separation while also imparting energy to facilitate the transport of the separated fluid. Numerical simulations are used to analyze the internal flow dynamics, power requirements, and separation efficiency of this DGLS. A comparison with experimental results is conducted to validate the reliability of the numerical model. The effects of liquid-phase viscosity on the internal energy consumption and separation performance of the DGLS are explored at various flow rates. The simulation results indicate that for a given viscosity, the degassing rate of the separator decreases while the liquid removal rate increases as the inlet flow rate rises. Furthermore, it is observed that higher viscosity leads to poorer separation performance, with a decrease in turbulent kinetic energy near the rotating axis and an increase in turbulence intensity near the wall. At lower flow rates, the effectiveness of liquid-phase outlet pressurization improves with increasing viscosity. However, at higher flow rates, increasing viscosity leads to a substantial decline in energy performance and a reduction in liquid-phase outlet pressurization. The increment in turbulent kinetic energy is greater than the square of the mean velocity, indicating a positive correlation between turbulence intensity and turbulent kinetic energy. These findings not only provide a theoretical basis for the prediction of flow losses within a DGLS and the efficient design of these separators, but also provide guidance for industrial applications involving high-viscosity fluids.

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.

Influence of guide groove structure on in-flow drag reduction in spiral axial gas-liquid mixing pumps

Abstract With the onset of the fossil energy crisis, demand for oil has skyrocketed, and the spiral axial flow gas-liquid mixing pump has emerged as the primary piece of equipment for deep-sea oil extraction. However, at high gas content, the problems of separation of mixed media from hydraulic components, gas-liquid separation and gas phase aggregation are faced. The difficulties of gas-phase aggregation and bubble trajectory in the impeller channel have received much attention, while the problem of increased medium flow resistance induced by flow separation has received less attention. The spiral axial gas-liquid mixing pump is numerically calculated using the Eulerian multiphase flow model and the SST k- turbulence model in this work. The pump is designed with the design flow rate Q = 100 m3/h, rotational speed n = 4500 rmin, and head H = 30m by arranging guide slots with different relative depths and different number of slots to reduce the dissipative vortices, thus reducing the flow resistance in the 1/5 region behind the suction surface. The findings reveal that when the relative depth of the slots is 1/7 and the number of guide slots arranged is 5, the highest drag reduction rate in this location is 69.6% under the design flow condition. When the relative depth of the guide channel is1/7 and the number of guide channels is 3, the performance of the mixing pump is improved most, with an efficiency increment of 1.9% and a head increment of 4.2%, which can provide technical support for the flow resistance reduction of gas-liquid mixing pumps.

Numerical investigation of dynamic gas–liquid separator by population balance model

Dynamic gas–liquid separator (DGLS) can efficiently separate gas and liquid phases and are widely used in aerospace, chemical, and petroleum engineering. The energy loss and separation efficiency within the DGLS are studied through the combination of numerical simulations and experiments. Three-dimensional transient Reynolds-Averaged Navier–Stokes equations were solved to analyze the fluid dynamics within the DGLS. The bubble aggregation and breakup in oil were simulated by using the population balance model. Experimental data were meticulously compared with numerical results to validate the accuracy and reliability of the numerical methods. The findings revealed a direct correlation between the inlet flow rate and various performance metrics of the DGLS. Specifically, as the inlet flow rate increased, the energy loss within the DGLS escalated, resulting in higher power consumption. The degassing rate of the DGLS exhibited a decreasing trend with increasing inlet flow rate, while the de-oiling rate showed an inverse relationship. The optimal performance of the separator was observed at an inlet flow rate of 140 m3·d−1, with ηg* and ηl* reaching 0.94 and 0.99, respectively. The relationship between the Qo and the η* and Po was fitted by a second-order polynomial. Moreover, the rotational speed of the DGLS demonstrated a positive correlation with energy consumption, accompanied by an increase in power output. However, the separation efficiency of the DGLS exhibited a non-linear relationship with rotational speed, peaking at a specific value before marginally declining. The optimization of degassing and dewatering rates occurred at a rotational speed of 2500 r·min−1. These findings underscore the importance of carefully adjusting operational parameters to achieve optimal performance and energy efficiency within DGLS.

