Continuous Phase Ratio Research Articles

Hydrodynamic and axial mixing studies in asymmetric rotating impeller column at high dispersed to continuous phase ratios

In the present work, hydrodynamics characteristics such as dispersed phase holdup (εD), Sauter mean diameter (d32), drop size distribution (DSD), and continuous phase axial mixing was investigated in an asymmetric rotating impeller column (ARIC). Water – heavy normal paraffin (HNP) liquid system was used in ARIC to carry out the experiments. The effect of operating parameters such as impeller speed (N), superficial velocity of the continuous phase (Vc) was investigated. Experiments were performed at several dispersed to continuous phase (O/A) ratios. Volume displacement method and an image analysis technique were utilized to investigate the εD and d32, respectively. The pulse tracer technique was used to study the axial mixing in the continuous phase. The εD and d32 were strongly influenced by the impeller speed. More than 50% increase in εD was noticed when impeller speed increases from 100 to 350 rpm. The increase in dispersion coefficients (Dc) is observed with impeller speed. Whereas, it was noticed that O/A has a significant impact on Dc. About 80% decrease in Dc was observed when O/A increases from 5 to 25. The generalize equations have been developed for the prediction εD, d32, and Pec.

Enhancing sweetness using double emulsion technology to reduce sugar content in food formulations

In this study, water-in-oil-in-water double emulsions containing saccharose at the outer aqueous phase were formulated and characterised to investigate the potential of double emulsion to enhance the perception of sweetness. We hypothesised that double emulsions containing saccharose at the outer aqueous phase will be detected immediately by taste receptors and evaluated as sweeter than single emulsions containing the same amount of saccharose. Emulsions were prepared with three dispersed phase:continuous phase ratios. The results of the analyses suggested that the phase ratio affected the particle size and rheological behaviour of the emulsions. However, no differences were observed in lipid digestion behaviour. The sensory analysis revealed that the formulation containing double emulsion was sweeter than the formulation containing oil-in-water single emulsion by approximately 75%. Therefore, the development of food products with reduced sugar content may be possible using double emulsions with enhanced sweetness. Industrial relevanceExcessive sugar consumption is an unhealthy diet associated with an increased risk of non-alcoholic fatty liver disease, obesity, diabetes, chronic diseases such as cardiovascular disease, certain types of cancer, and cognitive decline. Therefore, one of the responsibilities of the food industry is to reduce the sugar content of foods. Many food companies have significantly reduced the sugar levels of many products with the policies they have carried out and continue to do so. However, products produced with industrial solutions (especially using artificial sweeteners) to reduce sugar create sensory dissatisfaction in the consumers. Also, the body reacts to artificial sweeteners differently than it does to sugar. The double emulsion technology offers the opportunity to the food industry to reduce the sugar content of foods without causing any sensory loss in food and without the need for the use of an artificial sweetener.

Continuous Phase Control of Vanadium Dioxide Films

Abstract Vanadium dioxide (VO2) undergoes a metal-insulator transition (MIT) at approximately 68 °C, with associated sharp changes in its physical (e.g., optical, electrical, and mechanical) properties. This behavior makes VO2 films of interest in many potential applications, including memory devices, switches, sensors, and optical modulators. For ON/OFF like digital applications, an abrupt switching behavior is ideal. However, to continuously change VO2 metal/insulator phase ratio for analog-like operation, the intrinsic hysteresis characteristic of VO2 MIT renders the phase control becoming a formidable challenge. This paper considers the problem of controlling and tracking desired optical transmittance via continuous phase ratio change. The problem becomes worse while considering the differences of individual thin-film samples and the hysteresis associated with the phase change within a narrow temperature range. This paper reports a robust feedback controller using an optical transmittance measurement and based on an uncertainty and disturbance estimator (UDE) architecture. The proposed controller is capable of mitigating the adverse effect of hysteresis, while also compensating for various uncertainties. The effectiveness of the proposed methodology is demonstrated with experimental validation.

