Numerical study of mixing and heat transfer in mixed electroosmotic/pressure driven flow through T-shaped microchannels

This paper investigates mixing and heat transfer characteristics of mixed electroosmotic-pressure driven flow within a T-shaped microchannel. Two different mechanisms were proposed to enhance mixing efficiency within the channel. First, a non-uniform DC electric potential was embedded on the horizontal section of the channel which causes the straight streamlines to deviate and thus increases interfacial contact area and mass diffusion by absorbing ions into electrodes. Next, a ribbed channel configuration was proposed. It is shown that due to separation, recirculation zones appear behind the obstacles which helps in enhancing mixing efficiency. Finally a combined effect of ribbed channel and wall zeta potential was investigated. The numerical results show that due to presence of non-uniform zeta potential, the induced vortices are pushed into the middle of the channel and thus mixing enhances drastically by using this scheme. Intensity of mixing was computed for all cases and it was found that for any Reynolds number, there exists a Schmidt number value which below that specific value, imposing electric field reduces mixing. Finally, heat transfer was studied for all introduced cases for a constant uniform heat flux imposed at the walls. The obtained local average Nusselt number indicates that employing zeta potential has an important effect on the mixture temperature within the channel and at the outlet of the channel.