A Numerical Study of the Global Performance of Two Static Mixers

Abstract

Viscous liquids have to be homogenized in continuous operations in many branches of processing industries; and therefore, fluid mixing plays a critical role in the success or failure of many industrial processes. The use of static mixers has been utilized over a wide range of applications from simple blending to complex chemical reactions. Generally, a static mixer consists of a number of equal stationary units, placed on the inside of a pipe or channel in order to promote mixing of flowing fluid streams. These mixers have low maintenance and operating costs, low space requirements and no moving parts. A range of designs exists for a wide range of specific applications. The shape of the elements determines the character of the fluid motion and thus determines the effectiveness of the mixer. There are several key parameters in the design procedure of a static mixer. Some of the most important ones are: the degree of mixing of working fluids, pressure drop across the mixer, and residence time distribution of fluid elements. An ideal static mixer provides a highly mixed material with low pressure drop and similar traveling history for all fluid elements. To choose a static mixer for a given application or in order to design a new static mixer, besides experimentation, it is possible to use powerful computational fluid dynamics (CFD) tools to study the performance of static mixers. This paper extends previous studies by the authors on industrial static mixers and illustrates how static mixing processes of single-phase viscous liquids can be simulated numerically. Using different measuring tools, the global performance and costs of two static mixers are studied.