Definition of Desired Process Result

The process result of heat transfer is a heat transfer coefficient. For dispersion it is a drop or particle size and size distribution. For blending in tanks it is blend time to achieve a certain degree of mixing. The equivalent for mixing in pipeline flow is not as clear. Alloca and Streiff (1980) proposed using a radial coefficient of variation, and this concept is now widely accepted. Since it is unique in the process industries to pipeline flow, it merits some extended discussion. 

the initial degree of nnmixedness, CoVq, depends on how much needs to be mixed. The following table is illnstrative. 

the smaller the amount added, the greater the initial CoV or state of unmixedness. We define a mixing task as reducing from an initial coefficient of variation (CoVq) to a final chosen CoV which is independent of the initial coefficient of variation (CoVq). It is believed that the performance of a motionless mixer is set by this mixing task and is independent of the magnitude of the initial or final valnes. Some recent unpubhshed data challenge this, but until better data are obtained, we will presume that the mixer performs as a reducer of variance. This is the assumption of most vendors. 

2 Other Characterization Measures. Many other mixing measures have been developed. Several of them have been taken from work on mixing of particulate solids. However, in miscible liqnid blending and gas mixing there will always be diffusion at the lowest and final scales to finish off the process. There is also no mechanism for de-mixing as can occur with solids due to particle mass differences. 

In recent years the advances in computational fluid mechanics (CFD, computational fluid dynamics) and its application to mixing (CFM, computational 

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