Abstract:

An experimental investigation was conducted with a high-speed camera to explore the hydrodynamics characteristics of slug flow in a microchannel with a cross-section of 1 mm×1 mm. Pure carbon dioxide and water were used as working fluids. The influence of superficial gas and liquid velocities and the wettability of microchannel on the two-phase flow pattern and mass transfer was investigated. In the hydrophilic microchannel, bubbly flow, bubbly-slug flow and slug flow were observed. In the hydrophobic microchannel, asymmetric slug flow, elongated asymmetric slug flow, stratified flow were found. It was shown that in slug flow of the hydrophilic microchannel, the length of bubble increased generally with the increase of superficial gas velocities and the decrease of superficial liquid velocities. The length of liquid slug decreased generally with the increase of superficial gas velocities, and increased firstly and then decreased generally with the increase of superficial liquid velocities. As the improvement of superficial gas and liquid velocities, the liquid volumetric mass transfer coefficient k_La increased. The liquid volumetric mass transfer coefficient k_La in the hydrophilic microchannel was higher than that in the hydrophobic microchannel.

Key words: microchannel, gas-liquid two-phase flow, slug flow, hydrodynamics characteristics, mass transfer, hydrophilic, hydrophobic

摘要：

在1 mm×1 mm矩形截面下微通道内,以二氧化碳-水为工作流体,研究壁面润湿性和气液表观流速对气-液两相流型和气液传质的影响,并研究了气、液表观流速对弹状流流体力学性质的影响。在亲水微通道中观测到了泡状流、泡状-弹状流、弹状流;在疏水微通道中观测到了非对称弹状流、拉长的非对称弹状流、分层流。实验表明亲水微通道中弹状流区域下气泡长度大体上随气相表观流速的增大而增大,随液相表观流速的增大而减小;液弹长度大体上随气相表观流速的增大而减小,随液相表观流速的增大先增大后减小;液侧体积传质系数k_La均随气、液相表观流速的增大而增大,随通道壁面润湿性的增强而增大。

关键词: 微通道, 气-液两相流, 弹状流, 流体力学性质, 传质, 亲水, 疏水