chimney

chimney

1. Geology

a. a cylindrical body of an ore, which is usually oriented vertically

b. the vent of a volcano

2. Mountaineering a vertical fissure large enough for a person's body to enter

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chimney [′chim‚nē]

(building construction)

A vertical, hollow structure of masonry, steel, or concrete, built to convey gaseous products of combustion from a building.

(electronics)

A pipelike enclosure that is placed over a heat sink to improve natural upward convection of heat and thereby increase the dissipating ability of the sink.

(geology)

pipe spouting horn

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Chimney

A vertical hollow structure of masonry, steel, or reinforced concrete, built to convey gaseous products of combustion from a building or process facility. A chimney should be high enough to furnish adequate draft and to discharge the products of combustion without causing local air pollution. The height and diameter of a chimney determine the draft. For adequate draft, small industrial boilers and home heating systems depend entirely upon the enclosed column of hot gas. In contrast, stacks, which are chimneys for large power plants and process facilities, usually depend upon force-draft fans and induced-draft fans to produce the draft necessary for operation, and the chimney is used only for removal of the flue gas. See Fan

For fire safety, chimneys for residential construction and for small buildings must extend at least 3 ft (0.9 m) above the level where they pass through the roof and at least 2 ft (0.6 m) higher than any ridge within 10 ft (3 m) of them. Some stacks extend as high as 500 ft (150 m) above ground level, thus providing supplementary natural draft.

A chimney or stack must be designed to withstand lateral loads from wind pressure or seismic forces (earthquakes), as well as vertical loads from its own weight. Small chimneys used in residential construction are commonly made of brick or unreinforced masonry, while stacks are usually made of steel. Tall steel chimneys of small diameter cannot economically be made self-supporting and must be guyed. Concrete chimneys may be plain or reinforced. Except for rectangular flues and chimneys commonly used in residential construction, masonry chimneys are usually constructed of perforated radial brick molded to suit the diameter of the chimney. See Brick, Loads, dynamic, Masonry, Mortar, Reinforced concrete, Truss