A chimney is a system for venting hot flue gases or smoke from a boiler, stove, furnace or fireplace to the outside atmosphere. Flue gas is Gas that exits to the atmosphere via a Flue, which is a pipe or channel for conveying exhaust gases from a fireplace oven Furnace, Boiler Smoke is the collection of airborne solid and liquid Particulates and Gases ref> ''Smoke Production and Properties'' - SFPE Handbook of Fire Protection Engineering A boiler is a closed vessel in which Water or other Fluid is heated A stove is an enclosed heated space The term is commonly taken to mean an enclosed space in which fuel is burned to provide heating either to heat the space in which the stove is situated A furnace is a device used for Heating The name derives from Latin fornax, Oven. A fireplace is an architectural element consisting of a space designed to contain a Fire, generally for Heating but sometimes also for Cooking Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five They are typically almost vertical to ensure that the hot gases flow smoothly, drawing air into the combustion through the chimney effect (also known as the stack effect). Combustion or burning is a complex sequence of Exothermic chemical reactions between a Fuel and an Oxidant accompanied by the production of Stack effect is the movement of air into and out of buildings Chimneys, Flue gas stacks, or other containers and is driven by Buoyancy. The space inside a chimney is called a flue. A flue is a duct, Pipe, or Chimney for conveying Exhaust gases from a Fireplace, Furnace, Water heater, Chimneys may be found in buildings, steam locomotives and ships. In the US, the term smokestack (colloquially, stack) is also used when referring to locomotive chimneys. The term funnel is generally used for ship chimneys and sometimes used to refer to locomotive chimneys. ^[1][2]. Chimneys are tall to increase their draw of air for combustion and to disperse pollutants in the flue gases over a greater area so as to reduce the pollutant concentrations in compliance with regulatory or other limits.

Chimney stacks on a building in Newcastle upon Tyne, England

Chimney pots in London, England, seen from the tower of Westminster Roman Catholic cathedral

The term chimney may also be applied to natural features, particularly in rock formations. Newcastle upon Tyne ( (often shortened to Newcastle) is a city and Metropolitan borough of Tyne and Wear, England This is a List of rock formations meaning isolated scenic or spectacular surface rock outcrops

History

Romans used tubes inside the walls to draw smoke out of bakeries but real chimneys appeared only in northern Europe in the 12th century. Ancient Rome was a Civilization that grew out of a small agricultural community founded on the Italian Peninsula as early as the 10th century BC Industrial chimneys became common in the late 18th century.

Chimneys have traditionally been built of brick, both in small and large buildings. Early chimneys were of a simple brick construction. Later chimneys were constructed by placing the bricks around tile liners. To control downdrafts venting caps (often called chimney pots) with a variety of designs are sometimes placed on the top of chimneys.

Seagull sits on top of a hot gas cooling chimney at The World of Glass St. Helens UK. St Helens ( is a large town in Merseyside, England It is the largest settlement of the Metropolitan Borough of St Helens with a population of just over 100000

In the eighteenth and nineteenth centuries, the methods used to extract lead from its ore produced large amounts of toxic fumes. Characteristics Lead has a dull luster and is a dense, Ductile, very soft highly In the north of England, long near-horizontal chimneys were built, often more than 3 km (2 mi) long, which typically terminated in a short vertical chimney in a remote location where the fumes would cause less harm. England is a Country which is part of the United Kingdom. Its inhabitants account for more than 83% of the total UK population whilst its mainland Lead and silver deposits formed on the inside of these long chimneys, and periodically workers would be sent along the chimneys to scrape off these valuable deposits.

Construction

Due to brick's limited ability to handle transverse loads, chimneys in houses were often built in a "stack", with a fireplace on each floor of the house sharing a single chimney, often with such a stack at the front and back of the house. Today's central heating systems have made chimney placement less critical, and the use of non-structural gas vent pipe allows a flue gas conduit to be installed around obstructions and through walls. For the Grand Central Records albums see Central Heating (Grand Central album and Central Heating 2.

