Using the Mapping Method different designs of SMX motionless mixers are analyzed and optimized. The three design parameters that constitute a specific SMX design are: The number of cross-bars over the width of channel, N(x) , the number of parallel cross-bars per element, N(p) , and the angle between opposite cross-bars θ. Optimizing N(x) , somewhat surprisingly reveals that in the standard design with N(p)  = 3, N(x)  = 6 is the optimum using both energy efficiency as well as compactness as criteria. Increasing N(x) results in under-stretching and decreasing N(x) leads to over-stretching of the interface. Increasing N(p) makes interfacial stretching more effective by co-operating vortices. Comparing realized to optimal stretching, we find the optimum series for all possible SMX(n) designs to obey the universal design rule N(p)  = (2/3) N(x) -1, for N(x)  = 3, 6, 9, 12, ….

http://www.mate.tue.nl/mate/pdfs/9924.pdf

Understanding and Optimizing the SMX Static Mixer.

Laminar mixing of shear thinning fluids in a SMX static mixer

The performance of KM static mixers has been assessed for the blending of Newtonian and time-independent non-Newtonian fluids using planar laser induced fluorescence (PLIF). A stream of dye is injected at the mixer inlet and the distribution of dye at the mixer outlet is analyzed from images obtained across the pipe cross section. The effect of number of mixing elements, fluid rheology, and apparent viscosity ratio for two-fluid blending have been investigated at constant mixture superficial velocity of 0.3 m s−1. Aqueous solutions of glycerol and Carbopol 940 are used as the working fluids, the latter possessing Herschel–Bulkley rheology. The PLIF images have been analyzed to determine log variance and maximum striation thickness to represent the intensity and scale of segregation, respectively. Conflicting trends are revealed in the experiments, leading to the development of an areal-based distribution of mixing intensity. For two-fluid blending, the addition of a high viscosity stream into the lower viscosity main flow causes very poor mixing performance, with unmixed spots of this component observable in the PLIF image. © 2013 The Authors AIChE Journal published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers AIChE J, 60: 332–342, 2014

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Use of an areal distribution of mixing intensity to describe blending of non‐newtonian fluids in a kenics KM static mixer using PLIF

A SMX static mixer was used to disperse highly viscous Newtonian liquids into less viscous, Newtonian and non-Newtonian fluids without surfactants. The investigation covered the effect of the dispersed phase volume fraction, the viscosity ratio between the phases, the mixer length and the power draw. The flow regime was kept laminar in all the experiments with a dispersed phase content up to 25% and viscosity ratios ranging from 1 to 400. The experimental conditions allowed neglecting the affect of coalescence mainly because of the high viscosity of the continuous phase. The effect of the dispersed phase viscosity and volume fraction on the average drop size was quantified. The size distributions were obtained by image analysis. Using the 'process viscosity' concept, it was possible to collapse all the average diameters on a single master curve by using the energy consumption in the mixer as the shift variable between the experiments. A performance comparison against the Kenics mixer was made using literature results. The results showed that the SMX mixer is much better adapted to the dispersion task mainly due to its internal structure.

Liquid/Liquid Viscous Dispersions with a SMX Static Mixer

Mass transfer and hydrodynamic characterization of structured 3D electrodes for electrochemistry

An experimental study of the flow pattern in the wall region of an SMX static mixer was performed by using electrochemical shear rate sensors. Electrochemical signals were related to the local shear stress and the fluctuating rate of the velocity gradient. Signal fluctuation analysis allowed one to define the flow regimes inside the static mixers. The laminar flow was characterized by a time-constant evolution of the velocity gradient, while the turbulent flow corresponded to the stabilization of the fluctuating rate of the velocity gradient for high values of pore Reynolds number, defined by considering the static mixer as a porous medium and by using a capillary model. The transition from a laminar flow to an intermediate flow occurred at a pore Reynolds number of about 200. The turbulent flow was observed at a pore Reynolds number of between 1500 and 3000.

K. Hirech

Papers

Experimental Investigation of Flow Regimes in an SMX Sulzer Static Mixer

Effect of a liquid dispersed phase on the wall flow structure in static mixer