The Cfd Simulation Of Gas-liquid Two Phase Flow In Capillary

Since the twentieth century, one of the important trends in the development of natural science and engineering technology is micromation. Due to the great development of Micro Total Analysis Systems and Micro-Electro-Mechanical Systems, microchemical technology has become a brand-new but important trend within the area of chemical engineering, such as capillary distillation, microchannel reactor and so on. Research has shown that compared to conventional macroreactors, the efficiency of gas-liquid mass transfer in microreactors is 2~3 times higher . Due to the size of microchannel mainly lying in submillimeter scales, microreactors own large surface-to-volume ratio, combined with the short transport path, thereby enhancing heat and mass transfer dramatically. The mass production capability needed for industrial application, currently, is achieved by simple replication of microreactor units, there by shortening the development time from laboratory to commercial production. Research on the gas-liquid two phase flows herein might help to understand the mechanism of gas-liquid mass transfer in the capillary, thus promoting the development of microchemical technology.For gas/liquid two-phase flow at low gas speed in a capillary, the Taylor slug flow regime is the most commonly encountered flow pattern. The present study adopted commercial computational fluid dynamics (CFD) package, Fluent 6.3.26, to deals with the numerical simulation of the Taylor flow in a capillary under 2D model. By varying gas/liquid speed, the development process, pressure drop, gas/liquid slug lengths of the gas-liquid two phases were studied. it was found that there existed eddies at the gas-liquid interface, which serves to promoting the mass transfer; with the increase of gas/liquid velocity, the pressure drop became bigger. The gas and liquid slug lengths at various gas/liquid velocity were obtained and found to be in good agreement with the literature data to a certain extent.Finally, a 3D model was established to compare with 2D model. It was found that velocity distribution, gas and liquid slug lengths, and gas-phase distribution in the channel shared in common in both models. However the pressure drop of 3D model was higher than that of 2D model, about 20%. Besides, the mass transfer model for 2D countercurrent operation in the capillary was constructed, which used VOF to establish numerical computational model taking surface tension momentum source and mass transfer source into account, to quantificationally describe the mass transfer process of gas-liquid two phase countercurrent flow in the capillary.