Droplet Size Of Dispersed Phase Research Articles

Predicting Human Dermal Drug Concentrations Using PBPK Modeling and Simulation: Clobetasol Propionate Case Study

Quantitative in silico tools may be leveraged to mechanistically predict the dermato-pharmacokinetics of compounds delivered from topical and transdermal formulations by integrating systems of rate equations that describe permeation through the formulation and layers of skin and pilo-sebaceous unit, and exchange with systemic circulation via local blood flow. Delivery of clobetasol-17 propionate (CP) from DermovateTM cream was simulated using the Transdermal Compartmental Absorption & Transit (TCATTM) Model in GastroPlus®. The cream was treated as an oil-in-water emulsion, with model input parameters estimated from publicly available information and quantitative structure-permeation relationships. From the ranges of values available for model input parameters, a set of parameters was selected by comparing model outputs to CP dermis concentration-time profiles measured by dermal open-flow microperfusion (Bodenlenz et al. Pharm Res. 33(9):2229–38, 2016). Predictions of unbound dermis CP concentrations were reasonably accurate with respect to time and skin depth. Parameter sensitivity analyses revealed considerable dependence of dermis CP concentration profiles on drug solubility in the emulsion, relatively less dependence on dispersed phase volume fraction and CP effective diffusivity in the continuous phase of the emulsion, and negligible dependence on dispersed phase droplet size. Effects of evaporative water loss from the cream and corticosteroid-induced vasoconstriction were also assessed. This work illustrates the applicability of computational modeling to predict sensitivity of dermato-pharmacokinetics to changes in thermodynamic and transport properties of a compound in a topical formulation, particularly in relation to rate-limiting steps in skin permeation. Where these properties can be related to formulation composition and processing, such a computational approach may support the design of topically applied formulations.

CFD-PBE Simulation of Flow Dynamics and Mass Transfer in Two-Stage Countercurrent Mixer-Settler

Flow condition and mass transfer behavior of liquid–liquid extraction in a two-stage countercurrent extractor are investigated experimentally and numerically. CFD-PBE simulation is adopted to analyze the impact of operating parameters, including impeller speed, residence time, and organic-aqueous ratio of feed flow on volume fraction and droplet size of dispersed phase and volumetric mass transfer coefficient. Droplet size distribution is calculated by considering breakage and coalescence of dispersed phase. The allocation of dispersed phase between stages is found to be determined by impeller speed. Meanwhile, the allocation of dispersed phase between mixers and settlers is governed by residence time and organic-aqueous ratio of feed flow. Turbulence intensity, volume fraction, and droplet size distribution are revealed to be dominating parameters that affect the spatial nonuniform distribution of volumetric mass transfer coefficient. The mass transfer rate can be improved by increasing impeller speed in two stages. Higher residence time and organic-aqueous ratio of feed flow, however, have opposite effects on mass transfer rate in stage-1 and stage-2.

CFD modeling of the turbulent dispersion of liquid droplets in a vessel using a correlation based on local droplet size distribution

Macro-mixing of two immiscible liquid in a stirred tank is strongly influenced by the turbulence generated due to the rotating impeller, consequently affecting the dispersion of the formed liquid droplets. The present study conducted a CFD numerical analysis on the liquid-liquid mixing in a stirred tank that has adopted the Rushton turbine impeller based on the Eulerian-Eulerian approach, coupled with a local turbulence and empirical equations-based dispersed phase droplet size correlation. The simulation results have clearly demonstrated that the proposed local droplet size distribution correlation can well model the distribution of dispersed phase drops in the stirred tank comparing with the experimental data and the results published in the open literature. In particular, it has been found that CFD modeling coupled with the proposed size distribution correlation can reasonably predict dispersed phase volume fraction above the impeller region and the salient characteristics of liquid-liquid macro-mixing in the tank. The likely mechanism that controls the droplet size distribution was also discussed.

Development of Ficus religiosa extract-loaded emulsion system for topical application: Characterization and stability evaluation

Purpose: To develop, optimize and characterize a topical (W/O) emulsion containing 4 % Ficus religiosa extract for cosmeceutical purposes.
 Methods: The ethanol extract of Ficus religiosa was obtained by Soxhlet method. Various formulations were developed using paraffin oil, emulsifier (Abil®-EM 90) and purified water at different proportions, and their physical stability was assessed under different stress conditions, to enable selection of the most stable formulation. The optimized formulation based on stability studies was chosen for evaluation of different physical properties, i.e., color, liquefaction, phase separation, centrifugation, pH, droplet size and rheology, under accelerated conditions for 12 weeks.
 Results: The optimized formulation (F4) contained ethanol extract (4.0 %), Abil®-EM 90 (3.5 %), paraffin oil (14.0 %) and purified water (78.5 %), and remained stable on centrifugation under all stress conditions. The pH of the formulation remained within the specified range for human skin pH i.e. 4.5 – 6.0, and droplet size of dispersed phase also persisted within the size range of macroemulsion (1 – 100 μm) throughout the study period. Rheological properties of the formulation showed shear thinning response, and flow index value less than 1 resulted in pseudoplastic flow of emulsion.
 Conclusion: These results suggest that the optimized emulsion system was stable and can serve as a good medium for topical delivery of various natural substances.

