Numerical investigation and optimization of indirect freeze desalination

Access to potable water with standard quality is an inevitable component of human's lives. Freeze desalination, by consuming lower energy compared to other techniques, relies on the exertion of a cold source which is then accompanied by simultaneous rejection of impurities from water. Regarding this, a numerical study on freeze desalination in a hollow cylinder is carried out to determine the effects of the design variables such as heat flux, hydraulic diameter, initial salt concentration, and freezing time on the ice mass, ice salinity, ice generation speed, and Nusselt number on the cold surface of the inner tube. Results show that increasing the value of heat flux from -250 W/m(2) to -1000 W/m(2) imposes 3.9 times faster ice generation speed while decreasing the desalination rate by 22%. In opposite, increasing the hydraulic diameter from 2 to 8 cm, reduces the ice generation speed by 41% but improves its quality by 23.5%. Also, ice production and salinity would both increase with the freezing time which imposes a limit for freezing duration. Multi-objective optimization and artificial neural network with the purpose of obtaining the highest ice mass with lowest salinity are employed. Finally, multistage freeze desalination is explored to reach WHO standards.