Closed feed water heaters are of which type?

• A. Tube and shell
• B. Plate and Frame
• C. Air-Cooled
• D. Spiral

Answer: (A)

Closed feedwater heaters heat the feedwater by transferring heat from steam without mixing the two fluids. The standard construction for this service is a tube-and-shell heat exchanger. This design handles the high pressures and temperatures typical of boiler feedwater and turbine exhaust, provides strong sealing, and is straightforward to maintain and inspect. Plate-and-frame heat exchangers can be used in smaller or lower-pressure duties, but they don’t scale as well for the large, high‑pressure service found in many power plants. Spiral heat exchangers and air-cooled designs exist, but they’re not as well suited for this application due to limits in pressure handling and heat transfer efficiency.