Liquid Entrainment Research Articles

The molecular nature of the eliminating azeotropy in water–acetonitrile system by ionic liquid entrainer using FTIR and DFT calculations

This study focused on investigating the structure and hydrogen-bonding characteristics of 1-ethyl-3-methylimidazolium acetate ([EMIM][OAc])-water-acetonitrile mixtures aiming at revealing the molecular intrinsic of the azeotropy breaking by ionic liquid entrainer. Our approach combined FTIR with density functional theory (DFT) calculations applying the CN stretching vibration region as the responsive indicator of the microenvironment to discern the structural and hydrogen-bonding properties of the H2O‒CH3CN and [EMIM][OAc]‒CH3CN binary systems and [EMIM][OAc]−H2O−CH3CN ternary systems. Distinct interaction models were observed between [EMIM][OAc] and CH3CN compared to those in water and CH3CN system, leading to different influences on the CN stretching vibration region. Excess peaks associated with H2O−CH3CN, CH3CN self-aggregator, and IL−CH3CN interaction complexes were identified. The interaction strength between [EMIM][OAc] and CH3CN was notably more potent than that between water and CH3CN. Consequently, IL had the ability to disrupt the interaction complex of water-acetonitrile with the formation of the IL−CH3CN complex. This species transformation during the mixing process elucidated the characteristics of phase equilibrium shift in the azeotrope system.

Investigation of acoustic effect on liquid residue ejection from the closed vessel with a drain valve

The concept, schematic solution, and methodology for liquid residue passivation using additional acoustic impact based on a gas jet emitter when introducing gas into a closed vessel (CV) containing liquid residue have been developed. A methodology for numerical modeling of the process of liquid droplet entrainment from the CV using the Ansys Fluent software package has been developed, based on gas supply into the tank. The method consists of two interrelated physical-mathematical models (PMM): 1) PMM of gas introduction into CV taking into account additional acoustic impact and creation of two-phase flow structure with subsequent entrainment of liquid droplets through the drain valve into the environment; 2) PMM of acoustic cavitation occurrence in the liquid volume taking into account the assessment of vapor occurrence inside the liquid with subsequent use of these results as initial conditions in PMM on formation of two-phase gas flow. The influence of additional acoustic impact during gas introduction into the CV on the ejection of liquid residue was evaluated. The results showed that accounting for acoustic cavitation increases the entrainment of liquid droplets by approximately 40%.

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

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

Experimental study on effect of pressure on ADS-4 liquid entrainment characteristics in T-junction

Liquid entrainment phenomenon can occur in the T-junction formed by the vertical ADS-4 pipeline and the hot pipe section during SBLOCA process in AP1000 reactor. At present, most of the studies on the liquid entrainment phenomenon in T-junction with large branch pipe concentrate on the atmospheric pressure condition, which is difficult to accurately reflect the real state of the accident process. The liquid entrainment experiments were carried out at 0.1–0.4 MPa on ADETEL facility. The results show that there will be obvious reverse flow phenomenon in the branch at 0.1 MPa and the phenomenon disappears gradually with the increase of pressure. Furthermore, the occurrence of intermittent two-phase slug flow in the horizontal tube was observed at lower pressures. As pressure increases, the entrainment process will become more continuous and stable, with a concomitant reduction in intermittency. The steady-state entrainment liquid level and the onset of entrainment liquid level both decrease with increasing pressure, indicating that increasing pressure can facilitate the liquid entrainment amount. The existing correlations cannot accurately estimate the entrainment amount during SBLOCA in nuclear reactor with a deviation of more than +100% between the predictions and experimental data.

Fluid Dynamics Studies on Bottom Liquid Detachment from a Rising Bubble Crossing a Liquid–Liquid Interface

The detachment regimes and corresponding detachment height of lower liquid from a coated bubble during the bubble passage through an immiscible liquid–liquid interface were studied. High-speed imaging techniques were used to visualize the lower liquid detachment from a rising bubble near the interface. Analysis of industrial slag samples by a scanning electron microscope (SEM) was also carried out. The results indicate that the detachment height of lower liquid from a rising bubble showed a distinct correlation to penetration regimes. Bubble size and a fluid’s physical properties exerted a significant influence on the detachment height of the lower liquid. The detachment height for medium bubbles (Weber number: 4~4.5; Bond number: 2.5~7.5) varied significantly with increasing bubble size, which contributes to the lower liquid entrainment in the upper phase due, significantly, to the higher detachment height and large entrainment volume. The maximum detachment height for large bubbles is limited to approximately 100 mm due to the early detachment with the liquid column at the interface though large bubbles transporting a larger volume of lower liquid into the upper phase.

