Performance optimization of microreactors by implementing geometrical and fluid flow control in the presence of electric field: a computational study

摘要

A two dimensional rectangular microchannel with circular micropillars was modeled in the presence of an electric field. Continuity and Navier-Stokes equations were solved along with convection-diffusion equation using finite element method. Reaction phenomenon was applied via a partial differential equation on the reaction surfaces and electric force was added as a source term to the transport equations. Velocity, concentration and electric potential distributions were obtained, with the aid of which, capture efficiency and average surface concentration of reaction surfaces were calculated. To ameliorate the reaction rate, different designs of reaction surfaces were investigated; the designs with four, five and six micropillars. The importance of flow specifications in the microreactor was inspected through varying a non-dimensionalized parameter, i.e. Peclet number. The electric field was implemented on the microchannel's upper and lower walls and its effect on the performance of the device was studied. Different voltages were applied and the results were compared to the case without an electric field. The efficiency of the microreactors was observed to be dependent on the geometry of the reaction surfaces as well as the inlet velocity magnitude of the bulk flow and the electric field magnitude. It was observed that by increasing the inlet velocity, the flow regime became convection dominant. Therefore, the diffusion effect was minimized and the efficiency of the device lessened. It was also observed that in all cases, the presence of the electric field enhanced the reaction efficiency by pushing the flow towards the reaction surfaces. The six micropillar arrangement was shown to be the optimum design by analyzing both capture efficiency and average surface concentration.