Droplet string

Figure L The droplet-string transition, viewed through a microscope. When an emulsion is sheared between parallel platens, droplets of the suspended phase (top) coalesce to form strings (bottom), with decreasing shear rate.

Pathak JA, Migler KB. Droplet-string deformation and stability during microconfined shear flow. Langmuir 2003 19(21) 8667-8674. 

Perl-mutterpapier, n, naereous paper, -rohr, n, -rohre, /. bead tube (tube filled with glass beads), -sago, m. pearl sago, -salz, n. micro-eosmic salt, -samen, m. seed pearl, -schicht, /. nacreous layer, -schnur, /. string of beads or pearls row of droplets, -seide, /. embroidery silk ardassine, -spat, m, pearl spar (pearly dolomite), -stein, m, perlite adu-laria. -sucht, /. bovine tubereulosis. -weisa, n. pearl white. 

Vertical surface collectors can readily provide information on relative drift (e.g., the amount of drift from one field trial compared to another). However, it is difficult to obtain absolute data unless the precise collection characteristics are known for the droplet size spectrum at the point of spray collection, wind speed and air turbulence intensity. " The SDTF conducted studies in wind tunnels to compare the collection efficiency of different types of drift collector used in its field studies. These studies showed that collection efficiency on strings was several orders of magnitude higher for 0.8-mm diameter cotton string than for 2-mm diameter polyethylene line and vertical o -cellulose strips or squares. The higher collection efficiency for the cotton... 

A long, stationary droplet or "thread" of one fluid in another can break up into a string of smaller droplets, and this breakup mechanism has been further treated for slowly moving bubbles by Flumerfelt and co-workers (69,70). In tubes, thread breakup produces bubbles whose lengths are on the order of four times the diameter of the unbroken thread. The incorporation of this mechanism into a constricted tube model for dispersion flow in porous media is described in the chapter by Prieditis and Flumerfelt. 

The primary objective of the work reported here was to determine whether flames from atomized fuel could be stabihzed similarly in a refractory tube and whether such flames would also produce low concentrations of NO. . To simplify analysis of the process, a single string of uniformly sized droplets was used. Two regimes can be conceived one in which the droplets are completely evaporated prior to ignition and the other in which ignition occurs prior to complete evaporation. All of the results reported here fall in the first category. 

Illustrative photographs of the string of droplets formed upon leaving the capillary tube are shown in Figure 2. The droplets attain a spherical shape in a short distance and are free of satelhtes. 

Figure 2. Spontaneous emulsification in Long Beach crude oil-caustic system (a) initiation of fingering action and formation of water in oil droplets (h) termination of fingering action and formation of water in oil droplets (c) threads of oil droplets (d) formation of very thin strings and appearance of oil droplets in aqueous phase and (e) appearance of buds of oil at the oil-aqueous interface...

It was known that jets about to disintegrate first become wavy or varicose, then break up into a string of equal-sized detached masses that form droplets. Similarly, the experimentally observed regular cellular pattern in free convection suggested that the displacements (or velocities, etc.) resulting from the introduction and growth of disturbances would be spacially periodic, and that the different modes by which a system would fall away from an unstable equilibrium could be characterized in terms of one, two, or three time-independent wavelengths. 

Nowadays, entrainment traps with string orifices are adopted. The vertical mesh orifice can be used as the section for final separation of liquid drops (Fig. 2.12, a), or to carry out preliminary separation and droplet coagulation (Fig. 2.12, b). In the latter case, the final separation of droplets is achieved in a horizontal mesh installed before the gas output branch pipe. In some gravitational gas-oil separators, the gas-liquid stream is directed toward a special reflector called a deflector (or baffle). The wall of the vertical separator can also act as a baffle. As a result of an impact of the liquid-gas mixture against the obstacle, the initial separation of gas from liquid occurs. To ensure smooth flow of liquid without foaming, separators are provided with a series of horizontal and inclined surfaces -shelves, cones, or hemispheres. 

The body of a string droplet catcher consists of a set of separating packages (sections), each of which is composed of rows of frames with stretched threads made from wire, nylon, etc. The threads are oriented parallel to gravity and perpendicular to gas flow. Frames and packages are placed in series. 

So, to determine the CE of a string droplet catcher section, it is sufficient to know the CE of a single frame K... 

If we have a gas-liquid mixture with the volume concentration of liquid Wo = 5 10 " m /m at the entrance of the string droplet catcher, then at the exit, we have Wi = 4 10 m /m. The dependence of t on gas velocity U is shown in Fig. 19.10. For the chosen values of parameters, the critical velocity, i.e. the velocity at which S = S r, is equal to Uc = 1.56 m/s. It means that when U < UcP, the efficiency of the droplet catcher section is practically equal to zero. Keep in mind that if drop have different radii, then the critical Stokes number will be determined by the average radius of drops. 

From (19.31), it follows that an increase in the flow velocity reduces the minimum radius of droplets that can be captured, and thereby increases the capture efficiency (CE) of the string droplet catcher. On the other hand, an increase in the flow velocity can destabilize the liquid film formed on the string surface, stripping drops away from the surface, and thus, reducing the CE. 

The number of strings rows chosen according to this inequality, will ensure the operation of string droplet catcher without ablation of droplets. 

Determination of the critical gas flow rate and the CE of a separator equipped with a string droplet catcher orifice requires a preliminary determination of gas-liquid flow parameters in the entire system, including the supply pipeline, the settling section of the separator, and the droplet catcher orifice - in the same way as it was done earlier for a separator with a centrifugal orifice. The outcome is the following pair expressions for the CE s of a vertical and a horizontal separator... 

Each layer of the grid will be modeled by two frames with stretched strings located perpendicularly to each other. We can then use the results from the previous section. If all drops in the oncoming flow running into the mesh bundle have the same size, then the CE of the mesh droplet catcher is... 

Vs Effectiveness coefficient of separator with string droplet capture ... 

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