The Density Profile of Hard Sphere Fluids around a Hard Nanotube in a Nanofluid (A Density Functional Theory Study)

It is well known that the nanofluids have bulk thermal conductivities orders of magnitude higher than the base liquids. Recently, Kurmar et al [1] reported an inhanced thermal conductivity of about 20% for a nanofluid of only 0.00013% Au nanoparticles in water. It is so interesting that this anomalously high thermal conductivity of nanofluids can not be formulated by classical models such as those attributed to Maxwell and Hamilton-Crosser and Bruggeman and it has been clearly shown that the measured thermal conductivity enhancements are much greater than those calculated from these conventional models [2].This is because these classical models are only dependent on the thermal conductivity of the solid and liquid and their relative volume fraction and do not include the effects of particle size and interface between the particles and fluid. However there are evidences that this aligned solid-like structure of fluid molecules at the interface of nanoparticle is a governing factor in heat conduction from solid wall to adjacent liquid [3]. So without considering the interfacial effect between the nanoparticles and fluid we can not interpret the enhanced thermal conductivity of nanofluids. Base on this conception, models for calculating thermal coductivities of nanofluids have been proposed [4] and it has been shown that the theoretical results on effective thermal conductivity of nanofluids with interfacial shells are in good agreement with the experimental data. Because of the critical role of layering structure in thermophysical properties of nanofluids, in this paper we have generated the density profile of a hard sphere fluid outside and inside of an open cylinder with hard walls as an admissible model of a nanotube using DFT.