Boiler is an apparatus to produce steam. Thermal energy released by combustion of fuel is transferred to water, which vaporizes and gets converted into steam at the desired temperature and pressure.
The steam produced is used for:
Ø Producing mechanical work by expanding it in steam engine or steam turbine.
Ø Heating the residential and industrial buildings.
Ø Performing certain processes in the sugar mills, chemical and textile industries.
Boiler is a closed vessel in which water is converted into steam by the application of heat. Usually boilers are coal or oil fired.
A boiler should fulfil the following requirements;
Ø Safety. The boiler should be safe under operating conditions.
Ø Accessibility. The various parts of the boiler should be accessible for repair and maintenance.
Ø Capacity. The boiler should be capable of supplying steam according to the requirements.
Ø Efficiency. To permit efficient operation, the boiler should be able to absorb a maximum amount of heat produced due to burning of fuel in the furnace.
Ø It should be simple in construction and its maintenance cost should be low.
Ø Its initial cost should be low.
Ø The boiler should have no joints exposed to flames.
Ø The boiler should be capable of quick starting and loading.
The performance of a boiler may be measured in terms of its evaporative capacity also
called power of a boiler. It is defined as the amount of water evaporated or steam produced is in kg per hour. It may also be expressed in kg per kg of fuel burnt.