Integration of CFD and RTD analysis in flow pattern and mixing behavior of rotary pressure exchanger with extended angle

In this study, the computational fluid dynamics (CFD) approach combined with the residence time distribution (RTD) analysis was implemented to examine the mixing performance and flow pattern of rotary pressure exchanger (RPE). Based on oscillatory Reynolds number, a flow regime classification was established for RPE. A concept of extended angle of RPE was proposed, and then, its effects on mixing behavior were evaluated by CFD simulation in laminar model. Meanwhile, flow pattern in RPE was quantified by RTD study, and was well captured in the flow field analysis. In addition, the effects of operating conditions on the mixing and flow pattern were discussed. According to the results, it was shown that the extended angle of RPE is beneficial for mixing control, and a minimum volumetric mixing rate was achieved when the extended angle is +/- 30 degrees compared with other configurations. In different operating conditions, the mixing rate was minimized at an oscillatory Reynolds number of about 178. Moreover, the smaller RTD variance, the closer was the flow pattern to an ideal plug flow, leading to a lower volumetric mixing rate of RPE. This study indicates that the RTD and CFD simulation are capable for mixing study and flow analysis in RPE device, and they are complementary and verifiable with each other.