Parallel flow of immiscible liquids in a microreactor: modeling and experimental study

Two-phase parallel flow can be utilized in microreactor engineering for performing reactions and extractions, and also for achieving efficient phase separation at the exit of the microreactor. Typical laminar flow at the microscale allows two phases to flow in parallel without mixing, allowing highly controlled conditions for a specific chemical process. Since the liquid with the higher viscosity has a tendency to occupy a larger fraction of the microchannel, the position of the interface can be controlled through the adjustment of flow rates. The prediction of the position of the interface is important for microreactor design and operation and requires the solution of the governing equations of fluid mechanics. In this work, the theoretical description for two-phase parallel flow, based on the Navier-Stokes equations in three dimensions was expressed with a mathematical model and validated with experimental observations. The movement of the interface was achieved through the adjustment of fluid properties according to the position of the central streamlines. The predicted position of the interface was in good agreement with experimental data. A correlation for the flow rate ratio required for positioning the interface in the middle of the channel for various viscosity ratios was proposed, as well as a correlation for the prediction of the parallel to slug transition for a water/n-hexane system.