Abstract: This invention includes a heat exchanger that can be operated with a combustion turbine. This heat exchanger can be operated in either a simple cycle mode of operation or a combined cycle mode of operation. Preferably, the heat exchanger has a first heat transfer stage, a second heat transfer stage, a bypass stack and a damper. The damper and the bypass stack are preferably disposed between the first and the second heat transfer stages. Hot fluid can be received into the heat exchanger from the combustion turbine and directed through the heat transfer stages where heat is transferred from the hot fluid to the cooling medium flowing through the tubes of the heat transfer stages. Preferably, the hot fluid enters the heat exchanger upstream of the first heat transfer stage. After flowing through the first heat transfer stage, the hot fluid can be directed by the damper to either the bypass stack or the second heat transfer stage.