Flow Rate Of Continuous Phase Research Articles

Power-efficient mass transfer of a novel pulsating multi-packed bed liquid - liquid extractor

This paper presents the development and performance evaluation of a new pulsating packed bed contactor designed for optimized diffusion-controlled liquid-liquid operations. Targeting applications like aromatics separation in petroleum, phenol removal from wastewater, and heat-sensitive material extraction (e.g., antibiotics), the contactor offers substantial advantages over traditional mechanical systems – notably, lower power consumption for equivalent production rates. Using the widely studied extraction of acetic acid from toluene-acetic acid by water as a model system, this work comprehensively investigates the factors impacting mass transfer within the pulsating contactor. Key variables explored include physical properties of the feed solution, oscillation frequency and amplitude, initial concentration of solute, flow rates, bed height, packing diameter, and bed spacing. Results reveal a significant enhancement in mass transfer with increasing frequency, amplitude, initial concentration, continuous phase flow rate, and dispersed phase flow rate. Interestingly, while increasing bed height initially improves mass transfer up to a specific point, further height increase exhibits a diminishing return. Packing sphere diameter shows minimal impact, while bed spacing has a negligible effect. A novel dimensionless equation effectively correlates the pulsating multi-packed bed data for broader applicability. To assess economic viability, the study also measures the mechanical power consumption under various operating conditions. Finally, diverse potential applications across pharmaceuticals, chemicals, biochemicals, petroleum, and nuclear fuel reprocessing are highlighted, showcasing the broad utility of this innovative mass transfer technology.

Experimental modeling of slip velocity in an L-shape pulsed packed extraction column using response surface methodology

The “L-shaped pulsed packed extraction column,” a distinctive form of extraction column, is used in this study to examine the impacts of operational parameters and the physical features of the liquid systems on the slip velocity in a pilot plant. This assessment is done using response surface methodology (RSM). The operational factors of pulsation intensity, dispersed phase flow rate, and continuous phase flow rate are examined through the use of central composite design (CCD) on slip velocity. In the absence and presence of a mass transfer agent (acetone), two common liquid-liquid systems—butyl acetate and water and toluene and water—were used as the chemical systems. Interfacial tension, dispersion phase flow rate, and pulsation intensity are among the parameters that have been found to have a substantial impact on slip velocity. However, the slip velocity was either unaffected or was very slightly affected by the continuous phase flow rate and the mass transfer agent's presence. In addition, new practical models with R2 > 0.93 are presented to predict slip velocity by RSM. Finally, new comprehensive correlation based on dimensional analysis procedure, is put out to precisely forecast the slip velocity. For all of the investigated operating parameters and chemical systems, there was good agreement between predictions and experiments.

Study of Drop Size Distribution in RTL Contactor

The present work studied the drop size distribution in the RTL contactor using two liquid-liquid systems, xylene-acetone-water and kerosene-acetone-water. Process variables studied were: rpm (10-50 min-1), continuous phase flow rate (4-12 l/h), dispersed phase flow rate (4-12 l/h), and concentration (0.1-0.5 mole/l). It was found that Sauter mean drop diameter (d32) decreased with increasing rpm and continuous phase flow rate, and decreasing dispersed phase flow rate and concentration. An empirical correlation, with a correlation coefficient equal to (92.6%), relating d32 with process variables was developed having the form:

Forecasting Sauter mean droplet size and examining the range of droplet sizes in a Tenova liquid–liquid extraction column

