Abstract:

The mass transfer process of growing bubbles has important effect on the design and optimization of gas-liquid contacting devices. By investigating a single carbon dioxide bubble growing in a sodium carboxymethyl cellulose (CMC) solution, the effects of gas velocity, concentration of CMC solution, and diameter of the needle on gas-liquid mass transfer were examined. The shape, surface area and volume of growing bubble were captured by a dynamic contact angle analysis instrument with a micro-CCD camera and the liquid mass transfer coefficient k_l was calculated. The results show that the mass transfer coefficient increased with the solution viscosity as CMC concentration increased from 0.2% to 0.8%, with the diameter of the needle changing from 2.5 mm to 4 mm, and with the gas injection rate increased from 1 ml·min^-1 to 9 ml·min^-1.

Key words: non-Newtonian fluid, bubble growth, mass transfer, carbon dioxide

摘要：

气泡生成过程中气液传质是气液接触设备的设计、优化的重要参考指标。以二氧化碳气泡在羧甲基纤维素钠(carboxymethyl cellulose,CMC)溶液中生成过程中的传质为研究对象,分别考察了气速、CMC溶液浓度、针头直径对气泡生成过程气液传质的影响,采用具有CCD显微相机的动态接触角分析仪测量了气泡形状、表面积和体积的变化,进而获得气泡生成过程气液传质系数k_l。实验结果表明,CMC浓度从0.2%增加到0.8%,黏度逐渐增大,传质系数随CMC浓度的增大而增大;针头直径从2.5 mm增加到4 mm,传质系数也随之增大;气速从1 ml·min^-1增加到9 ml·min^-1,传质系数也逐渐增大。

关键词: 非牛顿流体, 气泡生成, 传质, 二氧化碳