Investigation of emulsification in static mixers by optical measurement techniques using refractive index matching

• Two immiscible fluids with the same RI as porous structure produced by rapid prototyping.
• A setup for simultaneous PIV and LIF in two-phase flow through porous structures.
• Dependence of droplet size on flowrate, volumetric transport fraction and position in the bed.
• The porous structure with larger changes in the free cross-section produces smaller droplets.

This study compares a two-phase flow through a foam-like porous structure and a Sulzer SMXTM static mixing element. Refractive index matching between two immiscible fluids and the internal structures enables optical measurements to be performed. The droplet size and position within the internal structures were observed by laser-induced fluorescence. The results show that at low flowrates, droplets follow preferred paths, whereas at higher flowrates, they are more homogeneously distributed within the structures. The droplet size distribution was found to be well represented by the Sauter mean diameter. Measuring along the axis of the two static mixers, we found that droplets disintegrate more quickly in the foam-like porous structure. As both geometries have the same porosity and hydraulic diameter, we conclude that the change in the free cross section is also an important parameter. We observed that in the geometry with large changes in the free cross section, the droplets are smaller.

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