Assessment of different methods of analysis to characterise the mixing of shear-thinning fluids in a Kenics KM static mixer using PLIF

The performance of Kenics KM static mixers has been determined for the blending of two shear-thinning fluid streams with identical or different rheology. Planar Laser Induced Fluorescence (PLIF) has been used to obtain the concentration distribution at the mixer outlet by doping one fluid stream with fluorescent dye upstream of the mixer inlet. The effect of scale of the static mixer, total flow rate, flow ratio between the fluid streams and inlet configuration have been investigated. The applicability of different methods to characterise mixing performance is examined by comparing conventional mixing measures such as coefficient of variation and maximum striation area against recent alternative methods presented in the literature, such as the areal distribution method developed by Alberini et al. (2014). A method of characterising individual striations by determining their distribution as a function of size and concentration is also presented. These findings illustrate the complexity of information-rich PLIF images, and highlight how different methods of analysis may be appropriate given the dependencies of the downstream process. © 2014 The Authors.