Bubble behavior and heat transfer mechanisms of deposited nanoparticles in pool-boiling process

Abstract

Deposited nanoparticles critically influence solid-liquid interactions and bubble growth in pool-boiling heat transfer, but the underlying mechanism of heat transfer induced by the combined wettability of the deposited nanoparticles and substrate remains unclear. Here, the effects of the size (12–192 nm³) and wettability (neutral and hydrophilic) of Cu nanoparticles deposited on wettable (hydrophobic, neutral, and hydrophilic) Cu substrates were investigated from a nanoscale perspective via molecular dynamic simulations. The results indicate a small size (12–108 nm³) initiates bilateral nucleation on nanoparticles followed by upward coalescence, resulting in detachable vapor films. However, neutral nanoparticle–substrates with a nanoparticle size of 192 nm³ are characterized by bubbles nucleating simultaneously on the sides and top, detaching after bidirectional coalescence; this reduces the vapor film formation time by 50 % and the bubble nucleation volume growth rate by 89.2 %. Finally, hydrophilic nanoparticle–substrates exhibit top-dominated nucleation and coalescence pathways, preventing vapor film formation. Regardless of the substrate, for hydrophilic nanoparticles, bubble nucleation consistently initiates on the nanoparticle sides and proceeds upward. Additionally, enhanced nanoparticle–substrate wettability decreases the interfacial thermal resistance by 87.9 %, while larger nanoparticles reduce it by 75.1 %. Hydrophilic nanoparticle–substrates strengthen facilitate the formation of a solid-like liquid layer. Reducing the interfacial thermal resistance promotes liquid Ar atoms to absorb more energy, resulting in enhanced heat transfer.