Liquid Flow Rate Research Articles

Experimental characterization of dynamics of bed‐scale liquid spreading in a trickle bed

AbstractWe report measurements performed to understand the effects of gas (QG) and liquid (QL) flow rates, surface tension (σGL), liquid viscosity (μL), and particle diameter (dp) on dynamics of local liquid spreading, pressure drop, and overall liquid holdup in a pseudo‐2D trickle bed. We show that an increase in the gas‐phase inertia leads to a decrease in the lateral liquid spreading, whereas an increase in the liquid‐phase inertia leads to an increase in the lateral liquid spreading. We also show that an increase in dp causes a reduction in the lateral liquid spreading. Using dimensionless numbers (AB and We), we propose a regime map showing contributions of different forces to the local liquid spreading. We show that the interplay between the inertia and capillary forces governs the liquid distribution near the inlet, whereas the relative contribution of gravitational force increases toward the outlet. Finally, we propose a relation between AB and We for “bed‐scale” liquid spreading.

Influence of Complex Multiphasic Flow on the Thiuram Electrosynthesis in a Microchannel Reactor.

As an important sustainable method for chemical synthesis, organic electrosynthesis experienced a renaissance in recent years for its excellent atom economy. Although microchannel reactors have been proposed to advanced electrosynthesis devices to obtain low energy cost and high reaction performance, the complex multiphasic flow in the electrochemical microchannels are very less reported and the effects of flow condition on the electrosynthesis reaction are less reported. Taking the electrosynthesis of tetraethyl thiuram disulfide (TETD) as a typical case, we developed a visualized electrochemical microchannel reactor equipped with fluorine-doped tin oxide (FTO) loaded glass electrode to investigate the gas-liquid-liquid triple phase flow pattern and the main factors influenced the response current at certain applied cell voltage. The gas-liquid-liquid hybrid flow with low gas hold-up and high liquid flow rate was found crucial for preventing coverage of TETD on the electrode, which provided 23.1 % low current attenuation ratio at 3.0 V cell voltage. The research not only exhibited the complex evolution mechanism of the response current, but also showed the importance of flow condition control for balancing the work efficiency and energy consumption of electrosynthesis process.

Modeling and experimental study on a photochemical microscale continuous oscillatory baffled reactor

AbstractHerein, the first photochemical microscale continuous oscillatory baffled reactor, that is, Photo‐μCOBR, was designed and evaluated. Computational fluid dynamics simulations were used to optimize the key structural parameter and operating conditions. Then, the mixing process was simulated and the μCOBR was shown to be more than 23 times faster than the straight channel both under oscillating conditions. Finally, a glass Photo‐μCOBR was fabricated by femtosecond laser internal engraving technology, and the photocatalytic gas–liquid oxidation of dihydroartemisinic acid was performed. A yield of 65.9% was achieved in a residence time of ~120 s and at a gas–liquid flow rate ratio of 1:3 (vs. 18.6% in the capillary photomicroreactor under identical conditions). The results in this work offer guidelines for the design and operation of microscale COBRs, and the as‐fabricated Photo‐μCOBR displays good potential for gas–liquid photochemical reactions.

Effects of atomizer outlet style on the flow characteristics and dust suppression application

The efficiency of spray dust removal depends significantly on the flow and spray characteristics of the atomizer. This paper established a spray diagnosis system capable of exploring the flow and spray characteristics on the swirl effervescent atomizer. The experimental results indicate that these characteristics were primarily influenced by three key factors: working pressure (Pi), air-liquid mass flow ratio (ALR), and atomizer outlet type. The liquid mass flow rates and spray velocity were increased with Pi and ALR increasing. Conversely, the type of atomizer outlet has minimal impact on the liquid mass flow rate. Increasing the Pi and ALR reduces the spray particle size, boosts droplet velocity, and enhances spray dust removal efficiency. Furthermore, the special-shaped atomizers, square hole and convergent-divergent hole, exhibit favorable spray characteristics and pray dust removal efficiency. Under optimal parameters (Pi=0.6 MPa and ALR =0.18), the square hole of atomizer outlet induces a rapid reduction in the concentration of inhalable dust, achieving a maximum suppression rate of 97.57 %.

