Gas-liquid mass transfer in slug flow through narrow channels.

摘要

This thesis consists of experimental findings of gas-liquid mass transfer in slug flow through narrow channels. A single channel experimental setup was developed, in which the gas phase was Nitrogen and the liquid phase was sucrose solution of different concentrations. Circular channels with internal diameters of 0.9, 1.8 and 2.4 mm were used. A luminescent dissolved oxygen probe was used to measure dissolved oxygen in the liquid samples. A high speed camera was used to measure bubble velocities and bubble frequencies inside the narrow channels. Experiments were performed in order to study the influence of channel diameter, bubble velocity, length of gas and liquid slugs and liquid properties on volumetric mass transfer coefficient (kLa ). One of the key features of this study was the non-dimensional approach in characterizing mass transfer. The main outcome from this study was to capture the dependence of liquid properties and length of liquid slug on gas-liquid mass transfer. A non-dimensional empirical correlation to predict kLa was developed from experimental data and the predictions from the correlation were within +/-30 percent of experimental values. Experimental data were also compared with the gas-liquid mass transfer correlations available in literature. In addition to mass transfer studies, an attempt was made to study the hydrodynamic part of slug flow in narrow channels. From this effort, an universal flow map to identify the boundaries of slug flow with other flows such as bubbly flow, churn flow and annular flow in narrow channels was developed. A correlation to predict bubble velocities in narrow channels was developed as a function of Capillary number. An existing pressure drop correlation in slug flow through narrow channels was experimentally validated over a broader range of operating parameters. The findings from this study can be used to design narrow channel reactors such as HEX reactors and monolith reactors for gas-liquid mass transfer applications.