Steam Boilers, Engines, Nozzles and Turbines
When the circulation of water, in a boiler, is by convection currents which are set up during the heating of water, then the boiler is known as

Forced circulation boiler
Natural circulation boiler
Internally fired boiler
Externally fired boiler

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Steam Boilers, Engines, Nozzles and Turbines
In forced circulation type boiler

Water is converted into steam in one pass without any recirculation
Heating takes place at bottom and the water supplied at bottom gets converted into the mixture of steam bubbles and hot water which rise to drum
Feed pump is employed to supplement natural circulation in water wall type furnace
Water is supplied in drum and through down comers located in atmospheric condition it passes to the water wall and rises to drum in the form of mixture of water and steam

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