Effect of liquid properties on film behavior on the surface of an airfoil in a high-speed flow and subsequent atomization from the trailing edge

This study examines the behavior of ethanol or water films on the surface of a NACA 0012 airfoil placed in a high-speed air flow. New water film results complement previous measurements of time averaged ligament lengths and droplet sizes generated with the same airfoil. In addition, new data are obtained for ethanol. Air velocities up to 175 m/s are used with liquid flow rates between 1.4 cm2/s and 2.6 cm2/s. The liquid was introduced onto one side of the airfoil via 26 holes, each measuring 0.5 mm in diameter and spaced 1 mm apart. These holes are positioned 35 mm downstream from the leading edge and 65 mm upstream from the trailing edge. Film behavior on the vane is captured with front-lit high-speed video. The accumulation of liquid and breakup of ligaments are captured with backlit highspeed video. Phase Doppler interferometry is used to measure droplet size and simultaneous axial and pitch wise velocity 70 mm downstream of the trailing edge. Finally, laser diffraction is used to measure line averaged droplet sizes. The results indicate notable differences between ethanol and water films. The ethanol film spreads more extensively across the width of airfoil which is attributed due to its lower surface tension. The maximum ligament length for both liquids decrease with higher air velocity and increase with the liquid flow rate. A correlation for maximum ligament length is developed and captures the effect of liquid properties, flow rate, and air velocity. Furthermore, the variation in liquid volume flow rate did not impact droplet size. However, for a given air velocity, the Sauter Mean Diameter is found to depend on surface tension. On the dependency of droplet size on the Weber number, ethanol produced smaller droplet sizes at low values of Weber number. However, at relatively high Weber numbers, the droplet sizes for both water and ethanol were similar. This suggests that droplet size is influenced by factors besides surface tension at low Weber numbers but not at higher Weber numbers. In addition, the Nukiyama-Tanasawa model to fit the volume distribution curves is simplified by fixing p and q terms. Simplification makes the model easier to understand and implement.

Microfluidic mass transfer of supercritical CO2 in brine

In the context of carbon sequestration in saline aquifers, we investigate CO2 transport dynamics in brine under reservoir-like conditions (P = 8 MPa, T = 50∘C) using microfluidics. We quantify the mass transfer of supercritical CO2 in brine across a range of concentrations (0–1 M) and liquid flow rates (15–60 μL/min) for the first time. We find the volumetric mass transfer coefficient kLa ranges from 50.3 to 144.0 s−1, increasing with flow rate and, to a lesser extent, with salinity. More importantly, the kLa value for supercritical CO2 in brine at a higher temperature shows a significant enhancement of >50% compared to gas and liquid CO2 in water. Our analysis, incorporating a theoretical mass transfer model, points to a dominant contribution from the liquid film to the overall kLa, nearly doubling that of the emulsion caps, attributed to the thin film's larger surface area and dynamic renewal.

Evaluating a green liquid phase plasma discharge process and working mechanism for remediating cobalt contamination in water

Cobalt is a toxic heavy metal contaminant in water and wastewater causing health concerns and on the other hand, a valuable element to recycle. In this study, performance of a novel and green continuous liquid phase plasma discharge (CLPD) process was investigated for removal and recovery of cobalt from aqueous solution without use of any catalysts or chemicals. The CLPD reactor design features two conductive channels and stable electric discharge at the orifice of two dielectric plates sandwiched among the electrodes. The effects of operating factors of the CLPD process were evaluated with liquid flow rate (25–100 mg/L) and applied power (200–300 W), and the highest removal efficiency of cobalt (93 %) was obtained within 25 min at a 50 ml/min liquid flow rate and 300 W applied power. The CLPD energy efficiency for cobalt removal under this condition was 27.44 g kW-1h−1. Reaction kinetics with scavenger tests revealed that oxidative reactive species, i.e., hydroxyl radical and superoxide radicals, produced at the discharge zone were responsible for cobalt removal from water by producing cobalt oxide particles and the reaction pathways were proposed. The CLPD process not only allowed for the efficient removal of cobalt (II) from water but also synthesized cobalt oxides particles with averaged size of 2.75 µm, which can be applied as catalyst. The overall results indicated that the novel CLPD is a robust and highly effective process to remove and recover cobalt from water.

