Slug Length Research Articles

Improved severe slugging modeling and mapping

One of the common flow assurance issues in offshore production facilities is riser-based severe slugging. This phenomenon can also occur in horizontal wells, hindering oil and gas production. Severe slugging is a cyclic process that occurs in the late life of reservoirs when there is not enough energy available from the reservoir to push the liquid out of the riser. It is highly undesirable as it results in large fluctuations in pressure, oil, and gas flow rates at the outlet of the riser. To address this challenge, we propose an improved one-dimensional severe slugging modelthat enhances the blowout step of the slugging cycleand Compared to the existing one-dimensional models. For benchmarking, the performance of this proposed model has been compared with experimental data for lab-scale geometry and with the OLGA simulations for field-scale geometry and higher operating pressures. The results demonstrate moderate errors in predicting slug characteristics, affirming the model's reliability and applicability. Additionally, a severe slugging envelope prediction approach has been proposed utilizing the developed model. The proposed severe slugging envelopes modeling approach can demarcate the severe slugging flow region for a given pipeline riser geometry and predict severe slug characteristics, including slug length and slug time within that severe slug flow region. This work significantly contributes to flow assurance strategies in production, optimizing hydrocarbon extraction processes and minimizing operational disruptions.

Characterizing the development of gravity-driven slug flows using high-speed imaging and PIV-PLIF techniques

Although developing gravity-driven slug flow frequently occurs in oil and gas, and energy systems, its development dynamics remain underexplored; this gap, in turn, has left the underlying relationships between flow evolution and transport phenomena in these applications inadequately characterized as well. The present study experimentally investigates the spatiotemporal-spectral development of gravity-driven air–water and CO2-water slug flows in a vertical 25.4 mm ID pipe. Enhanced flow visualization techniques, utilizing high-speed imaging and particle image velocimetry-planar laser induced fluorescence (PIV-PLIF), were employed to determine the behaviors of gas and liquid phases and interactions at four positions along the pipe axis. A machine vision-based algorithm was employed to extract slug unit cell characteristics and instantaneous void fraction signals, allowing for a comprehensive statistical analysis of gas phase behavior across the flow domain. A novel algorithm was also developed to preprocess raw PIV-PLIF images, facilitating phase discrimination and noise reduction before PIV cross-correlation analyses are conducted. The results showed a logarithmic growth in the lengths of Taylor bubbles, liquid slugs, and slug unit cells along the pipe, with liquid slugs constituting nearly 60 % of slug units downstream. Taylor bubble length distributions correlated well with log-normal fits, while liquid slug and unit cell lengths transitioned from log-normal patterns upstream to near-normal distributions downstream with broader and less peaked shapes. Taylor bubble velocities and appearance frequencies of the flow structures declined exponentially along the pipe, with Taylor bubble velocities showing narrower and more peaked near-normal distributions downstream. Instantaneous void fraction signals exhibited fewer, wider peaks and troughs with reduced small-amplitude oscillations downstream. The analysis of the signals indicated a complete bubbly-to-slug transition at Z/D=30. Gas-liquid phase interactions, classified as almost-zero, weak, and strong, impacted liquid phase velocity profiles and the behavior of Taylor bubbles, with minimum stable liquid slug lengths of 8–9 D and a wake length of 1.8 D observed. Empirical correlations were developed to represent the spatiotemporal-spectral aspects of flow development, with spectral parameters, particularly liquid slug frequency, identified as the most reliable indicators of the fully developed region, predicting entrance lengths of 114.0 D and 113.4 D for air–water and CO2-water, respectively. Gas density was found to strongly influence flow characteristics and transition, accelerating the approach to the fully developed region.

