Analysis of inlet and gap effect in hydrodynamics and mass transport performance of a multipurpose electrochemical reactor: CFD simulation and experimental validation

This work deals with the reaction environment analysis (hydrodynamic and mass transport characterization) inside the flow channel of a parallel plate electrolyzer. Different electrode gap and inlet configurations were tested using computational and experimental techniques. Computational methods are based on numerical solution of mathematical models that describe fluid dynamics inside reactor meanwhile, experimental characterization was carried out by means of residence time distribution (RTD) and limiting current tests. In order to evidence the phenomenological influence of hydrodynamic pattern generated by different design parameters, a 3-D diffusion-convection model was implemented taking into account the local velocity vectors obtained by solution of Navier-Stokes equations to obtain theoretical RTD and by diffusion-convection equation in order to describe hydrodynamics and overall mass transport performance. Average Re numbers considered in this work were between 102 <= Re <= 702, which are characteristic of a laminar flow regime. Velocity fields obtained by CFD analysis evidenced the existence of prominent jet flow zones, particularly when 45 degrees inlet angle is used. These effects diminished with 60 degrees inlet angle configuration. RTD analysis also showed important tailing, indicating presence of internal flow by-passing channeling effects. Mass flux distribution (associated with global mass transport coefficient and limiting current) obtained by CFD analysis evidenced the existence of non-homogeneous distribution provoked by the flow pattern inside of our reactor. From phenomenological point of view, the analysis carried out in this work, demonstrates that mass flux distribution is strongly influenced by geometric design parameters of a multipurpose parallel plate reactor. The higher mass transport coefficient was obtained with 7 mm of interelectrode gap and 60 degrees inlet angle configuration. (C) 2018 Elsevier Ltd. All rights reserved.