Multiple-Effect Distillation
In this method, the seawater is evaporated in an evaporator chamber, and the heat of this vapor is then used in the second chamber, in which the seawater is already present. The process goes chamber-through-chamber a number of times. This facilitates low losses of energy. The condensation of vapor occurs in each chamber, and the pure water is collected from each chamber.
Flash Distillation
In this process, first of all seawater is heated below its boiling point. Then the preheated water is passed through another chamber in which it is subjected to decrease the pressure below its vapor pressure, and thereby the water starts boiling. Now, the vapor generated is condensed to get pure water.