Numerical simulation of indirect freezing desalination using lattice Boltzmann method

With the increasing demand for freshwater for drinking, industrial, and agricultural purposes, desalination of seawater is a significant solution. Freezing desalination is a less costly process compared to other thermal methods; thus, it can be a proper alternative choice in the desalination industry. Numerical simulation of this process is advantageous in the design and optimization of this technology. The modeling of this process with common computational fluid dynamics methods is computationally expensive due to the small time scale of freezing. In this study, we develop a lattice Boltzmann method to solve the momentum and energy equations. This method is coupled with the finite difference discretization of species transport equation for the concentration of salt. A two-dimensional cavity filled with 35 g/L saltwater with one cold surface is investigated. The desalination process at three different times is analyzed. Also, the effect of changing the position of the cold wall in the presence of gravity is examined. The left and top surface cooling presents higher desalination efficiency as the purification efficiency is twice as the bottom surface cooling in terms of brine salt concentration. It was also found that reducing the temperature of the cold wall can have a more significant effect on desalination efficiency rather than changing the position of the cooling surface. The brine concentration obtained from the top cooling surface after 30 min at 250 K was 7.803%, while that of the bottom surface cooling after 10 min at 230 K was 8.40%.