Definition of macro- and micro-mixing

The first of the five stirring operations listed in Section 1.1 is homogenization. The term homogenization concerns the equalization of concentration and temperature differences, which is by far the most important and the most frequently carried out stirring operation. Its objective is the production of a uniform molecularly homogeneous mixture (solution). 

In this connection it is important to be able to ascertain the smallest material ball attainable and to estimate the homogenization time, which is thereby required. Mixing or stirring power has to be expended to decrease the diffusion length or decrease the size of the segregated liquid balls. According to the statistical theory of turbulence due to Kolmogorov [143, 289], see Section 1.4.2, the size of the liquid balls can be estimated  

According to this formula the size of the material balls in a relatively intensive mixing operation with P/pV = 1 W/kg in water at room temperature (v = 10 m /s) is 32 pm and in pure glycerine at room temperature (v = 10 m /s) is already 5.6 mm. From this it is evident that viscous material systems always remain to a certain extent segregated, since their state can only be influenced to a comparatively small extent by the stirrer power (2 oc e  

In contrast to macro-mixing, which represents the scale-dependent homogenization process, the subsequent micro-mixing as a molecular process is not scale- 

The quantitative understanding of micro-mixing time is discussed in connection with homogenization in pipes in Section 8,6.1. 

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