The current paper presents the mixed convection of nanofluid flow between eccentric channels. The present research is the first simulation which studies the simultaneous effects of eccentricity and Richardson number on the nanofluid flow. Two different thermal boundary conditions are considered: case A (heat flux is applied on the inner channel) and case B (heat flux is employed on the outer channel). In this paper, convective heat transfer coefficient and skin friction coefficient are surveyed based on dimensionless eccentricity, nanoparticle concentration, boundary condition, and Richardson number. In case A and Richardson number of 0.1, the maximum and minimum convective heat transfer coefficient occur in concentricity and positive dimensionless eccentricity, respectively. Meanwhile, the highest and lowest skin friction coefficient on the inner channel happen, respectively, in concentricity and negative dimensionless eccentricity. Also, the convective heat transfer coefficient increases by the nanoparticle concentration increment from 0 to 0.04. Moreover, nanoparticle concentration does not affect the skin friction coefficient. In case B, convective heat transfer coefficient decreases by increasing the dimensionless eccentricity. Consequently, this article shows that applying heat flux on the channels, eccentricity and nanoparticle concentration are important parameters in the heat exchanger performance.