CFD simulation on shear-thinning gas-liquid dispersion in coaxial mixer

doi:10.11949/j.issn.0438-1157.20161749

Abstract

Abstract:

Gas-liquid mixing equipment has broad industrial applications for its good performance in gas dispersion with increased contact area between gas and liquid phases. In order to understand gas-liquid dispersion in industrial process of shear-thinning liquid system under different working conditions, appropriate rotation mode was first determined experimentally by studying overall gas holdup and relative power demand and effect of apparent gas velocity, system viscosity, and stirring speed on gas holdup and bubble size was then investigated by population balance and multiple size group model simulation. Results showed that, coaxial mixer in contra-rotation mode had larger overall gas holdup and better gas pumping capacity than mixer with single inner impeller or coaxial mixer in co-rotation mode at conditions of ideal gas-liquid dispersion and same power consumption. Increasing apparent gas velocity forced more homogeneous gas holdup and larger bubble size. Increasing system viscosity reduced impeller affecting zone and homogeneity of gas holdup but increased bubble size. Increasing stirring speed enlarged affecting area of circular vortex and extended high gas holdup area.

Key words: shear-thinning system, gas-liquid flow, coaxial mixer, gas holdup, numerical simulation

摘要：

气液搅拌设备因其良好的适用性被广泛应用于过程工业中。为更好地比较不同工况下剪切变稀体系中的气液分散情况，通过实验研究整体气含率和相对功耗确定适宜的转动模式，进而模拟研究表观气速、体系黏度、搅拌转速对气含率和气泡尺寸的影响。结果表明，相同功率下内外双桨反向旋转模式在理想气液分散条件下，相较于单轴内桨和内外双桨同向旋转模式具有更高的气含率和更好的气体泵送能力；表观气速的增加有利于气泡的均匀分散，但气泡尺寸也会随之增大；有效黏度的增加使得搅拌桨的影响区域变小，不利于气泡的均匀分散，气泡尺寸也随之增大；搅拌转速的增加使得循环涡流的影响区域变大，高气含率区不断扩大。

关键词: 剪切变稀体系, 气液两相流, 同心双轴搅拌釜, 气含率, 数值模拟

CLC Number:

TQ051.7

LIU Baoqing, ZHENG Yijun, LIANG Huili, WANG Manman, JIN Zhijiang. CFD simulation on shear-thinning gas-liquid dispersion in coaxial mixer[J]. CIESC Journal, 2017, 68(6): 2280-2289.

刘宝庆, 郑毅骏, 梁慧力, 王曼曼, 金志江. 剪切变稀体系同心双轴搅拌釜内的气液分散模拟[J]. 化工学报, 2017, 68(6): 2280-2289.

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