Dispersed-phase concentration, effect

The values of AE and AS (Table 1) suggest that the probe motion in frozen water and solutions of silica is the slipping by the rigid lattice, but in other cases this is the motion in viscous medium of surface water layers [12]. A kind of compensation effect reveals at that with rising the disperse phase concentration. That means a symbate increase of AE and AS, which is characteristic of the spin label motility in water-protein matrix [12]. 

The utility of the model to predict the effects of interdroplet mixing on extent of reaction was demonstrated for the case of a solute diffusing from the dispersed phase and undergoing second-order reaction in the continuous phase. For this comparison the normalized volumetric dispersed-phase concentration distribution is deflned as fv(y) dy equal to the fraction of the total volume of the dispersed phase with dimensionless concentration in the range y to y -i- dy, where y = c/cq and... 

Effect of Dispersed Phase Concentration. In any application of these microemulsion systems to polyn rization processes, it would be desirable to maximize polymer yield. This can be accomplished by maximizing the acrylamide ratio at constant surfactant loading or, of course, the acrylamide ratio (as well as the water ratio) to the surfactant can be fixed and the total amount of surfactant in the system increased. Therefore, the effect of total dispersed phase concentration on the phase behavior was investigated. The dispersed phase concentration was defined as a volume fraction equalling the total volume of surfactants + acrylamide -l- water divided by the total volume. 

In Eulerian-Eulerian (EE) simulations, an effective reaction source term of the form of Eq. (5.32) can be used in species conservation equations for all the participating species. The above comments related to models for local enhancement factors are applicable to the EE approach as well. It must be noted that interfacial area appearing in Eq. (5.32) will be a function of volume fraction of dispersed phase and effective particle diameter. It can be imagined that for turbulent flows, the time-averaged mass transfer source will have additional terms such as correlation of fluctuations in volume fraction of dispersed phase and fluctuations in concentration even in the absence... 

The interfacial tension can undergo significant changes if the polarity of the medium is altered, such as in the stability/coagulation transition caused by the addition of water to hydrophobic silica dispersions in propanol or ethanol [44,52,53]. Also, the addition of small additives of various surface-active substances can have a dramatic effect on the structure and properties of disperse systems and the conditions of transitions [14,16,17,26]. The formation and structure of stable micellar systems and various surfactant association colloids, such as microemulsion systems and liquid crystalline phases formed in various multicomponent water/hydrocarbon/surfactant/alcohol systems with varying compositions and temperatures, have been described in numerous publications [14-22,78,79,84-88]. These studies provide a detailed analysis of the phase equilibria under various conditions and cover all kinds of systems with all levels of disperse phase concentration. Special attention is devoted to the role of low and ultralow values of the surface energy at the interfaces. The author s first observations of areas of stable microheterogeneity in two-, three-, and four-component systems were documented in [66-68],... 

Coalescence rates depend on both dispersed phase concentration and physicochemical factors. Except for strongly coalescing systems, coalescence effects are minimal at concentrations less than 5%. 

Suppression of domain coalescence in the melt flow regime is one of the most important effects of the interfacial reaction on morphology and morphology development. Simdararaj and Macosko [33] have conducted a careful study of morphology as a function of dispersed phase voliune fraction in reactive and non-reactive blends to discern the influence of the reaction. Figure 5.9 illustrates the dependence of the dispersed phase domain size on the dispersed phase concentration for typical uncompatibilized blends. At dispersed phase concentrations less than about 0.5 wt.% the system is dilute enough that coalescence is insignificant due to the very low frequency of dispersed phase domain... 

The (-f) sign in the exponent applies when A > 1 and the (—) sign when A < 1. This relationship provides for a minimum dispersed phase size when A = 1. However, it is noteworthy that this relationship was obtained for blends with dispersed phase concentrations of approximately 20wt.% and thus certainly includes effects of coalescence. The... 

The prediction of drop sizes in liquid-liquid systems is difficult. Most of the studies have used very pure fluids as two of the immiscible liquids, and in industrial practice there almost always are other chemicals that are surface-active to some degree and make the pre-dic tion of absolute drop sizes veiy difficult. In addition, techniques to measure drop sizes in experimental studies have all types of experimental and interpretation variations and difficulties so that many of the equations and correlations in the literature give contradictoiy results under similar conditions. Experimental difficulties include dispersion and coalescence effects, difficulty of measuring ac tual drop size, the effect of visual or photographic studies on where in the tank you can make these obseiwations, and the difficulty of using probes that measure bubble size or bubble area by hght or other sample transmission techniques which are veiy sensitive to the concentration of the dispersed phase and often are used in veiy dilute solutions. 

This is an oversimplified treatment of the concentration effect that can occur on a thin layer plate when using mixed solvents. Nevertheless, despite the complex nature of the surface that is considered, the treatment is sufficiently representative to disclose that a concentration effect does, indeed, take place. The concentration effect arises from the frontal analysis of the mobile phase which not only provides unique and complex modes of solute interaction and, thus, enhanced selectivity, but also causes the solutes to be concentrated as they pass along the TLC plate. This concentration process will oppose the dilution that results from band dispersion and thus, provides greater sensitivity to the spots close to the solvent front. This concealed concentration process, often not recognized, is another property of TLC development that helps make it so practical and generally useful and often provides unexpected sensitivities. 

An evaluation of the retardation effects of surfactants on the steady velocity of a single drop (or bubble) under the influence of gravity has been made by Levich (L3) and extended recently by Newman (Nl). A further generalization to the domain of flow around an ensemble of many drops or bubbles in the presence of surfactants has been completed most recently by Waslo and Gal-Or (Wl). The terminal velocity of the ensemble is expressed in terms of the dispersed-phase holdup fraction and reduces to Levich s solution for a single particle when approaches zero. The basic theoretical principles governing these retardation effects will be demonstrated here for the case of a single drop or bubble. Thermodynamically, this is a case where coupling effects between the diffusion of surfactants (first-order tensorial transfer) and viscous flow (second-order tensorial transfer) takes place. Subject to the Curie principle, it demonstrates that this retardation effect occurs on a nonisotropic interface. Therefore, it is necessary to express the concentration of surfactants T, as it varies from point to point on the interface, in terms of the coordinates of the interface, i.e.,... 

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