Simulating the Impact of Vortex Generators on the Catalytic Methanol Synthesis in a 2D Channel Using Computational Fluid Dynamics

Catalytic methanol synthesis in a 2D rectangular microchannel reactor is modelled in OpenFOAM. This type of reactors offers several advantages from the fluid-dynamic viewpoint, such as enhanced mass and heat transfer, in addition to high single-pass efficiencies. However, the main drawback of these reactors is their limited methanol throughput as compared to their conventional fixed-bed counterparts. Therefore, the goal of this thesis is to analyse the impact of different thermo-fluid dynamic settings on methanol production, seeking for an optimal methanol yield. In the present analysis, only surface reactions are accounted for. They are implemented over the catalytic walls of the channel according to the Langmuir Hinshelwood-Hougen-Watson (LHHW) kinetics. Moreover, the diffusion phenomena between the involved chemical species in the reactor are addressed based on Fick’s law, under the assumption of a unity Lewis number. Accordingly, the synthesis simulations are conducted. The reactor achieves its best performance when the temperature at the catalytic walls ranges between 200-220°C. As the temperature increases further, the methanol yield continues to diminish. Concerning the flow characteristics, the reaction residence time proves to be the dictating factor, as greater volumetric concentrations of methanol yield result from the reduction in the bulk Reynolds number. Furthermore, elongating the zone at which the catalyst coating is applied enhances the methanol yield. Finally, vortex generators are introduced in the channel and the effect of transport-mediated mixing is investigated. At each individual Reynolds number, inducing flow mixing led to achieving greater yields. However, even at such flow characteristics, the reactor records its highest yielded mass fractions at the lowest simulated bulk flow velocities (highest reaction residence time).