Relationship between the thermal conductivity and shear viscosity of nanofluids

Nanofluids are dilute liquid suspensions of nanoparticles. Nanoparticles and liquid media, in such fluids, mix and interact at the nanoscale. Interactions between nanoparticles in nanofluids can lead to structuring of the particles. This paper discusses how the nanoparticle structuring affects the thermal conductivity and viscosity of nanofluids and how the two transport properties are related through the nanoparticle structuring. It is shown that the experimentally measured thermal conductivity enhancement and the viscosity increase due to the presence of nanoparticles can be interpreted by the aggregation of nanoparticles. It is also shown that modification of the conventional form of the effective medium theory by taking into account nanoparticle structuring information from the rheological analyses gives good agreement with experimentally measured thermal conductivity.