Computational fluid dynamics simulation of seawater indirect freeze desalination

Seawater desalination is regarded as an effective approach to overcome fresh water shortage, since around 71% of the earth’s surface is covered by seawater resources. Freeze desalination is based on the fact that dissolved salts diffuse from the solid phase (ice) into the liquid phase during the solidification process and less amount of salt would remain in the ice. The freeze desalination (FD) process consumes relatively low amount of energy which is a substantial advantage over other thermal desalination methods, since the latent heat of fusion is approximately 333.5 kJ/kg, almost one-seventh of 2256.7 kJ/kg, the latent heat of vaporization. Also pressure based methods such as reverse osmosis (RO) are more energy consuming. Regarding this, a computational fluid dynamics (CFD) simulation is carried out to model the salt separation process and predict the produced ice mass and its quality. In this paper, a constant heat flux of -1000 W/m 2 is applied for 60 minutes to the inner side of the tube in order to freeze the seawater solution. In order to have visual insights of results, contours of liquid fraction and salt mass fraction are presented. Results show that nearly 143 g ice with the desalination rate of 67% is produced which indicates the high separation efficiency of FD method. The effects of time, ice mass fraction and Nusselt number on the salinity of formed ice and ice generation speed are also investigated.

Keywords:

fresh water , freeze desalination , CFD simulation , salt separation