Simulation of hydrodynamic dispersion in gas/liquid microreactors

Abstract

Dispersion and spreading of concentration signals in gas/liquid microreactors is studied with methods of computational fluid dynamics (CFD). It is shown that conventional reactor designs exhibit a broad residence-time distribution due to convective signal dispersion. This result is supported by experiments monitoring the transport of a liquid plug introduced into the microreactor by a micro-dispenser. A new reactor design is proposed which exhibits a more favorable velocity profile by guiding the liquid stream over alternating platelets. With simulations based on the volume-of-fluid (VOF) method it is shown that a thin, continuous liquid film forms inside the reactor. Subsequently, the transport of concentration fields described by a convection-diffusion equation is studied. It is found that, due to the approximate plug-flow character of fluid motion within this film, concentration signals experience significantly lower dispersion than in the conventional design. The new reactor design will provide the basis of a new class of gas/liquid microreactors to be developed at the Institute of Microtechnology Mainz.