Numerical Investigation of the Flow Structure of Cryogenic Hydrogen in Corrugated Metal Flexhoses Due to Fluid Structure Interactions

Abstract In this paper, details of flow field characteristics and pressure drop of cryogenic hydrogen in corrugated metal flexhoses will be numerically evaluated using multiphase flow physics coupled with fluid structure interactions. Multiphase flow regime is often influenced by concentration ratio, shape factor, and orientation of the piping. Corrugated metal flexhoses are commonly used as part of cryogenic commodity transportation for their ability to operate in a large range of temperatures and pressures with a high degree of geometric flexibility. These sharp changes in the geometry of the flexhose convolutions are one of the leading factors of liquid and gas phase entrainment which can significantly reduce the efficiency of piping systems and fuel delivery systems to the engine components. The entrained gas phase hydrogen can eventually propagate in successive convolutes leading into the permanent entrapment of the gas phase hydrogen in the corrugations. The volume fraction up to 5% gas phase with various convolute heights and pitch will be evaluated, with a hose length to diameter ratio (L/D) range between 20 to 60 and a Reynolds number range between 5,000 to 350,000 based on the hose hydraulic diameter. The findings of the study contribute to a better understanding of multiphase flow physics of hydrogen in corrugated metal flexhoses.

A Gaussian process embedded feature selection method based on automatic relevance determination

In Gaussian Process, feature importance is inversely proportional to the corresponding length scale when applying the Automatic Relevance Determination (ARD) structured kernel function. Features can be selected by ranking them according to their importance. Among the ARD-based feature selection methods, no uniform score exists for quantifying the output variation explained by feature subsets. This study proposes two feature selection approaches using two cumulative feature importance scores, one titled derivative decomposition ratio and the other normalized sensitivity, to determine the optimal feature subset. The performance of the approaches is assessed to test if irrelevant features are accurately identified and if the feature rankings are correct. The approaches are applied to identify relevant dimensionless inputs for a hybrid model estimating liquid entrainment fraction in two-phase flow. The results reveal that the proposed methods can identify the optimal feature subset for the hybrid model without significantly worsening its Root Mean Squared Error.

Performance enhancement of lab scale flash evaporation desalination system with sponge demisters: A practical approach

The current work focuses on mitigating the challenges associated with steam-carrying effects during flash desalination. Through experimental trials in a controlled laboratory setting, the impact of varying experimental parameters on the steam carrying ratio, flashing factor and separation efficiency is studied. Results suggested that the steam carrying ratio decreased with decreasing water pool height but increased with the degree of superheat and liquid entrainment. The value of the steam carrying ratio is reduced by 76.25 % by implementing a sponge inside the flash chamber at the same superheat. Liquid entrainment is significantly affected by the separation height and initial surge tank pressure. A high liquid entrainment results in a significant evaporated mass difference between experimental and theoretical results. The vapour mass transfer during the experiments without sponge arrangement is approximately two times the mass obtained from theoretical calculation. The results indicate that liquid entrainment is reduced by about 92% by incorporating the sponge at constant experimental conditions. The experimental data with sponge agree well with the theoretical results, with a maximum error of 18%. Finally, separation efficiency is proposed to compare the amount of liquid entrainment removed from total entrainment.

Simulations With Compressible Multiphase Formulation on Heat Transfer Studies in a Rocket Thrust Chamber With Experimental Validation

Abstract In the combustor for rocket engines, liquid film cooling is a widely adopted technique for restricting the structural components to the acceptable bounds for the successful operation of the propulsion systems. Multiple cooling techniques for thrust chamber walls are favored along with the coolant film in propulsion systems operating at higher chamber pressures by incorporating an ablative cooling mechanism for the nozzle. The adoption of combination will result in challenges in simulation studies due to the presence of multiphase phenomenon in the system. The current article presents the effects of these two cooling methods on a thrust chamber wall studied through compressible multiphase formulations. A majority of the previous studies have used incompressible flow equations to model coolant film behavior and associated heat transfer. The present study utilizes an approach utilizing compressible multiphase flow to simulate the behavior of the compressible hot gas flow and the incompressible coolant liquid film accounting for phase change effects, vapor diffusion into hot gas, radiation effects on coolant surface, liquid entrainment, and blowing effects due to vapor formation at interface. Film-cooling effects on ablative nozzle accounting for pyrolysis phenomenon due to material decomposition governed by Arrhenius expression are also emphasized. The outcome of the numerical model showed good agreement with available test data in literature, and results from the tests done in-house. The model described in the present study was able to support the actual evidence of liquid film cooling being able to preserve the walls of the thrust chamber from severe internal thermal environment and prevent ablation on surface of nozzle.

