Bubble Size Distribution Research Articles

Enhancing control of air bubbles in water flows through laser-based surface wettability patterning

Air bubble injection has been a widely studied method for reducing frictional drag in fluid flows, especially in the marine industry. However, the lack of control over air bubble stability, size, and shape has hindered its widespread adoption. This study investigates the use of laser-based surface wettability modification techniques to address these challenges by enhancing control over air bubble behavior in water flows. We processed metal plates using nanosecond laser and chemical immersion to create wettability patterns consisting of regions of either superhydrophobicity or superhydrophilicity. Water tunnel experiments were conducted to observe the behavior of air bubbles over these different wettability patterns. The results revealed that surface wettability can be used to control the size and spatial distribution of air bubbles, which can enhance the energy cost-benefit of drag reduction methods in the marine industry. Moreover, this research offers new insights into the potential of laser-based surface wettability modification as a solution for improving the control of air bubble behavior in large-scale applications.

Experimental study on turbulent characteristics of dispersed bubbly flow in a narrow rectangular channel by two-phase PIV

Narrow rectangular channels are widely used in high heat flux applications, due to the high heat transfer efficiency and compact structure. However, a rare understanding was known about the two-phase turbulent characteristics. In this study, an experimental investigation of bubble and turbulent characteristics of dispersed bubbly flow in the narrow rectangular channel was carried out by using the high-speed camera and two-phase particle image velocimetry. The bubble size effect was studied independently using the continuous spectrum bubble generator. According to the results, the bubble size distribution conforms to a Weibull distribution, and the wall-peak void fraction distributions were found. Both turbulent enhancement and suppression were observed in current conditions. Large bubbles enhance turbulence intensity, while small bubbles suppress it. The eddy viscosity ratio ϕ characterizes the modification of turbulence intensity by bubbles, with a critical value of ϕ=1.

A novel approach for the development of edible oleofoams using double network oleogelation systems.

Whipped oleogels (oleofoams) are commonly stabilized by crystalline particles. Still, external factors like temperature fluctuations could change the state of the crystals (phase transitions), leading to the destabilization and disruption of oleofoams. Herein, a double network oleogelation system comprised of a primary crystalline network (using glycerol monostearate) and a secondary colloidal network (stabilized by soy protein isolate-anionic polysaccharides Mailard conjugates) is proposed as a novel strategy to overcome these challenges. It was observed that the incorporation of the secondary network resulted in a lower over-run, but a higher melting point, elasticity, foam stability, and more uniform bubble size distribution. This was explained by the strong interfacial stabilization provided by the colloidal network that can protect the crystalline particle against coarsening and oil drainage. These double network oleofoams, which could retain 41-48 % air (oleogel-based), display great potential for utilization in low-calorie lipid-based products.

Flow and temporal effects on the sonolytic defluorination of perfluorooctane sulfonic acid

The removal of per- and polyfluoroalkyl substance (PFAS) pollution from the environment is a globally pressing issue, due to some PFAS’ recalcitrant, bioaccumulative, and carcinogenic nature. Destruction via ultrasonic waves (sonolysis) is a promising contender for industrialisation due to; moderate power consumption, applicability to several PFAS and sample types, and limited by-products. Liquid flow rate through an ultrasonic reactor can affect the size, shape, and spatial distribution of ultrasonic cavities and hence their chemical activity. Such effects have not been studied during PFAS sonolysis, and temporal effects have not been studied much beyond the reactant concentration. Here, the effects of varying recirculating flow rate on the ultrasonic defluorination of perfluorooctane sulfonic acid (PFOS) and implications for industrial scale up are presented. Under the ultrasonic power (200 W L−1, 2.27 W cm−2) and frequency (410 kHz) used, flow rates of 79 and 214 ml min−1 enhanced defluorination up to 14 % during 30 min of treatment. However, these effects were temporal and most significant in the initial minutes of treatment. This indicated a dynamic bubble size distribution which stabilised after around 15 min. Defluorination rates of PFOS were compared with measured potassium iodide dosimetry, calorimetry, sonoluminescence (SL), and sonochemiluminescence (SCL). Flow rates which enhanced defluorination correlated moderately with enhanced SCL and negatively impacted SL, calorimetry, and dosimetry. Effects were attributed to perturbed cavity surfaces, leading to asymmetric cavity collapse, and the possibility of enhanced solvated electron production/interaction. SL, SCL, dosimetry, and calorimetric measurements were also temporal, and each showed different times to equilibrate. Flow rates of 439 and 889 ml min−1 returned all sonochemical measurements to the levels without flow, likely due to continued collapse temperature quenching by furthered bubble asymmetry. Flow also enhanced reactor cooling, which is significant for industrial temperature control. The pump energy consumed was small (≈1.9 %) compared to that of the amplifier and chiller, hence, PFOS defluorination was more cost-effective using flow. However, the effect may be limited for the longer treatment times needed for environmental remediation.

