Molecular Dynamics Study on the Boiling Behavior and Interfacial Heat Transfer of Ethylene Glycol/Water Mixtures

On the basis of the molecular dynamics method, molecular models of ethylene glycol (EG)/water mixtures were built to investigate the boiling behavior of eight solutions with different EG/water concentrations (x_EG = 0.25-1.00). The influence mechanism on boiling heat transfer was explored by analyzing the snapshots of liquid film boiling, the evolution of the void volume between molecules, the intermolecular interaction energy, the molecular trajectory, the average z-axis displacement of molecules, heat flux, interface thermal resistance, etc. The results indicate that the concentration of EG significantly affects the boiling behavior of the solutions. Critical parameters such as the time and temperature of the nucleation and film formation undergo nonmonotonic changes with an increase in x_EG, mainly due to changes in the dominant intermolecular interaction energies. Water molecules at the interface are more likely to escape from the wall and enter the interior of the liquid film, giving rise to microconvective flow, while EG molecules tend to adsorb onto the wall and mainly transfer energy by microconduction. The different dynamic behaviors of two kinds of molecules synergistically achieve heat transfer for the binary mixture. For the commonly used mixed solutions in engineering (x_EG = 0.25-0.60), the smaller the x_EG, the better the heat transfer performance, but film boiling occurs earlier. The data indicate that the average heat flux of the solution with x_EG = 0.60 is 3.8% lower than that of the solution with x_EG = 0.25, but the onset time of film boiling is delayed by 49.8%. This study provides a theoretical foundation for improving boiling heat transfer of nonazeotropic binary mixed solutions.