Volume Fraction Of Dispersed Phase Research Articles

Predicting phase inversion in agitated dispersions with machine learning algorithms

In agitated systems, the phase inversion (PI) phenomenon – the mechanism by which a dispersed phase becomes the continuous one – has been studied extensively in an empirical manner, and few models have been put forward through the years. The underlying physics are still to be fully understood. In this work, the experimental evidence published in literature is used to train machine learning models that may infer the inherent rules that lead to a given dispersion type (O/W or W/O), as well as predict the value of the dispersed phase volume fraction at the edge of the inversion point. Decision trees, bagged decision trees, support-vector machines, and multiple perceptrons are implemented and compared. Results show that it is possible to infer an ensemble of physical rules that explain why a given dispersion is O/W or W/O, where a strong “turbulence constraint” is identified. The intuitive rule that PI occurs at 50% dispersed phase almost never holds. Moreover, neural networks have shown a better performance at predicting the PI point than the other algorithms tested. Finally, a theoretical study is performed in an effort to produce a phase inversion map with the relevant operating variables. This study showed a strong nonlinear effect of the impeller-to-vessel size ratio and an asymmetrical behavior of the interfacial tension on the phase inversion points.

Modeling in food across the scales: towards a universal mass transfer simulator of small molecules in food

Multiscale modeling in food is the cutting-edge strategy to revisit food structure and food composition to meet specific targets such as bioavailability, oral perception, or to evaluate the contamination of food by chemicals. A special implementation of Langevin dynamics is proposed to describe mass transfer in structured food. The concepts of random walks over discrete times and physicochemical interactions are connected via an exact solution of the Fokker–Planck equation across interfaces. The methodology is illustrated on the calculation of effective diffusivities of small solutes in emulsions in relationship with their polydispersity, the volume fraction of dispersed phase d = [0.1, 0.4], the ratio of diffusion coefficients between the two phases, rD = [10−2, 102], and the partition coefficients between the continuous and disperse phases, K = [10−2, + ∞[. Simulated diffusion paths are detailed in 2D emulsions and the effective diffusivities compared with the core–shell model of Kalnin and Kotomin (J Phys A Math Gen 31(35):7227–7234, 1998). The same effects are finally tabulated for 3D emulsions covering the full range of food applications. The methodology is comprehensive enough to enable various extensions such as chemisorption, adsorption in the surfactant layer, local flows, flocculation/creaming.

A rheo-optic study of liquid/liquid systems with varying phases, volume fractions and viscosity ratios

There is a need to understand the rheology and structure of emulsion-based systems under flow, as they determine quality attributes of foods such as texture, stability and taste. However, simultaneous rheo-optical investigations are challenging partially due the limited (and expensive) equipment available. An in-house rheo-optical device has been used to study the effect of shear (steady shear at 250s−1; increasing-decreasing shear at 0-500-0s−1) on rheology and structure of O/W and W/O systems at viscosity ratios (viscosity of dispersed phase over viscosity of continuous phase) λ = 0.2−68 and volume fractions of dispersed phase φ = 0.05−0.3. The O/W and W/O systems had identical ingredients but inversed phases. First, development of the device and its potential to capture clear images under shear is reported. Then, results for O/W systems at steady shear are compared with predictive rheological models, which typically link relative viscosity with φ and λ. The effective medium model showed best agreement. On increasing-decreasing shear, strong link between rheology and structure was indicated. Finally, relative viscosities of the W/O systems were invariably lower than those of the O/W dispersions with similar φ and λ. The related obtained microstructures appeared to be largely determined by drop breakage, controlled by the viscosities of the individual phases rather than λ. This work indicates a close link between rheology and structure for the investigated systems, and it suggests that the link between morphology and viscosity is complex and depends on the nature of the investigated material.