A new type of Tenova pulsed extraction column was introduced in 2017. It is the newest generation of pulsed columns. Due to the internal equipment of this column and the lack of moving parts and the simplicity and speed of repairs and maintenance, it has been the focus of researchers in recent years. No correlations for predicting the mean drop size and drop size distribution of the Tenova column have been reported. The Sauter mean drop diameter and drop size distribution are investigated for a Tenova pulsed column with a diameter and an active height of 7.4 and 73 cm, respectively. Three standard chemical systems of isobutyl acetate-water, isobutanol-water, and toluene-water have been used. The effects of pulse intensity, dispersed and continuous phase flow rates have been taken into account. In each experiment, 200–300 drops have been analyzed in a total of 10,000 drops. The investigation covered a spectrum of physical properties, notably surface tension (within a range of 1.75–36 mN/m). Operating conditions including pulse intensity (in the range of 0.2–2 cm/s) and the flow rate of continuous and dispersed phases (in the range of 8–30 L/h) have been investigated. Methods based on artificial intelligence (AI) such as multilayer perceptron neural networks and gene expression programming were combined with a dimensional analysis approach to provide a new approach to estimating the mean drop diameter (d32). Experimental results have been compared with the equations found by other researchers in similar columns. The variation of drop size distribution has also been experimentally obtained.Methods based on artificial intelligence (AI) such as multilayer perceptron neural networks and gene expression programming were combined with a dimensional analysis approach to provide a new approach to estimating the mean drop diameter (d32). Experimental results have been compared with the equations found by other researchers in similar columns. The variation of drop size distribution has also been experimentally obtained.

CFD study of droplet formation in a cross-Junction microfluidic device: investigating the impact of outflow channel design and viscosity ratio

This study employed computational fluid dynamics (CFD) to investigate various regimes of droplet formation in a square microfluidic cross-junction device. The first part of the study focused on investigating the impact of viscosity ratios ranging from 0.1 to 5 on droplet characteristics under different flow rate ratios. The transition regime between the dripping and jetting exhibited particularly interesting behavior, with droplet volume being proportional to viscosity ratio. However, when conditions were far from the transition regime, the volume of droplets did not vary significantly with respect to viscosity ratios greater than one. The results of the study indicate the feasibility of reducing droplet volume to the appropriate level while minimizing the impact on the continuous phase's flow rate and the risk of transitioning to jetting. Moreover, in the final part of the study, we investigated the potential of shifting the transition boundary between the squeezing and jetting regimes. Our findings indicate that modifying the outflow channel's design can increase the frequency of droplet generation without altering the operating conditions for both the continuous and dispersed phases.

Dynamics of Non-Magnetic Droplets and Bubbles in Magnetic Fluids in Microfluidic Channels under the Influence of a Magnetic Field

The microfluidics of magnetic fluids is gaining popularity due to the possibility of the non-contact control of liquid composite systems using a magnetic field. The dynamics of non-magnetic droplets and gas bubbles in magnetic fluids were investigated for various configurations of magnetic fields, coatings, and channel geometries, as well as the rate of component supply and their physical properties. Optimal regimes for forming droplet and bubble flows were determined. The mechanism for non-contact control of the size of droplets and bubbles using a magnetic field is proposed in this article. The dependences of the sizes of non-magnetic inclusions in magnetic liquids on the continuous phase flow rate and the displacement of magnets were obtained. The obtained dependences of the volume of non-magnetic inclusions on the flow rate of the continuous phase follow the classic dependences. Changing the size of air bubbles can be achieved by shifting the magnet from −5 mm to +2 mm. The ratio of the maximum and minimum breakaway inclusion varies from 5 to 2 depending on the flow rates of the continuous phase. The range of changing the size of oil droplets with the displacement of magnets is from 1.1 to 1.51. These studies show how, with the help of various mechanisms of influence on microfluidic flows, it is possible to control the size of bubbles and droplets forming in microchannels. The obtained data can be applied for controlled microfluidic dosing and counting devices.

Formation of viscoelastic droplets in asymmetrical parallel microchannels

The dynamics of viscoelastic droplet formation in T-shaped asymmetric parallel microchannels are investigated using a high-speed camera. The effects of fluid viscoelasticity and flow rates of the two phases on the stability and uniformity of droplets, fluid flow distribution, and droplet formation period are explored. The results reveal that the viscoelasticity advances the transition from the squeezing stage to the rapid pinch-off stage, slows down the necking of rapid pinch-off stage and increases the duration of the stretching stage. It is found that the stability is significantly improved by increasing the continuous phase flow rate, and the droplet uniformity is affected by both the flow rates of the two phases and the fluid elasticity. In addition, prediction models for the fluid flow distribution, droplet size and droplet formation period are established. At last, the breakup mode of different elasticity filament and the satellite droplet size are studied. It is concluded that the increased elasticity contributes to the elimination of satellite droplets, and the satellite droplet size are affected by the fluid elasticity and the continuous phase flow rate.