In fact, many modern high-efficiency heating appliances do not require a chimney. Such appliances are typically installed near an outside wall, and a noncombustible wall thimble allows vent pipe to be run directly through the outside wall.

Carved brick chimneys characteristic of late Gothic Tudor buildings, at Thornbury Castle, 1514

Industrial chimneys are commonly referred to as flue gas stacks and are typically external structures, as opposed to being built into the wall of a building. Thornbury is a Market town in South Gloucestershire, England, approximately 12 Miles (19km north of the City of Bristol A flue gas stack is a type of Chimney, a vertical pipe channel or similar structure through which Combustion product gases called Flue gases are exhausted A flue gas stack is a type of Chimney, a vertical pipe channel or similar structure through which Combustion product gases called Flue gases are exhausted They are generally located adjacent to a steam-generating boiler or industrial furnace and the gases are carried to it with ductwork. Today the use of reinforced concrete has almost entirely replaced brick as a structural component in the construction of industrial chimneys. Concrete is a construction material composed of Cement (commonly Portland cement) as well as other cementitious materials such as Fly ash and Slag Structure is a fundamental and sometimes Intangible notion covering the Recognition, Observation, nature, and Stability of Refractory bricks are often used as a lining, particularly if the type of fuel being burned generates flue gases containing acids. A refractory is a material that retains its strength at high Temperatures ASTM C71 defines refractories as "non-metallic materials having those chemical and physical Modern industrial chimneys sometimes consist of a concrete windshield with a number of flues on the inside. The windshield or windscreen of an Aircraft, Automobile, Bus, Motorcycle, or Tram is the front Window

Flue gas stack at GRES-2 Power Plant in Ekibastus, Kazakhstan is 420 metres tall^[3]

The 300 metre chimney at Sasol Three consists of a 26 metre diameter windshield with four 4. Sasol (originally Afrikaans for Suid-Afrikaanse Steenkool en Olie - South African Coal and Oil is a South African company involved in mining energy chemicals 6 metre diameter concrete flues which are lined with refractory bricks built on rings of corbels spaced at 10 metre intervals. In Architecture a corbel (or console) is a piece of stone jutting out of a wall to carry any superincumbent weight The reinforced concrete can be cast by conventional formwork or sliding formwork. The height is to ensure the pollutants are dispersed over a wider area to meet legislative or safety requirements.

Chimney Tops

A chimney pot is placed on top of the chimney to inexpensively extend the length of the chimney, and to improve the chimney's draft. A chimney with more than one pot on it indicates that there is more than one fireplace on different floors sharing the chimney.

A chimney cap is placed on top of the chimney to keep birds and squirrels from nesting in the chimney. They often feature a rain guard to keep rain from going down the chimney. A metal wire mesh is often used as a spark arrestor to minimize burning debris from rising out of the chimney and making it onto the roof. A spark arrestor is a device intended to prevent combustible materials usually Sparks or other tiny flaming Debris, from escaping Although the masonry inside the chimney can absorb a large amount of moisture which later evaporates, rain water can collect at the base of the chimney. Sometimes weep holes are placed at the bottom of the chimney to drain out collected water.

Spanish Conquistador style wind directional cap found on many homes along the windy Oregon coast.

A chimney cowl or wind directional cap is helmet shaped chimney cap that rotates to align with the wind and prevent a back draft of smoke and wind back down the chimney. A cowl is a usually hood-shaped covering used to increase the draft of a Chimney and prevent back flow

A chimney damper is a metal spring door placed at the top of the chimney with a long metal chain that allows you to open and close the chimney from the fireplace.

