Viscous dissipative nanofluid convection in asymmetrically heated porous microchannels with solid-phase heat generation

Abstract

Under thermally non-equilibrium condition, the thermal performance of water–alumina nanofluid convection in asymmetrically heated porous media with internal heat generation is investigated analytically. The effects of thermal asymmetry, nanoparticle size and solid-phase heat generation on the thermal characteristics of nanofluid flow in porous microchannels are elucidated. Due to the effect of viscous dissipation, the heat flux at the channel wall is reversed, leading to the phenomenon of heat flux bifurcation when nanoparticle size increases. On the other hand, the solid-phase heat generation in porous medium induces the heat flux bifurcation at smaller nanoparticle size. The heat transfer enhancement of nanofluid is the largest for the case of symmetrical heating, with an increase of average heat transfer coefficient of 47% compared to that of the case of asymmetrical heating. In the presence of solid-phase heat generation, the heat transfer enhancement of nanofluid occurs over a larger range of Reynolds number. When the solid-phase heat generation is significant, a pronounced error can be induced in the simplified thermal equilibrium model.