Packed‐Bed Microreactor Under Taylor Flow for MOFs Catalyst Testing Demonstrated on Phenylacetylene Hydrogenation

AbstractMetal‐Organic Frameworks (MOFs) represent a highly promising class of materials with diverse applications, particularly as catalytic materials. However, their synthesis typically yields powders available only at laboratory‐scale quantities, usually in the gram range or less. This study addresses the challenge of testing limited amounts of MOF catalysts for demanding applications, such as multiphase gas‐liquid‐solid reactions in flow, utilizing a packed‐bed microreactor. Specifically, we investigate the performance of a nanoparticle (NP) ‐immobilized Pd@UiO‐66 MOF catalyst in the selective semi‐hydrogenation of phenylacetylene to styrene, serving as a model reaction. Maintaining the Taylor flow regime upstream of the catalyst bed was crucial to ensure reproducible and reliable experimental results. We conducted 88 experiments at varying liquid flow rates, temperatures ranging from 15 to 45 °C, and relative pressures spanning 0.28 to 8 bar. Styrene selectivity within the range of 80–92.3 % was achieved at phenylacetylene conversions below 20 %. Notably, the optimal condition for styrene selectivity (70 %) was attained at 98.9 % phenylacetylene conversion under the lowest H2 pressure and highest temperature, demonstrating the significance of low H2 concentration for achieving optimal styrene selectivity. Remarkably, the catalyst exhibited stable activity and selectivity over a 20 h testing period, indicating its robust performance under prolonged reaction conditions. This study demonstrates the potential of the proposed catalyst testing system as a rapid and efficient approach for early‐stage exploration studies, particularly when limited quantities of catalyst, typically in the gram scale or less, are available.

Detection of food additives based on an integrated self-injected metasurface microfluidic sensor.

Advanced sensing equipment exhibits high sensitivity and reliability in detecting food additives, enabling the practical assessment of the safety of processed foods. Currently, chemical detection methods are commonly utilized for identifying food additives. However, these approaches tend to be intricate and time-consuming. In this study, we designed and fabricated an integrated terahertz microfluidic sensor, which achieves high sensitivity by incorporating a metasurface within the microfluidic chip. The metasurface comprises metal wires and split-ring resonators, with three optional sensing sites within the frequency domain of 0.1-1.2 THz, thereby enhancing the reliability of the sensor. Additionally, the use of a self-injection micropump improves the stability of the liquid flow rate, preventing experimental errors caused by manual injection. Utilizing this sensor, we conducted concentration sensing experiments on potassium sorbate and sodium benzoate solutions, successfully identifying sugar-containing and sugar-substituted beverages with high sensitivity and rapid sensing speed. The average sensitivity of the sensor is 152.8 GHz·RIU-1. The results of this study provide a feasible method for the development of microfluidic metasurface sensors.

Detailed 3D URANS analysis of two-phase flow in an airlift pump

An airlift pump is a vertical tube that utilizes the buoyant effects of a gas to lift a liquid. Unlike a standard mechanical pump, the liquid flow rate through the airlift pump is not directly controlled; rather, it depends on the supplied gas flow rate, the tube length and diameter, and the relative height of the liquid supply free surface (submergence ratio). The present study uses the commercial CFD code ANSYS CFX to model the isothermal, 3D, transient flow in an airlift pump using water and air. The model applies pressure boundary conditions at both ends of the tube and specifies the mass flow rate of air through multiple openings in the side of the tube. The bottom of the tube is an inlet of water only and the outlet is a two-phase flow opening. A time-dependent, homogeneous, VOF two-phase RANS CFD modelling approach is used with the air treated as an ideal gas. This work found that a complete 3D domain was necessary for consistent prediction of the airlift performance and physically realistic two-phase flow structures. Statistical analysis of the two-phase flow structures was applied to characterize airlift pump instability and better understand the physics of the airlift pump.

Pumping-less 3D concrete printing using quick nozzle mixing

Nozzle technologies for 3D concrete printing have been evolving to balance the conflicting demands of buildability and pumpability. This study introduces a simplified approach that eliminates the need for pumping by developing a customized system, the parameters of which were evaluated. The effect of process parameters (i.e., the flow rates of liquid and solid materials) and mixture proportions (i.e., the ratios of powder to sand and liquid to solid) on the extrudability and print quality was explored. Furthermore, the mechanical properties and microstructure of concrete printed using the Quick Nozzle Mixing system were examined. Results show that Quick Nozzle Mixing Technology not only enables high-quality printing but also exhibits the potential for achieving better process efficiency and higher aggregate content. The water-to-solid ratio is a critical factor influencing extrudability and buildability. Due to anisotropy caused by this new method, printed concrete has a lower strength than cast concrete.