In the late Middle Ages in Western Europe the design of crow-stepped gables arose to allow maintenance access to the chimney top, especially for tall structures such as castles and great manor houses. Western Europe at its most general meaning means 'all the countries in the West of Europe ' A Crow-stepped gable is a stair-step type of design at the top of the triangular Gable -end of a building A gable is the generally triangular portion of a wall between the edges of a sloping roof A castle is a defensive structure seen as one of the main symbols of the Middle Ages. A manor house or fortified manor-house is a Country house, which has historically formed the administrative centre of a manor (see Manorialism

Chimney draught or draft

The stack effect in chimneys: the gauges represent absolute air pressure and the airflow is indicated with light grey arrows. The gauge dials move clockwise with increasing pressure.

(See the Flue gas stacks article for more details)

When coal, oil, natural gas, wood or any other fuel is combusted in a stove, oven, fireplace, hot water boiler or industrial furnace, the hot combustion product gases that are formed are called flue gases. A flue gas stack is a type of Chimney, a vertical pipe channel or similar structure through which Combustion product gases called Flue gases are exhausted Those gases are generally exhausted to the ambient outside air through chimneys or industrial flue gas stacks (sometimes referred to as smokestacks).

The combustion flue gases inside the chimneys or stacks are much hotter than the ambient outside air and therefore less dense than the ambient air. The density of a material is defined as its Mass per unit Volume: \rho = \frac{m}{V} Different materials usually have different That causes the bottom of the vertical column of hot flue gas to have a lower pressure than the pressure at the bottom of a corresponding column of outside air. Pressure (symbol 'p' is the force per unit Area applied to an object in a direction perpendicular to the surface That higher pressure outside the chimney is the driving force that moves the required combustion air into the combustion zone and also moves the flue gas up and out of the chimney. That movement or flow of combustion air and flue gas is called "natural draught/draft", "natural ventilation", "chimney effect", or "stack effect". HVAC (pronounced either "H-V-A-C" or occasionally " H-vak " is an Initialism or Acronym that stands for " Heating Stack effect is the movement of air into and out of buildings Chimneys, Flue gas stacks, or other containers and is driven by Buoyancy. The taller the stack, the more draught or draft is created.

Designing chimneys and stacks to provide the correct amount of natural draught or draft involves a number design factors, many of which require trial-and-error reiterative methods.

As a "first guess" approximation, the following equation can be used to estimate the natural draught/draft flow rate by assuming that the molecular mass (i. The molecular mass (abbreviated m of a substance, more commonly referred to as molecular weight and abbreviated as MW, is the Mass of one e. , molecular weight) of the flue gas and the external air are equal and that the frictional pressure and heat losses are negligible:^[4]

Drawbacks

A characteristic problem of chimneys is they develop deposits of creosote on the walls of the structure when used with wood as a fuel. The kelvin (symbol K) is a unit increment of Temperature and is one of the seven SI base units The Kelvin scale is a thermodynamic Creosote is the name used for a variety of products including wood creosote and coal tar creosote. Fuel is any material that is burned or altered in order to obtain energy Some types of wood, such as pine, generate more creosote than others. Deposits of this substance can interfere with the airflow and more importantly, they are flammable and can cause dangerous chimney fires if the deposits ignite in the chimney. Flammability is the ease with which a substance will ignite causing Fire or Combustion. A chimney fire is the Combustion of residue deposits referred to as creosote, on the inner surfaces of Chimney tiles Flue liners Stove Thus, it is recommended — and in some countries even mandatory — that chimneys be inspected annually and cleaned on a regular basis to prevent these problems. The workers who perform this task professionally are called chimney sweeps. A chimney sweep is a person who cleans Chimneys for a living History The occupation of chimney sweep is considered to be one of the oldest in the world as In the middle ages in some parts of Europe, a crow-stepped gable design was developed, partially to provide access to chimneys without use of ladders. A Crow-stepped gable is a stair-step type of design at the top of the triangular Gable -end of a building

Masonry (brick) chimneys have also proved particularly susceptible to crumbling during earthquakes. An earthquake is the result of a sudden release of energy in the Earth 's crust that creates Seismic waves Earthquakes are recorded with a Seismometer Government housing authorities in quake-prone cities like San Francisco and Los Angeles now recommend building new homes with stud-framed chimneys around a metal flue. The City and County of San Francisco is the fourth most populous city Los Angeles (lɑˈsændʒələs los ˈaŋxeles in Spanish) is the largest City in the state of California and the American West Bracing or strapping old masonry chimneys has not proved to be very effective in preventing damage or injury from earthquakes. Perhaps predictably, a new industry provides "faux-brick" facades to cover these modern chimney structures.

