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Mixing of layers

Turbulent flow results because of the radial mixing of layers to equalize flowrates. The mixing of the layers is due to the increased eddies and mass transfer occurs by eddy diffusivity. Turbulent diffusivity increases in proportion to mean flow velocity as depicted in Figure 2.10B. Figure 2.IOC represents plug flow which is unattainable in practice but does suggest a model... [Pg.77]

Ahmad et al. [3] investigated the mixing of layers of hot water and cold salt solution in baffled tanks (D = 28.8 and 90 cm) with centrally arranged ship s propellers, in which temperature differences were monitored with thermoelements placed at different heights in the liquid. They correlated the results with two composite pi-numbers ... [Pg.111]

On a thermodynamic ground, nanoscale mixing of layered silicates with polymers is only possible if the chemical structure of both components is such to grant favorable energetic interactions [4-8]. However, the morphology of experimental nanocomposites will be dependent on kinetics as well, and, consequently, on the pathway of their preparation. [Pg.51]

Figure 21.3 Scheme of different types of composite structures arising from the mixing of layered silicates and polymers, with corresponding TEM images. Adapted from Hussain et al. [4]. [Pg.399]

The experiment we have just described is not very satisfactory from a practical point of view, since it is very difficult to deposit a thin layer of solution between two bulk portions of solvent without some mixing. An experimentally more convenient method consists of layering equal volumes of solvent and solution so that a sharp boundary exists between them at x = 0, with c = Cq for... [Pg.631]

Loss of agitation causing stratification of immiscible layers. Insufficient mixing of reactants results in unwanted accumulation of unreacted reactants. Possibility of runaway reaction upon resumption of agitation. [Pg.61]

The disadvantage of lasers with nanosecond-picosecond pulse duration for depth profiling is the predominantly thermal character of the ablation process [4.229]. For metals the irradiated spot is melted and much of the material is evaporated from the melt. The melting of the sample causes modification and mixing of different layers followed by changes of phase composition during material evaporation (preferential volatilization) and bulk re-solidification [4.230] this reduces the lateral and depth resolution of LA-based techniques. [Pg.233]

Temperature Inversion in meteorology, a departure from the normal decrease of temperature with increasing altitude such that the temperature is higher at a given height in the inversion layer than would be expected from the temperature below the layer. This warmer layer leads to increased stability and limited vertical mixing of air. [Pg.550]

A thin layer of a mix of natural rubber, sulfur, precipitated silica, water, and some additives, such as carbon black and vulcanizing agents, is extruded on a paper support belt, calendered, and vulcanized as a roll in an autoclave under elevated pressure and temperature ( 180 °C). A modi-... [Pg.274]

The drawback of the described adsorbents is the leakage of the bonded phase that may occur after the change of eluent or temperature of operation when the equilibrium of the polymer adsorption is disturbed. In order to prepare a more stable support Dulout et al. [31] introduced the treatment of porous silica with PEO, poly-lV-vinylpyrrolidone or polyvinylalcohol solution followed by a second treatment with an aqueous solution of a protein whose molecular weight was lower than that of the proteins to be separated. Possibly, displacement of the weakly adsorbed coils by the stronger interacting proteins produce an additional shrouding of the polymer-coated supports. After the weakly adsorbed portion was replaced, the stability of the mixed adsorption layer was higher. [Pg.144]

Siemes and Weiss (SI4) investigated axial mixing of the liquid phase in a two-phase bubble-column with no net liquid flow. Column diameter was 42 mm and the height of the liquid layer 1400 mm at zero gas flow. Water and air were the fluid media. The experiments were carried out by the injection of a pulse of electrolyte solution at one position in the bed and measurement of the concentration as a function of time at another position. The mixing phenomenon was treated mathematically as a diffusion process. Diffusion coefficients increased markedly with increasing gas velocity, from about 2 cm2/sec at a superficial gas velocity of 1 cm/sec to from 30 to 70 cm2/sec at a velocity of 7 cm/sec. The diffusion coefficient also varied with bubble size, and thus, because of coalescence, with distance from the gas distributor. [Pg.117]

In one of several conceivable combinations of molecular weight and surface density, the binary brush forms a mixed, shorter layer and the extra length in and number of the longer chains is sufficient that these extra segments crowd one another in the outer layer and form an outer, stretched tethered layer. The Alexander analysis applied to the two-layer situation gives for the outer layer thickness of the mixture [132] ... [Pg.60]

As cooling occurs in the late fall and early winter, the thermal stratification breaks down, permitting mixing of the deep and surface layers. This allows the surface layers to be replenished with P. During the winter months, biological productivity in a temperate lake is limited by the availability of light rather than nutrients. [Pg.366]

However, the field of polymer day silicate has only started to speed up recently, mixing the appropriate modified layered silicate with synthetic layered silicates has long been known (Theng, 1979). The interest in these materials came from two important findings, first has been reported by Toyota research group of a Nylon-6 (N6)/Na-MMT nano-composites (Okada et ah, 1990) where very small amounts of layered silicate loadings resulted in the improvements of thermal and mechanical properties and second the findings of Vaia et ah (1993) about the... [Pg.31]

The interfaces here also have contribution to the hardness. For Samples 3 and 4, there are no obvious interfaces between Layers A and B because the individual layer thickness is so thin that it is hard to form sharp interfaces. It is more like a mixed structure according to the process. For Sample 5, the interfaces are possibly formed due to the increase of Layer A. So the hardness of Samples 3 and 4 is still much lower than monolayer A, but the hardness of Sample 5 is close to the monolayer A. [Pg.203]


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