Analysis of immiscible liquid-liquid mixing in stirred tanks by Electrical Resistance Tomography

In this work, the dispersion of diesel fuel in water in a baffled tank stirred by a Rushton turbine is investigated. The impeller speeds corresponding to the initial drawdown, the just dispersed regime and the completely dispersed regime are identified by suitable variables obtained by means of the Electrical Resistance Tomography technique. The effect of the dispersed phase volume fraction and of the impeller off-bottom clearance on the different dispersion regimes is considered. The impeller Froude number, the Archimedes number and a dimensionless distance between the liquid-liquid interface position and the impeller elevation are adopted for the data interpretation. For the investigated system, the local volume fraction profiles show that the completely dispersed condition is practically achieved above the just dispersed impeller speed, with negligible gradients of the local volume fraction distribution in the axial direction.

Subunit composition affects formation and stabilization of o/w emulsions by 11S seed storage protein cruciferin

The 11S globulin cruciferin is the major storage protein in Brassicaceae/Cruciferae seeds and exists as a hexamer in its natural configuration. Arabidopsis thaliana cruciferin is composed of CRUA, CRUB and CRUC subunits. Wild type (WT) cruciferin and cruciferins composed only of identical CRUA, CRUB and CRUC subunits were examined for their ability to form and stabilize oil-in-water (o/w) emulsions. All proteins (0.9% at pH 7.4 and 2.0), except CRUC, formed stable canola oil or triolein emulsions with a dispersed phase volume fraction of 22–23%. A fine emulsion was formed by CRUB at pH 7.4 with droplet sizes of 6.8 and 8.6 μm for canola oil and triolein, respectively. The presence of 0.5 M NaCl reduced the level of adsorbed protein and protein load at the interface at pH 7.4, and resulted in emulsions that were less stable. Emulsions of CRUA and CRUB (pH 7.4, zero ionic strength, canola oil or triolein) had higher stability than emulsions with WT cruciferin up to 15 days after formation. CRUC formed a stable emulsion only at pH 2.0. The low solubility, low surface hydrophobicity and compact structure of the CRUC protein may contribute to its inferior emulsifying properties at neutral pH; however, acidic pH-induced dissociation of the hexameric assembly improved these properties. The abundance and exposure of hydrophobic residues in the hypervariable regions, extended loop regions, and solvent exposed surfaces of cruciferin are critical factors affecting o/w interface stabilization.

Thermal conductivity of emulsion with anisotropic microstructure induced by external field

The structure formation influence on various macroscopic properties of disperse systems is poorly investigated in respect to emulsion systems. The present work deals with the experimental and theoretical study of the heat transfer in emulsions whose dispersed phase droplets are arranged into chain-like structures under the action of external force field. The studied emulsions are of water-in-oil and oil-in-water types; they are based on ferrofluid and contain dispersed phase droplets in a size range of the order of several tens of micrometers. It is demonstrated that the emulsion thermal conductivity grows notably under the effect of external magnetic field parallel to the heat flux and provoking structure formation. It is revealed that the maximal response of thermal conductivity on the magnetic field action takes place at the dispersed phase volume fraction of about 20–30%. The structure formation in magnetic field has been simulated, and the magnetic interactions of emulsion droplets with each other and with the sample boundaries have been considered and discussed. The macroscopic thermal conductivity of structured emulsions has been numerically calculated and compared with experimental data. The obtained results may be of interest in the development of potential applications of controlling the properties of colloids by magnetic field.

Electrical Conductivity of Field-Structured Emulsions

The structure formation influence on various macroscopic properties of fluid–fluid disperse systems is poorly investigated. The present work deals with the experimental study of the charge transfer in emulsions whose dispersed phase droplets are arranged into chainlike structures under the action of an external force field. The emulsions studied are the fluid system in which water droplets are dispersed in a hydrocarbon-based magnetic fluid. Under the effect of an external uniform magnetic field, anisotropic aggregates form from the emulsion dispersed phase drops. The low-frequency electrical conductivity of emulsions has been measured. It is demonstrated that the emulsions’ conductivity grows several times under the effect of magnetic field parallel to the measuring electrical field. The anisotropic character of the emulsion electrical conductivity in the presence of magnetic field has been demonstrated. It is revealed that the maximal response of conductivity on the magnetic field action takes place at the dispersed phase volume fraction of about 20%. The dynamics of the conductivity variation is analyzed in dependence on the magnetic field strength and the dispersed phase volume fraction. The obtained results may be of interest in the development of potential applications of disperse systems with magnetic-field-controllable properties.

