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Three different liquid−liquid systems were experimentally studied for flow pattern visualization in a helically coiled geometry. For the sunflower oil−water system, interfacial forces overcome inertial forces leading to slug flow patterns, contrary to the biodiesel−glycerol system in which inertial forces dominate over interfacial forces resulting in parallel-like flow patterns. For the sunflower oil−methanol system, a transition zone from slug flow patterns to parallel flow patterns was observed. A Weber−Ohnesourge flow map (WOFM) was developed for a wide range of interfacial tension, viscosities, and flow conditions, which predicts different flow patterns. This flow map is an important tool for the design of liquid−liquid processing equipment, which depends on the device geometry. The proposed WOFM was used to predict the flow patterns in a reactive liquid−liquid system, showing good agreement with the reactor performance and the flow map predictions.

Urban road dust can be enriched in different elements and hence it can pose a threat to human and environmental health. Proximal soil sensing allows the swift monitoring of such particles in order to drive attention to any possible risks. The goal of this study is to find the variation in concentrations found when using a portable X-ray fluorescence (XRF) proximal sensor for the determination of metals in road dust with different degrees of sample pretreatment. In general, although results are element dependent, sieving samples to a particle size of <250 µm is recommended. This study can help field workers to define an expected accuracy when using sensors in street dust analysis.