*evaporator*

n. 1. An apparatus for condensing vegetable juices, or for drying fruit by heat. [ 1913 Webster ]

2. Any device designed to evaporate a fluid. [ PJC ]

3. Specifically: The portion of a refrigeration system in which the refrigerant evaporates and thus absorbs heat. [ PJC ]

rotary evaporator (Chem.) a device used in laboratories in which a liquid is evaporated by reducing the pressure and applying heat, while rotating the liquid in a vessel such as a round-bottomed flask. The reduced pressure speeds the evaporation process and allows the evaporation to be conducted at temperatures lower than would otgherwise be possible, thus reducing decomposition of unstable substances. The rotation also serves to increase the surface area from which evaporation takes place and to reduce the effect of "bumping", the sudden burst of vaporization that can scatter liquid exposed to reduced pressure. [ PJC ]