Fabrication of monodisperse droplets and microcapsules using microfluidic chips: a review of methodologies and applications

Abstract Microfluidics has been applied in the preparation of monodisperse droplets and microcapsules due to its high encapsulation efficiency, its ability to create uniform particle sizes, and its capacity to control core–shell ratio and structure. To bring to the fore methodologies for the fabrication and application of monodisperse microcapsules using microfluidics, we present a review of the design, structure, materials, and surface modification techniques of various microfluidic chips. The review also covers fabrication methods, operating parameters and regulation methods of single and multiple monodisperse emulsion droplets fabricated from various microfluidic devices. Our findings show that particle size of monodisperse droplets depend mainly on microchannel characteristic size and flow rate, with particle size increasing with larger microchannel but decreasing with higher continuous phase flow rate. We additionally reviewed and compared various fabrication methods for monodisperse microcapsules, such as interfacial polymerization, free-radical polymerization, ionic cross-linking, and solvent evaporation. We further reviewed and examined the application of monodisperse microcapsules in biology applications, food engineering, composite materials development, and pharmaceutical industry. We found that high-throughput microfluidics for scale-up monodisperse microcapsule preparation towards uniform degradation and targeted release properties of monodisperse microcapsules would be key innovative direction for future applications.

Size Tunable Fabrication of Magnetic Alginate Microparticles Using Flow Focusing Microfluidics

AbstractThe size tunable formulation of magnetic alginate microparticles (MAMs) using a 3D flow‐focusing microfluidic device is reported. The droplet phase consists of iron oxide nanoparticles (IONPs) in an alginate solution and the continuous phase consists of fluorocarbon oils. The stability of IONP colloids in alginate and calcium ethylenediamine tetraacetic acid solutions using optical microscopy, dynamic light scattering, and zeta potential measurements is studied. These studies suggest that IONPs coated with polyethylene glycol (PEG) are most stable. MAMs using the PEG‐coated IONP colloid are then formulated and it is studied how MAM the average size and coefficient of variance vary as a function of droplet and continuous phase flow rates and viscosities. Droplet and MAM size decrease when the carrier flow rate or viscosity increases, and droplet and MAM size increase when droplet flow rate or viscosity increases. Crosslinking and drying of droplets result in MAMs whose diameter is ≈44% less than the original droplets while maintaining a population coefficient of variance below 8%. Conditions are identified that enable fabrication of MAMs with diameters between 30 and 60 µm with coefficients of variance of ≈6–7%. These results may guide future work exploring the role of MAM size on various applications.

Evaluation of the operating parameters impact on hydrodynamic parameters of horizontal pulsed sieve-plate column using response surface methodology

The uranium extraction process from leach liquor solution of Bandar Abbas ore with Alamine 336 in a horizontal pulsed sieve-plate column has been evaluated numerically. In this study; Alamine 336 with a concentration of 0.125 mol L−1, isodecanol with a concentration of 5% (v/v), and kerosene were used as the organic phase. The aqueous phase was a leach liquor solution containing 0.25 g L−1 uranium and 0.22 mol L−1 sulfate. In this study, the response surface methodology (RSM) was used to investigate the effect of three effective operating parameters in the pulsed column as pulse intensity and the continuous and dispersed phases flow rates on the hydrodynamic parameters such as dispersed phase holdup, slip and characteristics velocities. The obtained results show that the hydrodynamic parameters are strongly dependent on the pulse intensity and turbulence degree of the system. In addition, three new practical correlations based on operating parameters of a column are presented to predict the dispersed phase holdup, slip, and characteristics velocities by the RSM. The correlations presented by the response surface method showed a good prediction of the experimental data with a maximum R2 value of 0.98.