Research on the jet active control mechanism of gas-liquid separation in helical-axial multiphase pumps

In the field of deep-water oil and gas extraction, the intermittent gas blocking phenomenon in helical-axial multiphase pumps leads to decreased pump performance and reliability, severely limiting their large-scale application and promotion in engineering projects. To address this challenge, this study is based on the principle of jet flow field control to flow separation, utilizing external energy for active intervention to suppress the separation phenomena and improve the hydraulic efficiency within the impeller flow channel. The research reveals that the jets achieved a reconstruction of the internal flow in the helical-axial gas-liquid mixed transport pumps. Using orthogonal experimental methods, a preliminary predictive analysis of the factors influencing the effectiveness of the jet system was conducted. The study explored the impact of jet parameters on enhancing the performance of helical-axial gas-liquid mixed transport pumps from the perspective of diminishing gas aggregation at the trailing edge of the rotor cascade and curtailing backflow conditions, and established a mathematical model for the head and efficiency of helical-axial multiphase pumps under jet active control. Research indicates that the jet velocity significantly impacts the efficiency enhancement of multiphase pumps, with an optimal jet speed coefficient, Cjet = 10, identified. Beyond this speed, the benefits brought by increased jet velocity do not compensate for the costs of introducing high-speed jets, and instead, may lead to a reduction in the efficiency of the pump. Jet flow field control methods alleviate the suction side gas aggregation downstream of the jet holes and in the flow domain traversed by the jets, effectively reducing the aggregation of gas phases in the rear channel of the rotor and suppressing backflow near the trailing edge of the rotor cascade. Jet control measures strengthen the working capacity of the blade in the flow direction beyond 0.35 times the length of the streamline, expanding the working range of the blade and enhancing the work efficiency of the multiphase mixed transport pump. Higher jet velocities result in more significant enhancements of blade working power, especially under conditions of high initial gas content, where the relative increase in blade load is more pronounced.

Cyclone-coalescence separation technology for enhanced droplet removal in natural gas purification process

Natural gas is increasingly recognized as a clean energy source due to its high quality, low pollution levels, and abundant availability. However, certain gas fields contain complex components that require purification for efficient transportation and utilization. Addressing these issues involves efficient gas–liquid separation technology. Existing gas–liquid separation units face challenges such as efficiency, liquid entrainment, energy consumption, and the need for consumable replacement. This study focuses on a novel cyclone-coalescence separator that combines centrifugal and coalescence principles. Implemented in a high-acid natural gas purification plant in China, the cyclone-coalescence separator demonstrated efficiency primarily influenced by gas velocity and diameter. Optimal performance was observed with a 75 mm diameter reactor at velocities of 8–12 m·s−1, achieving a peak efficiency of 96%. The hydrophilic glass fiber with a monofilament structure can coalesce droplets effectively. In practical industrial use, under operational conditions, the hydrocyclone's liquid discharge rate is 89.6 kg·h−1 with an inlet concentration of 382.7 g·m3. Over a 400-h cycle, the cyclone-coalescence separator demonstrated superior separation performance with an average liquid discharge volume of 9.09 mg·kg−1, compared to 4.93 mg·kg−1 for the precision filter. This successful industrial implementation presents a promising approach to natural gas purification.

Numerical Modeling of Water Transport in a Microporous Layer-Coated Porous Transport Layer for a Polymer Electrolyte Membrane Water Electrolyzer with an Interdigitated Flow Field for Internal Gas-Liquid Separation

A novel design for interdigitated flow fields in polymer electrolyte membrane electrolyzers has been developed for both ground and space applications. This design separates oxygen and liquid water internally, eliminating the need for water circulators to remove bubbles and external gas-liquid separators with buoyancy. The capillary pressure in the hydrophobic microporous layer (MPL) of the anode porous transport layer facilitates internal separation of oxygen gas and pressurized liquid water. A finite element model (COMSOL Multiphysics) simulates water transport in the MPL, while electrochemical impedance spectra determine the electrochemical kinetic parameters for the model. The model takes into account the oxygen bubble coverage of the cathode, liquid water saturation in the MPL, and the current ratio between liquid water and water vapor at the MPL-cathode layer interface. The vapor from liquid water in the MPL is modeled to mix with oxygen for diffusion. A volumetric water evaporation rate as a linear function of liquid water saturation in the MPL is assumed, where the rate constant is estimated from vapor permeation tests.

Numerical Modeling of Water Transport in a Microporous Layer-Coated Porous Transport Layer for a Polymer Electrolyte Membrane Water Electrolyzer with an Interdigitated Flow Field for Internal Gas-Liquid Separation

A novel design for interdigitated flow fields in polymer electrolyte membrane electrolyzers has been developed for both ground and space applications. This design separates oxygen and liquid water internally, eliminating the need for water circulators to remove bubbles and external gas-liquid separators with buoyancy. The capillary pressure in the hydrophobic microporous layer (MPL) of the anode porous transport layer facilitates internal separation of oxygen gas and pressurized liquid water. A finite element model (COMSOL Multiphysics) simulates water transport in the MPL, while electrochemical impedance spectra determine the electrochemical kinetic parameters for the model. The model takes into account the oxygen bubble coverage of the cathode, liquid water saturation in the MPL, and the current ratio between liquid water and water vapor at the MPL-cathode layer interface. The vapor from liquid water in the MPL is modeled to mix with oxygen for diffusion. A volumetric water evaporation rate as a linear function of liquid water saturation in the MPL is assumed, where the rate constant is estimated from vapor permeation tests.

