Experimental Results for Dispersions

The experimental results for dispersion coefficients in gases show that they can be satisfactorily represented as Peclet number expressed as a function of particle Reynolds number, and that similar correlations are obtained, irrespective of the gases used. However, it might be expected that the Schmidt number would be an important variable, but it is not possible to test this hypothesis with gases as the values of Schmidt number are all approximately the same and equal to about unity. 

In this section, we will show some relevant experimental results for dispersions and compare them mainly to viscosity theoretical predictions. More detailed information on experimental results in the oscillatory regime as well is given in reference [5]. 

We need to understand under which conditions a colloidal system will remain dispersed (and under which it will become unstable). Knowing how colloidal particles interact with one another makes possible an appreciation of the experimental results for phase transitions in such systems as found in various industrial processes. It is also necessary to know under which conditions a given dispersion will become unstable (coagulation). For example, one needs to apply coagulation in wastewater treatment so that most of the solid particles in suspension can be removed. Any two particles coming close to each other, will produce different forces. 

The dependence of the cmc on the length of the insoluble block and its poly-dispersity was calculated, and reasonable agreement with experimental results for the PS-PI/hexadecane (Price etal. 1987) and PS-poly(sodium acrylate)/water systems (Astafieva et al. 1993) were obtained.The cmc was found to decrease as the polydispersity increased, in agreement with the calculations of Linse discussed above.The fraction of dispersed chains and molecular weight distributions of the dispersed chain and the micelles were found to be influenced by the dependence of the cmc of each component in the polydisperse mixture on the insoluble block length (Gao and Eisenberg 1993). 

We do not pursue the solution of this new packed-bed dispersion model but note that it can be used to explain Hiby s (1962) experimental result, for which the traditional parabolic model cannot provide a good explanation. 

Table 9-1 shows the experimental results for precipitation of bromide from equimolar mixtures of bromide and chloride determined by Kolthoff and Eggertsen compared with the values calculated on the assumption of homogeneous and heterogeneous solid solutions. It appears that in the absence of aluminum, when the precipitate remained colloidally dispersed, homogeneous distribution equilibrium was... 

The nature of the dependences n (u>) and nn(w) are known to be dependent on the signs of the coefficients fi and n2, respectively (1). Therefore, the experimental results for the ratio (5.53) can, in principle, be used to identify the spatial dispersion effects of the crystal matrix. However, the decay of the excited states of both the impurity and the matrix makes this difficult. If the levels of these states are wide enough then it becomes practically impossible to sneak up on the frequency fli(O) and to distinguish the impurity absorption from the matrix absorption. 

Kobayashi. et al. (1973 b) studied three cases (1) uniform respiration activity throughout mycelial pellets. (2) respiration activity as a function of age distribution within the pellet. (3) respirative activity adaptation to the local oxygen concentration within the pellet. In case 1. it was found that the effectiveness factor (Ej) is equal to the ratio of the specific respiration rate of a pellet to the respiration rate of well dispersed filamentous mycelia. The theoretical and experimental results for each case are given in Figure 4. It is seen that the three cases considered gave similar results and it is difficult to discriminate between them with the limited experimental data available. 

The boundary conditions were represented by Danckwerts equations [40]. The authors used the experimental results for axial dispersion from their previous investigations [29,30]. The differential equations were solved using several well-known approximations, which relate the number of overall transfer units with the number of true transfer units, as well as with the axial dispersion and with the extraction factor. 

For composite surfaces formed by dispersing particles in the matrix, an equation was derived with which the contact angles of liquids on composite surfaces could be more conveniently calculated from the contact angles and the volume tractions of the component materials. The experimental results for the contact... 

Fleischmann, M., Ghoroghchian, J. and Jansson, R.E.W. (1979) Dispersion in electrochemical cells with radial flow between paraUel electrodes part II. Experimental results for capiUary gap ceU and pump ceU configurations. Journal of Applied Electrochemistry, 9, 437. 

FIGURE 6.15 Comparison of Equation 6.40 with experimental results for foam volume, V(t), against time obtained by Pelton [48] for various concentrations of a hydrophobed silica-polydimethylsiloxane antifoam emulsion dispersed in a 5 g dm solution of commercial dishwashing liquid. Foam was generated by passing nitrogen through porous frit at gas flow rate of 7 cm s . Antifoam concentrations , 0.1 g dm A, 0.3 g dm , 0.5 g dm". Fit to results... 

A dispersion relationship describes the optical constant shape versus wavelength. The adjustable parameters of the dispersion relationship allow the overall optical constant shape to match the experimental results. For transparent materials, the most often used refractive index (n) wavelength (2) relationship is the Cauchy function, which has three adjustable parameters, namely Hq, A, and E ... 

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