Elucidating flow-directed 98% CO2 absorption using millimeter-sized coiled flow inverters: Nanocellulose-aided sustainable scope

The Sustainable Development Goals (SDGs) adopted by the United Nations drive the global efforts to discover a sustainable carbon capture method for the reduction of anthropogenic CO2 emissions. Concentrated alkanolamine solutions are being used as CO2 capture mediums for batch processes amid several disadvantages, such as energy intensiveness and poor efficiency. In this work, millimeter-sized coiled flow inverters (CFI) have been explored as a point-source CO2 capture tool for highly efficient, continuous operations. Solvent and CO2 gas flow rates are found to dictate the slug flow regime and, more specfically, slug lengths. High interfacial area and residence time remain the driving factors for enhanced CO2 capture using CFI. About 98% CO2 absorption efficiency has been achieved for 3% aqueous diethanolamine solution in CFI . The efficacy of nanocellulose, a sustainable nanomaterial has been unearthed for CO2 capture at low flow rate.

Pulsating Heat Pipe Performance Modeling with Liquid Metal Coolants Under Hypersonic Aerothermal Heating

Hypersonic heating loads concentrate at leading-edge compression areas to create excessively high local temperatures and thermally driven stresses. The fast and reliable thermal dispersion of heat pipes with significantly high thermal conductance can alleviate these localized thermal stiffness problems. The pulsating heat pipe (PHP) holds numerous advantages when compared to capillary, constant-conductance heat pipes for hypersonic thermal management applications, primarily because they lack a wicking structure. This paper numerically investigates thermal performances of a four-turn C103 niobium alloy PHP operating with lithium, potassium, sodium, and a eutectic sodium–potassium alloy (NaK-78) when exposed to heating conditions relevant to the hypersonic environment, investigating flight Mach numbers ranging from 6 to 8 and dynamic pressures ranging from 40 to 44 kPa. The robust thermofluidic properties of liquid metals, along with the powerful fluid pulsation induced in the PHP, can provide significant thermal transport from hot stagnant regions of the leading edge to the cooler trailing surfaces. Potassium showed superior thermal performance when compared to other liquid metal coolants under the presently tested conditions, with overall PHP thermal conductance as high as 34 W/K predicted for Mach 8 flight conditions. In contrast, sodium was associated with startup difficulties in the PHP; this paper attributes this to its significantly larger thermal conductivity, which can limit the vapor pressure difference over the liquid slug lengths. These predictions indicate an overall latent heat transfer dominance of around 70–95% in liquid metal PHPs.

Hydrodynamic characteristics of detachment length and flow mapping in T-junction circular microchannel

This study investigates the droplet formation process in T-junction circular microchannels, emphasizing the influence of wetting properties and contact angles under various operating conditions. A coupled Volume-of-Fluid (VOF)/Level-set multiphase model is employed for Computational Fluid Dynamics (CFD) simulations to accurately capture the microscale phenomena. The effects of contact angles ranging from 125° to 145°, two-phase flow velocities (0.04–0.25 m/s), and interfacial tension (0.035–0.055 N/m) are systematically analyzed. The findings reveal that these parameters significantly impact the detachment length and flow patterns, with four distinct flow regimes identified: dripping, slug, jetting, and annular flow. New dimensionless correlations for slug and detachment lengths are developed and validated through experimental data, offering improved predictive capabilities. The comprehensive flow mapping provided in this study enhances the understanding of multiphase flows in microchannels, offering valuable insights for the optimization of microfluidic device design and practical applications such as extractive desulphurization. These contributions present a novel approach to integrating contact angle effects into microfluidic research, addressing previously overlooked aspects and providing robust guidelines for future studies.

