boiler (redirected from Boilers)

boiler, device for generating steam. It consists of two principal parts: the furnace, which provides heat, usually by burning a fuel, and the boiler proper, a device in which the heat changes water into steam. A steam engine is driven by steam generated under pressure in a boiler. The amount of steam that can be generated per hour depends upon the rate of combustion of the fuel in the furnace and upon the efficiency of heat transfer to the boiler proper. Since the rate of combustion of the fuel in a furnace is largely dependent upon the quantity of air available, i.e., upon the draft, a sufficient supply of air is an important consideration in boiler construction. In some large installations the incoming air is preheated by the waste heat of the flue gases, and in order to increase the speed of combustion a forced draft (air at higher than atmospheric pressure) is often used. Two types of boilers are most common—fire-tube boilers, containing long steel tubes through which the hot gases from the furnace pass and around which the water to be changed to steam circulates, and water-tube boilers, in which the conditions are reversed. Water is changed to steam in these continuous circuits and also is super-heated in transit. This additional heating of the steam increases the efficiency of the power-generating cycle. The safety valve is used to prevent explosions by releasing steam if the pressure becomes too great. The construction of boilers in the United States is governed by the American Society of Mechanical Engineers' Boiler Construction Code. Progress in boiler design and performance have been governed by the continuous development of improved materials.

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boiler

Apparatus for converting a liquid to vapour. A boiler consists of a furnace in which fuel is burned, surfaces to transmit heat from the combustion products to the water (or other liquid), and a space where steam (or vapour) can form and collect. A conventional boiler burns a fossil fuel or waste fuel; a nuclear reactor may instead supply the heat. There are two types of conventional steam boiler. In a fire-tube boiler, the water surrounds the steel tubes through which hot gases from the furnace flow; easy to install and operate, fire-tube boilers are widely used to heat buildings and to provide power for factory processes, as well as in steam locomotives. In a water-tube boiler, the water is inside tubes, with the hot furnace gases circulating outside the tubes; water-tube boilers, which produce more and hotter steam, are used in ships and factories. The largest are found in the central-station power plants of public utilities; other large units are used in steel mills, paper mills, oil refineries, and chemical plants. See also steam engine.