In this work a concept of energetic efficiency of mixing is presented and discussed; a classical definition of mixing efficiency is modified to include effects of the Schmidt number and the Reynolds number. Generalization to turbulent flows is presented as well. It is shown how the energetic efficiency of mixing as well as efficiencies of drop breakage and mass transfer in twophase liquid-liquid systems can be identified using mathematical models and test chemical reactions. New expressions for analyzing efficiency problem are applied to identify the energetic efficiency of mixing in a stirred tank, a rotor stator mixer and a microreactor. Published experimental data and new results obtained using new systems of test reactions are applied. It has been shown that the efficiency of mixing is small in popular types of reactors and mixers and thus there is some space for improvement.
Energetic efficiency depicting the fraction of energy dissipation rate used to perform processes of drop breakup and mass transfer in two-phase, liquid-liquid systems is considered. Results of experiments carried out earlier in two types of high-shear mixers: an in-line rotor-stator mixer and a batch rotor-stator mixer, have been applied to identify and compare the efficiency of drop breakage and mass transfer in both types of mixers. The applied method is based on experimental determination of both: the product distribution of chemical test reactions and the drop size distributions. Experimental data are interpreted using a multifractal model of turbulence for drop breakage and the model by Favelukis and Lavrenteva for mass transfer. Results show that the energetic efficiency of the in-line mixer is higher than that of the batch mixer; two stator geometries were considered in the case of the batch mixer and the energetic efficiency of the device equipped with a standard emulsor screen (SES) was higher than the efficiency of the mixer equipped with a general purpose disintegrating head (GPDH) for drop breakup but smaller for mass transfer.