Which heat source is used for regenerative feedwater heating in marine systems?

Which heat source is used for regenerative feedwater heating in marine systems?

• A. Ambient air
• B. Cooling towers
• C. Exhaust steam or turbine bleed steam
• D. Direct combustion heat in the feedwater

Answer: (C)

Regenerative feedwater heating is about recovering energy from steam that has already done work in the turbine. In marine steam cycles, a portion of the exhaust or bleed steam is diverted to feedwater heaters to transfer heat to the incoming feedwater. This preheats the water before it enters the boiler, so the boiler doesn’t have to convert as much fuel energy into steam. The result is higher overall efficiency for the propulsion or power cycle and reduced fuel consumption. Ambient air isn’t a practical heat source for this purpose because it’s too cool and variable to provide the controlled, high-quality heat needed to meaningfully preheat feedwater. Cooling towers are used to reject heat from the condenser and are not arranged to preheat feedwater. Direct combustion heat in the feedwater would waste the potential efficiency gain from the turbine’s energy; burning fuel just to heat feedwater bypasses the regenerative advantage gained by using turbine exhaust or bleed steam.

Regenerative feedwater heating is about recovering energy from steam that has already done work in the turbine. In marine steam cycles, a portion of the exhaust or bleed steam is diverted to feedwater heaters to transfer heat to the incoming feedwater. This preheats the water before it enters the boiler, so the boiler doesn’t have to convert as much fuel energy into steam. The result is higher overall efficiency for the propulsion or power cycle and reduced fuel consumption.

Ambient air isn’t a practical heat source for this purpose because it’s too cool and variable to provide the controlled, high-quality heat needed to meaningfully preheat feedwater. Cooling towers are used to reject heat from the condenser and are not arranged to preheat feedwater. Direct combustion heat in the feedwater would waste the potential efficiency gain from the turbine’s energy; burning fuel just to heat feedwater bypasses the regenerative advantage gained by using turbine exhaust or bleed steam.