USCG Exam PracticeBoiler and steam propulsion fundamentals
The economizer is a heat-recovery surface found in a water-tube boiler. What fluid does it heat, and what is its heat source?
- A. It heats combustion air using waste steam from the main engine exhaust
- ✓ It heats incoming feedwater using waste heat from the flue gasesCorrect
- C. It heats saturated steam above its boiling point using the hottest combustion gases
- D. It heats boiler water in the lower drum using recirculated condensate
Why B is correct
The economizer preheats incoming feedwater by extracting heat from the flue gases after they have passed over the generating tubes. The superheater raises steam temperature above saturation, and an air heater (where fitted) warms combustion air; neither of those functions belongs to the economizer. (NAVEDTRA 14104 §4-1)
Cited:NAVEDTRA 14104 §4-1