The CNT/PSt-EA/Kevlar composite with excellent ballistic performance

This work reports a new type of ballistic composite which is prepared by integrating the carbon nanotube-polystyrene ethyl acrylate (CNT/PSt-EA) based shear thickening fluid (C-STF) with Kevlar fabric. Because the rheological property of the PSt-EA based STF is significantly enhanced by the CNT, the C-STF/Kevlar offers better ballistic property than Kevlar fabric. The ballistic test indicated that the ballistic limit velocity (vbl) of Kevlar could be improved from 84.6 m/s to 96.5 m/s by impregnating the C-STF. Here, the optimum addition of CNT for C-STF/Kevlar is 1.0% and excessive CNT addition reduces the reinforcement effect. Besides, as the volume fraction of dispersed phase in STF increased from 53.5% to 58.5%, the vbl increased from 92.9 m/s to 99.5 m/s. The fabric layer number also plays a critical role in the ballistic property of C-STF/Kevlar. By combining the finite element analysis (FEA) results of ballistic impact with the quasi-static puncture and yarn pull-out results, the enhanced anti-impact mechanism is obtained. It is found that the friction coefficient between the yarns is strengthened and the bearing area of the fabric is increased by doping STFs, thereby the ballistic performance of Kevlar is improved. This work achieves the regulation of ballistic performance of Kevlar composites.

Diesel Emulsion Fuels with Ultralong Stability

Water-in-diesel emulsions have garnered attention in recent years as a potential route to mitigate vehicular pollution. In this work, the formation, flow behavior, and microstructure of water-in-diesel microemulsions using an anionic surfactant, sodium bis(2-ethylhexyl) sulfosuccinate (AOT), is investigated and compared with the water–decane–AOT microemulsion system. Rheological measurements on the microemulsions indicate Newtonian behavior over a moderate range of shear rate. The viscosity of the microemulsions shows a weak dependence on the molar ratio of water-to-surfactant (ω) but increases significantly with the increase in the dispersed phase volume fraction (Φ). Dynamic light scattering (DLS) investigation of the microemulsions indicates a single exponential decay of the intensity autocorrelation functions over a wide range of water and AOT concentrations, indicating that the dispersed phase consists of a monodispersed population of water droplets. Results suggest that optimizing ω can regulate the...

The influence of emulsion parameters on physical stability and rheological properties of Pickering emulsions stabilized by hordein nanoparticles

In this study, the effect of pH (3–8), ionic strength (I, 0.01–1 M), protein particle concentration (C, 0.5%–2%), and dispersed phase volume fraction (Φ, 0.25–0.8) on the efficacy of hordein-based colloidal nanoparticles in the stabilization of Pickering structures was investigated. Colloidal particles were synthesized via anti-solvent method. Depending on pH and I, the average size and zeta-potential of hordein particles ranged from 425 to around 4000 nm, and +27.5 to −15.63 mV, respectively. The intense aggregation of particles at pH close to isoelectric point and also at high I led to poor formation and stability of Pickering emulsions. The overrun value was influenced by various emulsion parameters. At pH 3, triphasic (with the overrun value of 75%) and high internal phase (HIP) emulsions with an average droplet size of 15.6–86.7 μm were formed at Φ 0.25 and 0.8, respectively. At Φ 0.5 and 0.8, an elastic gel-like behavior (i.e., storage modulus (G′) > loss modulus (G″)) was observed over the applied frequency range. At Φ 0.25, a predominant viscous character (G">G′) was observed at low frequencies; while, at higher frequencies, G′ exceeded G″ due to the foam collapse. The morphology was studied by optical microscopy and confocal laser scanning microscopy (CLSM). Monitoring the physical stability using static multiple light scattering (MLS) revealed three destabilization profiles of foam-like, emulsion-foam and gel-like structures. The results of this study might help in designing triphasic Pickering systems (using plant-based proteins) and developing solid-like structured vegetable oils from the gel-like HIP emulsions.

