Effect of aggregation morphology on thermal conductivity and viscosity of al2o3–co2 nanofluid: A molecular dynamics approach

Transport properties such as thermal conductivity and viscosity of carbon dioxide play an impor-tant role in rapidly evolving applications such as industrial refrigeration and enhanced recovery from oil wells. Although the addition of nanoparticles in CO<inf>2</inf>-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 Al<inf>2</inf>O<inf>3</inf> nanoparticle aggregates in CO<inf>2</inf>. 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 nan-ofluid 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 mor-phologies result in different potential energies; we expect the results from this paper to provide insights into particle aggregation morphologies and control.