Influence of nanoparticle concentration on the flow regimes of crude oil – Nanosuspension in a microchannel

This paper presents the results of an investigation into the effect of silica nanoparticles on two-phase flow regimes in a Y-shaped microchannel. The following fluids were subjected to investigation: oil, water, and a water-based suspension containing SiO2 nanoparticles at a weight concentration of 1 ≤ φ ≤ 10 %. A systematic investigation of the flow regimes revealed the following: slug, parallel, and droplet regimes. The ranges of existence of the obtained flow regimes were determined and flow regime maps were constructed as a function of fluid flow rates and dimensionless numbers. The results of the study demonstrated that the slug length and frequency of slug formation are influenced by varying silica concentrations. Furthermore, the correlation between slug length and nanoparticle concentration remains consistent as the suspension flow rate increases. The dependence of the ratio of oil layer width to channel width for suspensions with varying nanoparticle concentrations was quantified. A mathematical simulation of two-phase flow of immiscible fluids was conducted. The results of the numerical simulation demonstrated the existence of the flow regimes that had been previously identified through experimentation. The aforementioned methodology may therefore be employed for the investigation of the two-phase immiscible flow of oil and nanosuspension.

An investigation on hydrodynamic behavior of horizontal gas–liquid intermittent flow by S-PLIF and parallel-wire conductance sensors

Horizontal gas–liquid two-phase flows widely exist in a variety of industrial fields such as the environment, chemical industry and energy. Intermittent flow, characterized by the quasi-periodic alternation motion of liquid slugs and large-scale Taylor bubbles, is the most prevalent flow pattern in horizontal gas–liquid two-phase flows. Comprehensive research on the hydrodynamic behavior of gas–liquid intermittent flow is essential for revealing the mass and heat transfer characteristics between phases, thereby establishing physical models of flow parameters. In this study, a structured planar laser-induced fluorescence (S-PLIF) system and paired parallel-wire conductance sensors (PWCSs) are designed to detect the gas–liquid interface structures and the hydrodynamic parameters. The S-PLIF system consists of a laser, a visualization box, a Ronchi ruling-plate and a pair of high-speed cameras. An optical linear prism forms a laser sheet in the transverse direction and the middle of the test section, and the cameras are positioned at 70° and 90° respectively to the plane of the laser sheet, referred to as S-PLIF70 and S-PLIF90. Under the laser excitation, bright and dark stripes generated by the Ronchi ruling-plate are deflected at the gas–liquid interface. The influence of total reflection can be effectively avoided by identifying the deflection position of the stripes, allowing for accurate detection of the gas–liquid interfacial structures. The effects of the interface fluctuations and detached bubbles on the S-PLIF70&90 results are investigated. Fluctuation and evolution characteristics of the gas–liquid interface are analyzed by probability density function (PDF) and power spectral density (PSD). Meanwhile, hydrodynamic parameters, i.e., Taylor bubble nose and tail velocity, Taylor bubble and slug length, and slug frequency, are detected by the PWCSs, and compared with previous correlations. The evolution characteristics of the interfacial structures and hydrodynamic parameters are uncovered as the flow condition changes.

Using machine vision algorithms for characterizing gas-liquid slug flows in vertical pipes

Slug flow, characterized by the distinctive interfacial structures of Taylor bubbles surrounded by liquid films and bridged by aerated liquid slugs, is a dynamically complex two-phase flow pattern exist in many oil and gas, and energy systems. Accurate and precise quantification of such complex flow behaviour is essential for optimal design, safe operation, and reliable modelling of these systems. Existing image-based measurement techniques mostly rely on offline image processing algorithms and are often limited to a narrow set of flow characteristics primarily focusing on Taylor bubbles. Such constraints not only impede real-time flow monitoring and regulation but also leave liquid slug characteristics unmeasured, resulting in an inability to accurately determine the flow characteristics and extract instantaneous void fraction signals. Present study examined the performance of adaptive thresholding (AT) and background subtraction (BS) algorithms in capturing slug flow characteristics. It was found that while the former excels in Taylor bubbles detection and the latter in small bubbles identification, neither individually addresses the accurate measurement of both flow structures' characteristics. This observation, along with the mentioned restrictions of existing algorithms are the main reason for developing the present combined machine vision-based algorithm. While unlocking the ability to extract instantaneous void fraction signals, this new approach facilitates online measurement of a wide range of key flow characteristics, including Taylor bubble length, velocity, void fraction, and surrounding liquid film thickness; liquid slug length and void fraction; and slug unit length, void fraction, and frequency. Parallel to the high-speed imaging, time-series void fraction data was collected using two capacitance sensors installed alongside the imaging area on the pipe, providing benchmark data essential for the validation of the new algorithm's accuracy. The comparisons demonstrated a high degree of accuracy and precision for the combined algorithm. Quantitatively, the new algorithm measured key unit cell characteristics with RMS errors ranging from 2 to 10 %, while the BS and AT algorithms exhibited wider RMS error ranges of 8–46 % and 2–53 %, respectively. This underscores the new algorithm's potential as a transformative tool for slug flow analysis.