The impact of lipases on the rheological behavior of colloidal silica nanoparticle stabilized Pickering emulsions for biocatalytical applications

The use of Pickering emulsions for biocatalytical applications has recently received increased attention in cases where hydrophobic reactants are involved. For process applications, knowledge of the emulsion’s rheology is crucial for the fluid dynamical design of equipment and selection of operating conditions. Colloidal silica nanoparticle stabilized Pickering emulsions usually exhibit shear-thinning behavior caused by a complex particle-particle network. While this has been observed by many authors, no publication has yet dealt with the rheology of silica nanoparticle stabilized Pickering emulsions containing enzymes. Thus, the aim of this study was to investigate the impact of the commonly used biocatalyst lipase (type and concentration), the dispersed phase volume fraction and the silica particle concentration on the rheological behavior of water-in-oil Pickering emulsions. For this purpose, the impact of the named parameters on the viscosity curves were measured. Lipases reduced the viscosities and transferred the rheological behavior from shear-thinning to Newtonian, which might be due to interactions of the lipase molecules via the formation of intermolecular disulfide bonds, which disturb the hydrogen-bond based silica particle-particle network. However, by increasing the dispersed phase volume fraction or the silica particle concentration the rheological behavior of emulsions became again shear-thinning. This work will help to produce bioactive Pickering emulsions with tailor-made characteristics.

Mass transfer coefficients of extracting Mo (VI) and W (VI) in a stirred tank by solvent extraction using mixture of Cyanex272 and D2EHPA

ABSTRACT In this study, the mass transfer evaluation of an agitated liquid-liquid system for the extraction of molybdenum and tungsten from aqueous sulfate solution was investigated. It was found from batch experiments for separation of molybdenum from tungsten that the initial aqueous pH, Cyanex272 and D2EHPA concentration, contact time, dispersed phase volume fraction and impeller speed were optimized at 1.3, 0.07 M, 0.29 M, 15 min, 0.09 and 280 rpm, respectively. The results indicate that a suitable composition for stripping is 1.5 M NH4OH and 0.6 M NH4F. Furthermore, a modified correlation based on dimensionless numbers was derived for the prediction of continuous phase mass transfer in the stirred tank with the presence of reactive extraction conditions.

A population balance model for large eddy simulation of polydisperse droplet evolution

In the context of many applications of turbulent multi-phase flows, knowledge of the dispersed phase size distribution and its evolution is critical to predicting important macroscopic features. We develop a large eddy simulation (LES) model that can predict the turbulent transport and evolution of size distributions, for a specific subset of applications in which the dispersed phase can be assumed to consist of spherical droplets, and occurring at low volume fraction. We use a population dynamics model for polydisperse droplet distributions specifically adapted to a LES framework including a model for droplet breakup due to turbulence, neglecting coalescence consistent with the assumed small dispersed phase volume fractions. We model the number density fields using an Eulerian approach for each bin of the discretized droplet size distribution. Following earlier methods used in the Reynolds-averaged Navier–Stokes framework, the droplet breakup due to turbulent fluctuations is modelled by treating droplet–eddy collisions as in kinetic theory of gases. Existing models assume the scale of droplet–eddy collision to be in the inertial range of turbulence. In order to also model smaller droplets comparable to or smaller than the Kolmogorov scale we extend the breakup kernels using a structure function model that smoothly transitions from the inertial to the viscous range. The model includes a dimensionless coefficient that is fitted by comparing predictions in a one-dimensional version of the model with a laboratory experiment of oil droplet breakup below breaking waves. After initial comparisons of the one-dimensional model to measurements of oil droplets in an axisymmetric jet, it is then applied in a three-dimensional LES of a jet in cross-flow with large oil droplets of a single size being released at the source of the jet. We model the concentration fields using $N_{d}=15$ bins of discrete droplet sizes and solve scalar transport equations for each bin. The resulting droplet size distributions are compared with published experimental data, and good agreement for the relative size distribution is obtained. The LES results also enable us to quantify size distribution variability. We find that the probability distribution functions of key quantities such as the total surface area and the Sauter mean diameter of oil droplets are highly variable, some displaying strong non-Gaussian intermittent behaviour.

