Mixing, or Segregation, can be defined using three dimensions. The instantaneous state of segregation has two dimensions:
the scale of segregation, and the intensity of segregation. The intensity of segregation is reported as the CoV in a blending
application, while the scale of segregation is reported as the striation thickness distribution, the drop size distribution, as
examples. Previous work has shown that the two dimensions contain different and independent information. The CoV tells
us nothing about the scale of segregation, and the scale of segregation contains no information about the range of
concentrations observed.
The exposure dimension conbines the intensity and scale of segregation with a third characteristic of the system to give a rate
of reduction in segregation. Many examples of exposure equations are given in the literature. The most familiar is the mass
transfer rate, where the scale of segregation can be related to the interfacial area, the intensity of segregation to the local
concentration gradients, and the tendency of the system to reduce segregation to the mass transfer coefficient, or the
molecular diffusivity. In this case, the exposure dimension is an integral combination of the local area and intensity of
segregation, so while it is correlated to both the scale and the intensity of segregation, it is not a linear combination of the
average measures.
In this talk, the exposure dimension will be reviewed in the context of existing literature and models. The goal is to
determine the underlying mixing variables which consistently drive a reduction in segregation, and the role that these
variables play in achieving a range of process objectives