A Colorful Mixing Experiment in a Stirred Tank Using Non-Newtonian Blue Maize Flour Suspensions

Abstract

A simple experiment designed to study mixing of a material of complex rheology in a stirred tank is described. Non-Newtonian suspensions of blue maize flour that naturally contain anthocyanins have been chosen as a model fluid. These anthocyanins act as a native, wide spectrum pH indicator exhibiting greenish colors in alkaline environments, blue tones in neutral conditions, and pink–violet colors in acid environments. Students used a continuous injection of a basic solution in an initially acidic environment to reveal mixing patterns and flow structures and to follow their evolution over time in a typical stirred tank configuration. These experiments aim to demonstrate, in a laboratory setting, basic concepts related to mixing: (i) the existence of mixing pathologies in laminar-stirred tanks; (ii) the complex rheology of some real suspensions; (iii) the effect of tank geometry on mixing performance; and (iv) the quantitation of mixedness and mixing evolution using digital color analysis.

Chirality enhanced shear‐free mixing of highly viscous fluids in an origami reactor

“…The chiral origami reactor designed in this work is expected to produce a shear‐free mixing effect on highly viscous fluids. Therefore, acid–base color change, 40 mixing index, 41 and the RGB average method 42 were used to determine the total mixing time (see Figure S5). The mixing index and RGB averaging methods were used to measure the mixing performance.…”

Origami-Based Bionic Reactor

“…The mixing time was used to define the mixing behavior. It is determined by the acid–base color change and the RGB average method (see Experimental Section and Figure S4a). Figure a shows that frequency is an essential factor in the mixing time.…”

Computer Vision for Kinetic Analysis of Lab- and Process-Scale Mixing Phenomena

“…Despite clear need for the chemical engineering community to maintain high-quality education and awareness of mixing challenges, , it can be argued that mixing phenomena are less often considered in chemistry education. , Mixing requirements are often neglected in small-scale chemical method development projects, speculatively due to the reasonable assumption that mixing is generally efficient on the small scale. Conversely, mixing phenomena are more obvious and critical (from both a safety and economic perspective) when reactions are scaled up.…”

“…From the aforementioned imaging innovations in mixing analysis, ,,,− ,,− ,,,− ,− most of these are disparately reported, differently encoded, and not comparable within a single platform. Herein, we employ a series of mixing case studies to compare analysis derived from the core Kineticolor platform, tracking an averaged color region over time, as well as newly integrated and spatially resolved mixing metrics.…”