Closed Feed Water Heater:

In the perfect closed feed water heater, the feed water is heated to the way out temperature of the extracted steam that leaves the heater below the exit temperature of the extracted steam since a temperature difference of at least a few degrees is needed for any effective heat transfer to occur. The condensed steam is then pumped to the feed water time or routed to the other heater or to the condenser via a device termed as a trap, that permits the liquid to be throttled to a lower pressure area though traps the vapor.


Advantages:

• Average temperature of heat addition to the cycle is raised.
• The thermal stresses in the boiler are decreased.
• Thermal efficiency will be raised.
• The condenser capacity is decreased.
• The hotter feed avoids the condensation of sulphur dioxide gases on economizer.

Disadvantages:

• Cost of the plant rises.
• Work done per kg of steam is decreased due to which boiler capacity is raised for a given output.