Modeling and simulation of air-water upward annular flow characteristics in a vertical tube using CFD

Annular flow refers to a special type of two-phase flow pattern in which liquid flows as a thin film at the periphery of a pipe, tube, or conduit, and gas with relatively high velocity flows at the center of the flow section. This gas also includes dispersed liquid droplets. The liquid film flow rate continuously changes inside the tube due to two processes-entrainment and deposition. To determine the liquid holdup, pressure drop, the onset of dryout, and heat transfer characteristics in annular flow, it is important to have proper knowledge of flow characteristics. Especially a better understanding of entrainment fraction is important for the heat transfer and safe operation of two-phase flow systems operating in an annular two-phase flow regime. Therefore, the objective of this work is to develop a computational model for the simulation of the annular two-phase flow regime and assess the various existing models for the entrainment rate. In this work, Computational Fluid Dynamics (CFD) in ANSYS FLUENT has been applied to determine annular flow characteristics such as liquid film thickness, film velocity, entrainment rate, deposition rate, and entrainment fraction for various gas-liquid flow conditions in a vertical upward tube. The gas core with droplets was simulated using the Discrete Phase Model (DPM) which is based on the Eulerian-Lagrangian approach. The Eulerian Wall Film (EWF) model was utilized to simulate liquid film on the tube wall. Three different models of Entrainment rate were implemented and assessed through user-defined functions (UDF) in ANSYS. Finally, entrainment for fully developed flow was determined and compared with the experimental data available in the literature. From the simulations, it was obtained that the Bertodano correlation performed best in predicting entrainment fraction and the results were within the ±30 % limit when compared to experimental data.

Amino acids to reduce the escape of organic amines in the CO2 capture process

Carbon neutrality and carbon peaking are important strategic policies for our country. Carbon dioxide capture technology is the bottom of the realization of this strategy, in which amine escape is an important issue for the development of this technology. Herein, the proposal to utilize amino acids for reducing volatilization of organic amines was introduced for the first time. Diethylaminoethanol (DEEA), widely applied and highly volatile, was selected as the primary target for volatility reduction, while hydroxyethyl ethylenediamine (AEEA) and piperazine (PZ) were chosen as the main absorbents for absorption and desorption processes. The effects of DEEA addition on the main absorbent, different types of amino acid additives on volatility, and amino acids on absorption and desorption performance were investigated, respectively. Glutamine (Tyr) demonstrated significant potential in reducing the volatilization of organic amines; when 2% Tyr was added during gas–liquid equilibrium experiments, it resulted in a 74.5% decrease in DEEA volatilization within the absorbent system. Simulated gas–liquid entrainment escape showed that CO2 loading reduced volatilization by 42.31%, with a further reduction of 53.93% achieved when loaded with 0.5 molCO2/mol amine; this loading also had a promotional effect on absorption and desorption processes. Moreover, Tyr exhibited excellent stability without generating any degradation products, thereby prolonging absorber lifespan and minimizing economic cost losses.

Liquid droplet entrainment in an annular flow boiling regime—A Bayesian regularization algorithm based study

Accurate prediction of the entrained liquid droplet fraction in an annular two-phase flow regime plays a crucial role for estimating the dryout type critical heat flux to identify the optimized flow characteristics in the thermal systems across different industries. Existing studies have provided different correlations based on the limited experimental data. However, these correlations are applicable to certain operating conditions. Therefore, the present study aims at applying a deep learning method, specifically an artificial neural network (ANN), to enhance the prediction of the entrained liquid droplet fraction. Experimental data from various works on annular flow, covering a wide spectrum of pressure and flow conditions, are utilized for training the ANN model. Eight input variables, viz, superficial gas velocity (JSG), superficial liquid velocity (JSL), gas viscosity (μG), liquid viscosity (μL), gas density (ρG), liquid density (ρL), pipe diameter (d) and liquid surface tension (σLV) are considered as input features. The entrained liquid droplet fraction is the single output feature. The present model employs the Bayesian regularization backpropagation algorithm for training. The present ANN model is compared against the performance of linear regression, decision tree and support vector machine algorithms, and found that the performance of the present Bayesian regularization neural network (BRNN) model is superior within ∼7.5% deviation. Further, the BRNN model is coupled with the film mass flow rate model to obtain the axial variation of the liquid film mass flow rate and good agreement is noticed when compared against the experimental data.

