Electroviscous effect and convective heat transfer of pressure-driven flow through microtubes with surface charge-dependent slip

Although electroviscous effect and convective heat transfer of pressure-driven flow in a microtube have been widely studied, the effect of surface charge on the boundary slip is less considered in previous studies in these fields. This present work develops closed form expressions of velocity distribution, temperature distribution and Nusselt number for hydrodynamically and thermally fully developed pressure-driven flow in a microtube considering the dependence of slip on the surface charge. On basis of these, the combined effect of surface charge and surface charge-dependent slip on the electroviscous effect and convective heat transfer of the pressure-driven flow are studied. The results show that slip length decreases with increasing magnitude of zeta potential of the solid-liquid interface, and this dependence of slip on surface charge inevitably affect the fluidic behavior and convective heat transfer. The slip can increase the Nusselt number by increasing the velocity of the pressure-driven flow, however, the zeta potential leads to a decrease in the Nusselt number by decreasing the velocity. When considering the dependence of slip on surface charge, there is a further reduction on the Nusselt number due to a further decreasing velocity induced by the decreasing slip length. Both a larger magnitude of zeta potential and a larger slip length lead to a larger misestimate of the flow rate and Nusselt number without considering the surface charge-dependent slip. The underlying mechanisms of these phenomena are analyzed.