Effect of aggregation morphology on thermal conductivity and viscosity of Al2O3-CO2 nanofluid: a molecular dynamics approach

Abstract

Transport properties such as thermal conductivity and viscosity of carbon dioxide play an important role in rapidly evolving applications such as industrial refrigeration and enhanced recovery from oil wells. Although the addition of nanoparticles in CO2-based fluid has been known to enhance these transport properties, a detailed study of the effects of nanoparticle aggregation and its effects on transport properties is missing. In this work, we evaluate the potential energies associated with stable morphologies of Al2O3 nanoparticle aggregates in CO2. Using molecular dynamics simulations and the Green?Kubo formalism, we estimate the thermophysical properties of interest. Results indicate that the enhancement in the thermal conductivity and viscosity of nanofluid is inversely proportional to the system potential energy, and nanoparticle aggregation results in thermal conductivity enhancement by up to 70% and in viscosity enhancement by up to 84% at a volume fraction of about 0.9%. Results also indicate that different aggregation morphologies result in different potential energies; we expect the results from this paper to provide insights into particle aggregation morphologies and control.