%regenerator%

n. 1. One who, or that which, regenerates. [ 1913 Webster ]

2. (Mech.) A device used in connection with hot-air engines, gas-burning furnaces, etc., in which the incoming air or gas is heated by being brought into contact with masses of iron, brick, etc., which have been previously heated by the outgoing, or escaping, hot air or gas. [ 1913 Webster ]