Surface area of droplets

Theoretically, the energy, E, required to generate droplets from a liquid or melt can be roughly estimated by that needed to create the surface area of droplets, i.e., the product of the surface area of droplets and the surface tension of the liquid ... 

The role of droplet size on drug stability stems from the correlation between droplet size and surface area, and between surface area of droplets and exposure of drug to the aqueous media. If the drug is relatively insensitive to aqueous media, this may not be a major issue however, for the converse situation, development of emulsions with relatively coarser droplet size may offer improved drug stability. Nonetheless, this should be balanced with physical stability of the emulsion as well as the efLciency of drug absorption after oral administration (Toguchi et al., 1990). 

Total Surface Area of Droplets iVolume Rate of Flow of Gas /... 

The above mean is also referred to as the mean length diameter, dy, because it represents the sum of the length of the droplets divided by the total number of droplets. It is also possible to express the mean droplet size in a number of other ways (Table 2). Each of these mean sizes has dimensions of length (meters), but stresses a different physical aspect of the distribution, e.g., the average length, surface area, or volume. For example, the volume-surface mean diameter is related to the surface area of droplets exposed to the continuous phase per unit volume of emulsion, As ... 

This relationship is particularly useful as it allows one to calculate the total surface area of droplets in an emulsion, an important parameter that can be used to estimate the emulsifier concentration required to produce a kineticaUy stable emulsion. An appreciation of the various types of mean droplet diameter is also important because different experimental techniques used to measure droplet sizes are sensitive to different mean values (24). Consequently, it is always important to be clear about which mean diameter has been determined in an experiment when using or quoting droplet size data. 

The formation of pyrolysis products will ultimately depend upon factors such as the following (i) the time that the askarel mixture is at a temperature which allows a reaction yield of significance (ii) the volume and surface area of droplets of askarel emitted in an eventful failure (iii) the availability of oxygen and (iv) the effect of soot particles on the dissipation of heat and the availability of oxygen. 

As the droplets pass through the evaporation region, solvent evaporates, and the droplets rapidly become much smaller. At the same time, because the surface area of the droplets gets smaller and smaller, the density of electrical charge on the surface increases until a point of instability is reached. 

Radicals generated from water-soluble initiator might not enter a micelle (14) because of differences in surface-charge density. It is postulated that radical entry is preceded by some polymerization of the monomer in the aqueous phase. The very short oligomer chains are less soluble in the aqueous phase and readily enter the micelles. Other theories exist to explain how water-soluble radicals enter micelles (15). The micelles are presumed to be the principal locus of particle nucleation (16) because of the large surface area of micelles relative to the monomer droplets. 

Water-cooling in towers operates on the evaporative principles, which are a combination of several heat/mass transfer processes. The most important of these is the transfer of liquid into a vapor/air mixture, as, for example, the surface area of a droplet of water. Convective transfer occurs as a result of the difference in temperature between the water and the surrounding air. Both these processes take place at the interface of the water surface and the air. Thus it is considered to behave as a film of saturated air at the same temperature as the bulk of the water droplet. 

The large surface area of whisker colusuts enables any stationary phase to be coated efficiently without droplet fomation and their sa >le capacity is such higher than HCOT columns. On the debit side, whisker surfaces are extremely active and very difficult to deactivate, and, because of the high degree of roughening, they are less efficient than MOOT columns. 

The effect of ultrasound on liquid-liquid interfaces between immiscible fluids is emulsification. This is one of the major industrial uses of ultrasound (74-76) and a variety of apparatus have been devised which will generate micrometer-sized emulsions (9). The mechanism of ultrasonic emulsification lies in the shearing stresses and deformations created by the sound field of larger droplets. When these stresses become greater than the interfacial surface tension, the droplet will burst (77,78). The chemical effects of emulsification lie principally in the greatly increased surface area of contact between the two immiscible liquids. Results not unlike phase transfer catalysis may be expected. 

Chlorella zofingensis cells are transferred to a growth medium, with a low nitrogen concentration (10% of normal concentration). After approximately 6-8 wk they develop a red colour, due to the decomposition of chlorophylls and synthesis of secondary carotenoids (stored in lipid droplets within the cytoplasm of the cells). At this stage the chloroplast are intact, although the surface area of thylacoids is mostly reduced. 

In linear EP of bifunctional monomers, such as S, with water soluble initiators, the monomer droplets do not compete with micelles in capturing radicals from the aqueous phase because the total surface area of the droplets is much smaller than that of micelles and growing particles. Nevertheless, if some radicals enter monomer droplets, rapid termination takes place. Therefore, polymerization in monomer droplets is negligible [88]. However, if in the crosslinking EP of 1,4-DVB a few radicals are captured by monomer droplets, they can polymerize completely because the recombination of radicals is suppressed by the gel effect. Moreover, in thermal initiation or in initiation by hydrophobic initiators, such as AIBN, radicals are formed predominantly in the hydrophobic phase, i.e. in monomer droplets and in micelles, and crosslinking EP is initiated in the organic phase. 

Surfactants have been explored widely for their effects on drug absorption, in particular using experimental animals (Gibaldi and Feldman, 1970 Gibaldi, 1976). Surfactants alter dissolution rates (of lipid materials), surface areas of particles and droplets, and membrane characteristics, all of which affect absorption. 

In developing the problem, a differential volume in the vapor above the liquid droplet is chosen, as shown in Fig. 6.12. The surface area of a sphere is 4irr2. Since mass cannot accumulate in the element,... 

Atomizers Atomization is the process of breaking up a continuous liquid phase into discrete droplets. Figure 24-22 shows the idealized process by which the surface area of a liquid sheet is increased until it forms droplets. Atomizers may be classified into two broad groups (see Fig. 24-23), pressure atomizers, in which fuel oil is injected at high pressure, and twin-fluid atomizers, in which fuel oil is injected at moderate pressure and a compressible fluid... 

In order to estimate the specific surface area of the dispersed organic droplets, the mean droplet size (Sauter diameter 32) has to be determined, which can be calculated according to the Okufi equation (Eq. 5) ... 

Tables Mean bubble and droplet diameters and resulting specific surface areas of the dispersed gas and organic phase...

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