We perform a 3D numerical modeling of reaction-diffusion dynamics in a Y-shaped microreactor, considering a fully developed combined electroosmotic and pressure-driven flow. The governing equations, based on a second-order irreversible reaction, are solved invoking a finite-volume approach for a non-uniform grid system. We demonstrate that the reaction is highly position dependent: more production is observed adjacent to the horizontal walls for a favorable pressure gradient, whereas both the wall and centerline are the regions of highest production when a back pressure is applied. We further show that, to achieve the maximum production rate, the EDL should be thick enough, the pressure gradient should be unfavorable, and both the diffusivities and the inlet concentrations of the reacting components should be identical. Although the same is true for the production efficiency, defined to be the ratio of the average production concentration to the inlet concentration of the limiting component, there is a main difference: when the inlet concentrations are the same the efficiency is minimal. Moreover, the concentration pick is inclined toward the component with either less diffusivity or less inlet concentration; the inclination is magnified when either the Debye length increases or an unfavorable pressure gradient is employed.
