Hydrothermal characteristics of a water-TiO2 nanofluid were evaluated numerically within annuli considering the effects of particle migration. The convective heat transfer coefficients increased at both inner and outer walls of the annulus by raising the concentration. Along the annulus, the friction coefficient decreased more rapidly at lower Reynolds numbers. Taking the particle migration into account, a nonuniform concentration distribution was observed at the annulus cross section, higher heat transfer coefficients were obtained at both walls, and the velocity profile became flatter. In addition, the influence of thermophoresis on the convective heat transfer proved to be more significant than that of Brownian diffusion.