Assessing sulfate-reducing bacteria influence on oilfield safety: Hydrogen sulfide emission and pipeline corrosion failure

With the further development of oilfield, excessive sulfate-reducing bacteria (SRB) has intensified odors and increased pipeline leakage incidents. Accurate predictive models of H2S emission and pipeline corrosion based on SRB content are essential for safety. This study analyzed the correlation between sulfide content and SRB content at different nodes in the injection-production system of Daqing Oilfield, and characterized the pipeline corrosion products using scanning electron microscopy (SEM), X-ray diffraction (XRD), and stereo microscope. Corrosion rates were investigated through 18 sets of orthogonal experiments, considering factors such as SRB, temperature, pH, liquid flow rate, CO2 partial pressure, and H2S partial pressure, and the main controlling factors of corrosion were identified. Finally, the risk models for H2S emission and corrosion rate based on SRB content were established under on-site operating conditions. The results show that a significantly positive correlated between SRB and sulfide content at different nodes, with the highest levels observed at the settling tank, indicating the highest risk of H2S emission. SRB contributed to corrosion in both water injection and oil collection pipelines, with more serious corrosion in the water injection pipeline. SRB and pH were identified as the main factors influencing corrosion rate. The H2S emission prediction model based on the correlation of SRB and sulfide was reliable, with an accuracy exceeding 90 % compared to the measured results. Additionally, the corrosion rate model for pipelines, related to SRB content, had an error of less than 7 %. To minimize risks, it is recommended to maintain a low risk environment in the injection-production system by sterilization and increasing the pH of water. This study has significant theoretical importance for ensuring the safe operation of injection-production systems.

Study on Gas-Liquid Coaxial Jet Foam Generator and Its Foaming Characteristics.

In order to solve the difficulty of the existing compressed air foam system with low FER and difficult in having both the FER and range. A new type of foam generator for CAFS was designed, an air-liquid coaxial foam generator, which produces foam with high FER (the ratio of the foam volume to the volume of the foam solution) and large output momentum. In this paper, experiments on the foam production performance of a gas-liquid coaxial jet foam generator were carried out with different parameters, such as liquid flow rate, gas flow rate, and foam output end diameter. The variation of FER, foam half-life, range, foam volume, and compressed air utilization rate with the experimental parameters were analyzed. The results show that the foaming performance of the foam generator tends to rise in the range of 8-12.4 m3/h at a fixed gas flow rate, the FER and foam half-life are negatively related to it, and the foaming performance tends to decrease in the range of 12.4-18 m3/h. The best foaming performance was achieved when the liquid volume of the foam generator was 12.4 m3/h. For the liquid volume value in different intervals, the foaming performance varies with the air supply volume. When the liquid volume is higher than 12.4 m3/h, increasing the air supply volume is beneficial to improve the foaming performance, and when the liquid volume is lower than 12.4 m3/h, increasing the air volume does not improve the foaming performance. The effect of the diameter of the foaming chamber on the foaming performance is not monotonic, and an optimum value exists. Compared with similar devices, the gas-liquid coaxial jet foam generator has strong advantages in FER and range and has better application prospects for fire control in restricted spaces.

Evaluation of Effective Interfacial Area in a Rotating Packed Bed Equipped with Dual Gas Inlets

This study investigates the effective interfacial area in a novel rotating packed bed (RPB) equipped with dual gas inlets instead of the conventional single-gas-inlet RPB. The aim is to enhance the mass transfer efficiency of gas-liquid contacting processes in RPBs by increasing the number of gas inlets to improve the spread of gas supply into the packing. The RPB is a promising gas-liquid contactor configuration known for its intensified mass transfer characteristics. However, the impact of additional gas inlets on the effective interfacial area of the packing remains unexplored. An experimental method assessed the interfacial area under varying operational conditions which include a liquid flow rate of 0.30-0.60 m3/h, a gas flow rate of 100-300 Nm3/h, and a rotation speed of 600-1000 rpm. At operating conditions covering the maximum rotation speed of 1400 rpm, gas flow and liquid flow rates of 300 Nm3/h and 0.60 m3/h respectively, the results showed that on average, 55 to 97% of the 2400m2/m3 specific packing area can be effectively utilized for gas-liquid mass transfer during separation operations using the RPB. Compared to results reported for single-gas-inlet RPBs using similar packings, the RPB with double gas inlet proved to provide higher utilization of the packing. By simply doubling the number of gas inlets, the findings provide valuable insights into optimizing RPB designs and operations which could enhance mass transfer efficiency for various chemical and environmental applications.