Performance analysis of a novel gas-liquid separator with industrial application

This paper presents a novel gas-liquid separator characterized by its distinctive geometric design, capable of handling different volume fractions and mass flow rates. The separator's performance is comprehensively assessed across various gas volume fractions, bubble sizes, and mass flow rate fluctuations. The study reveals that variations in vapor volume fraction substantially affect both separation efficiency and pressure loss. An increase in vapor volume fraction from 0.1 to 0.5 leads to a 25% reduction in separation efficiency and a 3.3-fold decrease in pressure loss. In contrast, changes in mass flow rate exert a relatively minor influence on separation efficiency. Specifically, increasing the mass flow rate from 15 to 30 kg/s results in a mere 4% decrease in separation efficiency, whereas pressure loss increases by a factor of 3.2.Additionally, a reduction in bubble size from 1000 µm to 200 µm causes a 33% increase in pressure loss and a 14% decrease in separation efficiency. The incorporation of a meshpad in this design promotes the formation of a forced vortex, thereby enhancing the separation process.

Novel rate-based modeling and mass transfer performance of CO2 absorption in rotating spiral contactor

For the process of CO2 absorption, existing gas-liquid contactors suffer from low mass transfer performance and low gas-liquid ratios. In this study, a rotating spiral contactor was developed to overcome these drawbacks and a novel rate-based model was developed to predict the CO2 absorption performance. The effective interfacial area (ae), overall volumetric mass transfer coefficient (KGae) and CO2 absorption efficiency (η) were investigated. The results showed that the ae was 913–1125 m2/m3 superior to the conventional contactor. In the range of gas–liquid ratio of 200–1800, the KGae and η were 1.4–10.1 kmol.m-3.h-1.kPa-1 and 40.5–99.6 %, respectively. The rate-based model predicted the KGae and η with the AARD of 6.71 % and 1.90 %, respectively. Also, it has better robustness even in highly nonlinear temperature and composition distributions. This study provides a potential contactor and a new modeling tool for CO2 capture and other gas-liquid separation.

Kinetics and dynamics of Gas-liquid separation and bubble generation in surfactant solutions: Role of bulk/interfacial properties and hydrodynamic conditions

Understanding the kinetics and dynamics of gas–liquid separation and bubble generation in surfactant solutions is important for many industrial applications. To explore the potential mechanisms affecting the physical properties (expansion ratio, bubble size, and foam stability) of foams and bubbles, the surface tension of the solution, including the equilibrium and dynamic properties, was investigated. Then, the morphology of the surfactant aggregates was explored by cryo-transmission electron microscopy (cryo-TEM). Based on these experimental results, the effects of various physical and chemical factors (including the relative concentration of surfactant, dynamic surface tension, surface coverage, surface elasticity, surface mobility, aggregate morphology, etc.) on the expansion ratio and bubble size were analysed to identify which “universal” parameters can explain the phenomenon for all aqueous solutions in the gas–liquid separation process. Research has shown that the morphology of aggregates in a solution largely determines the surface properties of the solution at 1.5 ms (surface tension, surface coverage, surface elasticity, and so on). These surface properties significantly affect the expansion ratio. However, no good correlation was found between bubble size and these surface properties because surfactant vesicles can directly affect bubble size. In addition, the liquid flow rate and gas–liquid ratio have a significant impact on the expansion ratio and bubble size. Ultimately, we found that the foam stability, bubble size, and expansion ration can be described by a simple linear relationship. Our research provides new opinions for further understanding the effects of bulk/interfacial properties and hydrodynamic conditions on the physical properties of bubbles in the gas–liquid separation process.

Experimental investigation on pressure drop characteristics of adiabatic two-phase flow in a Gyroid-structured channel

Recent advancements in additive manufacturing techniques have enabled the fabrication of intricate structures. Among these structures, triply periodic minimal surfaces (TPMSs) such as the gyroid, are particularly promising for heat and mass transfer applications owing to their higher surface area to volume ratios compared to conventional structures such as heat exchangers. This study experimentally investigates the pressure drop characteristics of single- and two-phase flows in a gyroid-structured channel under adiabatic conditions. In particular, using an additively manufactured test section with a gyroid-structured channel, the pressure drop characteristics of both single- and two-phase flows are analyzed. The results ofsingle-phase flow experiments reveal that the friction factor depends on the hydraulic diameter, which is defined by the internal volume and surface area of the channel. This suggests that in addition to the hydraulic diameter, other parameters such as porosity and wall thickness must also be considered. Subsequently, the two-phase pressure drop predictions of homogeneous and separated models are compared with the pressure drop data obtained from two-phase flow experiments. The results reveal that gas–liquid separation must be considered to accurately predict the pressure drop in regions influenced by gravitational effects. Furthermore, correlations for predicting the pressure drops both single- and two-phase flows within the operating constraints are proposed.