Molecular dynamics study of bubble nucleation characteristics of CH₄/C₂H₆ mixtures on nano-slotted surfaces.

This study aims to solve the problems of temperature slip, low nucleation density, and high superheat in microchannel boiling heat transfer of non-azeotropic mixtures, and to reveal the regulatory mechanism of nanoslotted surfaces on bubble nucleation. The bubble nucleation characteristics of CH4/C2H6 mixtures (composition ratios of 3:1, 1:1, and 1:3) were investigated on nano-slotted surfaces using molecular dynamics simulations, and comparatively analyzed the differences with smooth surfaces. A platinum-based nano-slotted model was constructed, utilizing the OPLS-AA force field and Lennard-Jones potentials to describe intermolecular interactions. Boiling phase transitions under varying heat source temperatures (200 K, 300 K, and 400 K) were simulated, and nucleation conditions were validated using coexistence curve and spinodal curve theory. The results show that nano-slotted surfaces significantly reduce the boiling initiation superheat by providing localized energy minimization points and surface heterogeneity, thereby promoting early triggering of nucleate boiling. Moreover, increasing the proportion of C2H6 increases the nucleation energy barrier, attributed to stronger van der Waals forces between C2H6 molecules, which increases the energy required for liquid-phase molecular escape. Higher C2H6 concentrations increase the energy demand for the phase transition, leading to a higher peak heat flux compared to pure CH4. However, excessive heat flux can lead to localized overheating and the liquid film dryout. This study provides theoretical insights for designing nanostructured surfaces and optimizing non-azeotropic mixtures in microchannel heat exchangers.