Countercurrent Gas-liquid Flow Research Articles

Deep deoxidation of water in a miniaturized annular rotating device: Experimental investigation and machine learning modeling

Conventional gas–liquid devices exhibit limitations, including inadequate dispersion efficiency and significant backmixing, leading to low conversion and large equipment volume. Thus, a miniaturized annular rotating device (m-ARD) was proposed based on microscale effects and rotating flow field to achieve efficient gas–liquid mass transfer and high conversion. Nitrogen-oxygenated water was selected as the experimental system to evaluate the performance of the m-ARD. The gas–liquid flow characteristics were investigated. The analysis focused on examining the impact of different factors on deoxygenation efficiency. The deoxygenation performance was optimized and compared with different devices. The study found that the m-ARD enables a continuous counter-current gas–liquid flow mode, with superior mixing performance and a narrow residence time distribution. The deoxygenated water with an oxygen concentration as low as 0.14 ppm can be produced, with a volumetric mass transfer coefficient (kLa) of 0.26 s−1, a theoretical stage value of 4.22, and a handling capacity of 30 mL/min under optimized experimental conditions. In addition, kLa was predicted using an artificial neural network model and showed good agreement with the simulated values. This work provides a promising reactor for chemical reactions that require high conversions.

Gas-liquid countercurrent flow characteristics in a microbubble column reactor

Countercurrent flow mode is widely utilized in many chemical unit operations due to its effective enhancement of mass transfer driving force. While the microbubble column reactor has garnered attention for its substantial gas–liquid specific surface area and fast mass transfer rate under the concurrent flow condition, countercurrent flow microbubble column reactors remain relatively underexplored. Consequently, in this study a novel microbubble generator device featuring gas–liquid co-crossing a microfiltration membrane was developed. This device could generate microbubbles with narrow size distribution, and proved suitable for integration into the countercurrent microbubble column reactor. Further investigation ensued to elucidate the operational principles of this dispersion method. Finally, the hydrodynamic behavior of the countercurrent microbubble column reactor was examined. Remarkably, a gas–liquid-specific surface area 2300 m2/m3 was reached, surpassing that of conventional bubble column reactors by a significant margin. New gas–liquid chemical processes and process intensification technologies could be developed accordingly.

Measurement of air-water counter-current flow rates in vertical annulus using multiple differential pressure signals and machine learning

Abstract Gas–liquid counter-current flow in vertical annulus is involved in several industrial fields such as petroleum engineering. For example, in coalbed methane wells with liquid pump drainage, obtaining the real-time flow rate of gas–liquid two-phase in the annulus is crucial for the development management of coalbed methane wells. However, due to complex flow conditions, this demand is difficult to achieve through traditional flow metering means. Therefore, this paper proposes a flow prediction method based on multi-group differential pressure signals and machine learning technology. Air-water two-phase flow experiments were carried out on a vertical annulus pipeline with inner and outer diameters of 75 mm/125 mm and adjustable eccentricity. The probability density function and power spectrum density of 3 groups of differential pressure signals collected at different height intervals in the annulus were used as model inputs. A gas–liquid two-phase flow prediction model was constructed based on the artificial neural network model, and the model hyper-parameters were optimized using Bayesian optimization. The results show that on the 440-group test dataset under the combined conditions of air superficial velocity of 0.06–5.04 m s−1, water superficial velocity of 0.03–0.25 m s−1, and pipeline eccentricity of 0, 0.25, 0.5, 0.75, 1, etc. This model can achieve average prediction errors of 9.12% and 29.34% for gas and water flow rates respectively. This method can be applied to the non-throttling, non-invasive measurement of phase flow rate under the condition of annulus air-liquid counter-current flow.

