Molecular insights into the effects of interfacial roughness and wettability on carbon dioxide nanofilm nucleation

Heterogeneous nucleation of carbon dioxide on heating surfaces is essential for advanced carbon utilization technologies. However, the underlying mechanism of carbon dioxide boiling under different interfacial roughness and wetting conditions has not been comprehensively investigated. In this study, molecular dynamics simulations are used to determine nanoscale bubble nucleation and boiling heat transfer behaviors of carbon dioxide. A rough surface with randomly distributed profiles is generated via Weierstrass-Mandelbrot function. Afterwards, the wettability states of carbon dioxide on copper substrates are identified across varying energy coefficients. During the non-equilibrium heating process, carbon dioxide nanofilm undergoes three distinctive stages, including diffusive evaporation, nucleate boiling, and explosive boiling. Meanwhile, several key features, encompassing molecular propagation, onset times of nucleation and explosive boiling, thermal conduction, and potential restriction, are systematically analyzed to elucidate the boiling mechanisms of carbon dioxide. Results demonstrate that the rough surface can promote the inception of bubble nucleation due to increased heat flux and reduced potential energy barrier. Furthermore, increasing solid-liquid interaction can improve boiling heat transfer efficiency before the energy coefficient is less than 2, after which the increased potential barrier inversely prevents the separation of bubble nuclei.