(272i) Investigation of Falling Liquid Film Flow On Multi-Baffled Plate

Falling liquid film flow accompanied by mass transfer is a common phenomenon in chemical processes, such as distillation and absorption. And it is found that different flow patterns of falling liquid film lead to different mass transfer efficiency. By changing the detailed configuration of corrugated sheet of structured packing, flow patterns of the falling liquid film flow on the packing can be changed. In this paper, a novel structured packing on which the liquid film flow with a new kind of flow pattern is proposed and mass transfer experiment demonstrate that the packing has a high mass transfer efficiency.

However, the complicated structure of the packing limits a deeply understanding of the mass transfer mechanism. So a simplified model called multi-baffled plate is proposed with the similar hydrodynamic characteristic. Based on the proposed model, experiment and numerical simulation are carried out with isopropanol desorption process on multi-baffled and ordinary plate respectively. Experimental results show that the mass transfer efficiency of multi-baffled configuration is about 50% higher than that of ordinary plate.

In order to investigate the detailed structure of the flow and mass transfer behavior, Computational Fluid Dynamics (CFD) model based on Volume of Fluid (VOF) method is developed, and marangoni effect induced by mass transfer is considered in the model. On the basis of the simulation results, it can be concluded that there are two important factors leading to the higher mass transfer efficiency on the multi-baffled plate. Firstly, the renewal rate is increased accompanied by vortices near the liquid film. When the liquid film flows across the junction of two baffles, the surface flow on the upstream plate is turned to be the bottom flow on the downstream plate, and the bottom flow on the upstream plate is turned to be the surface flow on the downstream plate. Secondly, flow instability is increased in the condition of the changing of flow direction at the junction of two baffles. Based on the reasons above, the mass transfer efficiency on the multi-baffle plates is increased.