Operation of iron-based monolithic catalyst packing ozonation for industry wastewater advanced treatment: The importance of gas–liquid flow patterns and wastewater flow regimes

In this study, from the feasibility verification of the lab-scale test to the working condition study of the pilot-scale test the large-scale engineering application of the display manufacturing industry wastewater advanced treatment by ozonation with iron (Fe)-based monolithic catalyst packing was finally realized. Different from chemical packings, the catalyst packing has large porosity and specific surface area, while the pore size is small, which meets the requirements of •OH reaction, and these characteristics are necessary for engineering applications. Under the three scales, the reaction procedure and the corresponding reactor structure were introduced in detail. The importance of gas–liquid flow patterns and gas distribution device on treatment effect were proved in pilot-scale test. The treatment effect under gas–liquid counter-current flow was better than that of co-current flow. Through the analysis of the working conditions, the working parameters for high wastewater quantity and high organic loading were obtained. The large-scale test achieved the same excellent treatment effect as the lab/pilot-scale test, after 5 years of operation, the average chemical oxygen demand (COD) removal was about 72.0 %, and the COD concentrations after treatment were all lower than 30 mg/L. The biochemical oxygen demand (BOD5) decreased from 10.22 to 2.50 mg/L on average. Under the short-circuiting phenomenon, the wastewater through the catalyst area unevenly and the organic pollutants were not effectively oxidized and decomposed. This also proved the importance of Fe-based monolithic catalyst packing in advanced treatment. This work proved the importance of gas–liquid flow patterns and wastewater flow regimes in the reactor, which can provide reference for other catalytic ozonation technology in large-scale engineering applications.

Flow regimes identification of air water counter current flow in vertical annulus using differential pressure signals and machine learning

This study investigates the gas–liquid two-phase counter-current flow through a vertical annulus, a phenomenon prevalent across numerous industrial fields. The presence of an inner pipe and varying degrees of eccentricity between the inner and outer pipes often blur the clear demarcation of flow regime boundaries. To address this, we designed a vertical annulus with adjustable eccentricity (outer and inner diameters of 125 mm and 75 mm, respectively). We conducted gas–liquid counter-current flow experiments under specific conditions: gas superficial velocity ranging from 0.06 to 5.04 m/s, liquid superficial velocity from 0.01 to 0.25 m/s, and five levels of eccentricity (e = 0, 0.25, 0.5, 0.75, 1). We collected differential pressure data at two distinct height distances (DP1: 50 mm and DP2: 1000 mm). We used vectors, composed of both the probability density functions (PDFs) of the differential pressure signals and the power spectral density (PSD) reduced via Principal Component Analysis, as features. Using the CFDP clustering algorithm—based on local density—we clustered the flow regimes of the experimental data, thereby achieving an objective and consistent identification of the flow regime of gas–liquid two-phase counter-current flow in a vertical annulus. Our analysis reveals that for DP1, the main differences in the PSD of various flow regimes occur within the 0.5–1 Hz range. Among the three flow regimes involved, the slug flow exhibits the highest power intensity, followed by the bubbly flow, with the churn flow having the least. In terms of differential pressure distribution, the bubbly and churn flows have a concentrated distribution, while the slug flow is more dispersed. For DP2, the PSD differences primarily exist within the 0.5–2 Hz range. The churn flow has the highest power intensity, followed by the slug flow, with the bubbly flow being the weakest. Here, the bubbly flow's differential pressure distribution is concentrated, while the slug and churn flows are more dispersed. Based on the results of the flow regime classification, we generated a flow regime map and analyzed the influence of annulus eccentricity on the flow regime. We found that in most cases, pipe eccentricity does not significantly affect the flow regime. However, in the transition region—such as the bubbly to slug flow transition zone—flows with medium eccentricity values (e = 0.5, 0.75) are more likely to transition to slug flow. We compared the visual recognition results of flow regimes with the clustering results. 4.04% of the total samples showed different results from visual recognition and clustering, primarily located in the flow regime transition area. Since visually distinguishing flow regimes in these areas is typically challenging, our methodology offers an objective classification approach for gas–liquid two-phase counter-current flow in a vertical annulus.