Design and experimental research of air-assisted nozzle for pesticide application in orchard.

This article reports the design and experiment of a novel air-assisted nozzle for pesticide application in orchard. A novel air-assisted nozzle was designed based on the transverse jet atomization pattern. This article conducted the performance and deposition experiments and established the mathematical model of volume median diameter (D50) and liquid flow rate with the nozzle design parameters. The D50 of this air-assisted nozzle ranged from 52.45 μm to 113.67 μm, and the liquid flow rate ranged from 142.6 ml/min to 1,607.8 ml/min within the designed conditions. These performances meet the low-volume and ultra-low-volume pesticide application in orchard. The droplet deposition experiment results demonstrated that the droplet coverage distribution in different layers and columns is relatively uniform, and the predicted value of spray penetration (SP) numbers SPiA , SPiB , and SPiC (i = 1, 2, and 3) are approximately 70%, 60%, and 70%, respectively. The droplet deposits on the foliage of the canopy (inside and outside) uniformly bring benefit for plant protection and pesticide saving. Compared with the traditional air-assisted nozzle that adopts a coaxial flow atomization pattern, the atomization efficiency of this air-assisted nozzle is higher. Moreover, the nozzle air pressure and liquid flow rate are considerably lower and greater than the traditional air-assisted nozzle, and these results proved that this air-assisted nozzle has great potential in orchard pesticide application. The relationship between the D50 and nozzle liquid pressure of this air-assisted nozzle differs from that of traditional air-assisted nozzles due to the atomization pattern and process. While this article provides an explanation for this relationship, further study about the atomization process and mechanism is needed so as to improve the performance.

Mass transfer of gas–liquid two‐phase flow in asymmetric parallel microchannels with liquid feed splitting

AbstractDue to size limitations, the gas–liquid absorption capacity of a single microchannel is limited, making it difficult to achieve large‐scale CO2 capture. Therefore, the parallel microchannels combining the advantages of high efficiency and large throughput stand out. However, when the operating condition is high gas–liquid flow rate ratio, the liquid phase between bubbles almost disappears after multiple distributions, which affects the amount of gas–liquid absorption. In this study, the numbering‐up of the asymmetric parallel microchannels in the gas–liquid absorption process was investigated by splitting the liquid feed stream in two. The flow patterns under different operating conditions were obtained. The flow and distribution of gas–liquid two‐phase flow were investigated, and the reason of the distribution deterioration caused by appearance of long slug bubbles was explained by the pressure drop distribution. The total liquid mass transfer coefficient and bubble residence time were derived and obtained, and the mass transfer was further discussed.

Bubble Induced Mixing In A Bubble Column With Counter-Current Liquid Flow

Bubble columns have been widely investigated over the last few decades, concentrating on the bubble parameters, and gas/liquid motion. However, mixing and often the resulting interaction between chemical reaction and hydrodynamics in the column are rarely analysed. For this reason, experiments with Laser Induced Fluorescence (LIF) applying Sulforhodamine G as fluorescent dye, and shadow imaging were performed in a square laboratory-scale counter-current flow bubble column at 21 different flow conditions and three different dye inlet positions. In these experiments the mixing efficiency was investigated by varying the bubble size, the gas and the liquid flow rates, to obtain the necessary data for a further understanding of mixing processes in bubbly flows. The strong influence of the bubble presence, their size and the counter-current liquid flow rate on mixing in the column is obvious from these results. Bubble induced mixing leads to a good homogenisation inside the column, compared to a flow without bubbles. Also, the larger the bubbles the higher the bubble induced upward velocity, which leads to a better mixing. The highest counter-current liquid flow rate led to a more concentrated dye jet, which was less dispersed than at lower liquid flow rates, while the moderate counter-current liquid flow rate (11.1 l· min-1) has been found optimal for mixing in the investigated cases. The combination of large bubbles generated with the 3.6 mm capillaries, and a moderate counter-current liquid flow rate led to the best mixing performance in the bubble column.

