Abstract: The effect of the electrical double layer (EDL) on pressure-driven liquid flow and heat transfer in a flat microchannel are investigated under asymmetric boundary conditions including unequal zeta potentials and unequal heat fluxes on two walls. A mathematical model of pressure-driven liquid flow in microchannels is constructed. Electrical potential of EDL, liquid flow and thermal characteristics is determined using the Poisson-Boltzmann, the modified Navier-Stokes and the energy equations, respectively. The analytical solutions of the electrical potential, the velocity field and the temperature field are obtained by solving these three coupled equations. The influences of electrokinetic parameter(K), zeta potential, ratio of two zeta potentials and heat flux ratio on electrical potential, velocity distributions, temperature distributions and heat transfer rate are discussed in detail. Results show that the wall zeta potential strongly affects the electrical potential distributions in microchannels, then the change of flow-induced streaming potential will affect the velocity profile, thereby affecting the temperature distributions and heat transfer. Therefore, EDL has a significant effect on electrokinetic flow in microchannels, compared with that in conventional Poiseuille flow without EDL effect, there is an apparent difference in the flow and heat transfer characteristics between them.

Key words: Electrical double layer(EDL), Heat flux, Microfluidics, Nusselt number, Zeta electrical potential