Bubble self-organization in pulsed annular gas-solid fluidized beds

Pulsating the gas flow in rectangular, quasi-2D fluidized beds can turn the chaotic bubble flow into a regular bubble pattern. Bubbles form a rising triangular lattice, leading to a scalable flow structure with controllable properties, such as narrow bubble size distribution, distance between bubbles, and residence time. This overcomes challenges encountered in conventional units, like flow maldistribution and non-uniform contact. In this work, we reproduced a similar, dynamically structured flow in a cylindrical annular geometry. Regular bubble patterns emerge along the circumference of the cylinder. The absence of lateral walls and strongly curved boundaries could cause instabilities. This study presents an operating window for creating spatiotemporally structured flows and compares the flow properties in quasi-2D rectangular and annular systems, quantifying the impact of curvature and, effectively, lateral walls on flow behavior. These insights offer new opportunities for modularization of fluidized bed operations.

The foam reinforced with Janus amphiphilic graphene oxide to control steam channeling in heavy oil reservoir

Foams have been considered effective diverters to decrease the mobility in the steam channel for heavy oil-recovery processes. Due to the high weight of chemical additive loss caused by adsorption to the rock surface and the poor thermal stability of these additives, the result of surfactant or polymer is usually unsatisfactory. To avoid these problems, nanoparticles can be utilized as novel assistants to enhance the generation and stabilization of foams. In this research, an amphiphilic graphene oxide (H-GO2), which is very effective at low concentrations, is utilized to enhance the foam performance in the process of plugging steam channeling. Compared with the foam prepared by using surfactant alone, the foam height and half-life at a low concentration (0.05 wt%) of H-GO2 in bulk medium increased by approximately 151% and 341%, respectively. The size distribution of bubbles in the presence of 0.05 wt% H-GO2 is uniform, and H-GO2 creates the gas-liquid interface film three times thicker than that of the surfactant without H-GO2. As NaCl concentration increased from 0.5 to 5 wt%, more foam was generated in a shorter time, and the half-life became longer. Excess NaCl causes less foam formation and a shorter half-life. Foam generation and stabilization are reduced with the CaCl2 concentration in solution increasing from 0 to 10 wt%, or the temperature increasing from 150 to 240 ℃. Corefloods with coinjected CO2 and water containing 0.05 wt% H-GO2 and surfactant can double the resistance factor of foam in the porous medium, compared with coinjection of CO2 and water containing only surfactant. The additional oil recovery of foam generated by surfactant alone is 14.6%. It is extraordinary that the increased recovery of 31.4% can be obtained by introducing only 0.05 wt% H-GO2 into the same foam. This work may provide a reference for steam channeling control in the steam injection development process of heavy oil oilfields.

A comparative study on the measurement of surface bubble size distributions in dry aqueous foams using optical methods

The measurement of bubble sizes in aqueous foams based on images of the surface is a typical method used in laboratory and industrial scales. In this article the relationship between the size distribution of the facet areas and the bubble size of wall-touching bubbles is investigated. To achieve this an invasive sampling approach is used for in-situ collection of wall-touching bubbles in dry foams, while the surface is imaged in parallel. Bubble and facet size distributions are obtained using automated image processing. It is shown that sharp peaks in the bubble size distribution will appear smoother in the facet size distribution. This results in an overestimation of polydispersity by the surface measurements. Furthermore, it is observed that the mean equivalent diameter of the facets is on average 6% smaller than the bubble diameter obtained using the sampling method. An approach proposed by Wang and Neethling (2009) gives a good approximation of the relation between facet and bubble size and can be used to reduce potential uncertainties in surface based bubble size measurements.

