Study on Friction Coefficient of Liquid Flow through a Rectangular Microchannel with Electrokinetic Effects

The influences of the electrical double layer (EDL) field near a solid-liquid interface and induced electro kinetic field on pressure-driven liquid flow through micro channels are analyzed. The equation governing the EDL field in the cross section of rectangular channels is a nonlinear, two-dimensional Poisson-Boltzmann equation. A body force caused by the EDL field and induced electro kinetic field is considered in the equation of motion. The governing equations are numerically solved with the use of a finite control volume scheme. The electro kinetic effects on the flow velocity and the friction coefficient for the micro channel are discussed. The results show that the flow velocity in micro channel predicted by the model with electro kinetic effect is lower than that predicted by the the macro scale fluid theory (without electro kinetic effect). The friction coefficients predicted by the model with electro kinetic effect were found to be higher than that predicted by the macro scale fluid theory. It is different from that the friction coefficient predicted by the macro scale fluid theory for a rectangular channel is dependently only on the aspect ratio (H/W). The friction coefficient of the micro scale liquid flow is influenced by the ionic concentration of the liquid, the zeta potential and the size of micro channels. The friction coefficient increases as the ionic concentration of the aqueous solution decreases in the same micro channel. And stronger deviations were observed as the hydraulic diameter decreases with the same aspect ratio.