Flow pattern and pressure drop analysis of two-phase segmented flow driven by a thermomagnetic pump

The two-phase segmented flow is a flow pattern in which two immiscible fluids alternate in a flow channel with distinct segments. In this study, a thermomagnetic pump operated by heat and an external magnetic field was used to drive the flow and the temperature-sensitive magnetic fluid (TSMF) was chosen as the continuous-phase fluid to generate a two-phase segmented flow. The dispersed-phase fluid was selected as air or deionized water driven by a syringe pump. The two-phase segmented flow experiments were conducted to investigate the relation between segment length and the dispersed-continuous phase flow rate ratio at the air flow rate from 0.90 ml/h to 4.49 ml/h for air-TSMF experiment and water flow rate from 0.36 ml/h to 0.72 ml/h for water-TSMF experiment. The ratio was proportional to the bubble/droplet length and inversely proportional to the slug length. The air/water length per channel width can be up to 3.28 and 1.79, respectively, at the highest air/water flow rate in the current experiment. Moreover, the pressure drop was measured to increase with the dispersed-continuous phase flow rate ratio. The maximum pressure drop was observed as 428.2 Pa in the water-TSMF experiment with the highest water flow rate and the maximum pressure drop was 314.7 Pa for the air-TSMF experiment. These findings provide valuable insights for controlling the segment length in the two-phase segmented flow driven by a thermomagnetic pump and it could be used as precise control of liquid/gas fuel delivery in a micro-propulsion system in small satellites.

A core element CFD model for a two phase microfluidic fiber extractor

This work presents a CFD model of a semi-restricted annular microfluidic system. This model represents a novel type of commercial extractor called a fiber extractor (FE). Flows between the fibers are confined and microfluidic. Fiber extractors represent a powerful approach to process intensification. Extraction, heat transfer, and phase separation are all replaced by a single, low energy-use, low footprint process. This work describes the interplay of process conditions affecting phase structures and sizes for two immiscible fluids (corn oil and water), interfacial areas, and pressure drops. Increasing the contact angle of the two fluids at the fiber surface decreased the slug length; increased the number of slugs. An important phase transition, a phase inversion, was recognized. Instability of the slug size during transition was noted. Increasing flow rates increased the interfacial areas. Interfacial tension did not affect the slug size, but an increase in oil viscosity did reduce slug length. All slug sizes were micron order. The greatest increase in pressure drop was due to an increase in overall flow rate or viscosity. This ideal model will lead to improved control of the complex formation of interfacial area and therefore greater extraction efficiency and minimized energy use.

