Patterns annular, dispersed

In annular flow, liquid flows as a thin film along the pipe wall and gas flows in the core. Some liquid is entrained as droplets in the gas core. At veiy high gas velocities, nearly all the liquid is entrained as small droplets. Inis pattern is called spray, dispersed, or mist flow. 

Reading Figure 2-40 type flow pattern is probably annular, but could be wave or dispersed, depending on many undefined and unknown conditions. 

Cas/Liquid Micro Flow Dispersive Mixers Generating Slug and Annular Patterns... 

The need for analytical (flow-pattern) characterization in advance of the experiment is less than for the dispersive mixers forming slug and annular flow patterns, because the dispersion typically is formed in an attached tube. This tube is commonly made of glass and mostly of larger inner diameter. Hence visual inspection by the operator is routinely possible. 

Annular flow. In annular flow there is a continuous liquid in an annulus along the wall and a continuous gas/vapor phase in the core. The gas core may contain entrained droplets—dispersed mist—while the discontinuous gas phase appears as bubbles in the annulus. This flow pattern occurs at high void fractions and high flow velocities. A special case of annular flow is that where there is a gas/vapor film along the wall and a liquid core in the center. This type is called inverse annular flow and appears only in subcooled stable film boiling (see Sec. 3.4.6.3)... 

Comparison of the boundaries of the observed flow patterns with the analytical criteria derived by Quandt showed that the bubble, dispersed, and annular flow patterns are subclasses of a pressure gradient-controlled flow. Similarly, flow patterns identified as slug, wave, stratified, and f ailing film are subclasses of a gravity-controlled situation. 

Three main flow patterns exist at various points within the tube bubble, annular, and dispersed flow. In Section I, the importance of knowing the flow pattern and the difficulties involved in predicting the proper flow pattern for a given system were described for isothermal processes. Nonisother-mal systems may have the added complication that the same flow pattern does not exist over the entire tube length. The point of transition from one flow pattern to another must be known if the pressure drop, the holdups, and the interfacial area are to be predicted. In nonisothermal systems, the heat-transfer mechanism is dependent on the flow pattern. Further research on predicting flow patterns in isothermal systems needs to be undertaken... 

The basic assumptions implied in the homogeneous model, which is most frequently applied to single-component two-phase flow at high velocities (with annular and mist flow-patterns) are that (a) the velocities of the two phases are equal (b) if vaporization or condensation occurs, physical equilibrium is approached at all points and (c) a single-phase friction factor can be applied to the mixture if the Reynolds number is properly defined. The first assumption is true only if the bulk of the liquid is present as a dispersed spray. The second assumption (which is also implied in the Lockhart-Martinelli and Chenoweth-Martin models) seems to be reasonably justified from the very limited evidence available. 

Kosterin (K3) investigated the effect of tube inclination on flow patterns for air-water systems. As tube inclination increases, the flow patterns become more dispersed tube slope is an important variable at the lower liquid or gas rates. At high gas rates, when annular or dispersed flow normally occurs in horizontal tubes, tube inclination has little effect on flow-pattern. 

Disperse dyes of the azo and anthraquinone types, on the other hand, are used in hair tints. They also give annular color patterns, which are relatively durable because of the poor solubility of the dyes in aqueous systems. They can be combined with other classes of dyes. 

A flow-pattern map comprises dispersed flow, annular flow, slug-dispersed flow and slug-annular flow [278]. The highest specific interface measured amounts to 16 000 m2/m3. A porous surface structure (100 cm2) in the reaction channel can be generated by a sulfurhexafluoride plasma etch process with silicon nitride masking [278],... 

Sizing of flashing steam condensate return lines requires techniques that calculate pressure drop of two-phase flow correlations. Many correlations have been presented in the literature [15,16,19,23]. Most flow patterns for steam condensate headers fall within the annular or dispersed region on the Baker map. Sometimes, they can fall within the slug flow region however, the flashed steam in steam condensate lines is less than 30% by weight. 

Another type of gravity-flow, vertical contactor with a rotating axial shaft is the rotating disk contactor developed by the Shell Development Company [R1, R2], shown schematically in Fig. 4.28. It consists of alternate annular stator disks attached to the outer shell and circular rotor disks attached to the rotating shaft. Rotation of the central shaft, at peripheral speeds up to 6 m/s, provides controlled dispersion of the two phases and sets up a toroidal flow pattern within each stator compartment. There are no settling chambers, and the two phases drift past each other in countercurrent flow. 

Fig. 4.2 Photographs of ionic liquid-water two-phase flow patterns in microchannels, a Plug flow, b Disturbed plug, c Plug and drain, d Intermittent flow, e Dispersed flow. f. Quasi annular flow, g Throat annular flow, h Rivulet annular flow, i Drop flow, j Irregular flow...

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