Experimental Investigations and Numerical Studies of Two-Phase Countercurrent Flow Limitation in a Pressurized Water Reactor: A Review

Gas–liquid two-phase countercurrent flow limitation (CCFL) phenomena widely exist in nuclear power plants. In particular, the gas–liquid countercurrent flow limitation phenomena in a pressurized water reactor (PWR) during a loss-of-coolant accident (LOCA) or a small-break loss-of-coolant accident (SBLOCA) play an important role in nuclear reactor safety research. Over several decades, a series of experimental investigations and numerical studies have been carried out to study the CCFL phenomena in a PWR. For the experimental investigations, numerous experiments have been conducted, and different CCFL mechanisms and CCFL characteristics have been obtained in various test facilities simulating different scenarios in a PWR. The CCFL phenomena are affected by many factors, such as geometrical characteristics, liquid flow rates, and fluid properties. For the numerical studies, more and more numerical models were presented and applied to the calculations of two-phase countercurrent flow over the past several decades. It is considered that the computational fluid dynamics (CFD) tools can simulate most of the two-phase flow configurations encountered in nuclear power plants. In this paper, the experimental investigations and the numerical studies on two-phase countercurrent flow limitation in a PWR are comprehensively reviewed. This review provides a further understanding of CCFL in a PWR and gives directions regarding future studies. It is found that relatively fewer investigations using steam–water under high system pressures are performed due to the limitation of the test facilities and test conditions. There are a number of numerical studies on countercurrent two-phase flow in a PWR hot leg geometry, but the simulations in other flow channels were relatively rare. In addition, almost all of the numerical simulations do not include heat and mass transfer. Thus, it is necessary to investigate the effects of heat and mass transfer experimentally and numerically. Furthermore, it is of significance to perform numerical simulations for countercurrent two-phase flow with a fine computational grid and suitable models to predict the formation of small waves and the details in two-phase flow.

Effect of liquid viscosity on the gas–liquid two phase countercurrent flow in the wellbore of bullheading killing

Studying the gas–liquid two-phase countercurrent flow under high liquid viscosities is key in designing the well-killing parameters of the bullheading method; however, currently, in-depth research on this issue is limited. Herein, using a self-designed vertical visualization wellbore gas–liquid two-phase flow experimental system with a tube diameter of 0.1 m and liquid viscosity in the range of 1–50 mPa s, a simulation experiment of bullheading killing was conducted. The effects of liquid viscosity on the bubble morphology, bubble migration, and gas–liquid countercurrent flow pattern were analyzed, and the mechanism of back pressing of gas during the well-killing process of the bullheading method in a large-scale tube was revealed. Moreover, the influencing factors and variation in the critical displacement of bullheading were analyzed. The results revealed that the stability of Taylor bubbles increased and the number of small bubbles decreased with the increase in liquid viscosity, resulting the gradual shrinkage or disappearance of the churn flow and bubbly flow, expansion of the region of slug flow, and downward movement of the transition boundary between bullet-cup flow and slug flow. On approaching the critical liquid displacement during the process of simulated bullheading, Taylor bubbles rapidly dissociated into small bubbles and turned around during the rising process, forming a gas–liquid downward flow, following which the gas was successfully pressed back. In addition, our analysis revealed that the press-back effect is not always positively correlated with the viscosity of the kill fluid. The critical displacement of the well-killing fluid first decreased and then increased with an increase in the liquid viscosity. Finally, based on the experimental results, an improved calculation method for the critical displacement of bullheading considering the influence of liquid viscosity was established, which could provide important theoretical guidance for the parameter design of bull heading.

