Abstract: A recuperative heat exchanger for a gas turbine or similar source of intermittent heat having an auxiliary heating unit that provides heat to maintain the heat exchanger at a substantially constant temperature when heat being exhausted from the gas turbine varies. Included also are controls that vary the supply of heat being given off by the auxiliary heating unit to compensate for changing operating conditions and provide a gradual heating or cooling of the unit to preclude thermal distortion and structural damage from an unstable temperature.