Influence of Viscosity Ratio on the Mixing Process in a Static Mixer: Numerical Study

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• 作者：Må ; rten Regner ; Karin &Ouml ; stergren ; Christian Trä ; gå ; rdh
• 刊名：Industrial & Engineering Chemistry Research
• 出版年：2008
• 出版时间：May 7, 2008
• 年：2008
• 卷：47
• 期：9
• 页码：3030 - 3036
• 全文大小：245K
• 年卷期：v.47,no.9(May 7, 2008)
• ISSN：1520-5045

文摘

The mixing process in a Lightnin Series 45 static mixer, 40 mm in diameter, has been investigated usingcomputational fluid dynamics and the volume of fluid (VOF) method, a method developed for immisciblefluids but here used for miscible. The mixing process was investigated for two liquids that had viscositiesranging from 0.003 to 51.2 Pa s, and the volumetric flow rate proportion between the liquids was variedbetween 1/1 and 4/1. The flow rate was 0.1 m/s, and two Reynolds numbers, 1 and 70, were investigated.The mixer performance was evaluated using the rate of striation thinning, and it was found that the greaterthe difference in viscosity the worse the mixer performance. This effect is due to the difference in elongationrate between the liquids, which exists until equilibrium in shear stress has been reached at the interface betweenthe liquids. For higher Re numbers close to a point when secondary motions start to have significance for therate of striation thinning, a lower viscosity of the added liquid results in an increase in mixing performance.It was further found that the VOF method can be used to model the mixing of dissimilar liquids in staticmixers, but since the thickness of the striations decreases rapidly with the number of mixer elements, theVOF method is most suitable when investigating mixing processes over a small number of mixer elements.