High Gas Flow Rates Research Articles

Uniform generation of water slugs in air flowing through superhydrophobic microchannels with T-junction

This article describes an approach to render all walls of a rectangular microchannel superhydrophobic by coating them with hydrophobically modified silica nanoparticles. Differences between the coated nanoparticles in terms of feature size and structure resulted in different contact angle hysteresis (CAH) on the channel walls. The generation of water slugs in a continuous air flow was experimentally studied in the superhydrophobic microchannels with T-junction. The breakup mechanism of water slugs was proved to accord with the squeezing regime by analyzing the data collected from pressure sensor and high-speed camera at the T-junction. A home-made optical measurement system was employed to investigate the uniformity of the water slugs, which was characterized by the standard deviation and coefficient of variation of slug length. The results showed that superhydrophobic microchannels with CAH lower than 15° could produce uniform water slugs in a slug flow pattern, whereas those with CAH of nearly 30° led to unstable flow. Lower CAH and higher gas flow rate were preferred to reduce slug length and improve slug uniformity. An empirical scaling law was established to predict the slug length and was based on the finding that the total length and number of water slugs in the microchannel were controlled by the volumetric flow ratio of water to air and water flow rate, respectively. This work provides a novel microfluidic platform to generate uniform liquid-in-gas slugs under moderate ranges of air flow rate from 5 mL min−1 to 30 mL min−1 (6 < ReG < 40) and volumetric flow ratio of water to air from 1/300 to 1/2, and this performance benefits from superhydrophobic coatings with low CAH.

Effect of shielding gas flow on welding process of laser-arc hybrid welding and MIG welding

The influence of shielding gas on welding process of laser-arc hybrid welding (LAHW) and metal inert-gas welding (MIG) was investigated by the computational fluid dynamics analysis (CFD) and high-speed photography. The results show that the process stability of MIG under high gas flow rate is poorer than that of LAHW. And the force of gas flow Fg can hinder the droplet transfer, whether MIG or LAHW. But the vaporization-induced recoil force Fv in LAHW helps to reduce this kind of hindrance and keep the process stability. Next, it can be found that the shielded gas flow mode in the main welding area cannot be changed significantly by increasing the shielding gas flow rate, while high gas flow rate can increase the area of high argon concentration and benefit the spread of molten metal.

Analysis of the interaction between particles and gliding arc discharge in a spouted bed reactor

In this paper, the interaction between particles and gliding arcs in a spouted bed reactor combined with gliding arc discharge was investigated using a high-speed camera. Based on the images captured by the camera, we evaluated the retention time for gliding arcs, the contact frequency of particles with the gliding arc, and the passage area of the gliding arc until its disappearance. The effects of the gas flow rate; electrode angle, which is same as the cone angle of the spouted bed; and applied voltage of gliding arcs were investigated. The retention time for gliding arcs was extended by a high applied voltage, the passage area was increased at a high gas flow rate, and the contact frequency was increased by decreasing the electrode angle. The results obtained here can support the optimization of particle treatment processes in a spouted bed with gliding arc discharge.

Effect of zoning on mixing and mass transfer in dual agitated gassed vessels

Gas–liquid multi-phase processes are widely used for processes that require reactions. To increase productivity in these reactions one potential method is to increase the gas flow rate into the vessel. This means that it is important to understand how these reactors perform at high gas flow rates, which can create problems such as zones within the vessel. This paper investigates the mixing performance and the mass transfer in dual agitated systems at high gas flow rates. Two configurations have been compared a 6 blade disk turbine (Rushton turbine) below either a 6 Mixed flow Up-pumping or down-pumping agitator. Zoning has been identified by Electrical Resistance Tomography which affects the mixing time within the vessel, with increasing agitation rate potentially increasing the mixing times at high gas flow rates. At these high gas flow rates the zoning also affects the mass transfer meaning that it is not constant within the whole vessel. However, dividing the vessel into the key zones allows the mass transfer rate to be predicted with a single equation.

