Dispersion Characteristics

The Peclet number, uLjD, when written in the form (L /D)l(Llu) is seen to be a ratio of characteristic dispersion time to characteristic residence time and the Damkohler number can, in similar manner, be considered as a ratio of characteristic residence time, L/u, to characteristic reaction time, l/feCA " [59]. 

Dyeing Characteristics. Disperse dyes, high melting crystalline compounds w ith low solubility in the dye hath, are most frequently used for cellulose acelate and triacetate fibers. 

It is often useful to write a model equation such as Equation 8-121 in terms of dimensionless variables. This introduces the Peclet number NPe = uL/De>1, which represents the ratio of characteristic dispersion time to characteristic convection time (residence time), and the Damkohler number,... 

Figure 2.10 Characteristic dispersion mechanisms in canopies from local sources close to an isolated obstacle source outside wake/canyon, showing impaction of the plume from Source (1), wake entrainment (E) and detrainment (D) from Sources 1 and 2. Note how the plume profile G(z) has a split structure in the wake with unentrained component Gp0 and detrained component Gpw. Gc denotes the typical outline of a cloud emitted upwind, showing the additional longitudinal dispersion associated with the blocking and wake effects. Here the reference cloud outline in the absence of buildings is shown as a dashed line with small circles, with streamwise dimension crj0.

Figure 2.12 Characteristic dispersion mechanisms in canopies in the case of multiple buildings (see also Figure 2.3) On discrete/obstacle scale (for well-separated buildings, b/d 1) plume dimensions less than obstacle width.

Later the magnetic stirrer is operated in a defined manner and dispersion begins. The graph plotting transmission versus time provides a measure for dispersion velocity. When the transmission curve reaches a plateau the best possible (stationary) dispersion obtainable with this device has been reached. By applying ultrasound to the liquid the degree of dispersion can be further increased in most cases. The test results may be used to define several characteristic dispersion conditions of the material e.g. the ratio of transmission at a given time to transmission at stationary dispersion or final dispersion due to ultrasound. 

Closer observation of the aggregation time scale shows that it is inversely proportional to the characteristic total aggregate number density Nt, which is related to the characteristic disperse-phase volume fraction 0p. When the system is dilute (i.e.

[Pg.5]

Charlaix et al. (1988) also conducted a study of NaCl and dye transport in etched transparent lattices. A fully connected square lattice with a lognormal distribution of channel widths and a partially connected hexagonal lattice (a percolation network) were considered. They concluded that the disorder and heterogeneity of the medium determined the characteristic dispersion length. From experimental data on the percolation network, they showed that this dispersion length was close to the percolation correlation length, p. 

The characteristic dispersion of the measured values that could reasonably be attributed to the measurand. 

For nematic LCs, theory predicts a characteristic dispersion law Tiz(coo) oc [36, 37]. This is exactly what we observe for the monomeric 8 and dimeric systems 7. Although a somewhat higher exponent is evaluated for the polymers 4, there is no doubt that collective order fluctuations occur in these systems, likewise [174]. 

We have selected two characteristic dispersion conditions for our analyses (1) stable atmospheric stratification (Pasquill-class F) with a wind speed of 2 m/s and (2) neutral atmospheric stratification (Pasquill-class D) with a wind speed of 5 m/s. The mixing layer was estimated to be 200 m for stable and 500 m for neutral stratification. Although the actual meteorological conditions vary continuously during the transport of pollutants, most of the time the actual dispersion conditions varied between the two selected cases. 

Function in Formula Thickener, suspending agent in water-based systems or o/w emulsions Use Concentration 2% in creams and lotions 2% in antidandruff shampoos Solubility Characteristics Disperses in water... 

Solubility Characteristics Disperses in water to form clear thixotropic gels Formulating Characteristics Disperse in water prior to addition of other ingredients. Gives synergistic effect with organic polymers Form Supplied Powder... 

Chemical Description Copolyester of diethylene glycol, 1,4-cyclohexanedimethanol, dimethyl isophthalate, and dimethyl sodiosulfoisophthalate Trade Name AQ 55S Polymer Function in Formula Film former, dispersant Solubility Characteristics Disperses in hot water... 

Use Concentration 0.5-2% in shampoos/conditioners 1-2% in permanent wave solutions Solubility Characteristics Dispersions in water Form Supplied Water emulsion, 40% solids Supplier ISP... 

Water-Based Solution Adhesives. Solution adhesives based on water dispersions and aqueous emulsions are steadily gaining in use largely at the expense of solvent-based adhesives. These are rarely true solutions, with the exception of the viscosity modifiers often used to adjust flow characteristics. Dispersions... 

However, it may not be true for laboratory studies, especially in differential reactors, or for reactors with more complicated flow leading to large characteristic dispersion lengths. Results similar to (12.7.2-12a) for more complex rate forms, including adiabatic reactors, have been derived using formal perturbation techniques — see Turian [1973],... 

For automated powder handling systems and to achieve reduced mix cycle times, Alcan SF E grades can be supplied at higher densities to achieve enhanced flow characteristics. Dispersion, top-cut and electrical characteristics are maintained. 

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