Effects Of Electric Double Layer And Viscous Dissipation In Microcapillary

In this study, effects of electric double layer (EDL) near the solid-liquid interface and viscous dissipation on pressure-driven liquid flow characteristics and heat transfer through a microcapillary are analyzed. As both effects were previously postulated to have certain contrary influences on flow characteristics, this analysis aims to study the interaction between the two effects via a control volume method based CFD technique. The Poisson-Boltzmann equation is used to describe EDL field near the channel wall. An additional body force due to the presence of EDL is considered in the Navier-Stokes equation. Temperature fields are explored via the energy equation with consideration of the viscous dissipation term. Variations of thermophysical properties are readily incorporated to induce a thorough observation of any coupling or adjoined effects from the two phenomena. Overall results demonstrate that in a short microchannel, when diameter decreases, EDL effects are significant, resulting in higher fluid temperature and friction, as well as reduced flow rate. Also, the effect increases with decreasing solution concentration. However, when channel length is long and flow rate is high, viscous dissipation effect dominates. It is concluded that in microchannel studies, the two effects are always present and contributing to the flow characteristics.