Heat Transfer Dynamics of Liquid Sodium: Nanoscale Insights into Phase Change Characteristics and Leidenfrost Effects

Liquid alkali metals hold great potential in applications requiring efficient heat transfer, such as nuclear power plants, solar energy systems, and process technology. Their high latent heat of vaporization and exceptional thermal conductivity make them promising alternatives to conventional heat transfer fluids like air, water, and molten salts. Understanding the phase change characteristics of liquid alkali metals under non-equilibrium heating conditions is crucial for optimizing their performance in such applications. This study employs molecular dynamics simulations to investigate the nanoscale phase transition behavior of a thin liquid sodium layer, a representative alkali metal, in contact with a gold surface. After initial equilibration, the wall temperature is increased linearly to a target value over various heating periods. Temporal changes in temperature, pressure, center of mass, and wall heat flux are monitored for qualitative heat transfer analysis, while average heat flux and evaporative mass flux provide quantitative evaluation. The results reveal diverse phase change modes, including an intriguing phenomenon where the liquid sodium film undergoes explosive boiling, resembling the “Leidenfrost” effect, even at temperatures significantly below its critical point. The onset time and wall temperature for explosive boiling vary across heating conditions, offering essential insights for preventing the “boiling crisis” in sodium-based thermo-fluid systems. These findings advance the understanding of phase change phenomena in liquid alkali metals and their implications for high-performance heat transfer applications.