Comparative Analysis Of Brightness-Based Laser-Induced Fluorescence (BBLIF) And Structured Planar Laser-Induced Fluorescence (S-PLIF) For Film Thickness Measurement In Two-Phase Flow

Improved understanding of the interactions between gas and liquid phases in gas sheared film flow is crucial for n improved capability to employ computational modelling in the future to optimize systems, thereby reducing environmental impact, increasing efficiency, and enhancing productivity. This abstract compares two techniques for measuring the thickness of the film in different regimes visible in a rectangular cross-section gas-sheared liquid film rig, namely previously published Brightness Based Laser Induced Fluorescence (BBLIF) data and Structured Planar Laser Induced Fluorescence (S-PLIF) from the current investigation. The study presents and compares examples at a specific liquid flow rate (8 litres per minute) for superficial gas velocities in the range 1 m/s to 10 m/s, noted as being in different flow regimes. The investigation reveals that the S-PLIF technique produces results that are within the uncertainty bands of the BBLIF data for most scenarios. However, in the transition regime, statistical variations emerge. The frequency content of the two film heights is analyzed using a Hilbert-Huang Technique. This shows clearer results for the S-PLIF than for BBLIF which is attributed to the erratic values that can occur in BBLIF when total internal reflection occurs. It is concluded that the S-PLIF technique demonstrates promise as a reliable method for determining film thickness which is highly advantageous as it can be applied to images obtained with seeded flow intended for PIV analysis. The S-PLIF film thickness data can be used for generating automated masks for PIV analysis concurrently conducted in both the gas and liquid phases. This advancement facilitates the enhanced capability to advance understanding of complex fluid dynamics and optimize system performance.

Characterising Horizontal Two-Phase Flows Using Structured-Planar Laser-Induced Fluorescence (S-PLIF) Coupled With Simultaneous Two-Phase PIV (S2P-PIV)

Understanding the physics that underpins the behaviors of two-phase flows is immensely useful for a diverse number of industries, including oil and gas, nuclear, and aerospace. Stratified air-liquid two-phase flows are amenable to the application of two-phase PIV, but this is often only possible if PIV processing parameters can be chosen to match the separate gas and liquid phase image sets. Accurate interface location detection is, therefore, extremely important to facilitate appropriate masking during analysis. This paper examines the effectiveness of using the Structured-Planar Laser Induced Fluorescence (S-PLIF) method to aid in the accurate capture and processing of simultaneous two-phase PIV (S2P-PIV) for a gas-sheared liquid flow. Prior S2P-PIV work made use of direct interface detection, using contrast on images from the air-side camera. However, this method proved limiting in higher gas shear cases when the highly wavy nature of the flow prevented the camera from seeing all of the interface. An alternative prior approach using the liquid-side camera and the planar laser-induced fluorescence (PLIF) technique often led to large errors due to reflections from the free surface. Interface detection using the S-PLIF method facilitates a clearer delineation between the two phases through analysis of the change in the structure of the incident light, significantly reducing errors generated by the traditional PLIF. This then facilitates higher quality PIV analysis, both because interface identification is far more accurate and also because frame specific masking of the individual phases can be more automated. This paper presents air/water data from a rectangular channel with a liquid flowrate of 8 litres per minute and superficial gas velocities in the range 1 - 14 m/s. Data capture of the two phases is concurrent with the developed S-PLIF approach used to locate the interface, enabling separate and more accurate PIV analysis of the two phases over a wider parametric range than was previously possible. The data analysis shows that the transition to the disturbance/roll wave regimes is associated with a change in the liquid’s axial velocity profile and a significant increase in normalized axial velocity root-mean-square velocity fluctuation. Data sets from this work can be used to accurately describe high-speed gas-sheared two-phase flows that will be extremely useful for CFD model development and validation.

Characteristic parameters measurement and flow prediction of slug flow based on ultrasound technology

Slug flow exists over a wide range of gas and liquid flow rates. For the case of smaller liquid volume fraction, this paper proposes a method for accurately identifying the flow structure of horizontal pipe slug flow based on the ultrasonic inner wall echo signal at the top of the pipe. The arrival and departure time of the slug is determined by analyzing the amplitude of the inner wall echo signal from both the test signal and reference signal and the rate of change of the test signal, respectively. Based on the accurate flow structure identification results, characteristic parameters can be calculated including the length ratio between the liquid film zone and the slug unit (lf/lu) and the average liquid film thickness in the liquid film zone (hf). The system of equations describing the relationship between the two parameters and the two-phase flow rates is constructed. By solving it, the flow rates of gas and liquid can be predicted. Experiments are carried out with the superficial velocity of gas and liquid ranging from 0.8 to 2.5 m/s and 0.1 to 0.4 m/s, respectively, where the pipeline’s inner diameter is 50 mm. The experimental results indicate that the mean absolute percentage errors for the predicted gas and liquid flow rates are 12.9605 % and 6.3517 %, respectively.