Ionic liquid-assisted extractive distillation for separating of ethyl acetate/isopropanol from chemical wastewater: Molecular insights and process intensification

The effective separation of ethyl acetate (EAC)/isopropanol(IPA)/water azeotrope from industrial wastewater significantly reduces environmental risks and recycling resources. An azeotrope separation technique was proposed, combining ionic liquid mixed entrainer and dividing wall column extractive distillation (DWC-ED). The selectivity and solubility of 225 ionic liquids were calculated based on the COSMO-RS model. The molecular polarity of EAC, IPA, H2O, dimethyl sulfoxide (DMSO), and [EMIM][AC] was studied, and 1-ethyl-3-methylimidazolium acetate ([EMIM][AC]) was determined as the best solvent. In addition, the interaction mechanism between [EMIM][AC] (or DMSO) and EAC/IPA/H2O was studied using the quantum chemistry (QC) theory. Independent gradient model (IGM), interaction energy, and atoms in molecules (AIM) analysis showed that hydrogen bonds and vdW forces were formed between [AC]− anion and H2O/IPA/EAC, and the interaction energy was gradually weakened, which significantly improved the performance of extractive distillation process. The results showed that the total annual cost (TAC) and energy consumption of IL-based mixed solvent extractive distillation were reduced by 36.04 % and 37.72 %, respectively, compared to the single DMSO extractive distillation process. The TAC and energy consumption of the DWC-ED process were 44.61 % and 51.43 % lower than the benchmark processes.

An experimental study on air-oil flow patterns in horizontal pipes using two synthetic oils

Investigations on the gas-oil mixture flow of highly viscous oils have become increasingly significant in various industries for the past couple of years. This study examines the characteristics of air-oil flow patterns to understand the effect of the oil phase's thermophysical properties and flow rates on flow patterns. An experimental study was conducted to visualize the air-oil mixture flow in horizontal pipes. The diameters of the horizontal pipes were selected as 20 and 40 mm, respectively. Two different oils having substantially different viscosities were employed as the liquid phase. Based on the visualization results, air-oil mixture flow is categorized into seven flow patterns: stratified smooth, stratified wavy, annular, plug, slug, bubbly, and dispersed bubble flows. Along with representative images, this study demonstrates the essential characteristics of individual flow patterns. Furthermore, it discusses the influence of each phase's flow rate, oil viscosity, and surface tension on flow patterns. The processes of liquid entrainment in stratified wavy flow, bubble tip breakup in plug flow, and liquid slug aeration in slug flow are also illustrated, respectively, with the corresponding sequential representative images and schematic diagrams.

Numerical study of Two-Phase flow behavior during dryout in a Two-Phase closed thermosyphon under thermal boundary conditions

This paper presents a two-dimensional axisymmetric two-phase closed thermosyphon (TPCT) model filled with R-134a refrigerant using the Volume of Fluid (VOF) method, Lee model, and Continuum Surface Force (CSF) method within Computational Fluid Dynamics (CFD) and simulates the flow characteristics inside the TPCT during the occurrence of dry out. Specifically, it discusses the two-phase flow in the condensation and evaporation sections when dry out occurs. The results indicate that the condensation section exhibits varying forms of vapor–liquid interface waves at different times. Phenomena such as liquid carryover and entrainment become increasingly prominent over time, contributing significantly to refrigerant blockages and dryout in the evaporation section. The mechanism behind dryout in the evaporation section is revealed to be the result of the initially continuous falling film being disrupted by fluctuations in the liquid–vapor interface, leading to the premature drying of thin liquid films in the troughs of these waves.

Spontaneous Transfer of Droplets across a Microfluidic Liquid-Liquid Interface.

The droplet transfer across an interface in a microchannel is extensively utilized in diverse fields; however, it is challenging to drive droplets to penetrate the interface at such a small scale. In this study, a novel flow pattern of droplet transfer is observed and the mechanism is investigated; accordingly, an accurate prediction equation for determining the critical condition of droplet transfer is proposed. Meanwhile, the liquid film entrainment is also observed, which leads to the formation of an oil-in-water-in-water system. This study serves as a valuable reference for further studies on the mechanism of droplet transfer and provides practical guidance for its industrial application.

