Molecular Dynamics Study of Contact Angle Effect on Maximum Critical Heat Flux in Nano-patterned Pool Boiling

Molecular dynamics (MD) simulations were employed to investigate the effect of wettability (via contact angle variation) on nanoscale pool boiling heat transfer of a liquid argon thin film on a horizontal copper substrate topped with cubic nano-pillars. The liquid-solid potential was incrementally altered in order to vary the contact angle between hydrophilic (θ~63°) and super hydrophobic (θ~155°), and the resulting effect on heat transfer was observed. For each contact angle the superheat was gradually increased to initiate nucleate boiling and eventually pass the critical heat flux (CHF) into the film boiling regime. Results indicate that the maximum CHF is achieved on a somewhat hydrophobic substrate (θ~124°-132°). The data indicates that there is a quadratic relationship between CHF and contact angle, and an optimal contact angle exists that is neither super hydrophilic nor super hydrophobic. As the contact angle increases the superheat required to reach the CHF condition also increases.