Nanofluids that are produced by dispersing nanoparticles into traditional heat transfer fluids, show greater thermal conductivities than regular fluids. An interfacial nano-shell between the nanoparticle and the base fluid was used to derive an expression for the effective thermal conductivity of nanofluids. Unlike with traditional models, the effective thermal conductivity predicted by the present model is not only affected by the ratio of the thermal conductivities of the particle and the media and their relative volume fractions, but is also affected by the nanoparticle radius and the thermal conductivity and thickness of the interfacial nano-shell. The calculated results predicted by this model agree quite well with available experimental data. (C) 2014 Elsevier B.V. All rights reserved.