Regenerator

n. renewer, one who restores to good condition; reformer, one who changes; one who re-creates

A regenerative heat exchanger is a type of heat exchanger where the flow periodically reverses directions. This type of heat exchanger can have thermal efficiency as high as 95% to 99%, transferring almost all the relative heat energy from one fluid flow to the other. The fluid at each end is at essentially a constant temperature, regardless of the flow direction.
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n. regenerator, renewer, one who restores to good condition; reformer, one who changes; one who re-creates

n. regenerator, renewer, one who restores to good condition

(n.)
One who, or that which, regenerates.
  

(n.)
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.