Numerical Analysis of Flow in a Microreactor

Abstract

Biofuels are a type of fuel of natural or biological origin. It has become very popular because it is a clean and renewable energy, unlike traditional fossil fuels. Biodiesel is a monoalkyl ester obtained by reacting triacylglycerols (from plants, used cooking oil, animal fats) with an alcohol (usually methanol or ethanol). One of the main biofuels available today is biodiesel. In addition to other important uses, biodiesel is mainly used in vehicle fuels, mixed with regular diesel made from petroleum. Microreactor technology, an important method of process intensification, offers numerous potential benefits for the process industries. Two-phase reactions with mass transfer limitations can be carried out advantageously on a small scale in a slow two-phase flow microreactor. Depending on the flow conditions - such as the mass flow rate, the ratio between phases, and the density and viscosity of the fluids involved - various characteristic distributions of the phase geometries can be formed. The aim of this work is to study the behavior of flow through a capillary microreactor for biodiesel production using the homogeneous flow model where the two-phases travel at equal velocities and mix well, therefore they can be treated as if there is only one phase. A computational fluid dynamics (CFD) approach is then used to numerically simulate this type of flow. The flows are modeled by the twodimensional incompressible Navier-Stokes equations written through the streamfunctionvorticity formulation, which are approximated by the Finite Element Method, using a mesh of quadrilateral elements. A computer code based on this methodology was developed and a verification process was carried out before it was used to simulate the problem. The code was then used to simulate the flow in a microreactors' section (Fig. 1), and the results were compared with those found in the literature, making it possible to verify that the methodology presented is indeed capable of correctly simulating flows inside a microreactor.