Multi-physical field cross-scale simulation of brine freezing process in microchannel fluid flow considering suspended ice crystals

Freeze method using microchannel systems offers high separation efficiency but faces challenges in controlling ice blockage caused by suspended crystals and wall dendrite growth. This study develops a dynamic phase-change model integrating the Phase Field Method (PFM) and Lattice Boltzmann Method (LBM) to investigate crystallization in brine microchannels under flow conditions. A novel multiscale computational strategy is proposed: phase and concentration fields are resolved at the mesoscale near solid-liquid interfaces, while macroscopic temperature fields are derived from their averaged values, significantly reducing grid coupling iterations and enhancing computational efficiency. Experiments using a cryo-crystallization system validate the model, demonstrating excellent agreement in ice morphology, solute distribution, and blockage dynamics. Results reveal that suspended ice crystals accelerate microchannel blockage by 2.5-fold compared to scenarios without them, driven by synergistic interactions between suspended crystals and wall dendrites. The PFM-LBM framework provides critical insights into phase transitions, solute migration, and flow-thermal coupling, offering theoretical guidance for optimizing microchannel-based freeze desalination systems and addressing ice-related challenges in broader cryogenic applications.