Liquid-liquid dispersions in intensified impinging-jets cells

The formation of dispersions of two immiscible liquids in a confined impinging-jets cell was studied experimentally. The jets of the liquids formed at two opposing channels and collided in a main channel, which was perpendicular to the previous two. Jet channels with diameters either 0.25 or 0.5mm and main channels with diameters either 2 or 3mm were used. The jet velocities varied from 0.17 to 6.2m/s and the dispersed to continuous phase ratios varied from 0.05 to 0.28. Deionised water and kerosene (Exxsol D80: ρ=795kg/m3 and μ=1.73mPas) were used as test fluids. Drop sizes were measured with high-speed imaging. It was found that the total velocity of the two jets was the main parameter that affected both the average drop size and the interfacial area, whilst the dispersed to continuous phase flow rate ratio was less significant. Both phases could become continuous depending on the phase flowrate ratio; drops were, however, larger in the organic continuous dispersions. The interfacial area produced with the impinging-jets cell was almost 3 times larger than in capillary contactors at similar conditions (umix=0.024–0.19m/s). The size of the main channel affected the drop size and smaller drops formed in the large channel compared to the small one. With increasing energy dissipation rate, ε, in the impingement zone, the Sauter mean diameter decreased following a relation of the form ∼ε−b. Apart from the lower velocities, the drop sizes did not change significantly at distances equal to 15 channel diameters downstream the impingement area.

Effect of process conditions on equilibrium, reaction kinetics and mass transfer for triglyceride transesterification to biodiesel: Experimental and modeling based on fatty acid composition

Detailed reaction kinetics of oil transesterification were studied based on mechanism and reaction scheme of individual triglyceride, diglyceride, monoglyceride, glycerol and fatty acid methyl ester containing different combinations of gadoleic, linoleic, linolenic, oleic, palmitic and stearic acids determined by high-performance liquid chromatography. Pre-exponential factors and activation energies were correlated with molecular structure in terms of chain lengths and double bonds by response surface models. The activation energies of forward reactions were 47–61kJmol−1 with backward ones being 31–49kJmol−1, depending on component structure. Mass transfer during initial emulsion phase was acknowledged by determining diffusivities, distribution coefficients, molar volumes, boiling points and viscosities of individual components. Model was validated for a wide range of temperatures, hydrodynamic conditions, dispersed and continuous phase ratios, and methanolysis catalyst concentrations. Rotational speed had the most profound influence on the duration of transport phenomena-limited region spanning the latter to 27min upon use of 100rpm. Economics of the process were finally evaluated in terms of alcoholysis cost and price breakdown. Proposed methodology may be usefully applied to transesterification syntheses employing heterogeneous catalysis and enzymes, as well as various renewable resources such as microalgae lipids, waste oils, bioethanol and biobutanol.

Control of encapsulation efficiency in polymeric microparticle system of tolmetin

Ethylcellulose microparticles containing tolmetin sodium, an anti-inflammatory drug, were prepared by a solvent diffusion method based on the formation of multiple W/O1/O2-emulsion. The drug used was TOL, which is water-soluble and n-hexane was used as the non-solvent. Important parameters in the evaluation of a microencapsulation technique are actual drug loading, the encapsulation efficiency, the yield, solvent systems, dispersed phase to continuous phase ratio (DP/CP ratio), composition of continuous phase, drug distribution in microparticles and stability of primary emulsion. A small volume of internal aqueous phase and volume of organic solvent were favorable to achieve high drug encapsulation efficiencies. Since drug release during the initial stages depends mostly on the diffusion escape of the drug, major approaches to prevent the initial burst have focused on efficient encapsulation of the drug within the microparticles. For this reason, control of efficiency and the extent of initial burst are based on common formulation parameters. Most parameters affect encapsulation efficiency and initial burst by modifying solidification rate of dispersed phase. In order to prevent many unfavorable events such as pore formation, drug loss, and drug migration that occur while the dispersed phase is in the semi-solid state, it is important to understand and optimize these variables.

