Thermodynamically consistent phase field modeling of ice crystallization in H 2 O − N a C l solutions: Mechanisms of solute inclusion and interface dynamics

• Development of a thermodynamically consistent phase field model • Chemical potential calculations considering the non-ideality of saline solutions using the Pitzer Model • Simulation of interface dynamics and dendritic ice growth under various cooling conditions • Validation against the Stefan problem demonstrates higher interface velocities and increased solute trapping in dendritic regimes • Improved predictive capability for solidification phenomena beyond conventional models This article explores the freeze crystallization process in water-sodium chloride ( H 2 O − N a C l ) solutions, occurring between 273.15 K and the eutectic point at 252.05 K. During this process, two phases are formed: a solid ice phase and a liquid phase of concentrated solution. To simulate this phenomenon, a thermodynamically consistent phase field model with diffuse interface is developed. Key innovations include a unified energy formulation, the use of the Pitzer model to simplify chemical potential calculations, and a novel pseudo-component approach to ensure consistency with the H 2 O − N a C l phase diagram. The model is validated against the sharp interface model as conventional method in Chemical engineering and provides critical insights into the destabilization of interfaces caused by solute expulsion, leading to dendritic growth under high undercooling. These findings highlight the phase field model’s capability to accurately capture complex interface dynamics and offer valuable guidance for optimizing freeze crystallization processes.