Modeling and experimental data of the flow of highly concentrated emulsions in porous media

This paper gives a theoretical model which allows to predict changes of the blockade of the porous bed during the flow of non-Newtonian emulsions. It takes into account much more process and material parameters than the formulas published in the literature till now: like size of dispersed phase droplets, emulsion concentration and rheological parameters of heterogeneous, non-Newtonian liquid. Using the model it is also possible to predict changes of bed permeability, its blockade, as a result of oil droplets capture. Model calculations were verified with experimental data and satisfactory correctness was obtained. The work contributes to the development of the description of the transport of multiphase substances, with complex rheological properties, through porous structures. The results of the research may find practical application during the development of methods of intensifying oil production, as well as the assessment of the penetration of complex pharmaceuticals in dermal structures.

Effect of Composition and Interfacial Tension on the Rheology and Morphology of Heavy Oil-In-Water Emulsions.

Rheological and morphological properties of heavy crude oil-in-water (O/W) emulsions have been studied. Two series of emulsions were considered: first, the surfactant type remained constant, while the continuous phase content was varied and second, the surfactant type was varied while the continuous phase content remained constant. Under stress-controlled shearing, all samples exhibit viscoplastic behavior. The rheological properties are directly related to the morphology of the emulsions which vary in size of dispersed phase droplets and their inherent structure. Adding a surfactant characterized by a high value of interfacial oil–water tension results in a decrease in the yield stress (which is a measure of the interparticulate structure strength). The same effect is attained by increasing the water content. Meanwhile, these two factors determine the viscosity which can be much lower than that of the basic heavy crude oil if the O/W type of emulsions has been created. Special attention was paid to the viscoelastic properties which have been scarcely reported. Correlations were found between the surfactant properties, composition of the emulsion, and rheological characteristics of emulsions (yield stress, apparent viscosity, and viscoelastic properties), which allows for reduction in the crude oil viscosity down to a low enough level acceptable for pipe transportation.

An investigation of the droplet size distributions in a cyclone reactor for liquid‐liquid heterogeneous reactions using FBRM and PVM

AbstractA multi‐element process coupled cyclone reactor for the liquid‐liquid heterogeneous reaction was proposed. This paper presents the investigation of dispersed phase droplet size distributions near the wall surface using FBRM and PVM. To translate a chord length distribution (CLD) measured by the FBRM instrument into its droplet size distribution (DSD), a CLD‐DSD transformation model was proposed. Moreover, the effects of operational parameters on the droplet size distributions were studied. The results show that the total inlet flow plays a decisive role on the dispersed phase droplet size distributions, while the influence of feed ratio is mainly reflected in inhibiting the probability of droplet coalescence. In comparison, the influence of overflow ratio on the droplet size distributions can be neglected.

Material properties of cocoa butter emulsions: Effect of dispersed phase droplet size and compression speed on mechanical response

Water-in-cocoa butter (CB) emulsions material properties were investigated using uniaxial compression test. Emulsions containing 20% (wt%) water and with a range of droplet size were manufactured to assess the role of defect size on emulsions mechanical properties. Although differences were not significant within the tested droplet size range, results showed a decreasing trend in the values of mechanical parameters at fracture with increasing structural defect size. The mechanical response of bulk CB and emulsions was also investigated at different compressive rates. Materials visco-elastic behaviour was confirmed by their strain-hardening behaviour at increasing test speed with bulk CB always displaying the highest mechanical strength. In the light of these results and microscopy evidences, it was hypothesised that droplets are only partially bonded to the CB network therefore playing a stress-concentration role by promoting fracture initiation. The addition of water droplets also resulted in a reduction of the overall network internal degree of connectivity: when large deformations are applied, droplet-matrix de-bonding occurs at the particle-fat network interface promoting fracture propagation and thus explaining the weakening structural effect of droplets.