Large eddy simulations of bubbly flows and breaking waves with smoothed particle hydrodynamics

For turbulent bubbly flows, multi-phase simulations resolving both the liquid and bubbles are prohibitively expensive in the context of different natural phenomena. One example is breaking waves, where bubbles strongly influence wave impact loads, acoustic emissions and atmospheric-ocean transfer, but detailed simulations in all but the simplest settings are infeasible. An alternative approach is to resolve only large scales, and model small-scale bubbles adopting sub-resolution closures. Here, we introduce a large eddy simulation smoothed particle hydrodynamics (SPH) scheme for simulations of bubbly flows. The continuous liquid phase is resolved with a semi-implicit isothermally compressible SPH framework. This is coupled with a discrete Lagrangian bubble model. Bubbles and liquid interact via exchanges of volume and momentum, through turbulent closures, bubble breakup and entrainment, and free-surface interaction models. By representing bubbles as individual particles, they can be tracked over their lifetimes, allowing closure models for sub-resolution fluctuations, bubble deformation, breakup and free-surface interaction in integral form, accounting for the finite time scales over which these events occur. We investigate two flows: bubble plumes and breaking waves, and find close quantitative agreement with published experimental and numerical data. In particular, for plunging breaking waves, our framework accurately predicts the Hinze scale, bubble size distribution, and growth rate of the entrained bubble population. This is the first coupling of an SPH framework with a discrete bubble model, with potential for cost-effective simulations of wave–structure interactions and more accurate predictions of wave impact loads.

Estimating mixed gas fluxes with geochemically informed broadband acoustic methods: What the flux?

Over the past few years, improvements in broadband split-beam echosounders have made it possible to obtain precise measurements of bubble-size distribution and density of gas seeps. Here, we model acoustic volume backscattering of a group of bubbles with a multi-modal size distribution that we matched to real-time acoustical measurement over a gas seep. The results are profiles of bubble size distribution descriptors (e.g., distribution type and parameters), density and ratio of the various components (i.e., gas composition). To test the ability of this methodology to differentiate gas flux composition and estimate gas flux magnitudes, we applied it in a semi-automated fashion on broadband data (12 to 250 kHz) acquired in the Bay of Plenty (NZ) over mixed gas seeps (e.g., CO2, CH4). Model outputs were compared with real-time dissolved gas measurements to constrain gas composition, magnitude, and ground-truth methodologies. The method can be applied to a variety of marine seeps to produce regional flux estimations, improving oceanic carbon budgets and our understanding of downstream feedbacks, such as localized deoxygenation or ocean acidification.

Defining that je ne sais QUOI of seep sites: An overview of the Quantitative Ocean-Column Imaging (QUOI) voyage to offshore New Zealand

Detecting and characterizing oceanic seep sites is of considerable interest for the geoscience community due to their influence on global climate, ecological significance, connection to resources of high value, and, in many locations including New Zealand, their cultural importance. Modern acoustic systems provide the means for quantitative analysis of seep systems by collection of backscattered energy by gas bubbles and associated water column phenomena and surrounding seafloor. The July 2018 international, multi-institution Quantitative Ocean-Column Imaging (QUOI) voyage aimed to develop protocols and methodologies for identifying and quantifying seafloor and water-column backscatter data associated with bubble seep sites utilizing a large range of active acoustic systems and direct sampling methods. Here, we will provide an overview of QUOI voyage goals and research activities at several locations offshore of New Zealand, including the Calypso hydrothermal vent field in the Bay of Plenty. Gas bubble and hydrothermal fluid emission were captured in acoustic water column data, video transects, and direct sampling operations. More than 3000 individual seep bases were identified in the Calypso hydrothermal vent field, occupying approximately 9 of 115 km2 of mapped seafloor. Efforts are underway to characterize the bubble size distribution of seep sites and quantify carbon flux to the atmosphere using a combination of broadband acoustic methods and in-situ measurements.

Viscous effects on gas-liquid hydrodynamics for bubble size determinations in different Newtonian and non-Newtonian fluids using a CFD-PBM model

Often, culturing during bioprocessing generates severe conditions that modify the viscosity of the culture media. The change in viscosity leads to different microenvironments governed by viscous effects-mediated hydrodynamics. For example, different bubble size distributions are dispersed inside a bioreactor due to viscous effects. Traditionally, the mathematical modeling framework used in numerical simulation of the bubble size distribution in (bio)reactors is based on breakup and coalescence models valid only in the inertial subrange of turbulence. Hence, applying the traditional models for breakup and coalescence in viscous fluids can result in inaccurate model predictions because the dissipation subrange of turbulence is not considered. This work focuses on the numerical prediction of the bubble size in a stirred bioreactor using the concept of the complete energy spectrum of turbulence to enable viscous effects in the breakup and coalescence models. The breakup and coalescence models are used within the population balance equation (PBE), coupled with computational fluid dynamics (CFD). The emphasis of the PBE-CFD simulations is placed on gas–liquid hydrodynamics aspects related to viscous Newtonian and non-Newtonian fluids applications. In bioreactor zones where viscosity effects occur, the use of the complete energy spectrum of turbulence facilitates the calculation of the transition between dissipation and inertial subranges of turbulence. It is shown that the numerical simulations captured viscous effects-mediated hydrodynamics. Considering these findings, using the complete energy spectrum of turbulence in PBE-CFD simulations is a promising approach for numerical bubble size prediction.

