Numerical Investigation and Estimating Correlation of Micromixing Performance of Coaxial Mixers

Abstract

In view of the significance, complexity, and difficulty of micromixing in viscous system, coaxial mixers with wide adaptability to viscosity are first combined with micromixing. The effects of feeding position, rotation mode, and impeller type on the micromixing performance of coaxial mixers are investigated numerically with the standard engulfment model and eddy dissipation concept model, and a dimensionless estimating correlation of segregation index X s is established based on the Buckingham π theorem. The results show that feeding near the discharge zone of the impeller favors the micromixing and Rushton turbine impeller (RT) is better qualified as the impeller near feeding point compared to six-straight-blade turbine impeller (SBT) and six-pitched (45°)-blade turbine impeller (PBT). At the same specific power consumption, the coaxial mixer has better micromixing performance with PBT + RT as inner impeller than with SBT + RT, and the difference of segregation index resulting from the rotation mode is small. Moreover, the proposed correlation is validated to be suitable for qualitative evaluation of micromixing performance of coaxial mixer consisting of inner impeller combining PBT and RT and outer anchor.

Study on the Numerical Model of Dense Solid Suspension Driven by a Coaxial Mixer

“…47 In addition, it was also found that the calculation using the SG method required very short time steps to accomplish convergence. Considering successful applications of the MRF method in coaxial mixers had been reported, 32,39 the MRF method was selected at last. The top of the stirred tank was defined as the symmetry boundary, and the data between different zones was transferred through interfaces.…”

“…In addition, it was also found that the calculation using the SG method required very short time steps to accomplish convergence. Considering successful applications of the MRF method in coaxial mixers had been reported, , the MRF method was selected at last.…”

“…Specially, the standard k –ε model can be divided into three different models, namely, mixture, dispersed, and per phase, where the mixture model is recommended owing to its relatively accurate results and minor calculation. , Recently, some modified k –ε models have been used in simulations of stirred tanks, such as the RNG k –ε model and the realizable k –ε model. Compared with the standard k –ε model, these models can give more accurate results in a low Reynolds number and swirling flows. , Therefore, simulation results of the standard k –ε mixture model, RNG k –ε mixture model, and realizable k –ε mixture model were compared in this study.…”

“…Compared with the standard k−ε model, these models can give more accurate results in a low Reynolds number and swirling flows. 38,39 Therefore, simulation results of the standard k−ε mixture model, RNG k−ε mixture model, and realizable k−ε mixture model were compared in this study.…”

Experimental Study on Micromixing Characteristics of Coaxial Mixer in Solid–Liquid Systems

“…Based on the above experimental results, it is found that the micromixing performance of a coaxial mixer is affected by structural, operational, and physical parameters. The effects of these parameters seem to be independent, but actually related to each other, which makes the evaluation of the micromixing performance of the coaxial mixer very complicated . To solve this difficulty, an effective method is to establish corresponding mathematical expressions to correlate parameters.…”