Heat Transfer Characteristics of Mixed Electroosmotic and Pressure Driven Flows Under Constant Heat Flux

Abstract

Analytical solution for the heat transfer characteristics of steady electroosmotic flows with an arbitrary pressure gradient are obtained for two-dimensional straight micro-channels. Both thermally developing and fully developed regions are considered for hydraulically fully developed mixed flows under isoflux channel wall conditions. In mixed flow cases, the governing equation for energy is not separable in general. Therefore, we introduced a new method that considers the extended Graetz problem. Heat transfer characteristics are presented for low Reynolds number micro-flows where the viscous and electric field terms are very dominant. Our analytical techniques are verifled by obtaining an excellent agreement with existing literature for slug, pressure driven, and pure electroosmotic flow cases. In the fully developed region, the Nusselt number of mixed flow is independent of the thermal Peclet number for a particular Joule heat and imposed surface heat flux. The entry length of mixed flow significantly depends on the applied pressure gradient to the electroosmotic flow.