Generalized correlation for onset flooding velocity in vertical channels

Flooding due to gas-liquid counter-current flow might significantly impact engineering applications such as boilers, heat exchangers, and nuclear reactors. Despite the extensive body of literature, there is still a notable disagreement on the appropriate definition of the characteristic length regarding the onset flooding velocity in rectangular and annular channels. The primary motivation for this study is to examine which geometric dimension is the most suitable to predict the onset of flooding velocity. This study measured the onset of flooding velocity in one circular and two different annular channels. The channel geometries are considered such that the hydraulic diameter trend is inverse to the average circumference. The study's findings show that the hydraulic diameter cannot be used as a characteristic length for annular and rectangular channels to describe the onset flooding velocity. Instead, the average circumference for the annular channel and channel width for rectangular channels exhibit superior performances. The flooding air velocity was increased by increasing the average circumference of the annular channel or channel width for the rectangular channel. New Wallis-type generalized relationships are derived based on the wide range of channel geometries and dimensions. The novel generalized empirical correlation could be defined regardless of the channel geometry.

Numerical modeling of horizontal stratified two-phase flows using the AIAD model

In nuclear reactor safety research, the countercurrent gas-liquid two-phase flow in the hot leg of a pressurized water reactor (PWR) has attracted considerable attention. Previous work has proven that the algebraic interfacial area density (AIAD) model implemented in ANSYS CFX can effectively capture the gas-liquid interface and avoid the loss of information regarding the interfacial structure, which occurs after phase averaging in the Euler–Euler two-fluid approach. To verify the accuracy of the AIAD module implementation in ANSYS Fluent, the model based on the experimental data from the WENKA facility is validated in this work. The effects of the subgrid wave turbulence model, turbulence damping model, and droplet entrainment model are simultaneously investigated, which have been shown to be important in the previous work with CFX. The results show that the simulations are considerably and significantly deviate from the experiments when the turbulence damping is not considered. The free surface modeling of two-phase flow can be optimized by using the droplet entrainment model. The consistency between the simulation and experimental results is not enhanced after the subgrid wave turbulence model is adopted. Further investigations regarding the implementation of the subgrid wave turbulence model are necessary.

Gas-liquid flow seal in the smooth annulus during plunger lifting process in gas wells

Liquid leakage and gas slippage through the annulus between an upward moving plunger and vertical tubing significantly reduce the uploading efficiency of the accumulated liquid during plunger lifting in gas wells. Understanding the characteristics of gas-liquid two-phase flow in the annulus during plunger lifting process is crucial to enhance the fluid seal and to improve the plunger lift technology, but investigations of this important issue in literature is extremely limited. In this paper, we employ VOF-CFD numerical approach to provide a computationally efficient flow model to account for interactions between loading liquid, producing gas and the lifting plunger in gas wells. Results from simulations are consistent with both the in-door experimental data and field observations, thus allowing us to reproduce detailed characteristics of gas-liquid flow in the annulus during plunger lifting process. The actual conditions in gas wells are simulated, in which the plunger upward velocity is ranged in 2 m/s ≤ vp ≤ 10 m/s and the gas density is ranged in 13.9 kg/m3 ≤ ρg ≤ 80.9 kg/m3. Numerical results indicate that with the plunger lifting velocity increasing, the liquid leakage flow rate increases, the gas slippage flow rate decreases, and the gas-liquid countercurrent annular flow in the annular space transforms to the co-current upward annular flow. Based on the interface instability analysis, we reveal the mechanism of gas-liquid flow seal in the annulus which is promoted by the droplet entrainment and is weakened by the droplet deposition. A simple dimensionless coefficient is proposed to evaluate the uploading efficiency of the accumulated liquids by the plunger in gas wells, the bigger value of the coefficient represents the better performance of liquid sealing during plunger lifting process. The optimal diameter ratio between the plunger and tube (0.96), as well as the optimal diameter-length ratio of the plunger (0.13) are proposed to improve the plunger lift technology.