Modeling of the Effect of the Gas Flow Rate on the Fluid Flow and Open‐Eye Formation in a Water Model of a Steelmaking Ladle

In ladle metallurgy of steelmaking, the role of gas injection into the metal bath is been studied to a great extent as it improves the quality of steel. The size of the open‐eye is associated with higher emulsification of top slag, which intensifies metal–slag reactions, and information about the position and size of the open‐eye is important for effective alloying practice. Moreover, the open‐eye has an effect on the energy balance since it increases heat losses. In this work, experimental measurements and numerical simulations are performed to study the effect gas flow rate on the formation of the open‐eye in a steelmaking ladle. A one‐fifth scale water model is constructed for studying gas injection with single and dual plug configurations. For the numerical modeling, the Multiphase Volume of Fluid (VOF) model is used for simulating the system including the behavior of the slag layer. The physical modeling results show that the open‐eye area changes from 9.22 to 198.34 cm2 when the gas flow rate varies from 0.75 to 15 SLM using a single plug. The effect of the number of plugs on the open‐eye area for the same range of flow rates mentioned above is also studied. The two open‐eye areas generated due to the gas injected through the dual plugs change from 37.59 to 231.1 cm2 when the gas flow rate is increased from 0.75 to 7.5 SLM for each plug in the physical modeling. The numerical simulation results of the open‐eye area are found to be in good agreement with the experimental data obtained from the water model. During the gas stirring process, the slag layer is deformed such that the thickness of the slag becomes thick near to the wall and thin near the slag eye at high gas flow rates. In dual plug system, the two open‐eyes tends to merge and form a huge open‐eye at high flow rates that suits for better alloying purposes. The high‐flow velocity near the surface, which could damage the ladle refractory, tends to be reduced in dual plug system when compared to single plug system.

STAGES OF PERIODIC GASLIFT TECHNOLOGIES DEVELOPMENT AT MARGINAL WELLS IN VIETSOVPETRO JV

Background The paper discusses the experience of the introduction and development of periodic gaslift technologies at the fields of Vietsovpetro JV. Aims and Objectives Analysis of the periodic gaslift effectiveness in the conditions of Vietsovpetro JV. Results The experience of periodic operation of marginal wells confirmed the efficiency of transfer of low-yield gaslift wells to periodic operation, both by increasing the flow rate of the well and reducing the specific gas consumption, and by preventing parafin deposits in the lift. Based on the analysis results of the operating gaslift wells, it is recommended to transfer to the periodic operating mode of a well with a high specific flow rate of gaslift gas (> 1000) and water-oil factor (> 20 %) with a relatively low flow rate (≤ 3-5 tons/day).

The process intensification of CO2 absorption in Hilbert fractal reactor fabricated by a 3D printer

ABSTRACT CO2, as a major greenhouse gas, contributes greatly to the global warming. Increasing the efficiency of CO2 capture and utilization has becomea worldwide challenge. In the present research, Hilbert fractal reactor was fabricated via 3D printing technology for process intensification of ethanolamine (MEA) CO2 absorption. The performance of the Hilbert fractal reactor was investigated and compared to the serpentine reactor. For constant gas and liquid flow rates, the CO2 removal efficiency, the absorption rate, and the assumption of MEA increased with increasing concentration of MEA. In the comparison with the serpentine reactor, the CO2 removal efficiency in Hilbert fractal reactor is higher than that in the serpentine reactor at the relative low gas flow rate. The continuous bending in the Hilbert fractal reactor enhances the shear stress of the fluids, and the gas phase is segregated into the small bubbles which significantly increase the interface mass transfer. Under the relative high gas flow rate, the residence time of CO2 is short and the flow pattern in Hilbert reactor turns into the annular flow which adverse to CO2 absorption rate, and the advantage of Hilbert fractal reactor over serpentine reactor becomes negligible. The maximum CO2 removal efficiency of 57% was obtained in Hilbert fractal reactor.

Numerical simulation of bypass evaporation system treating FGD wastewater using high temperature flue gas

ABSTRACTA novel zero-liquid discharge (ZLD) technology for desulfurization wastewater treatment is put forward in this paper. A ZLD reconstruction project performed on 2 × 320 MW desulfurization system was taken as the research object, to study the evaporator structure and the key factors affecting spray evaporation through CFD numerical simulation. The result shows that when the evaporator diameter is 2.4 m, the central density difference and the temperature difference of evaporator outlets are 0 kg/L and 0°C, under this condition, the wall sticking can be avoided effectively, and the uniformity of evaporator's outlet flow field is improved. As for the same amount of wastewater, small atomized particle size, high flue gas flow rate and high flue gas temperature are conducive to complete evaporation, and the optimum atomized particle size is 100–150 μm, flue gas velocity is 3–4 m/s and flue gas temperature is 250–260°C. In order to reduce adverse impact on the main flue duct, the optimized design scheme that extracting flue gas before and after the air preheater is put forward in the purpose of energy saving.

