Multi-physical field simulations of directional seawater freeze-crystallisation under a magnetic field

Ice crystals produced through freeze-desalination of seawater often contain salt pockets that impede the desalination rate. The researchers used phase-field and lattice Boltzmann methods to analyse the influence of magnetic fields on crystal subcooling and the growth law of seawater crystallisation. Results showed that using a DC magnetic field increased the directional growth of ice crystals, leading to a 103.9 % increase in ice crystal area and a 13.05 % reduction in salt pockets compared to no magnetic field. Increasing the strength of the magnetic field improved the overall desalination rate by 25.8 %. The application of an AC magnetic field enhanced the ice crystal area by 37.8 % and the overall desalination rate by 17.0 %, but also increased salt pockets by 11.6 %. The step magnetic field did not affect the crystal area but enhanced the overall desalination rate by 14.3 %. Overall, this study demonstrates the potential for improving the efficiency of freeze desalination by controlling magnetic fields during the sea-ice growth process.