An intensification of mass transfer process for gas-liquid counter-current flow in a novel microchannel with limited path for CO2 capture

Microchemical technology shows prospect in the process intensification field of carbon capture and storage, however, there remain great challenges in microchemical technology for gas-liquid mass transfer with counter-current flow. In this work, we proposed a micro-apparatus with confined structure for gas-liquid counter-current flow mass transfer. The flow patterns on the confined structure, steady flow and bead flow, were observed, furthermore, the critical flow rate between them was measured. The influences of confined structure geometry, surface tension and viscosity of liquid on the meniscus at the gas-liquid interface were studied. The operation window of micro-apparatus with different types of confined structures was examined. The liquid loading and gas loading of micro-apparatus with S1005 were tested to be 230 μL/min and 500 mL/min, respectively. The system of absorption of pure CO2 in a 1 M NaOH solution was used to study the mass transfer. The average liquid side mass transfer coefficient of 25.1 × 10−5 m/s was measured at liquid flow rate of 30 μL/min and gas flow rate of 300 μL/min, which proves that the micro-apparatus achieves the process intensification of CO2 absorption.

Effects of fluid properties on interfacial and wall friction factors under counter-current flow limitation in a vertical pipe with sharp-edged lower end

A gas–liquid counter current flow may possibly occur in the U-tubes of the steam generator in a PWR due to loss of the residual heat removal during mid-loop operation. For safety analysis based on the one-dimensional multi-fluid simulation, correlations of the interfacial and wall friction factors are required. Experiments on air-glycerol water solution counter-current annular flows in a circular vertical pipe of 20 mm in diameter and 400 mm in length with a sharp-edged lower end, hence, were carried out to investigate the effect of the liquid viscosity on the flow structure and the interfacial and wall friction factors. The liquid flow rate, the pressure gradient and the liquid volume fraction were measured to evaluate the friction factors. The time-strip flow visualization technique was applied to flow images in the pipe for detailed observation. The obtained conclusions are as follows: (1) the flows under CCFL condition in the present study can be classified into two regimes, i.e. the rough film with disturbance waves forming at the lower pipe end (RF-I) and the disturbance waves flowing upward with dissipation and regeneration (RF-II), (2) the interfacial friction factor is independent of the liquid viscosity and mainly determined by the balance between the inertial and buoyant forces. The gas Froude number, JG*, is the primal dimensionless group in correlating the interfacial friction factor, (3) the wall friction factor can be correlated in terms of the liquid Froude number JL*, the liquid Reynolds number ReL and the dimensionless pipe diameter D*, and (4) the correlations of the friction factors were proposed. The applicable ranges of the correlations are 0.58 ≤ JG*1/2 ≤ 0.78, 0.01 ≤ JL*1/2 ≤ 0.10, 0.15 ≤ ReL ≤ 178 and 7.28 ≤ D* ≤ 17.79.

Experimental study on air-water countercurrent flow limitation in a vertical tube based on measurement of film thickness behavior

The gas-liquid counter-current flow limitation (CCFL) is closely related to efficient and safety operation of many equipment in industrial cycle. Air-water countercurrent flow experiments were performed in a tube with diameter of 25 mm to understand the triggering mechanism of CCFL. A parallel electrode probe was utilized to measure film thickness whereby the time domain and frequency domain characteristics of liquid film was obtained. The amplitude of the interface wave is small at low liquid flow rate while it becomes large at high liquid flow rate after being disturbed by the airflow. The spectral characteristic curve shows a peak-shaped distribution. The crest exists between 0 and 10 Hz and the amplitude decreases with the frequency increase. The analysis of visual observation and characteristic of film thickness indicate that two flooding mechanisms were identified at low and high liquid flow rate, respectively. At low liquid flow rate, the interfacial waves upward propagation is responsible for the formation of CCFL onset. While flooding at high liquid flow rate takes place as a direct consequence of the liquid bridging in tube due to the turbulent flow pattern. Moreover, it is believed that there is a transition region between the low and high liquid flow rate.

