Two-phase viscosity

The simplest way to compute line friction in two-phase flow is to adopt some kinds of mean properties of the mixtures and to employ the single phase friction eqnation. The main problem is the assignment of a two-phase viscosity. Of the number of definitions that have been proposed, that of McAdams et al. [Trans. ASME... 

Atomization. A gas or Hquid may be dispersed into another Hquid by the action of shearing or turbulent impact forces that are present in the flow field. The steady-state drop si2e represents a balance between the fluid forces tending to dismpt the drop and the forces of interfacial tension tending to oppose distortion and breakup. When the flow field is laminar the abiHty to disperse is strongly affected by the ratio of viscosities of the two phases. Dispersion, in the sense of droplet formation, does not occur when the viscosity of the dispersed phase significantly exceeds that of the dispersing medium (13). 

Properties of Component Phases As discussed in the preceding subsection, dispersions of gases in liquids are affected by the viscosity of the hquid, the density of the liquid and of the gas, and the interfacial tension between the two phases. They also may be affected directly by the composition of the hquid phase. Both the formation of bubbles and their behavior during their lifetime are influenced by these quantities as weh as by the me(manical aspects of their environment. 

In calciilating the power required for mixers, a reasonable estimate of the average density and viscosity for a two-phase system is satisfactoiy. 

Many times solids are present in one or more phases of a solid-hquid system. They add a certain level of complexity in the process, especially if they tend to be a part of both phases, as they normally will do. Approximate methods need to be worked out to estimate the density of the emulsion and determine the overall velocity of the flow pattern so that proper evaluation of the suspension requirements can be made. In general, the solids will behave as though they were a fluid of a particular average density and viscosity and won t care much that there is a two-phase dispersion going on in the system. However, if solids are being dissolved or precipitated by participating in one phase and not the other, then they will be affected by which phase is dispersed or continuous, and the process will behave somewhat differently than if the solids migrate independently between the two phases within the process. 

It follows that since the addition of metal oxides has such a profound effect on the properties of liquid silicates such as the viscosity, that the Reynolds number of liquid silicates in metal-silicate liquid two-phase systems will influence the boundary layer thickness to a greater extent than in the liquid metals and alloys, mainly because of the higher viscosity of the silicate. 

Lube oil extraction plants often use phenol as solvent. Phenol is used because of its solvent power with a wide range of feed stocks and its ease of recovery. Phenol preferentially dissolves aromatic-type hydrocarbons from the feed stock and improves its oxidation stability and to some extent its color. Phenol extraction can be used over the entire viscosity range of lube distillates and deasphalted oils. The phenol solvent extraction separation is primarily by molecular type or composition. In order to accomplish a separation by solvent extraction, it is necessary that two liquid phases be present. In phenol solvent extraction of lubricating oils these two phases are an oil-rich phase and a phenol-rich phase. Tne oil-rich phase or raffinate solution consists of the "treated" oil from which undesirable naphthenic and aromatic components have been removed plus some dissolved phenol. The phenol-rich phase or extract solution consists mainly of the bulk of the phenol plus the undesirable components removed from the oil feed. The oil materials remaining... 

Mucus gel is propelled toward the epiglottis by a two-phase ciliary beat cycle. Forward mucus movement occurs during the effective or power phase of the cycle, when cilia fully extend and traverse an arc perpendicular to the epithelial surface (Fig. 5.24). Claw-like structures, 25-35 nm long, project from each cilia tip and appear to assist in the mechanical transfer of momentum from cilia to mucus gel. Maximum mucus velocity depends on the extent cilia penetrate the epiphase during the power phase, periciliary and mucus gel viscosity, and cilia density. 

Beaded polymeric supports are produced by a two-phase suspension polymerization in which microdrops of a monomer solution are directly converted to the corresponding microbeads. The size of a microdroplet is usually determined by a number of interrelated manufacturing parameters, which include the reactor design, the rate of stirring, the ratio of the monomer phase to water, the viscosity of both phases, and the type and concentration of the droplet stabilizer. 

To understand how the dispersed phase is deformed and how morphology is developed in a two-phase system, it is necessary to refer to studies performed specifically on the behavior of a dispersed phase in a liquid medium (the size of the dispersed phase, deformation rate, the viscosities of the matrix and dispersed phase, and their ratio). Many studies have been performed on both Newtonian and non-Newtonian droplet/medium systems [17-20]. These studies have shown that deformation and breakup of the droplet are functions of the viscosity ratio between the dispersity phase and the liquid medium, and the capillary number, which is defined as the ratio of the viscous stress in the fluid, tending to deform the droplet, to the interfacial stress between the phases, tending to prevent deformation ... 

The flow behavior of the polymer blends is quite complex, influenced by the equilibrium thermodynamic, dynamics of phase separation, morphology, and flow geometry [2]. The flow properties of a two phase blend of incompatible polymers are determined by the properties of the component, that is the continuous phase while adding a low-viscosity component to a high-viscosity component melt. As long as the latter forms a continuous phase, the viscosity of the blend remains high. As soon as the phase inversion [2] occurs, the viscosity of the blend falls sharply, even with a relatively low content of low-viscosity component. Therefore, the S-shaped concentration dependence of the viscosity of blend of incompatible polymers is an indication of phase inversion. The temperature dependence of the viscosity of blends is determined by the viscous flow of the dispersion medium, which is affected by the presence of a second component. 

Large Scale Polystyrene-Ethylbenzene High Viscosity Two-Phase Flow Test Report, DIERS/.AIChE, 1986, 76 pages. 

The process starts with a one-phase flow of a low-viscosity PA salt solution and ends with a two-phase flow with the viscous PA melt along the tube wall and steam through the middle. A stream separator and a finishing reactor are attached to the polymerization tubes. 

---