Novel axial-tangential corrugated inner cylinders in Taylor-Couette reactors: CFD analysis of Taylor vortex modulation, turbulence, and mixing efficiency

CFD simulation of shear flow and mixing in a Taylor–Couette reactor with variable cross-section inner cylinders

Effect of varying surface structures of the inner rotating cylinder on characteristics of droplet formed in a liquid–liquid Taylor-Couette (TC) reactor is investigated. Two novel surface structures of inner cylinders, designed with axially corrugated surface (N40) and with typical three-dimensional roughness (NZ40), respectively, were adopted for the investigation. The high-speed camera visualization was used to measure the droplet size while CFD modelling was applied to predict the fluid dynamics of TC flows with such two inner cylinders and a smooth surface inner cylinder, thus revealing the effect of inner cylinder configuration on the droplet formation in the TC flows. The experimental results have clearly indicated that both the rotation speed and surface configuration variation of the inner cylinders affect the generated droplet size and distribution. As the rotation speed increases, the droplet size is obviously reduced for all types of inner cylinder configurations. Compared with the conventional smooth surface inner cylinder, the two new types of inner cylinders with special surface structures can produce much smaller droplets, especially for the case of N40 surface structure inner cylinder, with which the smallest droplet size was found at all the experimental conditions. CFD modelling results have demonstrated that the surface configurations of inner cylinder can significantly affect the turbulence generation, consequently altering the distributions of turbulent kinetic energy and local turbulence shear strain rate. As a result, the droplet size was found to be controlled by the change of the local turbulent dissipation rate that was strongly associated with the surface structures of inner cylinders. Empirical correlations that correlate the droplet size with the Weber number and Reynolds number were proposed based on the high-speed camera visualization data.

Simulation of Taylor–Couette reactor for particle classification using CFD

Modeling and Simulation for Feasibility Study of Taylor-Couette Crystallizer as Crystal Seed Manufacturing System

The quality of graphene sheets significantly depends on the degree of oxidation of graphite and the methods used for synthesis. Therefore, selecting an eco-friendly and cost-effective process is an important step in order to increase the oxidation level. The latest studies show that Taylor–Couette reactors are one of the best options to improve the oxidation level of graphite. Graphene suspensions show shear-thinning behavior, and the emergent flow structures in TC flows significantly influence the oxidation degree. In this study, we investigated the flow patterns of shear-thinning fluids in a TC reactor. The effect of radius ratio, power-law index and the rotating direction of the cylinders on the flow patterns and their critical values is studied experimentally in a Taylor–Couette flow that occurred between concentric cylinders. The Reynolds numbers defined with the wall shear viscosities (Rei and Reo) are used for evaluating the critical conditions of various flow structures. The results demonstrate that fluid properties and radius ratio may have significant destabilization effects in forming non-axisymmetric flow patterns and change their critical values. The characteristics of various flow regimes are altered substantially with increasing inner cylinder speed. A strong influence of the rotation direction of the outer cylinder on flow structures and their critical Reynolds numbers has also been revealed in this study. The obtained results also provide a deeper understanding of fluid–suspension interactions in TC reactors. These new findings will help in designing and developing more efficient TC reactors to be used in synthesizing high-quality graphene products.

This paper investigates the flow structure and flow pattern transition within a conical ribbed Taylor–Couette reactor (TCR), which is 4 mm in gap width and 200 mm in height, via particle image velocimetry (PIV) and numerical simulation methods. The effect of various parameters on the vortex structure and on flow transition, including the structural parameters of the ribs (rib spacing and rib width) and the operating parameters (Taylor number and axial Reynolds number), were investigated. Without axial flow, the ribbed TCR can control the flow structure while maintaining the symmetry of the flow field. Under certain conditions, a Taylor vortex pair can form between the ribs, with the down vortex rotating clockwise and the up vortex rotating counterclockwise. The axial dimension of the Taylor vortex can be controlled by adjusting the rib spacing, which can be summarized into four different conditions according to the size of the rib spacing. With axial flow, the axial Reynolds number greatly impacts the Taylor vortex structure within the ribbed TCR, and as the axial Reynolds number increases, the up vortex appears to be compressed and the down vortex appears to be stretched. The double vortex flow pattern between the ribs is eventually transformed into a single vortex. The critical axial Reynolds number for flow pattern transition is defined and correlated with the Taylor number and rib spacing. The results show that the critical axial Reynolds number is positively proportional to the Taylor number and is inversely proportional to rib spacing. The empirical correlation equation developed in this study shows strong predictive power and is validated using the experimental results. Overall, this study provides a comprehensive understanding of the flow structure and pattern transition within a ribbed TCR and lays the foundation for the further optimization of TCR design.

