A molecular dynamics study of phobic/philic nano‐patterning on pool boiling heat transfer

Heat transfer on the microand nano-scales has quickly become an important area of research and development due to its implications for use in MEMS/NEMS devices and electronics cooling [1–4] in the past decade. As these devices become more powerful with reduced volume/surface they will in turn generate more heat in a small area within a short time period, which needs to be removed as efficiently as possible. Boiling heat transfer on micro/ nanocale substrates has the capacity for rapid large heat flux removal, and as such has previously been implemented in small-scale devices [5], although the mechanisms driving this type of nanoscale heat transfer are not well understood. Pool boiling heat transfer has long been looked at experimentally and numerically as a means of meeting the high heat flux removal requirements. The effect of contact angle on critical heat flux (CHF) was investigated [6, 7], showing that CHF is adversely affected by large contact angles (hydrophobicity), while smaller (hydrophilic) contact angles increase the heat transfer coefficient and improve CHF. Abstract Molecular dynamics (MD) simulations were employed to investigate the pool boiling heat transfer of a liquid argon thin film on a flat, horizontal copper wall structured with vertical nanoscale pillars. The efficacy of phobic/philic nano-patterning for enhancing boiling heat transfer was scrutinized. Both nucleate and explosive boiling modes were considered. An error analysis demonstrated that the typical 2.5σ cutoff in MD simulations could underpredict heat flux by about 8.7 %, and 6σ cutoff was chosen here in order to maintain high accuracy. A new coordination number criterion was also introduced to better quantify evaporation characteristics. Results indicate that the argonphobic/philic patterning tends to either have no effect, or decrease overall boiling heat flux, while the argon-philic nano-pillar/argon-philic wall shows the best heat transfer performance.