The rapid separation of a saturated liquid of a single component into a vapour and a liquid when it passes through a throttling valve to a lower pressure. As a single-stage vapour–liquid separation process, the liquid mixture is partially vaporized by heating and reducing the pressure, allowing the vapour to form at the expense of the liquid adiabatically. The vapour is allowed to reach equilibrium with a residual liquid, and the resulting vapour and liquid phases are separated and removed. It may be operated as either a batch or continuous process. It is also known as equilibrium distillation. The process in which both the liquid and vapour are cooled to the saturation temperature of the liquid at the reduced pressure, which forms the basis of vapour compression cycles used for refrigeration. The flash process is isenthalpic since it involves no work, and is also known as an adiabatic flash.