Molecular dynamics study on the bubble nucleation characteristics of Cu-Ar nanofluids on groove surfaces with different wettability

Abstract

Although nanofluids demonstrate remarkable thermal properties as advanced heat transfer media, the synergistic effects of surface wettability and micro-groove structures on the bubble nucleation dynamics in nanofluids remain poorly understood. In this study, molecular dynamics simulations employing the Lennard-Jones potential function were utilized to investigate the bubble nucleation behavior of Cu-Ar nanofluids on surfaces with varying wetting grooves, thereby uncovering the underlying microscopic mechanisms. A comprehensive investigation was conducted to examine the bubble nucleation characteristics in nanofluids across four distinct surface configurations: 1. hydrophilic groove surface (surface #1), 2. hydrophobic surface at the bottom of the groove (surface #2), 3. hydrophobic surface on the side of the groove (surface #3), 4. hydrophobic groove surface (surface #4). The findings demonstrate that the presence of hydrophobic regions on grooved surfaces (Surface #2 and Surface #3) significantly diminished the impact of crystallized argon atoms on bubble nucleation, consequently enhancing the nucleation process. Notably, Surface #3 demonstrated the highest bubble growth velocity, achieving a nucleation time of merely 805 ps, which was approximately 20 % faster than the 1000 ps observed on Surface #1. Furthermore, the bubble nucleation temperature on Surface #3 reached a minimum of 97 K, indicating a 4.1 % decrease relative to the nucleation temperature on Surface #1. The nucleation mechanism on Surface #4 is distinct from other surfaces, characterized by the continuous vaporization of liquid argon atoms and their subsequent escape into the initial cavity, thereby facilitating bubble nucleation. These discoveries offer crucial theoretical foundations for the optimization of heat exchanger surface designs, thereby facilitating the improvement of heat transfer efficiency of nanofluids in devices operating under high heat flux conditions.