Mass transport in a novel two‐fluid taylor vortex extractor
Mass transport in a novel two‐fluid taylor vortex extractor
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DOI：
10.1002/aic.690461208
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发表时间：
2000-12
期刊：
影响因子：
3.7
通讯作者：
G. Baier;M. Graham;E. Lightfoot
中科院分区：
文献类型：
--
作者：
G. Baier;M. Graham;E. Lightfoot
旋转流中的流动不稳定性可以作为液-液萃取的一种新途径。两种互不相溶的液体在同向旋转的同轴圆柱体之间的环形空间中由于离心力而径向分层。当内圆筒旋转超过临界速度时，泰勒涡流在一种或两种流体中形成。虽然流型产生相对少量的界面表面积，但由于局部涡旋运动，该表面对于相间传质是高度活跃的。通过添加逆流轴向流，也可以进行有效的连续加工。这种流动产生了可行的提取过程，特别是对于容易分离的流体对，因此对于目前市售的设备具有有限的处理选择。本文论证了具有逆流轴向流的双流体泰勒-库埃特流在实践中是可以实现的，并通过实验和计算探讨了该流的传质特性。实验上，当涡刚出现时，轴向弥散减小，相间传质开始增加。随着转速的增加，萃取性能不断提高，传质系数与泰勒涡的强度成正比。这表明，即使相对旋转速率更大，也可以获得非常高的提取效率。此外，传质边界层理论，结合计算流体力学，提供了一个可靠的方法来预测萃取性能。
Flow instabilities occurring in rotating flows can be exploited as a new approach to liquid-liquid extraction. Two immiscible liquids are radially stratified by centrifugal force in the annulus between corotating coaxial cylinders. When the inner cylinder is rotated above a critical speed, Taylor vortices form in one or both of the fluids. Although the flow pattern yields a relatively small amount of interfacial surface area, the surface is highly active for interphase mass transfer due to the local vortex motion. By adding countercurrent axial flow, efficient continuous processing is also possible. This flow yields a viable extraction process, particularly for fluid pairs that are easily emulsifiable and therefore have limited processing options with the current equipment commercially available. This article demonstrates that two-fluid Taylor-Couette flow with countercurrent axial flow is achievable in practice and explores, experimentally and computationally, the mass-transfer characteristics of the flow. Experimentally, when the vortices first appear, axial dispersion decreases and the interphase mass transfer starts to increase. Upon further increase in differential rotation rate, the extraction performance continues to improve, with the mass-transfer coefficient proportional to the strength of Taylor vortices. This suggests that very high extraction efficiencies can be obtained with even larger relative rotation rates. Furthermore, mass-transfer boundary-layer theory, in combination with computational fluid dynamics, provides a reliable method for predicting the extraction performance.