Abstract: Efficiently modulating the velocity distribution and flow pattern of non-Newtonian fluids is a critical challenge in the context of dual shaft eccentric mixers for process intensification, posing a significant barrier for the existing technologies. Accordingly, this work reports a convenient strategy that changes the kinetic energy to controllably regulate the flow patterns from radial flow to axial flow. Results showed that the desired velocity distribution and flow patterns could be effectively obtained by varying the number and structure of baffles to change kinetic energy, and a more uniform velocity distribution, which could not be reached normally in standard baffle dual shaft mixers, was easily obtained. Furthermore, a comparative analysis of velocity and shear rate distributions is employed to elucidate the mechanism behind the generation of flow patterns in various dual-shaft eccentric mixers. Importantly, there is little difference in the power number of the laminar flow at the same Reynolds number, meaning that the baffle type has no effect on the power consumption, while the power number of both unbaffle and U-shaped baffle mixing systems decreases compared with the standard baffle mixing system in the transition flow. Finally, at the same rotational condition, the dimensionless mixing time of the U-shaped baffle mixing system is 15.3% and 7.9% shorter than that of the standard baffle and the unbaffle mixing system, respectively, which shows the advantage of the U-shaped baffle in stirring rate.

Key words: Dual shaft, “U-shaped” baffle, Flow pattern, Mixing time, Power demand

摘要： Efficiently modulating the velocity distribution and flow pattern of non-Newtonian fluids is a critical challenge in the context of dual shaft eccentric mixers for process intensification, posing a significant barrier for the existing technologies. Accordingly, this work reports a convenient strategy that changes the kinetic energy to controllably regulate the flow patterns from radial flow to axial flow. Results showed that the desired velocity distribution and flow patterns could be effectively obtained by varying the number and structure of baffles to change kinetic energy, and a more uniform velocity distribution, which could not be reached normally in standard baffle dual shaft mixers, was easily obtained. Furthermore, a comparative analysis of velocity and shear rate distributions is employed to elucidate the mechanism behind the generation of flow patterns in various dual-shaft eccentric mixers. Importantly, there is little difference in the power number of the laminar flow at the same Reynolds number, meaning that the baffle type has no effect on the power consumption, while the power number of both unbaffle and U-shaped baffle mixing systems decreases compared with the standard baffle mixing system in the transition flow. Finally, at the same rotational condition, the dimensionless mixing time of the U-shaped baffle mixing system is 15.3% and 7.9% shorter than that of the standard baffle and the unbaffle mixing system, respectively, which shows the advantage of the U-shaped baffle in stirring rate.

关键词: Dual shaft, “U-shaped” baffle, Flow pattern, Mixing time, Power demand