Molecular dynamics study on enhanced nucleate boiling heat transfer on nanostructured surfaces with rectangular cavities

Nanostructured surfaces have been proved to bring remarkable enhancements in nucleate boiling heat transfer, which are particularly attractive in thermal energy fields. To fully understand the effects of nano cavities on nucleate boiling and elucidate the underlying enhanced mechanisms, a comparative molecular dynamics study on nucleate pool boiling heat transfer of liquid argon over the plain copper substrate and nanostructured substrates with different rectangular cavities is performed. The nano-cavities have the same depth of 5 nm and different widths of 3 nm, 5 nm and 8 nm. The bubble dynamics behavior on various surfaces is observed based on simulation snapshots. The results manifest that the rectangular nano-cavity can significantly reduce time and wall superheat required for the onset of nucleate boiling, as well as delay the transition from nucleation boiling regime to film boiling regime. The incipient nucleation time tin can be reduced to 990 ps from 5600 ps. Additionally, compared with the plain substrate, the rectangular nano-cavity can result in a striking decrease in boiling initiation temperature, which is up to 59 K. The underlying enhanced mechanisms are well elucidated based on the structural feature of the rectangular nano-cavity and simulation results. The liquid inside the rectangular cavity can obtain additional thermal energy from sidewalls, leading to a significant local heat accumulation effect and the heat transfer efficiency reinforcement. It is found there is a coupling enhancement effect of heat accumulation when the width of rectangular cavity is smaller. Consequently, the 3 nm wide nano-cavity can achieve maximum enhancement. These findings provide crucial evidence at the nanoscale to verify that nano-cavity can significantly enhance nucleate boiling not only by reducing nucleation time but also by decreasing the boiling initiation temperature. This study is of importance to promote further insights into the enhanced mechanism of nucleate boiling at the nanoscale and provide guidance for the performance improvement in boiling surfaces for advanced thermal energy systems. (c) 2022 Elsevier Ltd. All rights reserved.

Automated summary

Nanostructured surfaces with rectangular nano-cavities have been found to greatly enhance nucleate boiling heat transfer. The nano-cavities can significantly reduce the time and wall superheat required for the onset of nucleate boiling, as well as delay the transition to film boiling. The width of the rectangular cavity plays a crucial role in the heat accumulation effect and heat transfer efficiency.