Synergistic Effect of Frequently Found Ions in the Flotation of Pb-Zn Sulfide Ores on Air/Water Interface

The aqueous ions influence the properties of air bubbles and, therefore, the recovery of flotation. This study aims to reveal the synergistic effect of frequently found ions in the flotation of Pb-Zn sulfide ores. In this context, dynamic surface tension measurements, bubble coalescence time, Sauter mean diameter (SMD), bubble size distribution (BSD), and dynamic foam stability (DFS) measurements were carried out using artificial process waters (APWs). APW with the minimum ion concentration is expressed as “APW1” with the ionic strength (I) of 0.03 mol/dm3. The concentration of the ions in APW1 was increased by 3, 5, and 10 times, and thus APW3 (I = 0.08 mol/dm3), APW5 (I = 0.13 mol/dm3), and APW10 (I = 0.26 mol/dm3) were prepared, respectively. The results of this study indicated that the surface tension increased slightly in the presence of APW related to the ion concentration. Potassium ethyl xanthate (KEX) at high concentrations was effective in the reduction of surface tension. As the APW concentration increased, finer bubbles were obtained with a narrower size range. The stability of the foam increased with butyl glycol (BG) and APW concentration. There was no need to use a frother (BG) for the flotation experiments in the presence of APW1 or APWs with higher ionic strength.

Simply solvable model capturing the approach to statistical self-similarity for the diffusive coarsening of bubbles, droplets, and grains.

Aqueous foams and a wide range of related systems are believed to coarsen by diffusion between neighboring domains into a statistically self-similar scaling state, after the decay of initial transients, such that dimensionless domain size and shape distributions become time independent and the average grows as a power law. Partial integrodifferential equationsfor the time evolution of the size distribution for such phase separating systems can be formulated for arbitrary initial conditions, but these are cumbersome for analyzing data on nonscaling state preparations. Here we show that essential features of the approach to the scaling state are captured by an exactly-solvable ordinary differential equationfor the evolution of the average bubble size. The key ingredient is to characterize the bubble size distribution approximately, using the average size of all bubbles and the average size of the critical bubbles, which instantaneously neither grow nor shrink. The difference between these two averages serves as a proxy for the width of the size distribution. Solution of our model shows that behavior is controlled by a signed length δ that is proportional to the width of the initial distribution relative to that in the scaling state. In particular, δ is negative if the initial preparation is too monodisperse, and is positive if it is too polydisperse. To test our approach, we compare with data for quasi-two dimensional dry foams created with three different initial amounts of polydispersity. This allows us to readily identify the critical radius from the average area of six-sided bubbles, whose growth rate is zero by the von Neumann law. The growth of the average and critical radii agree quite well with exact solution, though the most monodisperse sample crosses over to the scaling state faster than expected. A simpler approximate solution of our model performs equally well. Our approach is applicable to 3d foams, which we demonstrate by re-analyzing prior data, as well as to froths of dilute droplets and to phase separation kinetics for more general systems such as emulsions, binary mixtures, and alloys.

Hierarchical bubble size distributions in coarsening wet liquid foams

Coarsening of two-phase systems is crucial for the stability of dense particle packings such as alloys, foams, emulsions, or supersaturated solutions. Mean field theories predict an asymptotic scaling state with a broad particle size distribution. Aqueous foams are good model systems for investigations of coarsening-induced structures, because the continuous liquid as well as the dispersed gas phases are uniform and isotropic. We present coarsening experiments on wet foams, with liquid fractions up to their unjamming point and beyond, that are performed under microgravity to avoid gravitational drainage. As time elapses, a self-similar regime is reached where the normalized bubble size distribution is invariant. Unexpectedly, the distribution features an excess of small roaming bubbles, mobile within the network of jammed larger bubbles. These roaming bubbles are reminiscent of rattlers in granular materials (grains not subjected to contact forces). We identify a critical liquid fraction [Formula: see text], above which the bubble assembly unjams and the two bubble populations merge into a single narrow distribution of bubbly liquids. Unexpectedly, [Formula: see text] is larger than the random close packing fraction of the foam [Formula: see text]. This is because, between [Formula: see text] and [Formula: see text], the large bubbles remain connected due to a weak adhesion between bubbles. We present models that identify the physical mechanisms explaining our observations. We propose a new comprehensive view of the coarsening phenomenon in wet foams. Our results should be applicable to other phase-separating systems and they may also help to control the elaboration of solid foams with hierarchical structures.