CFD–PBM simulation of two-phase flow in a pulsed disc and doughnut column with directly measured breakup kernel functions

The pulsed disc and doughnut column (PDDC) is a widely used type of liquid–liquid extraction equipment. Both the research and design of this type of equipment require in-depth knowledge of the dispersed phase droplet size distribution (DSD). The coupling of computational fluid dynamics (CFD) and population balance model (PBM) has exhibited a significant potential for predicting the DSD by considering droplet breakage and coalescence. In the present work, the CFD–PBM simulation is adopted to predict the DSD, and to investigate local liquid–liquid flow behaviors in a square-sectioned PDDC. The empirical correlations of the breakup kernels, which are based on our previous work [Hao Zhou et al., Direct measurement of droplet breakage in a pulsed disc and doughnut column. AIChE Journal, 2017, 63(9), 4188–4200], are implemented in the CFD code. For comparison, the kernel functions obtained by Coulaloglou and Tavlarides [Coulaloglou and Tavlarides. Description of interaction processes in agitated liquid–liquid dispersions. Chemical Engineering Science, 1977, 32, 1289–1297] are also tested. The class method with the fixed pivot technique is utilized to solve the population balance equations. The droplet size distribution predicted by the CFD–PBM simulation combined with the kernel functions that we have previously determined experimentally are observed to be more precise than those of Coulaloglou and Tavlarides. Accordingly, the CFD–PBM simulation results with the kernel functions of our proposed correlations are used to investigate the liquid–liquid flow behaviors in the PDDC. The influences of droplet size range and initial droplet size distribution at the dispersed phase inlet in the predicted DSD are discussed. The hydraulic performance of simulation results agrees well with experimental data. Local flow behaviors are illustrated to depict the typical flow characteristics of PDDC. The simulation results suggest that CFD–PBM method with the proposed PBM kernel functions is a promising approach for the simulation of liquid–liquid flow in the PDDC.

Peculiarities of rheological behavior of highly concentrated water-in-oil emulsion: The role of droplet size, surfactant, oil and ammonium nitrate content

An investigation was performed into the rheological behavior of highly concentrated water-in-oil emulsion (HCE). The experimental results show that HCE behaves as a shear-thinning fluid and there are two platforms in the flow curve. But, the second platform at high shear rate region can't be observed with the increase of the intensity of interaction between droplets caused by the decrease of the size of dispersed phase droplets. The recovery capacity of HCE underwent shear was affected by the size of dispersed phase droplets. Relatively strong resilience was observed when the droplet size of dispersed phase was small. However, the recovery capacity of HCE underwent oscillation was not affected by the droplet size. The nature of surfactant, oil and the AN content of dispersed phase have important effect on the rheology of HCE. The plateau zone of storage modulus goes to a higher level when the blended surfactant used as surfactant. There is optimal oil viscosity region within which the higher G' can be formed. The G′ of HCE decreases obviously, while the oil-water interfacial tension decreases. The G′ decreases with the increase of the concentration of ammonium nitrate.

A novel liquid-liquid cyclone reactor for ionic liquid catalyzed isobutane alkylation: Cold model investigation of the dispersed phase droplet size distribution

A novel liquid-liquid cyclone reactor for ionic liquid catalyzed isobutane alkylation: Cold model investigation of the dispersed phase droplet size distribution

Lightweight micro-cellular plastics from polylactide/polyolefin hybrids

Abstract Semi-crystalline polylactide (PLA)/polyolefin multi-component blends were used as precursors for the generation of a new class of micro-cellular polymers. Either a polypropylene-based elastomer (PBE) or polypropylene (PP) homopolymer were utilized as dispersed phases at the 10 wt% level. An epoxy-functionalized terpolymer (PEGMMA) was introduced (1 wt%) as a reactive compatibilizer to reduce the dispersed phase droplet size and provide sufficient adhesion between the matrix and dispersed phase. In addition, a polyalkylene glycol liquid (PAG) was added to the blend (4 wt%) to serve as a PLA plasticizer and interfacial modifier. The multicomponent blends exhibited significant increases in strain at break as compared to neat PLA and were subjected to a range of uniaxial strains (10–90%) at room temperature. These cold drawn materials exhibited nearly constant cross-sectional area and fine micro-cellular structures, as revealed by scanning electron microscopy. Distinct different voiding mechanisms observed for the PBE- and PP-containing blends were ascribed to the differences in the dispersed phase elastic moduli and deformability. The material density of cold drawn blends was reduced by up to 34% when compared to the precursor blends without a noticeable change in cross-sectional area. The novel low-density microcellular PLA blends demonstrated outstanding mechanical properties such as high strength, high modulus, substantial ductility, and a 14-fold increase in impact resistance as compared to PLA homopolymer.

