Numerical analysis for the effects of mixer shape on mixing behavior in flow-type supercritical hydrothermal mixers

For flow-type supercritical hydrothermal synthesis, designing a mixer that provides rapid and uniform mixing is necessary to produce nanoparticles with the desired characteristics. In this study, numerical simulations of the mixing behavior of supercritical and room-temperature water were performed to compare the mixing behavior of the T-junction without a tube, which uses only a T-junction, and that of the T-junction with a tube, in which a narrow tube is inserted into a T-junction. In the T-junction with a tube, a narrower high-temperature region where the temperature is over the critical temperature of water and a smaller recirculating flow were observed compared with those in the T-junction without a tube. In addition, mixers with various positions of the inserted tube were designed and numerical simulations were performed. It was found that the distributions of the high-temperature regions and locations of flow stagnation of flow varied in the mixer at each position of the inserted tube. • Flow-type mixers using T-junction and T-junction with inserted tubes were compared. • Narrower high-temperature region was observed in the T-junction with tube. • Smaller recirculating flow was observed in the T-junction with tube. • Mixing behavior was controlled by changing the positions of inserted tube.