Breakup-based preparation of ultra-thin solid-in-water-in-oil conformal droplets in a microchannel

Droplets encapsulating solid microparticles with a thin coating layer have extensive applications in the fields of biochemical, advanced materials, and inertial confinement fusion. In this work, the droplet break-up technique is employed to prepare solid–water–oil (S/W/O) conformal droplets with an ultra-thin coating layer. A microfluidic chip, consisting of a T-junction and a Y-junction, was designed and constructed for the controlled preparation of ultra-thin S/W/O conformal droplets by generating–splitting integration. The flow pattern, regime, and dynamic mechanisms of the S/W/O droplet break-up were also experimentally investigated. The results show that there are three break-up regimes: breakup, non-breakup, and transition. Two different modes are observed in the break-up regime: without solid core stagnation and with solid core stagnation. In the case of the solid core without stagnation, the neck goes through three stages: squeezing, transition, and pinch-off. When the solid core stagnates, the neck goes through one more solid core stagnation stage after squeezing. The stagnation percentage decreases as the dispersed phase capillary number increases and increases as the continuous phase capillary number increases. The coating thickness of the S/W/O droplet increases and then decreases as the continuous phase flow rate increases. The coating thickness of the daughter S/W/O droplet was significantly reduced and was less affected by the continuous phase flow rate.

Comparison of dispersed phase holdup and slip velocity in chemical systems with different interfacial tension in an L-shaped pulsed sieve-plate extraction column

The behavior of dispersed phase holdup (DPH) and slip velocity (SV) was studied in a new type of pulsed extraction columns, named “L-shaped pulsed sieve-plate column (LPSPC)” for five chemical systems, including water-kerosene, nitric acid-5% (v/v) TBP/kerosene, nitric acid-15% (v/v) TBP/kerosene, nitric acid-30% (v/v) TBP/kerosene, and uranyl nitrate-30% (v/v) TBP/kerosene. Then the impact of pulsation intensity, interfacial tension, and flow rate of dispersed and continuous phases, on DPH and SV was investigated. The results revealed that both DPH and SV were greatly influenced by the pulsation intensity, interfacial tension and flow rate of dispersed phase though the flow rate of continuous phase had a weaker effect. Finally, using the response surface method (RSM) and dimensional analysis procedure, new semi-experimental correlations were proposed to predict DPH and SV, which corresponded satisfactorily to the experimental data. The average absolute relative error (AARE) values of the correlations obtained by dimensional analysis for DPH and SV were about (6.56, 8.68%) and (5.52, 8.40%) for the horizontal and vertical sections, respectively.

Flooding behavior of the standard liquid–liquid extraction systems in a pilot plant L-type pulse packed extraction column: Experimental study

In this study, the two-phase pressure drop and flooding velocity were investigated in a pilot plant of a new type of extraction column entitled “L-shaped pulsed packed extraction column” using two liquid-liquid systems of butyl acetate-water and toluene-water in the presence of acetone as the mass transfer agent. The effects of operating variables, physical properties, and the presence of mass transfer on the flooding flowrate and pressure drop were considered. It is found that the pressure drop is strongly influenced not only by the flow rates of the continuous and dispersed phases, but also by the pulsation intensity. That is, increasing the values of these parameters increases the shear stresses and the flooding phenomenon to occur sooner. Surprisingly, it is observed that increasing the pulsation intensity and dispersed phase flow rate reduces the maximum throughput of the column but increasing the continuous phase flow rate enhances that. Furthermore, it is achieved that the interfacial tension is a physical property which has significant impact on the flooding and the presence of mass transfer only affect at the low pulsation intensity. Finally, a new correlation is proposed to accurately predict the flooding velocity. Good adaptation between predictions and experiments was found for all investigated operational conditions, chemical systems, and with and without mass transfer.