Reinforcement of polyolefins-based nanocomposites: combination of compatibilizer with high shear extrusion process

The structure and properties of polypropylene (IPP) and ethylene propylene copolymer (IEPR) blends filled with nanosilica have been investigated. The nanocomposites were prepared via direct melt mixing using high shear corotating twin screw extruder. The effects of the process as well as adding amaleated-Polyethylene MAPE compatibilizer were assessed by morphology studies, thermal analysis and mechanical testing. From SEM and TEM investigations, a separate dispersion of filler and rubber in the PP matrix prevails in the PP/EPR/SiO2 systems. Encapsulation of the filler particles into the elastomer takes place when MAPE is used, promoting filler/polymer interactions and resulting in a simultaneous improvement in stiffness and toughness. Interestingly, the results indicated that high-shear processing is an effective method to improve the dispersion of the EPR phase and fillers through the matrix. The dispersed phase droplet size was reduced with the increase of the shear rate by varying the screw rotation speed from 300 to 800 rpm, which induces a high shear stress exerted onthe materials. To sum up, what is expected from an efficient compatibilization-process association is the reduction of the dispersed elastomer domains characteristic size, their stabilization by creation of an interphase and thus, enhanced mechanical properties.

Pressure drop reduction of stable water-in-oil emulsions using organoclays

In this study, the influence of organoclays (OC) on the pressure drop of surfactant-stabilized water-in-oil (W/O) emulsions was studied. OC were tested as pressure loss reducing agents for stable W/O emulsions with 0.7 (concentrated) and 0.3 (diluted) water volume fractions. Pressure drop measurements were conducted in horizontal pipes with inside diameters (ID) of 0.0254-m and 0.0127-m. The results showed a significant reduction in the emulsion viscosity with the addition of OC and this effect was enhanced as the concentration increased. In addition, for the case of concentrated W/O emulsions, the addition of OC resulted in 25% reduction in the emulsion pressure drop in both test sections. For diluted W/O emulsion with only 0.3 water fraction, while no pressure drop reduction was observed in the laminar region, it was detected in the turbulent region and such effect was pronounced at high Reynolds numbers and high OC concentration. The observed results were explained in terms of emulsion dispersed phase droplet size. In the laminar regime, the friction factor for stable W/O emulsions was in a good agreement with single phase predictions. However, in the turbulent regime the friction factor for the multiphase system was below the predictions of single phase flow. OC proved to have a good potential as drag reducing agents by producing smaller and stable emulsion droplets hence suppressing the Reynolds' stresses.

Dynamic Network Model of Mobility Control in Emulsion Flow Through Porous Media

Modeling the flow of emulsion in porous media is extremely challenging due to the complex nature of the associated flows and multiscale phenomena. At the pore scale, the dispersed phase size can be of the same order of magnitude of the pore length scale and therefore effective viscosity models do not apply. A physically meaningful macroscopic flow model must incorporate the transport of the dispersed phase through the porous material and the changes on flow resistance due to drop deformation as it flows through pore throats. In this work, we present a dynamic capillary network model that uses experimentally determined pore-level constitutive relationships between flow rate and pressure drop in constricted capillaries to obtain representative transient macroscopic flow behavior emerging from microscopic emulsion flow at the pore level. A parametric analysis is conducted to study the effect of dispersed phase droplet size and capillary number on the flow response to both emulsion and alternating water/emulsion flooding in porous media. The results clearly show that emulsion flooding changes the continuous-phase mobility and consequently flow paths through the porous media, and how the intensity of mobility control can be tuned by the emulsion characteristics.

Morphology study of immiscible polymer blends in a vane extruder

AbstractThis study reports the morphology development of polymer blends in a novel vane extruder in which polymer mainly suffers from elongational deformation field. Rapidly cooled samples of polypropylene/polystyrene (PP/PS) are collected in the vane extruder after stable extrusion. Furthermore, the shape and size of the dispersed phase from initial to final stages are analyzed. In addition, in order to compare the final size of the dispersed phase, different immiscible blends, including polypropylene/polyamide and PP/PS, are prepared by vane extruder and twin‐screw extruder, respectively. The results show that the dispersed phase is made to change rapidly from stretched striations to droplets under the strong elongational deformation field in the vane extruder. Furthermore, the droplet size of dispersed phase of blends prepared by vane extruder is much smaller than that prepared by twin‐screw extruder, indicating that the vane extruder is more efficient in mixing for immiscible polymer blends. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

A simplified model of direct-contact heat transfer in desalination system utilizing LNG cold energy

