An evaporator is a device used to turn the liquid form of a chemical substance, such as water, into its gaseous form - vapor, therefore changing the substance's state of matter (phase transition). In this process, the liquid is evaporated, or vaporized.

Evaporators are commonly used to concentrate foods by using heat to evaporate water from the food. As the liquid is concentrated, its boiling point is elevated. Using low pressure, boiling of liquid foods (such as juices) is carried out at low temperatures and the heat labile food attributes are preserved.