Characteristics of counter-current gas-liquid two-phase flow and its limitations in vertical annuli

This paper aims to characterise the complex flow behaviour of counter-current gas-liquid flows in concentric vertical annuli over a wide range of gas and liquid flowrates. The experiments were performed with air and water in two different annulus sizes: (a) a 100 mm hydraulic diameter annulus with a 170 mm diameter outer pipe and a 70 mm diameter inner pipe; and (b) a 19 mm hydraulic diameter annulus between 44 mm and 25 mm pipes, to investigate the effect of flow geometry on flow structure. Flow regimes were identified quantitatively by applying fast Fourier transform (FFT) on the associated pressure fluctuation signals, collected at 10 Hz and 100 Hz frequency. Video images captured at 4,000 fps with a high-speed camera were used in a visual analysis of the flow regimes to verify the FFT results. Furthermore, flow regime transitions and their underlying mechanisms were determined by their associated pressure gradient and void fractions, as well as analysis of temporal pressure signals. The commonly described slug flow regime, consisting of stable Taylor bubbles traversing the length of the channel, was not observed in the larger annulus. However, the FFT of the pressure signals indicate that unstable Taylor bubbles form as a result of bubble coalescence but collapse due to instability at the gas-liquid interface, known as Rayleigh-Taylor instability. Therefore, the apparent slug-churn flow regime was classified as a highly turbulent heterogeneous flow, developing at superficial gas velocities from 0.265 to 3.968 m/s and superficial liquid velocities from 0.004 to 0.147 m/s. Interestingly, annular flow regime did not develop in either of the tested small and large annuli. The onsets of counter-current flow limitations, or flooding, were identified in the 100 mm hydraulic diameter annulus with gas flooding due to very high gas flow rates and liquid flooding due to very high liquid flow rates. The mechanism that initiates gas flooding was observed to be the formation of large waves flowing upward near the water inlet point, with counter-current flow observed below the water inlet point at the onset of gas flooding. Clarity was also provided on the concepts of flooding and zero liquid penetration for the cases of flow in a water filled channel and a falling film, and a new empirical correlation for the onset of flooding was developed.

Scaling ability of the counter-current flow limitation (CCFL) correlations for application to reactor thermal hydraulics

The limitation of gas-liquid counter-current flow is important for getting coolant to the core preventing heat-up. To illustrate the scaling dependence of counter-current flow in the downcomer, the upper core tie plate and the hot leg, some results are presented. Based on a derivation of the counter-current flow equations for vertical and horizontal flows, the scaling ability of existing correlations is shown for homogeneous vertical counter-current flow (Kutateladze-type equation) and separated horizontal flow in the hot leg during reflux-condenser conditions (Wallis equation). The large reactor scale heterogeneous counter-current flow in the downcomer and at the upper core tie-plate needed an extension of the Kutateladze-type equation. Bankoff suggested that for CCFL in perforated plates such as upper tie plate, a parameter that is a combination of actual length scale (Wallis parameter) and Laplace constant (Kutateladze parameter) will be required.

Hydrodynamics of the tridimensional rotational flow sieve tray in a countercurrent gas-liquid column

The hydrodynamic performance of the TRST in a gas-liquid countercurrent flow column was investigated experimentally in this article. The results show that the operating field can be divided into low and high loading areas according to the increasing rate of the pressure drop. The space utilization of the tray is low, and the flow patterns are mainly droplet-column and continuous film flows. The pressure drops of the tray at each installed locations are different, indicating that the gas-liquid load of each tray is unbalanced. Compared with concurrent flow operation, the range of gas flux is at least 45% less, and the liquid flux range is at least 37.5% less. Compared with other new tray types under countercurrent flow operation, the pressure drop of the TRST is smaller, less than 300 Pa, but the range of gas-liquid flux is also narrow. The empirical models of the pressure drops, loading curve, and flooding curve agree well with the experimental data.

