Information about Stove

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A Stove is a self-contained heating appliance which heats one space, either the individual room-space it is in (as with heating stoves), or just its own space (as with a cooking stove). Stoves may be an improvement on open fires in that they are easier to control, more efficient and create less pollution.

Efficiency

Open fire has three major disadvantages that prompted inventors even in the 16th century to devise improvements: it is dangerous, it produces much smoke, and the heat efficiency is poor. Attempts were made to enclose the fire to make better use of the heat that it generated and thus reduce the wood consumption. A first step was the fire chamber: the fire was enclosed on three sides by brick-and-mortar walls and covered by an iron plate. Only in 1735 did the first design that completely enclosed the fire appear: the Castrol stove of the French architect François Cuvilliés was a masonry construction with several fireholes covered by perforated iron plates. It is also known as a stew stove. Near the end of the 18th century, the design was refined by hanging the pots in holes through the top iron plate, thus improving heat efficiency even more.

In order to prevent air, and therefore smoke, from spilling back into the room a large updraft pulling air (and therefore heat) out of the chimney is needed. This both pulls heat away and pulls air from the rest of the house into the fire and then up the chimney. A fireplace consumes 200 to 600 cubic feet of air per minute, more for a very large fire. Even a mostly closed-off fireplace, for example a modern fireplace with glass doors closed, will use 50-150 cubic feet per minute. High airflow creates a draft which pulls heated air out of the house to be replaced with cold air leaking in from the outside. Second, in an open fire some of the combustible gas coming off the wood escapes and thus does not ignite and is lost. By controlling the inflow of air to allow only what a fire needs to burn, modern stoves can reduce the consumption of air to as little as 15-30 cubic feet per minute, though consumption varies.

Modern stoves also increase the completeness of combustion by capturing most of the heat from the combustion and exhaust through an extended system of flues inside a large thermal mass before the exhaust is vented to the outside air. More expensive stoves use a catalytic converter which causes combustion of the gas and smoke particles not previously burned. Other models use a design that includes firebox insulation, a large baffle to produce a longer, hotter gas flow path and pre-heating the air prior to its entering the combustion chamber. Modern enclosed stoves are often built with a window to let out some light and to enable the user to view progress of the fire. Glass or semi-translucent manufactured mica are common window materials.

Material

Masonry heaters were developed to control air flow in stoves. A masonry heater is designed to allow complete combustion by burning fuels at full-temperature with no restriction of air inflow. Due to its large thermal mass the captured heat is radiated over long periods of time without the need of constant firing, and the surface temperature is generally not dangerous to touch.

Metal stoves came into use in the 18th century. An early, and famous, example of a metal stove is the Franklin stove, said to have been invented by Benjamin Franklin in 1742. It had a labyrinthine path for hot exhaust gases to escape, thus allowing heat to enter the room instead of going up the chimney. The Franklin stove, however, was designed for heating, not for cooking. Benjamin Thompson at the turn to the 19th century was among the first to present a working metal kitchen stove. His Rumford fireplace used one fire to heat several pots that were also hung into holes so that they could be heated from the sides, too. It was even possible to regulate the heat individually for each hole. His stove was designed for large canteen or castle kitchens, though. It would take another 30 years until the technology had been refined and the size of the iron stove been reduced enough for domestic use. Stewart's Oberlin stove was a much more compact metal stove, patented in the U.S. in 1834. It became a huge commercial success with some 90,000 units sold in the next 30 years. In Europe, similar designs also appeared in the 1830s. In the following years, these iron stoves evolved into specialised cooking appliances with flue pipes connected to the chimney, oven holes, and installations for heating water. The originally open holes into which the pots were hung were now covered with concentric iron rings on which the pots were placed. Depending on the size of the pot or the heat needed, one could remove the inner rings.

Modern stove designs

A high-end stove called the AGA cooker was invented in 1922 by Swedish Nobel prize winner Gustaf Dalén. The AGA, and similar products such as the Rayburn Range are examples of always-on stoves which continue to burn fuel even when cooking is not being performed. Stoves (or ranges as they are also known) such as these are often used instead of boilers or furnaces to supply hot water and central heating to the rest of the house.

Corn and pellet stoves and furnaces are a type of biofuel stove. The shelled dry kernel of corn, also called a corn pellet, creates as much heat as a wood pellet but generates more ash. "Corn pellet stoves and wood pellet stoves look the same from the outside. Since they are highly efficient, they don't need a chimney; instead they can be vented outdoors by a four-inch pipe through an outside wall and so can be located in any room in the home." ^[1]

A pellet stove uses small, biological fuel pellets which are renewable and very clean-burning. Home heating using a pellet stove is an alternative currently used throughout the world, with rapid growth in Europe. The pellets are made of renewable material –- typically wood sawdust or off-cuts. There are currently more than half a million homes in North America using pellet stoves for heat, and probably a similar number in Europe. The pellet stove typically uses a feed screw to transfer pellets from a storage hopper to a combustion chamber. Air is provided for the combustion by an electric blower. The ignition is automatic, using a stream of air heated by an electrical element. The rotation speed of the feeder and the fan speeds can be varied to modulate the heat output.

Other efficient stoves are based on Top Lit updraft (T-LUD) or Woodgas or Smoke Burner stove a principle applied and made popular by Dr. Thomas Reed, which use small pieces of sticks, chips of wood or shavings, leaves, etc as fuel. The efficiency is very high up to 50 percent. As compared to traditional stoves which are 5 to 15 percent on an average.

Uses

When used for cooking, a kitchen stove or range is a form of cooker. In industrial usage, stove may refer to the place where fuel is combusted before being fed to a large heat consumer such as an open hearth furnace.

Emissions

In the United States, the Environmental Protection Agency created stricter emissions standards in the late 1980s. Maximum smoke output is limited to 7.5 grams per hour. The burn temperature in modern stoves can increase to the point where secondary and complete combustion of the fuel takes place. A properly fired masonry heater has little or no particulate pollution in the exhaust and does not contribute to the buildup of creosote in the heater flues or the chimney. and some stoves achieve as little as 1 to 4 grams per hour. This is roughly 90% less smoke than older stoves, which equates to nearly zero visible smoke from the chimney. This is largely achieved through causing the most possible material to combust, which results in a net efficiency of 60 to 70% as contrasted to zero to 30% for a fireplace. (net efficiency is the amount of heat energy transferred to the room compared to the amount contained in the wood, minus any amount central heating must work to compensate for airflow problems.

Origin

The Old English stofa meant any individual enclosed space, such as a room, and 'stove' is still occasionally used in that sense, as in 'stoved in'. Until well into the 19th Century 'stove' was used to mean a single heated room, so that Joseph Banks assertion that he 'placed his most precious plants in the stove' or René Descartes observation that he got 'his greatest philosophical inspiration while sitting inside a stove' are not as odd as they seem.

The Australian aboriginal " mjadastovanala " means fire hole.

See also

• Oven

References

External links

• Woodheat.org information on woodstoves
• Thomas “Electricity” Ahearn, Canada’s Thomas Edison
• Prolific American Inventor
• History of iron stoves – in German.
• Early Chinese stoves, with images.
• Early Japanese stoves, with a good image.
• How Gas Ranges Work Article by Apwagner.com
• How Electric Ranges Work Article by Apwagner.com