Numerical study of liquid/liquid slug flow in a capillary microreactor

Abstract

AbstractThe great advantage of microreactors is associated with an extremely large surface‐to‐volume ratio. Hence, microreactors permit promising operating conditions, such as almost‐perfect heat or mass transfer. This, of course, requires that the hydrodynamics is well understood. The hydrodynamics of a liquid/liquid slug flow in a micro‐capillary is characterized by a complex vortex structure in both the disperse and the continuous phase. The disperse phase, in our investigations, is not wetting the walls and, thus, a thin film of the continuous phase persist between the disperse phase and the wall. Due to this phenomenon, a relative movement between disperse and continuous phase is possible and, indeed, observed. Understanding of these complex phenomena allows for a control of the hydrodynamics, and thus, to tailor the heat and mass transport in a desired manner.Apparently, several effects influence the hydrodynamics. The main dimensionless groups are a Reynolds number, a Capillary number, and the ratio of viscosities and densities of both phases. To study the physics of this complex two‐liquid system, a modified level‐set method in conjunction with an immersed‐boundary formulation is engaged. Presently, the simulations are time‐dependent and axially‐symmetric in nature. The mesh resolution represents a challenge, as the spatial resolution has to resolve the thin film between the disperse phase and the wall adequately. All simulations are implemented within the software OpenFOAM. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)