High shear mixers: A review of typical applications and studies on power draw, flow pattern, energy dissipation and transfer properties

High shear mixers (HSMs), characterized by their highly localized energy dissipation, are widely used in process industries for dispersed phase size reduction and reactive mixing. Research findings on typical applications of HSMs have been summarized in this paper, namely liquid–liquid emulsification, solid–liquid suspension and chemical reactions, with an emphasis on the emulsification due to relatively intensive research in this area. The design and control of HSMs as chemical reactors need comprehensive knowledge of both the reactions kinetics and the HSMs hydrodynamics. Therefore, hydrodynamics of HSMs in terms of power draw, flow pattern and energy dissipation are then particularly reviewed from both experimental fluid dynamics (EFD) measurements and computational fluid dynamics (CFD) simulations. Limited reports on the mass and heat transfer properties in HSMs are also introduced to demonstrate their potential applicability to intensify chemical reaction processes. Due to difficulties and challenges emerged in the experimentations, CFD tools play an important role in the design, optimization and scale-up of HSMs, yet the prediction accuracies still need to be improved.

► High shear mixers for dispersed phase size reduction and reactive mixing.
► Power draw of batch HSMs are similar to stirred tanks.
► Power draw of in-line units has power number, flowrate and power loss terms.
► Jet, recirculation and re-entrainment in HSMs, and bypassing in in-line HSMs.
► Numerical prediction accuracy still needs to be improved.