Microfluidic study of effect of dispersed phase viscosity and continuous phase viscosity on emulsification in a cross-junction chip

Immiscible flow of oil phase and displacing phase with surfactant can cause emulsification during the oil development. However, it is still unclear how the viscosity of each phase influences the emulsification at the micro level. In this study, we investigated the flow regimes and emulsification of two immiscible fluids in a cross-junction device by using an oil-surfactant system and an oil-surfactant/polymer system. Based on the experimental data, we analyzed the flow regimes and draw flow regime maps of the two systems. Moreover, we established the new scaling laws that include the capillary number, the flow rate ratio, and the viscosity ratio of two phases to predict the droplet diameter or slug length. The findings indicated that there are four flow regimes in the oil-surfactant system, including threading, squeezing, dripping, and jetting regimes. Besides, a new type of flow regime, irregular dripping regime, appears in the oil-surfactant/polymer system. According to the regime maps, the area of dripping regime decreases with the increase of the viscosity of dispersed phase or continuous phase. For both systems, the regression equations with the viscosity ratio have better fitting effect than those without the viscosity ratio. Meanwhile, compared with the effect of viscosity ratio of two phases, the flow rate ratio of two phases has higher influence on droplet diameter and slug length. The experiments present detailed emulsification processes at pore scale and provide new insights for the prediction of emulsion droplets and slugs.

Prediction of slug length distribution in horizontal large-diameter gas/liquid pipeline systems

Large-diameter (ID ≥ 0.1524 m) pipeline network systems are widely used in the food industry for grain transportation, in the chemical and nuclear industries for steam/water thermal distribution systems, in the oil and gas industry for crude oil transportation and exploitation, and in urban water supply and drainage systems. Due to the favorable operational and geometrical conditions in surface gas/liquid pipelines, slug flow often prevails, dominating the horizontal and slightly inclined flow pattern map. Formed liquid slugs at large-diameter pipeline entrances and dip can grow, accelerate, and overtake other slugs, resulting in high-momentum and long slugs ranging in length from a few meters to a few hundred meters. The discrepancy of current mechanistic models to predict slug length in large diameter pipes, and the scarcity of large diameter slug length data motivated this work to propose a combined mechanistic and empirical approach to predict full slug length distribution in large diameter surface pipeline systems. A first-principle mechanistic mean slug length model is improved by optimizing its closure relationships using a large-diameter lab and field slug length database. Furthermore, an empirical large-diameter slug length standard deviation dimensionless model is proposed and statistically validated. The proposed mean and standard deviation slug length models are combined to construct a probability distribution and maximum slug length models. Validation of the proposed model revealed an absolute average error of 27% and 31% for the mean and maximum slug lengths, respectively, vastly outperforming all existing models.

Growth of solitary slugs in long pipes

We show that a pipe transporting gas and liquid can be operated at conditions where both stratified flow and slug flow are stable. In this bi-stable flow regime, it is possible to observe stratified flow or regular hydrodynamic slug flow, depending on the inlet conditions. However, it is also possible to get one single slug at a time in the pipe. The distinctive characteristic of such “solitary” slugs is that they grow continuously as they travel along the pipe and therefore, in long pipelines, they can reach lengths up to thousands of pipe diameters and flood the downstream process installations. We first show how the length of solitary slugs can be predicted using slug tracking simulations. Based on those transient simulation results, we provide an explanation for the slug growth and we propose a simple quasi-steady-state model allowing us to predict the slug length in good agreement with the transient simulations. Finally, we explain how we can determine the boundaries of the bi-stable flow regime in which solitary slugs occur.

Investigation of particle flow effects in slug flow crystallization using the multiscale computational fluid dynamics simulation

This article discusses the development of a new computational fluid dynamics (CFD) model, the MVP (MP-PIC coupled with VOF and PBE) method, which predicts the slug flow crystallization phenomenon. The model is capable of predicting the flow of gas–liquid-solid phases and the associated chemical and particle changes. The MVP model is validated through a comparison with an experimental study on LAM (L-asparagine monohydrate) crystallization, and the results demonstrate its ability to accurately predict the three-phase fluid flow with particle size variation. In particular, we have been able to predict the effect of slug length change on particle mixing and predict hydrodynamic factors such as the particle streamlines and the circulation number of the particle phase via case studies. Overall, the MVP model is expected to offer a new way to accurately predict slug flow crystallization and provide valuable information for the process intensification of crystallization.

