Molecular dynamics insights on thermophysical property enhancement of argon-based nanofluids through nanoparticle morphology and concentration optimization

This study employs molecular dynamics simulations to investigate the thermophysical properties of argon-based nanofluids (NF) that contains copper nanoparticles (Cu NPs). Our work focuses on the interplay between nanoparticle morphology, volume fraction, and thermal transport. The ensuing results demonstrate that Cu NPs significantly enhance the thermal conductivity (TC), with flake-shaped NPs yielding the highest improvement (28.67%) owing to their comparatively larger interfacial surface area and denser solid-liquid interfacial layers. Radial distribution function (RDF) analysis reveals that NPs introduce long-range ordered structures while preserving the base fluid’s short-range order, which explains the dual-order characteristics that underlies TC enhancement. Viscosity increases with the NP volume fraction, viz., up to 28% at 4%, respectively. This phenomenon can be attributed to the interfacial adsorption layers and intensified atomic friction, though it decreases at elevated temperatures owing to the weakened intermolecular interactions. Particle size inversely affects viscosity, with smaller NPs (1.6 nm) offering a higher TC at fixed volume fractions. Mean square displacement (MSD) analysis confirms the enhanced atomic mobility correlation with TC trends. Our study refutes the Brownian motion-driven thermal enhancement, emphasizing instead the interfacial layer formation and the NP morphology as the dominant mechanisms. These findings provide the guidelines for NF design: flake-shaped NPs at 1–3% volume fractions optimize heat transfer, whereas smaller NPs minimize the viscosity penalties. Further works should explore the hybrid NPs and surface functionalization for improving the performance.