Droplet–turbulence interactions and quasi-equilibrium dynamics in turbulent emulsions

We perform direct numerical simulations (DNS) of emulsions in homogeneous isotropic turbulence using a pseudopotential lattice-Boltzmann (PP-LB) method. Improving on previous literature by minimizing droplet dissolution and spurious currents, we show that the PP-LB technique is capable of long stable simulations in certain parameter regions. Varying the dispersed-phase volume fraction$\unicode[STIX]{x1D719}$, we demonstrate that droplet breakup extracts kinetic energy from the larger scales while injecting energy into the smaller scales, increasingly with higher$\unicode[STIX]{x1D719}$, with approximately the Hinze scale (Hinze,AIChE J., vol. 1 (3), 1955, pp. 289–295) separating the two effects. A generalization of the Hinze scale is proposed, which applies both to dense and dilute suspensions, including cases where there is a deviation from the$k^{-5/3}$inertial range scaling and where coalescence becomes dominant. This is done using the Weber number spectrum$We(k)$, constructed from the multiphase kinetic energy spectrum$E(k)$, which indicates the critical droplet scale at which$We\approx 1$. This scale roughly separates coalescence and breakup dynamics as it closely corresponds to the transition of the droplet size ($d$) distribution into a$d^{-10/3}$scaling (Garrettet al.,J. Phys. Oceanogr., vol. 30 (9), 2000, pp. 2163–2171; Deane & Stokes,Nature, vol. 418 (6900), 2002, p. 839). We show the need to maintain a separation of the turbulence forcing scale and domain size to prevent the formation of large connected regions of the dispersed phase. For the first time, we show that turbulent emulsions evolve into a quasi-equilibrium cycle of alternating coalescence and breakup dominated processes. Studying the system in its state-space comprising kinetic energy$E_{k}$, enstrophy$\unicode[STIX]{x1D714}^{2}$and the droplet number density$N_{d}$, we find that their dynamics resemble limit cycles with a time delay. Extreme values in the evolution of$E_{k}$are manifested in the evolution of$\unicode[STIX]{x1D714}^{2}$and$N_{d}$with a delay of${\sim}0.3{\mathcal{T}}$and${\sim}0.9{\mathcal{T}}$respectively (with${\mathcal{T}}$the large eddy timescale). Lastly, we also show that flow topology of turbulence in an emulsion is significantly more different from single-phase turbulence than previously thought. In particular, vortex compression and axial straining mechanisms increase in the droplet phase.

Droplet size distribution and mixing hydrodynamics in a liquid–liquid stirred tank by CFD modeling

Stirred tanks are the common unit operations employed for liquid–liquid dispersion in many industries. In this study, computational fluid dynamic (CFD) coupled with population balance modeling (PBM) were applied to simulate mixing of water in crude oils in a stirred tank equipped with Rushton turbine. An Eulerian multiphase model and standard k-ε turbulence model were employed to simulate the flow field inside the tank. Experimental results were then used to validate simulation results. The effect of impeller speed, volume fraction of dispersed phase, and oil viscosity on droplet size distribution were investigated in this work. An increase in agitation speed was found to decrease the mean and Sauter mean diameter while increasing the homogeneity of the system. A wider droplet size distribution profile was achieved at higher oil volume fractions with almost no significant change in droplet size. Additionally, increasing the viscosity of the oil phase resulted in a gradual shift towards smaller droplets and narrower droplet size distribution. Liquid–liquid dispersions were occurred in two different turbulent regimes depending on the viscosity of continuous phase. Related correlations for each regime were obtained and the values of maximum droplet size were fitted with the dimensionless numbers.

