Immiscible Continuous Phase Research Articles

Generation of monodisperse alginate microbeads and in situ encapsulation of cell in microfluidic device

A microfluidic method for the in situ production of monodispersed alginate hydrogels using chaotic mixing is described. Aqueous droplets comprising of alginate and calcium as a cross-linking agent were formed as an immiscible continuous phase, and then the alginate and calcium in the droplet came into contact and were rapidly mixed. Gelation of the hydrogel was achieved in situ by the chaotic mixing of the droplets in the microfluidic device. Important operating parameters included: the capillary number (Ca) and the flow rate of the continuous phase, which mainly influenced the formation of three distinctive flow regimes, such as fluctuation, stable droplets, and laminar flow. Under the stable formation of droplets regime, monodispersed alginate microbeads having a narrow size distribution (below 3% of CV) were produced in the microfluidic device and the size of the microbeads, ranging from 60 to 95 microm, could be easily modulated by varying the flow rate, viscosity, and interfacial tension. In addition, this approach can be applied to the encapsulation of yeast cells in alginate hydrogels with a high monodispersity. This simple microfluidic technique for the production of monodispersed hydrogels and encapsulation of biomolecules shows strong potential for use in biosensors, cell sensors, drug delivery systems, and cell transplantation applications.

The growth rate of gas hydrate from refrigerant R12

Experimental and theoretical investigations were presented dealing with three phase direct-contact heat transfer by evaporation of refrigerant drops in an immiscible liquid. Refrigerant R12 was used as the dispersed phase, while water and brine were the immiscible continuous phase. A numerical solution is presented to predict the formation rate of gas hydrates in test column. The solution provided an acceptable agreement when compared with experimental results. The gas hydrate growth rate increased with time. It increased with increasing dispersed phase flow rate. The presence of surface-active sodium chloride in water had a strong inhibiting effect on the gas hydrate formation rate.

Hydrodynamic behaviour of an ensemble of encapsulated liquid drops in creeping motion: a fluid-mechanic based model for liquid membranes

The free surface cell model is used with the Stokes approximation, to characterize the Newtonian flow of an ensemble of concentric two-phase liquid drops (i.e. globules) in steady, creeping motion through an immiscible continuous liquid phase. The drag on each globule is determined analytically, and its dependence on globule concentration in the ensemble is investigated. Closed form expressions are derived for the stream functions both in the continuous phase and within each globule phase. The effect of globule concentration on streamline patterns and flow velocity is also investigated. The drag and internal circulation patterns are analysed in the limiting situations of a single globule, a rigid sphere ensemble and a fluid sphere ensemble, and their dependence on globule concentration and the other flow parameters is determined.

Heat transfer in gas–liquid–liquid three-phase direct-contact exchanger

The heat transfer to dispersed droplets in an immiscible continuous phase is studied for the n-pentane–water system. The gas–liquid–liquid three-phase section of the exchanger is divided into two stages, where the volumetric heat transfer coefficients are developed, respectively. These models take into account the evaporation of continuous phase water into the dispersed phase and the two-phase droplets break-up. The calculated results showed good agreement with the experimental values.

Effect of Operating Conditions on Two-Phase Bubble Formation Behavior at Single Nozzle Submerged in Water.

The effects of operating parameters and physical properties of a dispersed phase on the volume change of a two-phase bubble formed in water as an immiscible continuous phase were experimentally investigated. The operating parameters are inner diameter of nozzle, vapor flow rate and temperature difference between water and vapor in the bubble. A larger two-phase bubble volume can be obtained by a larger nozzle inner diameter, higher flow rate, and lower temperature difference, and vice versa. The present mathematical model estimates well the two-phase bubble formation process.

A closed periodic condensation-evaporation cycle of an immiscible, gravity driven bubble

A closed periodic condensation-evaporation cycle of a two-phase vapour-liquid ‘bubble’ driven by gravity in an immiscible continuous phase with a vertical temperature profile is presented. The vertical column can also consist of two stratified layers of two different fluids of similar densities maintained at different temperatures. The cyclic motion of the bubble is due to latent heat transport and the ensuing differences in the relative densities. The immiscible liquid drop evaporates in a hot zone at the bottom, accelerates by buoyancy upward, reaches a subcooled region and reliquifies. Its motion is then reversed, with the heavier drop falling back toward the hot region. The characteristics of a Freon bubble-drop moving in water at various operating conditions are presented for transient and steady operations.

Crystallization in a dispersed phase

AbstractA study of a non‐conventional dispersed phase crystallizer, whereby the mother liquor feed is dispersed in an immiscible continuous phase and product withdrawn continuously from the agitated 3‐phase slurry is presented. A nucleation mechanism is suggested and relationships which enable an estimate of crystal size, growth rate and segregation effects are proposed. Continuous bench scale experiments indicated that no particular operational difficulties arise, provided the feed is properly dispersed, and verified the anticipated theoretical results.