Molecular dynamics study on phase change characteristics of liquid ammonia in hydrogen-rich environments

This study employs molecular dynamics simulations to study the phase change behavior of liquid ammonia within a hydrogen-rich environment under varying ambient pressure conditions, with a primary focus on the characteristics of the gas-liquid interface and the dissolution effect of ambient gas. The results indicate that the substantial cooling effect at low temperatures during the phase change of liquid ammonia under low ambient pressures impedes evaporation, while higher ambient pressures and a hydrogen-rich environment can suppress the cooling effect and facilitate phase change. It is noteworthy to observe that among the ambient gas components influencing phase change, hydrogen plays a dominant role. Furthermore, in high-pressure and hydrogen-rich environments, the gas-liquid interface thickness increases rapidly, and the interface can maintain a substantial width without collapsing. This implies that the phase change tends to be dominated by diffusion mixing. It must be mentioned that the improved phase change characteristics in the hydrogen-rich environment are also attributed to the high solubility of hydrogen in liquid ammonia. This property can be ascribed to both the higher diffusivity of hydrogen itself and the strong attraction of hydrogen molecules by liquid ammonia molecules.