Dynamics and mass transfer characteristics of CO2 absorption into MEA/[Bmim][BF4] aqueous solutions in a microchannel

Abstract The evolution of the size and velocity of CO2 bubble absorbed into MEA/[Bmim][BF4] aqueous solutions was in-line investigated by a high-speed camera. The coupling effect between the variation of volume and the velocity of bubbles was highlighted. According to the evolution of average mass transfer coefficient, the mass transfer performance in the whole flow process was studied. The results indicated that both the length and velocity of bubble decreased gradually in the flow process due to mass transfer. A linear correlation between the relative velocity (the ratio of average bubble velocity to two-phase superficial velocity) and the relative lost length (the ratio of the lost length to the initial length) was proposed. The increase in overall liquid-phase volumetric mass transfer coefficient (kLa) at higher gas flow rate could be ascribed to the shorter residence time and larger specific surface area. While the increase of kLa at higher liquid flow rate and MEA or [Bmim][BF4] concentration was resulted from intensified mass transfer. An empirical correlation of overall liquid-phase volumetric mass transfer coefficient was proposed taking the gas-phase Reynolds number, liquid-phase Reynolds number and Damkohler number into account.

Experimental investigation of airflow above waves in a horizontal pipe

We investigate the effect of waves on the airflow in horizontal two-phase pipe flow. Velocity fields in the gaseous phase were acquired by particle image velocimetry (PIV), while interfacial elevation was measured with conductance wave probes. The velocity fields were sampled on a wave-following coordinate system which allows for a decomposition of the velocity field into a mean, wave-coherent and fluctuating component by means of a three-component Reynolds decomposition. Additionally, coherent vortical structures were identified by the swirling strength criterion, and their distribution along the waves is investigated.Results suggest that the interaction between turbulent airflow and propagating waves in a pipe has a number of features reminiscent of wind-wave interaction in open systems. Above waves generated by sufficiently high gas flow rates, there is a distinct region of sheltered airflow, and a lifting of the critical layer on the leeward side of the crest. Streamlines of the phase-averaged flow field show a cat’s eye structure located close to the crest in this region. Above waves of moderate steepness, we observe a shear layer that remains adjacent to the wave surface. Above steeper waves and higher gas flow rate, this layer detaches from the surface just downstream of the crest. Shear layer separation above waves is traditionally linked to the onset of wave breaking, and it is interesting to note that the case where we observe a separated shear layer in the phase-averaged vorticity field is in a regime of amplitude saturation.The swirling strength criterion reveals that vortical structures are shed from the interface and populate the detached shear layer above the trough. Below the detached shear layer, there is a region populated by counter-rotating vortices. The critical height coincides with the border between these two regions.

Non-spherical particles in a pseudo-2D fluidised bed: Modelling study

Fluidised beds are used in a variety of processes because of their favourable mass and heat transfer characteristics. In this and many other processes, non-spherical particles are commonplace, which can drastically affect the fluidisation behaviour. In this study, we use numerical models to study non-spherical fluidisation behaviour in detail. A crucial step in the development of the numerical model is a detailed validation with experimental data. The validated model can then be used with confidence for further investigations. In this study, the results obtained from CFD-DEM modelling are compared with detailed experiments (Mahajan et al., 2017). The particles used are of spherocylindrical shape with an aspect ratio 4. We discuss the numerical modelling strategy including the DEM contact detection algorithm and accurate voidage calculation algorithm. The non-spherical single particle drag model of Hölzer and Sommerfeld (2008) is compared with a DNS drag model for spherocylindrical particles developed in-house. We propose two new voidage correction models and compare results with the (Di Felice, 1994) model. The pressure drop, bed height, particle orientation, particle circulation, stacking of particles and coordination number obtained from simulations are compared with experiments. The numerical measurements show good agreement with experiments. Similar to experiments, simulations show that rod-like particles are prone to interlocking behaviour. At high gas flow rates above the minimum fluidisation velocity, vigorously bubbling fluidisation is observed, with gas bubbles moving up through the center and particles moving down at the side walls. The orientation of particles in the fluidised state do not match with the experiments when hydrodynamic torque is neglected. The importance of hydrodynamic torque and multi-particle drag in CFD-DEM modelling of non-spherical particles is demonstrated through these results.

