Investigation of Freezing of Salt Solutions in Cells

Abstract

Phenomena of salt rejection during freezing process of saline solutions included in cells were investigated analytically and experimentally as a problem of heat and mass transfer with phase change. By experiments of freezing of the aqueous solutions of 2.0–15.0 wt percent sodium chloride, three regions—a solid, a solid-liquid and a liquid—were recognized to coexist together in the freezing process. In the solid-liquid region, when freezing proceeds, freezing fronts were found to occur stepwise within several adjacent cells. This phenomenon was due to the depression of the freezing point which was caused by salt rejection in the cells. Furthermore, the mechanism of the freezing process was clarified in connection with the constitutional supercooling of the solution. The analytical solutions for the freezing problem of saline solutions were obtained by an approximation of using apparent heat capacity involving latent heat of fusion released in the solid-liquid region, and applying the procedure of Newmann’s exact solutions for a semi-infinite body with phase change.