Numerical study on the characteristics of sodium heat pipes for space application at operation limits

Sodium heat pipes are important thermal conductive components in space nuclear power sources. They efficiently transfer heat within the range of 500–1000 °C by utilizing the latent heat of phase change. However, their maximum heat transfer capacity is limited by various factors. In this study, numerical simulations were conducted to investigate the operating conditions of sodium heat pipes when encountering different heat transfer limits, with a focus on analyzing the vapor–liquid distribution and axial temperature distribution in evaporator section. It is revealed that as reaching the heat transfer limits, sodium heat pipes exhibit wall temperature fluctuations in evaporator section. When encountering the viscous limit, liquid aggregation occurs within the wick, causing discontinuous flow. As reaching the sonic limit, a vapor blockage zone forms at the outlet of evaporator section, disrupting the flow circulation within heat pipe. For the entrainment limit, the liquid inside wick is carried away by vapor flow, reducing the amount of liquid involved in phase change cycle. As in the capillary limit, inadequate liquid reflux leads to thinner liquid layer, weakening the flow circulation. During the transition from the viscous limit to the sonic limit, no significant phenomena of phase distribution occur in the evaporator section. As the sonic limit and the entrainment limit act together, both vapor blockage and liquid entrainment occur, accompanied by liquid accumulation. The phenomena when the entrainment limit and the capillary limit act together differ from those occurring individually. The simulation results provide references for a deeper understanding of heat transfer limit mechanism and other operating characteristics.

Fluodynamics of a Column Filled with Glass Rings Using the Air-Water System

In the current study, we present the fluid dynamics of an absorption tower equipped with glass rings as fillings. The research involved investigating the variations in pressure drop concerning liquid (water) and gas (atmospheric air) flow rates. We thoroughly examined the impacts of these two flows, identifying specific ranges where flooding and liquid entrainment take place. Additionally, we pinpoint a critical threshold that signifies the maximum allowable combination of the two flows, denoted as Qwater/Qair, for effective tower operation.

Fluodynamics of a Column Filled with Glass Rings Using the Air-Water System

In the current study, we present the fluid dynamics of an absorption tower equipped with glass rings as fillings. The research involved investigating the variations in pressure drop concerning liquid (water) and gas (atmospheric air) flow rates. We thoroughly examined the impacts of these two flows, identifying specific ranges where flooding and liquid entrainment take place. Additionally, we pinpoint a critical threshold that signifies the maximum allowable combination of the two flows, denoted as Q<sub>water</sub>/Q<sub>air</sub>, for effective tower operation

APPLICATION OF TWISTER SUPERSONIC GAS-LIQUID SEPARATOR FOR IMPROVED NATURAL GAS RECOVERY IN A PROCESS STREAM

Natural gas is one of the most precious natural resources that generates foreign earnings for its host nation. Energy is the building block of modern society and natural gas is one of the cleanest primary energy sources. The production and subsequent recovery of natural gas is a challenging aspect of the entire natural gas value chain. One of the problems associated with natural gas utilization is the extraction and conditioning of the gas, as most of the fractions are extracted with certain percentages of water and other contaminants. To solve the problem of liquid carryover and gas entrainment in gas processing and recover an excellent volume of gas, several types of gas separators have been developed. This case study aims to solve the problem of gas wastage and recurrent plant downtime. Notore Chemical Industries is our focus as one of the largest natural gas consumers, situated in Rivers State Nigeria. The company has several plant downtimes due to the inefficiency of the conventional separator. The inefficiency of the installed knock-out drum separator in dispersing the condensate from the feed supplied by Nigerian Gas Company (NGC) and delivering the required dry gas to the plant battery limit has been one of the leading causes of the plant recording downtime. This work presents a reliable separation process using the Twister supersonic gas separator to recover a high percentage of dry natural gas (Methane). Feed gas data was collected from the plant after several visits and a computer-based simulation was conducted. From the simulation using the Aspen Hysys package, it was seen that the Twister supersonic gas separator is more efficient than the knockout drum separator. Less methane and less condensate were produced using the knockout drum separator at 0.699% and 0.092% respectively while the Twister supersonic gas separator produced methane and condensate at 95.15% and less condensate at 0.0047% respectively.