Effect of the phase ratio on the particle properties of poly(vinyl chloride) resins produced by suspension polymerization

AbstractThe effects of the dispersed phase to continuous phase ratio (weight of VCM (gr)/weight of water (gr) (φ = gVCM/gwater)) on the particle properties of a poly(vinyl chloride) (PVC) suspension were investigated experimentally. A series of experiments were performed with different φ values in a pilot‐scale reactor. The cold plasticizer absorption of the resin decreased with φ. Scanning electron micrographs showed that by the reduction of φ, many of the produced particles had a regular shape, a smooth surface, and greater porosity. An increase in φ caused a wider and multimodal particle size distribution of the produced PVC particles. The mean particle size and bulk density also increased with φ, whereas the molecular weight and polydispersity index did not change. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Kinetic and thermodynamic modeling of the formation of polymeric microspheres using solvent extraction/evaporation method

The formation of polylactide-co-glycolide microspheres loaded with a peptide using solvent extraction/evaporation methods involves intrinsic variables, such as solvent-polymer interaction parameters, and extrinsic variables, such as dispersed phase/ continuous phase ratio, temperature and dispersed phase composition. A mathematical model based on mass transfer was developed by incorporating these variables, and, by superimposing with the state of phase transition, the model was used to predict the microsphere properties. The mass transfer in the dispersed phase was based on diffusion theory and was a function of the driving force of chemical potential gradient and transport parameters. The solvent removal process involved solvent diffusion out of the dispersed phase followed by evaporation at the continuous phase/air interface, a process which can be facilitated by forced convective flow. Mathematically, the process can be expressed by coupling the equations for mass transfer in the dispersed phase and first order evaporation from the continuous phase. Two phase transitions, the viscous and glassy boundaries, were used to represent the phase transitions in the polymer solution. The phase transition can be superimposed on the composition profile in the dispersed phase; the solidification of microsphere can be evaluated from such a treatment.

Prediction of solvent removal profile and effect on properties for peptide-loaded PLGA microspheres prepared by solvent extraction/ evaporation method

Using a predictive mathematical model, several important extrinsic process variables were varied to simulate the process dynamics of microsphere formation. These included the composition profile in the dispersed phase, the solvent concentration profile in the continuous phase and the solvent removal profile in the dispersed phase. By superimposing the composition profile in the dispersed phase with the phase transition boundary, the progression of phase transition in microsphere formation can be evaluated. Low dispersed phase/ continuous phase ratio, high continuous phase-addition rate, high temperature, high heating rate and high initial polymer concentration in the dispersed phase contributed to enhanced solvent removal. The higher solvent removal led to a heterogeneous composition distribution in the dispersed phase and the early cross-over of the gelation point (viscous boundary) of the periphery region which initiates the onset of solidification in this region. These phenomena resulted in an increasing pore size, lower surface area, denser periphery, higher residual solvent and slower drug release. In addition, the progress toward the glassy boundary may also play a major role in the ultimate solvent residual. Slow solvent removal gave rise to a homogenous distribution of the components in the dispersed phase due to the delay of hardening. The extrinsic manageable parameters could be varied during microsphere formation to obtain the desired rate of solvent removal as well as the desired microsphere properties. The mathematical model was used to simulate such conditions to facilitate the experimental design for the desired microsphere properties.

Investigation on Process Parameters Involved in Polylactide-Co-Glycolide Microspheres Preparation

AbstractIndomethacin loaded polylactide-co-glycolide (PLGA) microspheres were prepared by emulsification solvent evaporation. The preparation involves several process parameters that can affect the morphological characteristics, the “in vitro” and “in vivo” dissolution behaviour of microspheres.The evaluation of three process parameters, emulsification stirring rate, emulsifier concentration and dispersed phase to continuous phase ratio was carried out in order to correlate them to some microsphere properties.Results show that the variables evaluated affect mainly microspheres drug content and, at less extent, particle size.