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.