Effect of lipid type, dispersed phase volume fraction and emulsifier on the physicochemical properties of nanoemulsions fortified with conjugated linoleic acid (CLA): Process optimization and stability assessment during storage conditions

Conjugated linoleic acid (CLA) although gains recognition as food supplement due to various physiological activities, its water insolubility and oxidative instability limit its applications in food systems. Oil-in-water nanoemulsions based on extra virgin olive (EVOO) or pomace oil (OPO) are considered excellent delivery systems offering high protection and controlled release of CLA. In the present study, CLA-loaded nanoemulsions were prepared using ultrasonic homogenization approach and the effect of storage temperature (25 °C or 4 °C) on the nanoemulsion physical and chemical stability was investigated. All formulations demonstrated good long-term physical and chemical stability; mean droplet diameter <300 nm during 60 days-storage (4 °C and 25 °C). CLA degradation (RCLA %) was lower in the nanoemulsions with 8 wt% lipid phase; specifically, nanoemulsions with 8 wt% olive pomace oil and 6 wt% Tween 20 (RCLA = 80.154% at 25 °C and RCLA = 84.165% 4 °C) after 2 months. Response surface methodology was used to optimize the preparation conditions (type and concentration of lipid phase and emulsifier) at different storage conditions and predict the optimum values of mean droplet diameter, ζ-potential and CLA retention. The minimum lipid concentration (4 wt%) exhibited the optimum values at both environment and refrigerated storage for EVOO nanoemulsions. However, nanoemulsion with 8 wt% OPO and 4 wt% Tween 40 (71.843% at 25 °C) or 6 wt% Tween 20 were the optimum condition regarding the highest chemical stability.

Using the full turbulence spectrum for describing droplet coalescence and breakage in industrial liquid-liquid systems: Experiments and modeling

A generalized model for breakage and coalescence kernels valid for the entire spectrum of turbulence is proposed and validated. Most of the available kernels in the literature indeed assume that in a turbulent liquid-liquid dispersion, the dispersed droplets have dimension in the inertial subrange, and are affected by eddies with size in the same subrange. These kernels are based on the Kolmogorov second-order structure function, which is valid only in the inertial subrange. However, in most industrially encountered situations, many droplets may have a size in the dissipation range, where the Kolmogorov second-order structure function does not apply. Therefore, a more general description of the energy transferred between these droplets and the turbulent eddies is needed to properly model breakage and coalescence events.In this work, the Coulaloglou and Tavlarides (1977) breakage and coalescence kernels have been modified through the implementation of the second-order structure function proposed by Davidson (2004), along with the Pope (2000) energy spectrum. Turbulent liquid-liquid dispersion experiments at high continuous phase viscosity are performed to test and validate the model. The generalized model is able to predict the experimental Sauter mean diameters at different viscosities, turbulent conditions and dispersed-phase volume fraction without any adjustment of the kernel parameters.

Macroporous scaffolds of cross-linked Poly(ɛ-caprolactone) via high internal phase emulsion templating

A high internal phase emulsion based ring-opening polymerization (HIPE-ROP) of ɛ-caprolactone (CL) was conducted to fabricate macroporous scaffold in a single-step. An oil-in-oil HIPE of CL was formed using high molecular weight olefin (C10-C16) dispersed in continuous medium comprised of CL, a bifunctional cross-linking monomer bis-ɛ-caprolactone-4-yl (BCY) and catalyst stannous octoate (Sn(Oct)2). The emulsion was stabilized using nonionic surfactant, pluronic F127 and polymerization was conducted at 120 °C without any inert atmosphere for a period of 8 h. Complete monomer conversion and cross-linking was achieved and am acroporous scaffold of desired shape was obtained, having in-situ generated porosity and interconnected pores. All chemicals were purposely used without any purification and the high temperature process prevented deactivation of catalyst. The HIPE-ROP developed in this way was found to be highly feasible for conducting otherwise moisture sensitive organo-metallic catalyst based ROP. The morphology of HIPE was directly transferred to macroporous structure of the scaffold in this process where pore size was reproducibly controlled by variation in volume fraction of dispersed phase and cross-link density. The resultant macroporous scaffold showed superior compressive loading and swelling capacity. The porous scaffolds also exhibited excellent osteoblast (MG63) attachment and proliferation. HIPE-ROP based macroporous scaffold of cross-linked PCL thus developed paved a new route to create porous scaffolds of aliphatic polyesters in a single step. The method also reflected high commercial viability by potential conversion into a continuous process.

