运动气泡近界面浓度场的激光测量及其传质特性的研究

CONCENTRATION FIELDS AND MASS TRANSFER BEHAVIOR NEAR A MOVING BUBBLE INTERFACE BY LASER TECHNIQUE

1引言迄今为止，有关两相流气泡的传质研究已有大量报道[1-4]。这些研究均是一种黑箱式的研究方法，着眼于宏观现象的观测、分析及回归，无法从机理上展示各种宏观传递现象的差异及其内在本质，固而其研究结果均带有很大的经验性和局限性。 随着化学工程基础理论研究的深入发展，需要进一步了解运动气泡逼近界面处浓度场的变化与分布。特别是由于运动气泡的特殊性，气泡在上升过程中要发生变形[5]，形成泡前区及尾涡区，在这两个区域内，界面阳近动力学特性及浓度场特性有很大差异，这就需要在更深的层次上研究这种微观差异。

A laser holographic interferometer with optical magnification was designed and used in this work for the study of concentration fields near the interface and mass transfer phenomena of a gas bubble moving against a countercurrent liquid stream. The concentration profiles in liquid phase near the frontal and rear interfaces of a bubble were measured quantitatively for the systems containing carbon dioxide as gas phase and methanol, ethanal and n-propanal as liquid phase respectively. It was found that the liquid phase concentration at a close distance to the interface in the order of 10-2mm, designated as quasi-interface concentration, was far from the thermo-dynamic equilibrium value. The concentration fields near the frontal and rear interfaces differed considerably, and such differences were affected by both the liquid phase velocity and equivalent diameter of the bubble. Inner circulation within a bubble was viewed from the hologram in the bubble formation stage, and it disappeared soon afterwards. Experimental results were discussed from the basic mass transfer equation by means of scale analysis.