The lag between micro- and macro-mixing in compressed fluid flows

•Simultaneous remote composition analysis on micro- and macro-scale.•Based on spat. and temp. resolved one-dimensional in situ Raman spectroscopy.•Lag between macro- and micro-mixing quantified spatially resolved.•Lag between macro- and micro-mixing quantified along a line.

We report the application of a novel optical Raman-based measurement technique for the simultaneous determination of the progress of mixing on the micro- and on the macro-scale. The introduced measurement technique is applicable to mixing systems containing one compound, which potentially can form hydrogen bonds, such as water, alcohols or amines, and does not rely on the addition of traces of indicator compounds. Here we demonstrate its applicability by analyzing the lag of micro-mixing behind macro-mixing when liquid ethanol is injected into a supercritical bulk environment mainly composed of carbon dioxide (CO2). While the degree of mixing on the macro-scale is determined from the ratio of the intensities of characteristic Raman signals of ethanol and CO2, the degree of mixing on the micro-scale is determined from the shape of the OH stretching vibration Raman signal of ethanol, which is a function of the development of hydrogen bonds.

Graphical abstractDownload high-res image (188KB)Download full-size image