Species Exposure As an Approach to Quantifying Mixer Performance

While bulk uniformity is easily determined using blendtime, experimentally it lacks the ability to describe local blending behavior. As an alternative to uniformity, the so-called “exposure” of secondary materials in a bulk material provides both local and bulk mixing characteristics. Exposure, as defined by Kresta et al., relates the contact area between multiple species, which allows mass and heat transfer to be analyzed through a similar metric [1]. It also unifies the analysis of rotating systems and static mixer systems with a universal mixing description. While the mathematical viability of this parameter has been studied, it has yet to be fully analyzed with the context of a time-varying, three-dimensional mixing system. Validation of exposure in both rotating and static mixed systems is presented here and the viability of it as a universal mixing descriptor is discussed.

[1] S. M. Kresta, A. Kukukova, J. Aubin. “A new definition of mixing and segregation: Three dimensions of a key process variable”. Chemical Engineering Research and Design 87 (2009) pp. 633-647