Rapid freezing process of static salt-containing droplets under salt exclusion

Abstract

In marine salt spray environment, the freezing process of Saline droplets is of great importance. Because the salt is almost insoluble in ice and its solubility is in the micromolar range, the brine freezes in the form of pure ice, and the salt ions are excluded to the unfrozen part of the system. When the salt is frozen rapidly, the difference of thermal and mass diffusion leads to the retention of brine and the ice entraps interstitial brine. A simulation method suitable for the fast freezing process of small droplets with low salinity on a cold substrate is proposed. The freezing process and salt migration characteristics of NaCl salt solution are studied. The results show that this method can reflect the solidification and the entrapment of brine. In addition, freezing becomes slower with the increase of salt concentration in the solution. Interestingly, under the background of low salinity, there is a certain linear relationship between freezing time and salinity, and the local temperature will greatly affect the salt concentration of the intercepted brine compared with the initial droplet salinity.