Other problems include "spalling" brick, in which moisture seeps into the brick and then freezes, cracking and flaking the brick and loosening mortar seals. Spall are flakes of a material that are broken off a larger solid body and can be produced by a variety of mechanisms including as a result of Projectile impact Corrosion

Modernist chimneys on the Casa Milà (Barcelona, Spain), by Antonio Gaudí. Catalan Modernisme (not to be confused with Modernism) was the Catalan equivalent to a number of fin-de-siècle movements such as Symbolism, Casa Milà, better known as La Pedrera ( Catalan for 'The Quarry' is a building designed by the Catalan Architect, Antoni Gaudí, Barcelona ( Catalan bəɾsəˈlonə Spanish baɾθeˈlona is the capital and most populous city of the Autonomous Community of Catalonia Spain () or the Kingdom of Spain (Reino de España is a country located mostly in southwestern Europe on the Iberian Peninsula.

Dual-use chimneys

Some very high chimneys are used for carrying antennas of mobile phone services and low power FM/TV-transmitters. Television ( TV) is a widely used Telecommunication medium for sending ( Broadcasting) and receiving moving Images, either monochromatic Special attention must be paid to possible corrosion problems if these antennas are near the exhaust of the chimney. Corrosion means the breaking down of essential properties in a material due to Chemical reactions with its surroundings

In some cases the chimneys of power stations are used also as pylons. However this type of construction is not very common, because of corrosion problems of conductor cables.

The Dům Dětí a Mládeže v Modřanech in Prague, Czech Republic is equipped with an observation deck. Prague (ˈprɑːg Praha (ˈpraɦa see also other names) is the Capital and Largest city of the Czech Republic. The Czech Republic ( ˈt͡ʃɛskaː ˈrɛpuˌblɪka short form in Česko ˈt͡ʃɛskɔ also called Czechia,

Cooling tower used as an industrial chimney

At some power stations, which are equipped with plants for the removal of sulfur dioxide and nitrogen oxides, it is possible to use the cooling tower as a chimney. The term nitrogen oxide typically refers to any Binary compound of Oxygen and Nitrogen, or to a mixture of such compounds Nitric Cooling towers are heat removal devices used to transfer process waste heat to the Atmosphere. Such cooling towers can be seen in Germany at the Power Station Staudinger Grosskrotzenburg and at the Power Station Rostock. Grosskrotzenburg Power Station (Grosskrotzenburg Staudinger Power Station is a modern Coal -fired thermal Power station in Grosskrotzenburg, Hesse Rostock Power Station is a Bituminous coal -fired combined heat and power plant operated by Kraftwerks- und Netzgesellschaft mbH (KNG located in Rostock At power stations that are not equipped for removing sulfur dioxide, such usage of cooling towers could result in serious corrosion problems.

Notable chimneys

See also

• List of chimneys
• Cooling tower
• Flue gas stack
• Stack effect
• Chimney fire
• Count Rumford

References

1. ^ C.F. Saunders (1923), The Southern Sierras of California
2. ^ Jules Verne (1872), Around the World in Eighty Days
3. ^ Diagram of 25 tallest flue gas stacks worldwide
4. ^ Natural Ventilation Lecture

External links

• Chimney Safety Institute of America
• Power Station Konakovskaya GRES, at which chimneys serve as electricity pylons
• The Fireplace through History
• Article about chimney breast removal
• European Chimney Association ECA; to find further information on chimneys