With the increasingly extensive utilization of liquefied natural gas (LNG) in China today, sustainable and effective using of LNG cold energy is becoming increasingly important. In this paper, the utilization of LNG cold energy in seawater desalination system is proposed and analyzed. In this system, the cold energy of the LNG is first transferred to a kind of refrigerant, i.e., butane, which is immiscible with water. The cold refrigerant is then directly injected into the seawater. As a result, the refrigerant droplet is continuously heated and vaporized, and in consequence some of the seawater is simultaneously frozen. The formed ice crystal contains much less salt than that in the original seawater. A simplified model of the direct-contact heat transfer in this desalination system is proposed and theoretical analyses are conducted, taking into account both energy balance and population balance. The number density distribution of two-phase bubbles, the heat transfer between the two immiscible fluids, and the temperature variation are then deduced. The influences of initial size of dispersed phase droplets, the initial temperature of continuous phase, and the volumetric heat transfer coefficient are also clarified. The calculated results are in reasonable agreement with the available experimental data of the R114/water system.

Study on Propylene Recovery in a Dispersed Absorption System-(Water-in-Oil) Emulsion System

The purpose of the paper is to investigate propylene recovery by a new absorption system, namely water-in-oil emulsion absorbent. Water in oil emulsion, in which kerosene used as oil phase with dispersed water droplet, is prepared to be as absorbent to absorb propylene. The effect of volume fraction dispersed phase, dispersed droplet size, and the stirring rate on propylene absorption rate are researched. Experimental results indicate that the absorption rate of propylene can increase 20% compared with traditional absorption method. The volume fraction dispersed phase should be appropriate, otherwise the enhancement absorption can not be attained. The appropriate number is 0.05 for this dispersion. The smaller droplet size of dispersed phase as well as the faster stirring rate can increase the propylene absorption rate. The mechanism of enhancement propylene absorption is attributed to the intensive turbulence in boundary layer between gas and liquid due to the movement of dispersed water droplets.

Experiments and network model of flow of oil-water emulsion in porous media

Transport of emulsions in porous media is relevant to several subsurface applications. Many enhanced oil recovery (EOR) processes lead to emulsion formation and as a result conformance originating in the flow of a dispersed phase may arise. In some EOR processes, emulsion is injected directly as a mobility control agent. Modeling the flow of emulsion in porous media is extremely challenging due to the complex nature of the associated flows and numerous interfaces. The descriptions based on effective viscosity are not valid when the drop size is of the same order of magnitude as the pore-throat characteristic length scale. An accurate model of emulsion flow through porous media should describe this local change in mobility. The available filtration models do not take into account the variation of the straining and capturing rates with the local capillary number. In this work, we present experiments of emulsion flow through sandstone cores of different permeability and a first step on a capillary network model that uses experimentally determined pore-level constitutive relationships between flow rate and pressure drop in constricted capillaries to obtain representative macroscopic flow behavior emerging from microscopic emulsion flow at the pore level. A parametric analysis is conducted to study the effect of the permeability and dispersed phase droplet size on the flow response to emulsion flooding in porous media. The network model predictions qualitatively describe the oil-water emulsion flow behavior observed in the experiments.

Morphology, rheology and dynamic mechanical properties of PP/EVA/clay nanocomposites

This paper reports on morphology, rheology and dynamic mechanical properties of polypropylene (PP)/ethylene vinyl acetate (EVA) copolymer/clay nanocomposite system prepared via a single step melt compounding process using a twin screw micro-compounder. Scanning electron microscopic (SEM) investigations revealed that the dispersed phase droplet size was reduced with incorporation of an organo-modified montmorillonite (OMMT). This reduction was more significant in presence of a maleated PP (PP-g-MAH) used as compatibilizer. Phase inversion in the compatibilized blends caused a further decrease in PP droplet size. The OMMT gallery spacing was higher in nanocomposites with EVA as matrix which could be attributed to higher tendency of OMMT nanoparticles towards EVA rather than PP. This enhanced tendency was confirmed by rheological analysis too. Transmission electron microscopy (TEM) results also showed that the majority of OMMT nanoparticles were localized on the interface and within EVA droplets. According to dynamic mechanical analysis, the compatibilized nanocomposites showed higher storage and loss moduli due to better dispersion of OMMT layers. The modulus enhancement of nanocomposites as a function of OMMT volume fraction was modeled by Halpin-Tsai’s-Nielsen expression of modulus for nanocomposites. The results of modeling suggested that the aspect ratio of the intercalated OMMT, in the form of Einstein coefficient (KE), plays a determining role in the modulus enhancement of nanocomposites.