Reheater

noun

1. A heater for raising the temperature of steam which has been used once and is to be used again, as in the low-pressure cylinder of a compound engine, or which has been cooled by traveling a long distance. Reheating dries and possibly superheats the steam and so lessens the cylinder losses.
2. An apparatus for restoring heat to a previously heated body which has entirely or partially cooled during some stage of a manufacture or process.