Non-Newtonian droplet breakup in a T-junction microdevice containing constriction induced asymmetric parallel branches

Here, we describe the breakup and post-breakup dynamics of a non-Newtonian droplet of xanthan gum aqueous solution in asymmetric parallel branch microdevices. Our experimental results reveal that the droplet breakup regimes, namely, obstruction, tunnel, combined, non-breakup, and parallel, are the functions of xanthan gum concentration and the continuous phase flow rate. We examined the influence of fluid properties on droplet breakup stages by varying the xanthan gum concentration in an aqueous solution that exhibited increasing shear-thinning and elastic properties with its concentration. Four sequential stages (squeezing, transition, pinch-off, and filament thinning) are identified during the droplet breakup process. We found that upstream pressure controlled the squeezing stage, and fluid properties mainly steered the filament rupture stage. A complex interaction between elastic, capillary, and inertial forces further divided the final stage into the stretching and fluid-drainage stages. The Hencky strain characterized the formation of a persistent cylindrical filament in the stretching stage that decayed exponentially in the fluid-drainage stage. Eventually, this study highlights the significance of parallel branches with asymmetric geometric confinements on droplet splitting. Enhanced asymmetry is observed for the elongated filament, emphasizing the dominance of feedback from the downstream confinement.

Droplet separation and sieving mechanism by grooved microchannel

A novel droplet sieving method utilizing grooved microchannel is proposed to achieve the monodispersity of droplets. The sieving performance and mechanism are investigated experimentally. Three different sieving flow regimes are observed in the experiment: incomplete sieving, complete sieving and main droplet rupture. The effects of different operating conditions on sieving efficiency are studied systematically. The results showed that when the total flow rate of the continuous phase in the main channel is lower, the small droplets would accumulate between the main droplets and could not be separated. Complete sieving could be achieved when the main body of the small droplet enters the sieving layer before arriving at the sieving channel. The larger continuous phase flow rate in sieving channel could create thicker sieving layer, which is conducive for small droplets to entering the sieving layer to achieve complete sieving. On the contrary, the higher continuous phase flow rate in the main channel would lead to thinner sieving layer, and the required flow rate in sieving channel would be higher to achieve complete sieving. Under the same sieving channel flow rate, the longer droplet is more apt to rupture. The sieving mechanism of droplets is proposed according to the force analysis in the channel. Whether the main droplet ruptures at the sieving junction depends on the combined action of the suction of the sieving channel, the interfacial tension, and the supporting force of the sieving groove.

Insights into the dynamics of non-Newtonian droplet formation in a T-junction microchannel

The non-Newtonian shear-thinning droplet formation mechanism in a T-junction microchannel is experimentally investigated using the aqueous solutions of xanthan gum as the dispersed phase and mineral oil as the continuous phase. Influences of both phase flow rates and polymer concentration on flow regime transition are explored. It is observed that the initial vertical expansion stage is present only for the Newtonian and lower shear-thinning systems. The droplet evolution rate shows the influence of continuous phase flow rate and shear-thinning properties on the dynamics of necking stages, viz., squeezing, transition, pinch-off, and filament thinning. Analysis of Ohnesorge number (Oh) reveals that inertial force dominates in the squeezing stage, whereas viscous and interfacial force control in the filament thinning stage. Longer and stable filament generation is detected as a discerning feature for non-Newtonian systems that appears more prominent with increasing dispersed phase shear-thinning properties. The results also indicate an inverse relation of droplet length with the continuous phase flow rate and xanthan gum concentration, while the droplet formation frequency and its polydispersity vary directly with those parameters.

미세액적 제조를 위한 다층 액적 분할 미세유체 시스템 개발

In this study, we present the multilayered symmetrical droplet splitting microfluidic system for preparation of microspheres. The microfluidic device was fabricated by conventional photolithography and PDMS casting. Multiple layers of microfluidic channels for symmetrical droplet splitting were stacked and integrated into a device. Each layer was designed to obtain 16 microdroplets from one droplet by droplet splitting. The droplet size was controlled with flow rate of dispersed phase (DI-water) and continuous phase (Mineral Oil with 3 wt.% SPAN80) by using a syringe pump. The droplet splitting behavior and production rate were analyzed by high-speed camera and inverted microscope in one layer of the microfluidic device. Additionally, the droplet size and size distribution were observed in each layer of the microfluidic device. The droplet size could be controlled by flow control of two phase flows with high uniformity of droplet size less than 5% coefficient of variation.

