Study On Local Mass Transfer Of Structured Packing With The Method Of Flow Visualization

In recent years, study on the structured packing developed slowly, because it was difficult to investigate local mass transfer on the surface of the structured packing without disturbing the flow field. Therefore, Emperical/Semi-emperical models are still dominant in determining hydrodynamic and mass transfer parameters although there exist errors around 15%-20% compared with the real situation. In order to improve this situation, local mass transfer on the surface of structured packing is employed to take the place of traditional average mass transfer.A chromochemical reactive mass transfer technique has been employed to calculate values of local mass transfer coefficients within structured packings. The true-color image processing method with the tool of high-resolution scanner is firstly used to deal with test samples. And the unit mesh on the surface of structured packing can be as small as 0.016×0.016 square millimeters. By the aid of wind tunnel, the calibration curve which represents the relation between local mass transfer rate and the color intensity is made. Then, three-dimensional map of local mass transfer coefficients is plotted depending on the calibration curve. The three-dimensional map clearly shows the existence of three peaks on different positions in a unit cell of the corrugated structured packing. On the other side, those areas with lower mass transfer rate will provide us for potential data in order to enhance the average mass transfer.Depending on the chromochemical reactive method, flow phenomena in different Reynolds numbers from 200 to 3000 are discussed, which displays that with the increasing of the Reynolds number, the mass transfer rate appears to be homogeneous and enhanced. Some tests on the perforated corrugations are carried out, indicating that the holes can enhance the mass transfer in the area of 3 to 4 millimeters nearby the hole.Computational fluid dynamics has been used to simulate the local mass transfer process within structured packing. Source term of the equation of mass transfer and diffusion has been provided by surface chemical reaction model. CFD has proved the existence of three peaks. Through the comparison between experiment and CFD in a unit cell, we can find that errors between CFD and experiment are higher in the trough and middle leeward face, about 30%. But CFD matches the experiment well on other positions with the errors in 20%.