  CO2 cooling systems are the wave of the future for industrial refrigeration.
CO2 refrigeration systems are gaining traction in recent years which involves
heat transfer between CO2 and the base fluid. The high viscosity of CO2 is of
interest to the oil and gas industry in enhanced oil recovery and
well-fracturing applications. A need arises to improve the thermal conductivity
and viscosity of CO2 to increase the efficiency of these significant
applications. Aggregation of nanoparticles is one of the crucial mechanisms to
improve the thermal conductivity and viscosity of nanofluids. Since the
aggregation morphology of nanoparticles is unclear so far, we have evaluated
the stable configurations of the aggregation of nanoparticles by determining
the potential energy of the different configurations system. In this paper,
Green-Kubo formalism is used to calculate the mentioned thermo-physical
properties of the different aggregated nanofluids. The nanofluid in this study
consists of alumina (Al2O3) nanoparticles and CO2 as a base fluid. Results
indicate that the enhancement in the thermal conductivity and viscosity of
nanofluid is inversely proportional to the potential energy of the system. The
results also mark that various morphologies of the aggregated nanoparticles
have different enhancements of thermo-physical properties of the nanofluid.
This study is conducive for the researchers to perceive the importance and
influence of aggregation morphology of nanoparticles and their stability on the
thermal conductivity and viscosity of nanofluid.