Formation dynamics and size prediction of bubbles for slurry system in T-shape microchannel

The bubble formation dynamics and size manipulation in the slurry of polystyrene microspheres in the microfluidic T-junction were visually investigated by a high-speed camera. Based on the evolution of the bubble neck with time, the formation process of bubbles is divided into three stages: filling, squeezing and pinch-off. The particle concentration has an obvious effect on the squeezing stage, while less impact on the filling and pinch-off stages. In the squeezing stage, the evolution of the dimensionless minimum neck width of bubbles with time could be described by a power-law relationship. The increase of the particle concentration or continuous phase flow rate could lead to the increase of body flow of the continuous phase and the enhancement of the squeezing force acted on the bubble neck, correspondingly, the power-law index α in the squeezing stage enlarges. Moreover, the bubble size increases with the increase of the gas phase flow rate and the decrease of the particle concentration and continuous phase flow rate. However, the effect of the particle concentration on the bubble size weakens with the increase of the continuous phase flow rate. In addition, a new prediction correlation of the bubble size for the slurry system in a T-shape microchannel was proposed with good prediction accuracy.

Dynamic interfacial tension and adsorption kinetics of nonionic surfactants during microfluidic droplet formation process

Surfactant adsorption plays an important role in the microfluidic droplet formation process, which manifested as dynamic interfacial tension phenomenon. Due to rapid droplet expansion and convection flow around the droplet, traditional methods of interfacial tension measurement are difficult to investigate the surfactant adsorption kinetics in microfluidic process. We thus developed a differential pressure based microfluidic platform and proposed an in-situ method to determine time-evolving interfacial tension during microfluidic droplet formation according to Young-Laplace equation in this research. Four classical nonionic surfactants: Triton X-100, Tween 20, Brij 56, and Brij 58 were tested with classical n-octant/water as the working system. The concentrations of these surfactants at interface were further determined from the measured interfacial tension based on Frumkin adsorption model. The adsorption rates of surfactant showed that increasing surfactant concentration in the bulk solution and flow rate of continuous phase both promoted surfactant adsorption in the cases of Tween 20, Brij 56, and Brij 58, indicating the mass transfer-controlled mechanism of adsorption kinetics. The average thickness of mass transfer boundary layer ranged from 0.1 to 5 μm was determined from the mass transfer rate and a correlation equation was proposed to predict the thickness. However, the adsorption mechanism of Triton X-100 turned to be kinetics-controlled for its high critical micelle concentration, which helped to determine the adsorption and desorption rate constants.

Single Microdroplet Breakup-Assisted Viscosity Measurement.

Recently, with the development of biomedical fields, the viscosity of prepolymer fluids, such as hydrogels, has played an important role in determining the mechanical properties of the extracellular matrix (ECM) or being closely related to cell viability in ECM. The technology for measuring viscosity is also developing. Here, we describe a method that can measure the viscosity of a fluid with trace amounts of prepolymers based on a simple flow-focused microdroplet generator. We also propose an equation that could predict the viscosity of a fluid. The viscosity of the prepolymer was predicted by measuring and calculating various lengths of the disperse phase at the cross junction of two continuous-phase channels and one disperse-phase channel. Bioprepolymer alginates and gelatin methacryloyl (GelMA) were used to measure the viscosity at different concentrations in a microdroplet generator. The break-up length of the dispersed phase at the cross junction of the channel gradually increased with increasing flow rate and viscosity. Additional viscosity analysis was performed to validate the standard viscosity calculation formula depending on the measured length. The viscosity formula derived based on the length of the alginate prepolymer was applied to GelMA. At a continuous phase flow rate of 400 uL/h, the empirical formula of alginate showed an error within about 2%, which was shown to predict the viscosity very well in the viscometer. Results of this study are expected to be very useful for hydrogel tuning in biomedical and tissue regeneration fields by providing a technology that can measure the dynamic viscosity of various prepolymers in a microchannel with small amounts of sample.