Performance analysis of a water–gas shift membrane reactor for integrated coal gasification combined cycle plant

In integrated gasification combined cycle (IGCC) systems, the water–gas shift reaction, which promotes the conversion of CO present in syngas mixtures into hydrogen, is an important step for hydrogen production. Application of the water–gas shift membrane reactor (WGSMR) in IGCC systems is an attractive option for CO2 capture compared with conventional methods because of smaller heat loss in gas purification and high CO conversion by selectively removing hydrogen from the reaction zone through the membrane. In this study, we proposed and evaluated commercial-scale WGSMR models combined with IGCC using reported laboratory-scale experimental data to optimize their operational parameters. Various models were developed using the Aspen Plus® Ver. 8.6 process simulator to investigate the impacts of hydrogen separation, pressure loss, and the flow direction between the sweep gas on the permeate side and syngas on the retentate side on the WGSMR performance with respect to CO conversion, H2 yield, and reactor temperature. The membrane reactor model gave approximately 20% higher CO conversion than a reactor model without H2 separation and approximately 4% lower CO conversion than a membrane reactor model with a pressure drop. A counter-current membrane reactor model gave approximately 2% higher CO conversion than a co-current model; the H2 yield on the permeate side was 9.3% higher in the counter-current model by separation of H2 through the membrane. A sensitivity analysis indicated that a high flow rate and low pressure of sweep gas are advantageous for H2 recovery, and high catalyst loading and high syngas inlet temperature are preferable for higher CO conversion.

Synergistic degradation of bisphenol A by pulsed discharge plasma with granular activated carbon: Effect of operating parameters, synergistic mechanism and possible degradation pathway

A hybrid gas-liquid pulsed discharge plasma (PDP) system combined with granular activated carbon (GAC) was established to investigate the bisphenol A (BPA) degradation. The results exhibit excellent synergistic effect in PDP with GAC system (combination system) for BPA degradation. 4 g amount of GAC, 20 mg/L BPA concentration, acidic solution condition and higher gas flow rate are beneficial for BPA degradation; The highest BPA removal efficiency, mineralization and kinetics constants can reach 98.7%, 34.6% and 0.075 min−1 respectively. The decreased O3 and enhanced •OH in water after GAC addition illustrate O3 can be catalyzed by GAC and lead to the formation of •OH. The radical scavenger test illustrates the role of •OH during BPA degradation. The aviation of nature and concentration of fluorophores during BPA degradation is explored by three-dimensional excitation emission fluorescence spectra. Organic acids including formic acid, acetic acids, oxalic acid and inorganic acid including nitric acid and nitrous acid can be produced during pulsed discharge and BPA degradation. The intermediates during the BPA degradation were identified by liquid chromatograph-mass spectrometer (LC-MS). Based on the intermediates, the proposed degradation pathway is presented. The SEM technology demonstrates that GAC can be regenerated by the discharge process.

Oxygen Atmosphere Annealing Effect on the Thermal Stability of TiO&lt;sub&gt;2-x&lt;/sub&gt; Based Films for Shutter-Less Infrared Image Sensors

In the present study, we examine the thermal stability of TiO2-x (TiO) and Nb:TiO2-x (TNO) films at different exposing temperatures for the as-deposited and oxygen-atmosphere annealed samples. In order to attain the good thermal stability characteristics, lower resistance of the TiO and TNO samples were annealed in oxygen gas atmosphere at a high flow rate (5 lit/min) of oxygen gas and annealing time (25 min). From the structural studies, it can be confirmed that the annealing process gives the incorporation of oxygen atoms to its vacant sites and the phase transition improvement from the amorphous to rutile structure. The annealed samples reveal the high resistivity and temperature coefficient of resistance (TCR) values than as-deposited samples. Furthermore, it was confirmed that the annealed samples exhibits a significant improvement of thermal stability compared to the as-deposited samples. As a result, the annealed TNO sample exhibits outstanding thermal stability as well as better bolometric performance. Consequently, this study reveals that the annealed TNO sample is appropriate for shutter-less infrared image sensor devices.

