Mixing is an essential component of nearly all industrial chemical processes, ranging from simple blending to complex multi-phase reaction systems for which the reaction rate, the yield and the selectivity are highly dependent upon the mixing performance. Consequences of improper mixing include nonreproducible processing conditions and lowered product quality, resulting in the need for more elaborate downstream purification processes and increased waste disposal costs. A wide range of working fluids in industrial mixers are non-Newtonian. The non-Newtonian fluid studied here is a member of the pseudo-plastic fluids group, characterized by a progressively decreasing slope or shear stress versus shear rate. These fluids are termed shear thinning; the viscosity decreases with increasing velocity gradient. In this paper, a previous study by the authors on an industrial helical static mixer is extended to illustrate how static mixing processes of single-phase pseudo-plastic liquids can be simulated numerically. A further aim is to provide an improved understanding of the flow pattern of pseudo-plastic single-phase liquids through the mixer. A three-dimensional finite volume simulation is used to study the performance of the mixer. A commercial software, FLUENT, is used in a part of the numerical simulation. The flow velocities, pressure drops, etc. are calculated for various flow rates, using the Carreau and the power law models for non-Newtonian fluids. The numerical predictions by these two models are compared to existing experimental data. Also, a comparison of the mixer performance for both Newtonian and pseudo-plastic fluids is presented.