Competitive methane bubble growth in aquatic muds

Methane (CH4) bubbles residing in shallow aquatic muds pose a significant threat to the environment. Impeded by the muddy sediment opacity and insufficient resolution for their characterization, past studies overlooked bubble interactions as they grow. Here, the competitive fracture-driven growth of CH4 bubble pair with different initial sizes in the aquatic muds is simulated, using a mechanical/reaction-transport numerical model. Mechanical and solute transport interactions were found to dominate at the different stages of the bubble growth, both retarding the smaller competitive bubble growth. The stress from large competitive bubble affects the inner pressure and diffusive CH4 flux to the smaller bubble, causing its slower initial growth (at t < 40 s). The large competitive bubble also diverts CH4 from the smaller one later on, thus inhibiting its growth even more. Bubble stress interactions may produce more laterally oriented smaller bubble and significant deformations of the larger one, both amplified under the decreasing distance between the growing bubble pair. Competitive bubble growth may shape a bubble size distribution pattern observed in the lab experiments and in situ, which may promote muddy sediment CH4 gas retention and produce gas domes. The latter acts as pockmark precursors whose formation induces a violent gas release to the water column and potentially to the atmosphere. Our study presents a basis for a proper upscaling to various effective gassy muddy sediment characteristics and gas retention evolution transient models, while preserving the single bubble growth descriptors. It contributes to evaluation and even reduction of a long-persisting uncertainty related to CH4 flux from the shallow aquatic sediments.

Supersonic Base Flow With and Without Propulsive Jets: A Brief Review

Supersonic base flow is encountered in many aerospace applications related to satellite launch vehicle, missiles and projectiles. The origin and evolution of large scale structures which govern the dynamics of the base flow is not properly understood. The presence of central propulsive jet further complicates the base flow characteristics. Different semi-empirical, experimental and numerical studies carried out in supersonic base flow is briefly reviewed. Various issues and challenges faced in CFD simulation of base flow problems are described. Apart from resolution of numerics, proper choice of turbulence model remains the key aspect in the Reynolds Averaged Navier Stokes (RANS) simulations. Prediction of axial distribution of centerline velocities and recirculation bubble size remain problematic in RANS simulation. Detached Eddy Simulation (DES) results show dependence on model constants. Large Eddy Simulation (LES) studies with proper filter and Sub Grid Scale (SGS) model is promising, but its applications are limited to canonical problems due to very high computational requirements. Direct Numerical Simulation (DNS) studies reported in the literature consider much lower Reynolds number and hence could not be compared with the experimental data. It is suggested to use RANS and DES methods with anchored turbulence model from well-designed experiments for design data generation. Efforts should be made to use higher order numerical methods (LES and DNS) to explore the origin and evolution of large scale structures observed in compressible base flow.

Numerical Measurement of the Effective Electrical Conductivity of Electrolyte-Gas Bubble Dispersions

Bubble formation during water electrolysis is inevitable. Apart from mass and heat transfer limitations, the presence of these bubbles causes a decrease in the local electrical conductivity of the electrolyte, thereby contributing further to the ohmic resistance of the system. Experimental and theoretical studies have shown that the effective electrical conductivity of an electrolyte-gas bubble dispersion depends on the volume fraction of gas bubbles. However, these studies do not provide insight into the dependence of conductivity on the geometric and spatial parameters of the dispersion, such as the size distribution of the bubbles or their spatial arrangement.Experimentally, the conductivity of such dispersions can be measured using the four-electrode conductivity measurement technique. In this talk, I will present a numerical rendition of this experimental technique to measure the conductivity of an electrolyte dispersed with gas bubbles, using the lattice Boltzmann method. The computational nature of the method lends itself well to investigating systems with different bubble size distributions and spatial configurations. The model also offers the flexibility to specify the surface charge density of the dispersed bubbles. The visualization of the ionic flux around these dispersed bubbles provides insights into the motion of ions along the paths of least resistance, and therefore a better understanding of the behavior of such systems.The effective conductivity of bubble dispersions with varying degrees of randomness in their spatial arrangement has been measured, ranging from a regularly packed array of bubbles to a completely random packing. We observed that the numerically measured conductivity deviates from that predicted theoretically at high bubble volume fractions. Moreover, for the same bubble volume fraction, different spatial arrangements yield different values of conductivity, thus highlighting the influence of spatial arrangement of the bubbles on the effective conductivity of the dispersion. Additionally, the spread (standard deviation) of the numerically measured conductivity about the mean value for a given bubble volume fraction is observed to be larger at moderate volume fractions, in comparison to very dilute and densely packed dispersions. This can be explained by the fact that at moderate bubble volume fractions, there is a larger probability for the formation of random bubble clusters that hinder the movement of ions. Such clusters are unlikely in dilute cases and are universal in the dense limit, and as a consequence, less variation in the resulting effective conductivity is observed for the two limiting cases. This furthermore indicates the importance of spatial arrangement on the effective conductivity of such dispersions.