Euler-Euler simulation and X-ray measurement of bubble chain in a shallow container filled with liquid metals

An Euler-Euler two-fluid approach was used to simulate the behavior of gas bubbles rising in a stagnant liquid metal. A single point injection with four gas flow rates resulted in the formation of bubble chains undergoing either slight or distinct oscillations of the bubble trajectories. A set of interfacial closures with a shear stress transport (SST) k-ω turbulence models was applied for simulating the transient behavior of the bubble chain. X-ray radiography measurements were conducted to establish an experimental data base for validating the numerical results. The experiments provide a visualization of the bubble chain in a flat container and allow determining the bubble size and integral void fraction. Two bubble induced turbulence (BIT) models (Rzehak and Krepper, 2013a, Sato et al., 1981) and a modified turbulent viscosity approach (Johansen et al., 2004) were applied within this study. For all gas flow rates, the Rzehak and Sato BIT model alone predicted a steady bubble chain in contrast to the oscillating bubble plume observed in the experiments. Without a BIT model the oscillating bubble chain can be predicted but the oscillation frequency is underestimated especially for high gas flow rates. In addition, calculations without a BIT model predicted over-dispersion of the averaged gas fraction through the whole fluid container for the high gas flow rates. The best results in terms of a satisfying agreement with the experimental data were achieved by adopting a modified turbulent viscosity approach proposed by Johansen together with the Rzehak and Krepper BIT model. These findings demonstrate the significance of the turbulence model.

Modeling of a transferred arc inside a crucible with gas injection through a hollow cathode

A transferred arc system consisting of a crucible type anode and hollow cathode with gas injection is being considered for melting and evaporation of materials to improve the heat transfer efficiency. Knowledge of arc behavior inside the crucible and the effect of gas injection through the cathode on the characteristics of the arc are required to optimize the process parameters for better process efficiency. The available literature on this is very limited. A 2D steady-state axi-symmetrical mathematical model of a DC transferred arc is developed and the plasma arc created between a hollow cathode with gas injection and a crucible anode is simulated. The effects of cathode geometry and gas flow through the cathode on the arc characteristics are studied for different electrode gaps and arc currents. The effect of gas flow through the cathode on the arc voltage is clarified for various electrode gaps and arc currents. The gas flow through the cathode is strong enough to push the arc root attachment from the center of the anode and the plasma covers the entire surface of the crucible bottom at higher gas flow rates. Irrespective of the gas flow rate, arc current, and arc length, the higher arc heating efficiency is achieved when the arc root attachment starts to move away from the center of the anode/arc voltage is minimal. The characteristics of the arc inside the crucible and open arc are compared for different flow rates of the gas injected through the cathode. The present model is validated by comparing the predicted results with previously published results.

DRILL Interface Makes Ion Soft Landing Broadly Accessible for Energy Science and Applications.

Polyoxometalates (POM) have been deposited onto carbon nanotube (CNT) electrodes using benchtop ion soft landing (SL) enabled by a vortex-confined electrohydrodynamic desolvation process. The device is based on the dry ion localization and locomotion (DRILL) mass spectrometry interface of Fedorov and co-workers. By adding electrospray emitters, heating the desolvation gas, and operating at high gas flow rates, it is possible to obtain stable ion currents up to -15 nA that are ideal for deposition. Coupled with ambient ion optics, this interface enables desolvated ions to be delivered to surfaces while excluding solvent and counterions. Electron microscopy of surfaces prepared using the device reveal discrete POM and no aggregation that degrades electrode performance. Characterization of POM-coated CNT electrodes in a supercapacitor showed an energy storage capacity similar to that achieved with SL in vacuum. For solutions that produce primarily a single ion by electrospray ionization, benchtop SL offers a simpler and less costly approach for surface modification with applications in catalysis, energy storage, and beyond.

Phase inversion phenomena in vertical three-phase flow: Experimental study on the influence of fluids viscosity, duct geometry and gas flow rate