Axial dispersion and CFD models for the extraction of levulinic acid from dilute aqueous solution in a Kühni column with 2-methyltetrahydrofuran solvent

1D axial dispersion and 3D CFD models for the extraction of levulinic acid from dilute aqueous solution by applying 2-methyltetrahydrofuran as a solvent are presented. The models are validated by comparison with the measured levulinic acid concentration profile data obtained in a bench-scale Kühni column. The 1D model contains NRTL parameters for the system levulinic acid-water-2MTHF. Correlations for drop size and hold-up for Kühni columns were taken from literature. The values for overall mass transfer coefficient ranged from 1.4E-5 to 2.2E-5 ms−1, and increased as a function of the rotor speed. The fitting of the column performance resulted in a very good prediction of the solute concentration profiles in the extraction column, and the average absolute value of relative error for the 1D model was 23%. CFD model visualized the column performance at the column height of 150.5–160 cm giving valuable information on back mixing, phase velocities, dispersed phase volume fraction, and mass transfer. Dispersed phase volume fraction and mass transfer contours revealed, that the mass transfer rate (app. 0.25 g L−1s−1) is at its highest just below the rotor, and that there are blind spots in the compartments close to the extractor and just above each down comer. Values for the dispersed phase volume fraction are highest in the same area where the mass transfer reaches the highest values. The highest slip velocity values (app. 0.03 m−1) are located in the tip of each compartment partition plates.General correlations, such as hold-up and drop size correlations, can successfully be applied in levulinic acid-water-2MTHF system reported in this work. The 1D axial dispersion model proved to be valuable tool for scale-up purposes, and CFD model, despite the long time needed for each simulation, gave useful information for the design purposes.

Formation and stability of W/O-high internal phase emulsions (HIPEs) and derived O/W emulsions stabilized by PGPR and lecithin.

Water-in-oil high internal phase emulsions (HIPEs) can provide interesting textures that could be used to reduce trans- and/or saturated fat content in food products. On the other hand oil-in-water emulsions can be found in a variety of food and beverages. Moreover, strategies aiming synthetic or semi-synthetic ingredients replacement by natural alternatives for food applications has been pursuit. For these purposes, the effect of partial replacement of PGPR by lecithin on properties of either W/O-HIPEs or O/W emulsions manufactured from the same initial composition but showing different volume fraction of dispersed phase were investigated aiming to understand the behaviour of emulsifiers' mixture in water-oil or oil-water interfaces. Firstly, water-in-oil HIPEs were produced using a rotor-stator device. At fixed total amount of emulsifier (2% w/w), W/O emulsions stabilized with LEC:PGPR ratios of 0.5:1.5 and 1.0:1.0 showed similar droplet size with a better kinetic stability compared to emulsions containing only PGPR. These results indicated good interaction between LEC and PGPR, which was also confirmed by dynamic interfacial tension profile and interfacial dilational rheology. In order to reduce the droplet size of W/O-HIPEs, these emulsions were subsequently subjected to high-pressure homogenization and interestingly phases inversion was observed. Confocal microscopy confirmed the phases inversion attributed to high input of energy leading to the formation of O/W emulsions. Then both W/O-HIPEs and O/W emulsions were investigated regarding LEC:PGPR mixtures as emulsifiers. All W/O-HIPEs showed shear thinning behavior and high viscosity at low shear rate whereas O/W emulsions showed low viscosity and Newtonian behavior. The increase of lecithin content in emulsifier mixture led to more stable O/W emulsions, whereas more stable W/O-HIPEs were produced by lecithin and PGPR mixtures ratio of 0.5:1.5 and 1.0:1.0.