Effects of wall slip and nanoparticles' thermophoresis on the convective heat transfer enhancement of nanofluid in a microchannel

Heat transfer enhancement with nanofluid appears to be an attractive work in recent years. In present work, a numerical formulation based on the Buongiorno model for convective heat transfer using Al2O3-water nanofluid accounted for the effects of Brownian motions and thermophoresis of nanoparticles, slip velocity and jump temperature at solid-fluid interface. Numerical investigations for laminar forced convection flows in a rectangle channel subjected to a uniform wall heat flux have been conducted. The numerical results show us that, the slip velocity can augment the heat transfer enhancement significantly due to the increase of the convection near the solid-fluid interface. Inversely, the jump temperature is not beneficial to the convective heat transfer because of the increased thermal resistance. The thermophoresis of particles affects heat transfer enhancement by changing local density, local viscosity, and local thermal conductivity. The thermophoresis of particles influences the skin friction coefficient also. The Nusselt number increases with the Reynolds number and particle volume fraction. The impact on the Nusselt number of Reynolds number will be receded in some extent because the thermophoresis velocity will be greater when the Reynolds number increasing. These numerical results help us to design micro-devices and understand the mechanism of heat transfer enhancement by adding nanoparticles in a microchannel.