Axial behavior of slugging flow in a gas–solid CFB riser using distributed ECVT with 64 electrodes

Understanding particle flow characteristics within circulating fluidized bed (CFB) reactors is crucial for enhancing reaction efficiency. To study the flow characteristics of Geldart D particles with a mean diameter of 3.0 mm and a bulk density of 1640 kg/m3 in a CFB riser with a height of 1090 mm, a 64-electrode electrical capacitance volume tomography (ECVT) sensor with a height-to-diameter ratio (HDR) of 12 is arranged on the CFB riser with an inner diameter of 59 mm. A distributed ECVT architecture under the control of a timing controller is formed to synchronously acquire capacitance data of two 32-electrode ECVT data acquisition systems. So, the three-dimensional axial flow imaging of a CFB riser with a branch pipe is realized with a 14-plane ECVT sensor. The flow rules of slugging flow in the CFB riser under gas velocities of 3.5 m/s, 2.86 m/s, and 2.5 m/s are analyzed from the continuous ECVT images, especially the process of rupture, decomposition, and collapse of particle slugs. The flow parameter characteristics, such as the solid fraction in the riser, the slug rising tail velocity, the slug length, and the spectral characteristics, are investigated. The experimental results demonstrate that the proposed distributed ECVT can effectively realize the collaborative operation of multiple ECVT data acquisition systems and then splice sub-ECT images to achieve complex space imaging.

Influence of a restriction on flow patterns, void fraction, and pressure drop in gas–liquid pipe flow

Subsurface safety valves play an important role in the hydrocarbon production process. The Brazilian industry is suffering significant losses due to the reduction of the useful life of this device, not to mention the risks associated with the operation and the environment. One possible reason for the failure of the subsurface safety valve’s reliability prediction may be the occurrence of two-phase flow in the well. For this reason, a set of twenty horizontal two-phase flow experiments was carefully designed to evaluate the influence of a simplified internal reduction in a steel pipe. Superficial velocities were considered in the range of 0.1 m/s and 2.0 m/s for water and, 0.33 m/s and 7.47 m/s for compressed air. The experiments were carried out in 2″-i.d. and 2-m-long steel pipes, being a tube with restriction and another without restriction. Both tubes have an upstream development length of 126 pipe diameters. Gamma-ray densitometry and a differential pressure transducer were used to measure void fraction and pressure drop, and a visualization window was used to observe the flow patterns. Among the main findings are the effects of void fraction and mixture velocity on pressure gradient, with different impacts on the restricted pipe (RP) compared to the unrestricted pipe (UP). The presence of the restriction generated significant changes in the upstream flow: the lengths of the liquid slugs were increased, appeased by the increase in local pressure necessary to overcome the resistance produced by the restriction. Downstream, the change was reflected in the rise of void fraction and decrease of slip ratio between the phases.

A Self‐Powered Multiphase Flow Detection Through Triboelectric Nanogenerator‐Based Displacement Current

AbstractAccurate measurement of complicated multiphase flow is crucial to the safety and efficiency of petroleum and chemical industrial facilities. However, the existing multiphase flow detection techniques are not applicable to pipelines in remote regions including deserts or deep seas, due to the high cost of providing a stable power supply. Herein, a self‐powered multiphase flow sensor, composed of a liquid‐driven triboelectric nanogenerator (TENG) ‐based signal generator, a ring‐type transmitter, and a string‐type receiver, is proposed. Theoretical modeling of displacement current between transmitter and receiver implies that the received current signal can accurately reflect the wetting state of the receiver, validated by a combined experimental (accuracy above 97%) and simulation study. Coupling with a quantitative analysis algorithm, a multiphase flow detection system with numerous receiver measurement points is developed to precisely monitor various flow parameters, including slug frequency (one point), slug length (two points), and flow pattern (four points), which is verified by spontaneous high‐speed camera recordings of water–air flow. The present work provides a paradigm‐shift way to develop a self‐powered, inexpensive, and accurate technique to detect multiphase flow at remote industrial facilities.

