Flash evaporation

Flash evaporation is the rapid vaporization of part of a liquid when pressure suddenly falls or temperature rises. The vaporization cools the liquid that remains.

Vapor–liquid equilibrium: The condition in which vapor and liquid coexist without net transfer between phases. The final vapor fraction depends on the equilibrium reached after the pressure or temperature change.
Multistage flash distillation: A desalination process that flashes heated seawater through successive chambers at decreasing pressures. Repeated flashes separate water vapor from concentrated brine.
Boiling: Vaporization that occurs throughout a liquid when its vapor pressure reaches the surrounding pressure. Flash evaporation follows an abrupt state change; boiling can continue under steady conditions.
Phase diagram: A chart showing which physical phases of a substance are stable at different temperatures and pressures. It locates the liquid and vapor states before and after a flash.
Flash evaporation desalination: A desalination method that evaporates a fraction of heated saline water by lowering its pressure. It applies successive pressure drops to separate freshwater vapor from brine.
Enthalpy: A thermodynamic state function equal to a system’s internal energy plus pressure multiplied by volume. An ideal throttling flash conserves enthalpy as pressure drops.
Steam distillation: A separation method that uses steam to distill heat-sensitive or water-insoluble compounds. Pressure reduction can flash steam and volatile compounds from heated mixtures.
Evaporation: The transition of molecules from a liquid surface into the gas phase. Flash evaporation is a rapid, bulk thermodynamic response within the broader process of evaporation.
Latent heat of vaporization: The energy required to convert a unit mass of liquid into vapor at constant temperature and pressure. Vapor formation draws this energy from the liquid and its surroundings.
Flash smelting: A metallurgical process that oxidizes sulfide concentrates in suspension to produce molten metal and sulfur dioxide. Despite its name, it is a rapid high-temperature reaction process, not liquid flash evaporation.

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