Study On Fluid Flow Characteristics In Rotating Packed Bed

The fluid flow in the rotating packed bed (RPB) is complex and the mass transfer efficiency shows significant diversities in different zones. It's important to get the flow characteristics of the fluid in the packing for RPB's study. Based on the previous studies, Computational Fluid Dynamics (CFD) software was used in this paper to get the data of fluid flow with simulating the process of fluid cut by packing. The flow field in the packing was reconstructed by the data and showed the flow characteristics of fluid.Combined with the mass transfer theory, different zones were analyzed to find the unique flow characteristics in the end-effect zone which makes the high mass transfer efficiency.In this paper, the calculation models and physical models of RPB were created. First, a single packing wire model was introduced to simulate the process of cutting fluid by packing. And then the RPB model with multilayer packing was calculated in the same way. The relationship between the fluid characteristics and the mass transfer efficiency in end-effect zone and main packing zone was found based on the comparison of the different zones'data and the single packing wire model's data.The simulation of the single packing wire cutting liquid column showed that many swirls was generated by the velocity gradient between the liquid surface and the liquid body when the packing wire cuts the liquid. The packing wire formed a gas passage after its motion path, and both sides of the liquid surface in the passage refreshed quickly due to the influence of swirls. In addition, packing wire diameter, speed, and surface properties affected the process of cutting liquid by packing wire. Likewise, the simulation of the multilayer packing model showed the similar flow field around the packing wire. For further analysis,Data was grouped by packing layers. The thickness of RPB's end-effect zone was calculated by the data of liquid flow patterns, velocity distribution, and the degree of turbulence. In addition, the dispersion degree of the end-effect zone was lower than the main packing zone and the cavity zone, while the vorticity magnitude was much higher than both of them. Furthermore, the vorticity magnitude showed the same trend as the mass transfer in the radial direction which means the surface with high update rate generated by the packing wire's cutting was extremely conducive to mass transfer. Because of the gap of velocity between the liquid and the packing in the end-effect zone, many surfaces with high update rate were generated during the cutting process, which made the mass transfer efficiency much higher than other zones.