Isolated slug traveling in a voided line and impacting at an end orifice

Driven by upstream high-pressure steam, liquid slugs in nuclear power plant pipelines impact the end orifice at high speed, leading to bursting pipelines and threatening the plant's safety. This research aimed to accurately and efficiently assess the dynamic behavior of an isolated slug driven by pressurized air in a voided line with an end orifice. An improved one-dimensional (1D) model for the slug motion and impact was established. The dynamic variation of the pressure at both the slug's tail and front, the variation of the slug length, and the frictional resistance coefficient in the model was obtained by three-dimensional (3D) computational fluid dynamics (CFD). Based on 27 cases with different pipeline diameters and tank pressures, it was observed that the driving air pressure had a quadratic relationship and that the slug length had a constant rate of decrease vs the slug tail displacement. Finally, the decrease in the driving air pressure behind the slug, the increase in the air pressure ahead of the slug, the holdup coefficient, and the friction factor obtained from the 3D CFD results were interpreted in the 1D model, and the velocity histories of the liquid slug were found to be in excellent agreement with the 3D CFD solutions.

Bubble generation mechanisms in microchannel under microgravity and heterogeneous wettability

Advances in hybrid surfaces have revealed interesting opportunities for multiphase flow control under microgravity, as the surface tension force is dominant in this condition. However, a comprehensive investigation of bubble generation rates and slug flow parameters remains challenging. This research integrates hybrid wettability and modified dynamic contact angle models to address this important knowledge gap. Using the computational capabilities of the IsoAdvector multiphase method, we performed detailed simulations of complex multiphase flow scenarios with the OpenFOAM package. We then validated these simulation results through rigorous comparison with available experimental data, thereby strengthening the accuracy and reliability of our numerical simulations. Our comprehensive research demonstrates the profound effect of altering contact angle distribution patterns on several critical parameters. These results highlight the precise control that can be achieved through the strategic manipulation of these patterns, offering the possibility of adjusting factors such as bubble production rate, slug length, bubble diameter, the relationship of flow residence to bubble movement, bubble movement speed in the channel, and pressure drop. Interestingly, altering these patterns can also induce asymmetric behavior in bubbles under microgravity conditions, a phenomenon that has significant implications for various applications. Such insights are crucial for fields such as heat transfer in energy systems, reaction mechanisms in chemical processes, multiphase flow control in petrochemical industries, fluid dynamics in aerospace engineering, and cooling mechanisms in electronic devices. With the ability to modulate these fundamental parameters, we gain valuable insights into the design and optimization of microchannel systems. Consequently, this research presents a more efficient and innovative approach to multiphase flow control, promising improved operational performance, and efficiency in various engineering applications.

Microreactor designed for efficient plasma-liquid segmented flows.

Microreactors were designed for gas-liquid plasma chemical processes and operated under segmented flows in a high aspect ratio (8.76) rectangular microchannel. First, the hydrodynamics of the gas-liquid flows generated at a T-junction was investigated for fifteen solvents commonly used in organic synthesis. The classical literature scaling laws were revised to describe the dependence of bubble and slug lengths, and bubble residence time on the liquid nature by introducing their liquid vapour pressure. Liquid film thickness and liquid residence time were estimated from residence time distribution experiments. Secondly, plasma could be successfully generated in these segmented flows for all the liquids. Due to the plasma dissipation of thermal energy, gas phase temperature increased and induced the lengthening of bubbles and the decrease in bubble residence time. The flow pattern was also impacted by the gas temperature increase. A flow map describing the evolution of the flow pattern under plasma conditions was built, enabling prediction of the flow pattern based on the liquid boiling point and dielectric constant. These microreactors have demonstrated great potential, and by adapting the synthesis solvent or the operating plasma conditions, they could find promising applications in gas-liquid plasma chemical processes.