Li(Ni0.6Mn0.2Co0.2)O2 (NMC622) cathode materials have been recognized as the next generation cathode materials due to its higher capacity and lower raw material cost than commercialized cathode materials such as NMC532. Thus, many industrial companies have been made every effort to commercialize and apply the NMC622 to lithium ion battery system such as energy storage system (ESS). However, production cost of NMC622 still has been recognized as expensive material to be applied in the industrial field and it becomes main issues to be overcome. CSTR (Continuous Stirred Tank Reactor) has been widely applied in the industrial field to produce the NMC622 precursor but it has initial long stabilization time as well as low production efficiency. This is caused by the original limitation of CSTR such as the low mass transfer rate and required complete mixing zone to stabilize the system. Thus, in this study, we suggest the novel reactor system that shows the higher mass transfer rate as well as higher production rate than those of CSTR. Developed novel reactor system uses the taylor-couette flows to induce higher mass transfer rate and production efficiency with uniform particle size distribution.In this study, we synthesized NMC622 using taylor-couette reactor to understand the function and mechanism of the operation. The effect of operating parameters, i.e. pH, operating rpm, and feed retention time, in the taylor-couette reactor, was investigated thoroughly to evaluate the feasibility to produce NMC622 precursor. Produced precursors are characterized using SEM, XRD, ICP, FIB, PSA. Then, cathode materials are prepared and tested using a galvanostatic intermittent titration method (GITT) to understand the electrochemical properties. This study verified that taylor couette reactor is feasible process to be applied to the commercial NMC622 production.Acknowledgement - This work was supported by the Korea Institute of Energy Technology Evaluation and Planning under the Energy Technology Development Program (20132020101750)

Li(Ni0.6Mn0.2Co0.2)O2 (NMC622) cathode materials have been recognized as the next generation cathode materials due to its higher capacity and lower raw material cost than commercialized cathode materials such as NMC532. Thus, many industrial companies have been made every effort to commercialize and apply the NMC622 to lithium ion battery system such as energy storage system (ESS). However, production cost of NMC622 still has been recognized as expensive material to be applied in the industrial field and it becomes main issues to be overcome. CSTR (Continuous Stirred Tank Reactor) has been widely applied in the industrial field to produce the NMC622 precursor but it has initial long stabilization time as well as low production efficiency. This is caused by the original limitation of CSTR such as the low mass transfer rate and required complete mixing zone to stabilize the system. Thus, in this study, we suggest the novel reactor system that shows the higher mass transfer rate as well as higher production rate than those of CSTR. Developed novel reactor system uses the taylor-couette flows to induce higher mass transfer rate and production efficiency with uniform particle size distribution.In this study, we synthesized NMC622 using taylor-couette reactor to understand the function and mechanism of the operation. The effect of operating parameters, i.e. pH, operating rpm, and feed retention time, in the taylor-couette reactor, was investigated thoroughly to evaluate the feasibility to produce NMC622 precursor. Produced precursors are characterized using SEM, XRD, ICP, FIB, PSA. Then, cathode materials are prepared and tested using a galvanostatic intermittent titration method (GITT) to understand the electrochemical properties. This study verified that taylor couette reactor is feasible process to be applied to the commercial NMC622 production.

Effect of shear-thinning behavior on flow regimes in Taylor–Couette flows

Process intensification of a catalytic-wall Taylor-Couette reactor through unconventional modulation of its angular speed

Taylor–Couette flow with superimposed axial flow is becoming increasingly accepted as a novel reactor type offering a wide range of mixing regimes within a single reactor vessel, depending on the operating conditions of the reactor. To exploit the potential of such a reactor fully, the mixing processes in the reactor have to be well understood. A variant of an established model to simulate flow in a Taylor–Couette reactor with axial flow is presented. The model, which is based on the description of the flow as a linked network of stirred tanks, attempts to develop a parameterisation of the mass exchange processes between Taylor vortices and the by‐pass stream on a rational basis. Some numerical results are presented and compared with results from the literature.© 2003 Society of Chemical Industry

Particle image velocimetry (PIV) was applied to characterize the morphological changes of flocs and to acquired velocity field data in the coagulation process in Taylor-Couette reactor. By use of PIV,the morphological of the flocs in the coagulation process can be characterized and described with good performance. It was shown that the flocculation efficiencies reached the maximum values and the size of the generated flocs in the coagulation process was the biggest when the roating speed was in the range between 20∼60 rpm. It was demonstrated that PIV can be exploited as a useful tool in the in-situ observation flocs during coagulation processes.

Mixing in a Taylor–Couette reactor in the non-wavy flow regime

Continuous synthesis of nickel/cobalt/manganese hydroxide microparticles in Taylor–Couette reactors

Particle image velocimetry (PIV) was used to measure the velocity field of the Taylor-Couette flocculation flow with different flocs as the tracer. It can be seen that these different flocs can be used as trace particles in PIV for flow field measurement. The results indicated that the velocity vector maps obtained by PIV with different flocs can express the variation characteristics of the flocculation flow field structure of the vortex. At the same time, the velocity vector field obtained by PAC flocs generated in real time as trace particle is almost similar to that obtained by FeCl3. The major changes of the flow field in the coagulation process are mainly due to the change of rotation speed rather than the change of flocculants type or dosage.