The Collaborative International Dictionary of English v.0.48:

Regenerator \Re*gen"er*a`tor\ (-?`t?r), 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]