Investigation of hydrodynamic behavior in random packing using CFD simulation

Computational fluid dynamics (CFD) simulations of countercurrent gas–liquid flow in random packings of Raschig rings were carried out in this study. This model used gravity simulation to construct the random packing structure, and a volume expansion-recovery method to improve the meshing quality. A simple feedback control scheme was applied to control the gas inlet flow rate so that pressure drop can be estimated. The generated characteristics of the packing structure such as the number of packing elements, dry surface area and porosity were found to be close to experiments. CFD predictions of hydrodynamics properties are also validated by the experimental data using a small column section. The results indicate that our CFD model was able to capture the essential hydrodynamics behavior of the gas–liquid countercurrent flow. Hence, the approach presented in this study can be used as a basis for studying the effect of detailed packing-geometry design on hydrodynamic and mass transfer characteristics.

Municipal solid waste landfill performance with different biogas collection practices: Biogas and leachate generations

This study investigated the performance of simulated landfills with different biogas collection practices, including upward biogas collection only (LT) and both upward and downward biogas collection (LTB). A simulated landfill was constructed using a stainless steel lysimeter equipped with a compression unit. Upward gas flow was favored in uncompressed MSW when both upward and downward gas flows were allowed (LTB). By reducing void ratio, the preferential flow direction of biogas was changed to downward gas flow along with gravimetric leachate drainage. In LT, porched leachate was formed because high flow resistance by countercurrent gas-liquid flow affected moisture redistribution. It was considered that high pressure buildup in gas-filled pores of LT enhanced uneven moisture distribution and resulted in inhibiting methane production. The cumulative methane volume produced from LTB was 2.5 times as much as that of LT.

Modelling of CO2 absorption in a rotating packed bed using an Eulerian porous media approach

The rotating packed bed (RPB) is a promising reactor for CO2 capture with liquid amine because of its high mass transfer rate and energy and space savings. The CFD simulations of RPBs generally use the volume of fluid (VOF) method, but this method is prohibitively expensive for 3D simulations, in particular for large-scale reactors. The Eulerian method is a promising and effective method; however, there are still several difficulties, such as the settings for the porous media models in the gas-liquid counter-current flow and the interfacial area between the gas and liquid. To overcome these difficulties in the Eulerian method, this paper uses a new porous media model, a novel liquid generation-elimination model for numerically investigating the gas-liquid counter-current flow in RPBs and a new interfacial area model derived from the VOF simulation. These new models, incorporating the two-film reaction-enhancement mass transfer model, have successfully simulated the CO2 capture process with monoethanolamine (MEA) solutions in a RPB under both low (30 wt%) and high (90 wt%) concentration conditions. The results show that the overall gas phase mass transfer coefficient (KGa) increases with increasing the rotation speeds and the liquid to gas mass flow rate (L/G ratio). The simulations were validated by the experimental data and the results were analysed and discussed.

Nonlinear wavy regimes of a gas-liquid flow between two inclined plates analyzed using the Navier–Stokes equations

The paper is devoted to a theoretical analysis of a counter-current gas-liquid flow between two inclined plates. We used the Navier-Stokes equations for both liquid and gas to compute the nonlinear wavy regimes of the flow over a wide variation of the liquid Reynolds number and the gas superficial velocity. The main interest is to analyze the variation of the free surface shape, u-velocities and phase velocity of the waves as the superficial gas velocity is increased. We do our investigation for relatively small values of the distance between the plates where the shear modes of the linear disturbances are stable and the gas flow is laminar. We found that with the superficial gas velocity increasing and starting from some critical value of this velocity, the dependences of the main characteristics of the waves demonstrate a qualitative modification. For example, at small values of the plate’s inclination angle the dependences of the gas friction coefficient and the averaged film thickness have a local minimum for different values of the liquid Reynolds number at this critical value of the gas superficial velocity. We observe an essential increasing of the portion of the wavy profile with negative values of the u-velocity on the interface starting with this critical velocity. The obtained critical velocities are in reasonable agreement with the onset of flooding observed in experiments and their values have a correct trend with the increasing of the liquid Reynolds number.