微通道内二氧化碳-水两相流动与传质实验研究

发布时间：2018-05-27 05:37

本文选题：微通道 + 气-液两相流　；参考：《大连理工大学》2015年硕士论文

【摘要】：由于微反应器在化工领域的巨大优势,微反应器中的过程强化以及气-液两相流的研究受到了人们密切的关注。本文通过实验对微通道内气-液两相流动和传质规律进行了研究,旨在掌握微通道内气-液两相流动及传质规律,为后期强化微通道内传质提供理论指导。制备了1×lmm矩形截面微通道,矩形通道由亲水性(0=-43.7°)的铜板加工制成,然后用十八烷基硫醇溶液处理得到疏水表面(0=-114.6°),利用高速摄像仪考察了不同壁面润湿性下矩形微通道内二氧化碳-水气-液两相流型。在亲水微通道中观测到了泡状流、泡状-弹状流、Taylor流,其中Taylor流是主要流型；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,其中拉长的非对称弹状流和分层流是主要流型。利用1×lmm矩形截面亲水微通道和内径为1.08mm、1.26mmm的圆形玻璃毛细管,选用二氧化碳-水为工作流体,利用高速摄像仪考察了气、液表观流速和通道当量直径对微通道内Taylor流流体力学性质的影响。实验表明,76.9%的气泡的长度通常为通道当量直径的2-5倍,85.3%的液弹的长度通常为通道当量直径的1-4倍,77.4%的泰勒单元的长度通常为通道当量直径的5-8倍；气泡和液弹长度大体上随气、液表观流速之比的增大分别增大和减小,泰勒单元长度随气相表观流速变化复杂,但随液相表观流速的增大而减小；通道内的气泡、液弹和泰勒单元长度随通道当量直径的增大而增大；气泡运动速度UB与液弹平均运动速度Uslug的大小关系为：UslugUB1.28Uslug。搭建了微通道内CO2-H2O气-液两相流动及传质研究实验平台,利用酸碱滴定法测定微通道中C02的吸收量,考察了气、液表观流速和通道壁面润湿性对微通道内气液传质的影响。实验表明,微通道接触器比常规尺度气-液接触设备的液侧体积传质系数KLα至少要高1-2个数量级；随着气、液表观流速的增大,液弹内循环区域液体流动速度增大,组分在液弹中的混合增强,同时,单位时间单位通道横截面积通过的气液两相传质面积增大,故液侧体积传质系数kLα增大；由于亲水微通道和疏水微通道中两相流型不同,亲水微通道中气液相界面积大,而且液弹内循环区域液体流动也更快,故液侧体积传质系数KLα随通道壁面润湿性的增强而增大。
[Abstract]:Due to the great advantages of microreactors in chemical industry, the study of process strengthening and gas-liquid two-phase flow in microreactors has been paid close attention to. In this paper, the law of gas-liquid two-phase flow and mass transfer in microchannels is studied through experiments. The purpose of this study is to master the law of gas-liquid two-phase flow and mass transfer in microchannels, and to provide theoretical guidance for the later enhancement of mass transfer in microchannels. A 1 脳 lmm microchannel with rectangular cross-section was prepared. The rectangular channel was fabricated by copper plate with hydrophilic (0 ~ 43.7 掳). The hydrophobic surface was then treated with octadecyl mercaptan solution to obtain the hydrophobic surface. The CO2 / water gas-liquid two-phase flow patterns in rectangular microchannels with different wall wettability were investigated by high speed camera. In hydrophilic microchannels, bubbly flow, bubbly slug flow, Taylor flow is the main flow pattern, asymmetric slug flow, elongated asymmetrical slug flow and stratified flow are observed in hydrophilic microchannels. The elongated asymmetric slug flow and stratified flow are the main flow patterns. A 1 脳 lmm rectangular section hydrophilic microchannel and a circular glass capillary with an inner diameter of 1.08 mm or 1.26 mm were used to investigate the gas, using carbon dioxide and water as the working fluid. The effects of liquid apparent velocity and channel equivalent diameter on the hydrodynamic properties of Taylor flow in microchannels. The experimental results show that the bubble length of 76.9% is usually 2-5 times of channel equivalent diameter and 85.3% of channel equivalent diameter. The length of liquid bomb is usually 1-4 times that of channel equivalent diameter, and the length of Taylor unit with 77.4% channel equivalent diameter is usually 5-8 times that of channel equivalent diameter. The increase of the ratio of liquid apparent velocity increases and decreases respectively. The Taylor cell length changes with the gas phase apparent velocity, but decreases with the increase of liquid phase apparent velocity. The length of liquid bomb and Taylor unit increases with the increase of channel equivalent diameter, and the relationship between bubble velocity UB and the average moving velocity of liquid bomb Uslug is: 1. 28 Uslug. An experimental platform for CO2-H2O gas-liquid two-phase flow and mass transfer in microchannels was set up. The absorption of CO2 in microchannels was determined by acid-base titration. The effects of gas and liquid apparent velocity and wettability on gas-liquid mass transfer in microchannels were investigated. The experimental results show that the volumetric mass transfer coefficient KL 伪 of microchannel contactor is at least 1-2 orders higher than that of conventional gas-liquid contact equipment, and the liquid velocity increases with the increase of gas and liquid apparent velocity. At the same time, the gas-liquid two-phase mass transfer area passing through the cross-sectional area of unit channel per unit time increases, so the volumetric mass transfer coefficient (KL 伪) of the liquid side increases, because the two-phase flow patterns in hydrophilic microchannels and hydrophobic microchannels are different. The gas-liquid boundary area is large in hydrophilic microchannels, and the liquid flow is faster in the liquid-bomb circulation region, so the liquid-side mass transfer coefficient KL 伪 increases with the enhancement of the wettability of the channel wall.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ052

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