A boiler is simply a sealed container in which hot liquid is heated. It uses a combustion cycle to generate heat, with the heat exiting the top of the boiler through a heat exchanger to the outside. In modern steam boilers, the water that enters the boiler is first heated, making it a sort of self-purging boiler. The heated or vented fluid doesn’t necessarily boil over, however. The heated or vented fluid exits the boiler either for re-use in different applications or final heating purposes, such as central heating, domestic water heating, boiler-powered electricity generation, cooking, or other septic applications.
A conventional boiler generally consists of a storage tank, an inlet pipe, and an exhaust system where combustion air is exhausted from the boiler. Feedwater systems are often used to provide water for the boiler, but there are also some modern boilers that use what is called an energy recovery venting system. An EGRV boiler doesn’t use the heat from the water for the purpose of producing heat, but rather the exhaust gases venting from the boiler act as a source of secondary heat for the surroundings.
Boilers have been in existence for more than two thousand years, starting out as simple open air furnaces used by village farmers to pump water and grind grain into flour. As the technologies advanced and more was learned about the workings of the flame, boiler systems were added to power plants to produce the needed steam to lubricate engines or melt steel for construction purposes. As the world’s powers shifted to a dependence on coal and oil for their energy sources, the need for reliable and inexpensive power generation in urban areas became critical. Governments and power plants became interested in developing more efficient and clean forms of generating electricity. Boilers have continued to evolve over the years to meet the needs of the developing world.