申論 5請將下列英文譯成中文：（20分）An economizer is a simple heat exchanger that consists of a bank of tubes.These tubes are connected with an inlet and outlet header located in a relativelycool gas temperature zone beyond the main generating bank of boiler. Theadditional heat is supplied to the feedwater from the economizer by cooling theflue gas. If oxygen is contained in the feedwater to the economizer, the oxygenis released when the external heat is applied. This may result in the tube andheader corrosion. The air heaters cool the hot flue gases by the incomingcombustion air instead of the feedwater in economizer.