Foaming Properties of Lignosulfonates in the Flotation Process.

The widely used technology for the selective flotation of copper and molybdenite using sodium hydrosulfide (NaSH) to depress copper sulfides creates environmental issues related to the potential emissions of toxic hydrosulfide gas (H2S) and bad odors. Previous studies showed that molybdenite flotation can be depressed by the action of lignosulfonates, but no significant progress has been made in studying the effect that these reagents have on the foaming/frothing phenomena in flotation. The objective of this work was to investigate the foaming properties of three samples of lignosulfonates through measurements of surface tension, foamability, bubble size distributions, and water recovery. A sugared sodium lignosulfonate (NaLS), a calcium lignosulfonate (CaLS), and a sample prepared by sulphomethylation of kraft lignin (KLS) were tested. It was found that all lignosulfonates displayed surface activity that decreased with pH and was related to the degree of anionicity and molecular weight. The NaLS lignosulfonate showed the highest dynamic foamability index (DFI) value, compared to that of the CaLS and KLS samples. The lignosulfonates tested in this study strongly affected bubble size. Water recovery tests performed using flotation experiments in a two-phase system showed that the KLS and NaLS samples had the strongest effect, which correlated with the surface tension, foamability, and bubble size results.

Numerical Simulation of Flashing Flows in a Converging–Diverging Nozzle with Interfacial Area Transport Equation

Flashing flows of initially sub-cooled water in a converging–diverging nozzle is investigated numerically in the framework of the two-fluid model (TFM). The thermal non-equilibrium effect of phase change is considered by an interfacial heat transfer model, while the pressure jump across the interface is ignored. The bubble size distribution induced by nucleation, bubble growth/shrinkage, coalescence, and breakup is described based on the interfacial area transport equation (IATE) and constant bubble number density model (CBND), respectively. The results are compared with the experimental data. Satisfactory prediction of the axial pressure distribution along the nozzle as well as the flashing inception, is achieved by the TFM-IATE coupling method. It was also found that the vapor production in the diverging section was overpredicted, and the radial gas volume fraction distribution deviated from the experiment. The radial diameter profiles exhibit opposite patterns at the nozzle throat and near the outlet, and similar trends can be observed for the superheated degree. A poly-disperse method is suggested to be introduced to describe the evolution of interfacial area concentration.

Computational investigation on the flow and mass transfer properties inside ejector of loop reactor based on CFD-PBM simulation

Conventional stirred kettle reactors suffer from inadequate gas-liquid mixing in many production processes, and their reaction rates are greatly limited. The loop reactor can achieve high mass transfer rates with low energy consumption. It is well suited for multiphase reactions with limited mass transfer and has the advantage of being excellent sealing and low cost. In this paper, ejector as the core of the loop reactor was investigated. Combining the Computational Fluid Dynamics (CFD) and Population Balance Model (PBM), the industrial-scale ejector model was constructed. The detailed motion behavior of bubbles and bubble size distribution were predicted. Due to the entrainment of the liquid phase, the gas enters the suction chamber and throat of the ejector, where the gas is mainly sheared and broken, providing a large specific surface area of the gas-liquid interface. Moreover, the flow and transfer properties were closely related to parameters such as nozzle-throat diameter ratio and liquid inlet velocity. Based on the results of the simulation, the gas-liquid mass ratio and the volumetric mass transfer coefficient were correlated with the structure and process parameters, and the correlation model was obtained, which provides guidance for the design of the loop reactor.