Improper sizing of pipelines and production tubings in the petroleum industry is often caused by lack of understanding of three-phase flow, which is characterized by gas flowing together with an immiscible water-oil mixture. There is the presence of a continuous liquid phase and a liquid dispersed phase, as observed in liquid-liquid flows, i.e., one can observe either a dispersion or emulsion of oil in water (o/w) or dispersion or emulsion of water in oil (w/o). The transition from o/w to w/o, or the other way around, is defined as phase-inversion. This phenomenon is characterized by a sharp increase in the pressure gradient, leading to significant pressure loss in the oil production system. The goal is to investigate the effects of oil viscosity, channel geometry (circular pipe or annular duct) and superficial gas velocity on the phenomenon of phase inversion in vertical liquid-liquid-gas flows, using oil with three different viscosities (ranging from 70 mPa s to 280 mPa s), tap water and compressed air as working fluids. The experiments were carried out in three different geometries: (i) glass pipe of 50 mm i.d., (ii) glass pipe of 95 mm i.d. and (iii) concentric annular duct with 95 mm of hydraulic diameter (glass outer pipe and PVC internal pipe). The experiments were performed under equivalent Reynolds number to evaluate the geometry effect. New data as total pressure gradient and volumetric fractions were obtained for all geometries. The results suggest that the extrapolation of results obtained in circular pipes with low viscosity oil and low gas flow rates to annular-duct flow with viscous oils and high gas flow rates can lead to significant errors.

Experimental investigation on a GAX based absorption heat pump driven by hybrid liquefied petroleum gas and solar energy

In this study, we presented a detailed experimental investigation of an air source liquefied petroleum gas (LPG)-solar driven absorption heat pump (LSAHP) using Generator Absorber heat eXchanger (GAX). The GAX absorption heat pump with a nominal heating capacity of 55 kW uses ammonia-water as working pairs and is powered by hybrid energy sources: a 45 m2 parabolic trough solar collector (PTC) and a direct-fired liquefied petrol gas (LPG) burner. The thermal performance of the PTC was characterized with selected on-sun conditions. Results showed that solar thermal efficiency can reach up to 53.55% with direct normal insolation of 450 W/m2 and inlet thermal oil temperature of 191 °C. Three operation modes were identified based on the driven energy sources: (i) LPG-Solar hybrid mode, (ii) Solar only mode, and (iii) LPG only mode. Under the average ambient temperature of 17.52 °C, 20.0 °C, 8.77 °C the averaged COPs of three modes are 1.54 (mode i), 1.63 (mode ii) and 1.20 (mode iii) respectively. Solar energy contributions reached 40.2% and 55.10% in mode i and mode ii separately which demonstrated the feasibility of the coupling of PTC and GAX heat pump to reduce the dependence on fossil fuel. The impact of operation conditions (ambient temperature, inlet hot water temperature, and LP gas flow rate) on the heating capacity and system performance were investigated under steady-state conditions. Results indicated that higher ambient temperature, higher gas flow rate, and lower inlet hot water temperature benefit the heat pump performance, among which the influence of ambient temperature is the greatest. COP reaches 1.47 with 19 °C ambient temperature and 35 °C inlet hot water temperature. It’s worth noting that COP’ achieves 1.82 under the same condition if we exclude the heat loss of flue gas.

Characteristics of bubble-induced liquid flows in a rectangular tank

Bubbly flows are frequently encountered in many industrial applications where multiphase contact is used to promote heat, mass and momentum transfer. These include applications where both chemical and physical processes occur, such as wastewater treatment and biological aeration systems. We investigated the behaviour of underwater-generated bubble swarms, which were produced at the bottom of a 1-m3 square tank from a 5-mm nozzle and allowed to rise by buoyancy in still water. Instantaneous velocity fields around the bubbles were obtained using Particle Image Velocimetry (PIV) seeded with 10–15-µm poly-dispersed fluorescent particles and gas flow rates ranging from 2 to 15 L/min (1.7–12.8 m/s). A continuous laser was used to obtain the time-resolved field, and a pulse laser was used to obtain the mean velocity fields. Images were captured at up to 2000 fps. After interrogation, a post-processing validation algorithm was employed to identify and remove vectors produced by bubbles and the interface, essentially producing vector fields of the liquid phase only. Proper orthogonal decomposition analysis was carried out on 1000 realisations of each gas flow case to identify dominant flow structures, and the flow was decomposed into its constituent spatial and temporal modes. We established that induced vortices in the liquid phase more clearly manifest at far streamwise locations shown by the spatial mode at lower gas flow rates and are clearer in the temporal mode at high gas flow rates. The mean streamwise and spanwise liquid velocities increased with the gas flow rate, and the streamwise bubble velocities can be well described by a top-hat profile curve. Finally, an analysis was done to estimate the bubble entrainment coefficient using the slip velocity and the gas buoyancy flux.