Dispersive mixing definition

For simple fluids, also known as Newtonian fluids, it is easy to predict the ease with which they will be poured, pumped, or mixed in either an industrial or end-use situation. This is because the shear viscosity or resistance to flow is a constant at any given temperature and pressure. The fluids that fall into this category are few and far between, because they are of necessity simple in structure. Examples are water, oils, and sugar solutions (e.g., honey unit hi.3), which have no dispersed phases and no molecular interactions. All other fluids are by definition non-Newtonian, so the viscosity is a variable, not a constant. Non-Newtonian fluids are of great interest as they encompass almost all fluids of industrial value. In the food industry, even natural products such as milk or polysaccharide solutions are non-Newtonian. 

It is possible to define an evaluation index for the mixing state by using the definition of multi-component mixedness in the previous section. The following discussion focuses on the mixing state of the continuous phase and the dispersed phase with a particle size distribution. 

The distribution of the dispersed particle size is divided into m - 1 groups in the order of size, and each group is considered to be individual component. Additionally, the continuous phase is treated as another component. From this consideration, the mixing can be treated as m-component mixing, and the multi-component mixedness defined by Eq. (2.43) in the previous section can be applied. The extended definition of mixedness for the mixing of the continuous phase and dispersion phase can be expressed as... 

In order to achieve simultaneous suspension of solid particles and dispersion of gas, it is necessary to define the state when the gas phase is well dispersed. Nienow (1975) defined this to be coincident with the minimum in Power number, Ne, against the aeration number, 1VA, relationship (see Fig. 12 [Sicardi et al., 1981]). While Chapman et al. (1981) accept this definition, their study also showed that there is some critical particle density (relative to the liquid density) above which particle suspension governs the power necessary to achieve a well-mixed system and below which gas dispersion governs the power requirements. Thus, aeration at the critical stirrer speed for complete suspension of solid particles in nonaerated systems causes partial sedimentation of relatively heavy particles and aids suspension of relatively light particles. Furthermore, there may be a similar (but weaker) effect with particle size. Wiedmann et al. (1980), on the other hand, define the complete state of suspension to be the one where the maximum in the Ne-Ren diagram occurs for a constant gas Reynolds number. 

XV), but this evidence is probably not definitive since a similar discrepancy exists for other proteins as well. Although the interactions of L-amino acid side chains with a right-handed helix will be different from those with a left-handed helix, rotatory dispersion is primarily a function of the helical skeleton rather than side-chain interactions and cannot at present distinguish among helices of different sense mixed with disordered regions. 

Matz (208) also has reported on the improvements obtained with the use of lecithin in the production of cookies. Cookie dough is drier and more machinable with the use of lecithin. Lecithin improves the dispersion of fat so that it more readily mixes with sugar, flour, and other ingredients. Improved emulsification also reduces mixing times. Overdevelopment of the dough can result in lack of tenderness in the cookie. The release quality of lecithin improves the extrudabihty and release from the die, improving definition of impression. 

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