Condensation

Condensation is the change in matter of a substance to a denser phase, such as a gas (or vapor) to a liquid. Condensation commonly occurs when a vapor is cooled to a liquid, but can also occur if a vapor is compressed (i.e., pressure on it increased) into a liquid, or undergoes a combination of cooling and compression. Liquid which has been condensed from a vapor is called condensate. A device or unit used to condense vapors into liquid is called a condenser. Condensers are used in heat exchangers which have various designs, and come in many sizes ranging from rather small (hand-held) to very large.