what is furnace?

Answer 1

1.A furnace is a device for heating air or any other fluid. In British English the term is used exclusively to mean industrial furnaces which are used for many things, such as the extraction of metal from ore (smelting) or in oil refineries and other chemical plants, for example as the heat source for fractional distillation columns.
en.wikipedia.org/wiki/Furnace
2.A heating system that uses the principle of thermal convection. When air is heated, it rises and as the air cools it settles. Ducts are installed to carry the hot air from the top of the furnace to the rooms. Other ducts, called cold air returns, return the cooler air back to the furnace.
www.nachi.org/glossary/f.htm
3.Various kinds of furnaces are noticed in the Bible, such as a smelting or calcining furnace, (Genesis 19:28; Exodus 9:8,10; 19:18) especially a lime-kiln, (Isaiah 33:12; Amos 2:1) a refining furnace, (Proverbs 17:3) Nebuchadnezzar’s furnace, a large furnace built like a brick-kiln, (Daniel 3:22,23) with two openings one at the top for putting in the materials, and another below for removing them; the potter’s furnace, Ecclus. 27:5; The blacksmith’s furnace. Ecclus. 38:28. ...
www.ccel.org/ccel/smith_w/bibledict.f.html
4.An enclosed space for the burning of fuel. There are many kinds of furnaces, the type depending upon the fuel and the use to which the heat produced within it is put. Most familiar are the furnaces used in the heating of buildings. In the hot-air furnace, fuel is burned within an inner wall and air, led into a space between the inner and the outer wall, is heated and is led away to the various rooms of the building. ...
www.greenwoodtechnologies.com/glossary.htm

FOR different types of furnaces and uses, pl. click:
http://en.wikipedia.org/wiki/Furnace

Answer 2

Furnace is a device used to melt ores and extract metals from them in metallurgical processes. It can use fossilfuels or electricity to produce heat. Electric furnace is used for aluminium and copper extraction and for other metals techniques may differ.

Answer 3

1) A furnace is a device for heating air or any other fluid. In British English the term is used exclusively to mean industrial furnaces which are used for many things, such as the extraction of metal from ore (smelting) or in oil refineries and other chemical plants, for example as the heat source for fractional distillation columns.

2)an enclosed chamber in which heat is produced to heat buildings, destroy refuse, smelt or refine ores, etc.

Answer 4

a furnace is an equipment to heat a thing ( normally referred in technical terms to heat an ore or a metal)

Answer 5

furnace is a contraption that can sustain a fire. Basically, it has fire in it and it can sustain a flame for a long time. It can be used to heat objects like metal... anything.

Answer 6

something where fire is at very high degree tempereture, e.g blast furnace.

Answer 7

A furnace is a device used for heating.

In American English, the term furnace on its own is generally used to describe household heating systems based on a central furnace (known either as a boiler or a heater in British English), and sometimes as a synonym for kiln, a device used to fire clay to produce ceramics.

In British English the term furnace is used exclusively to mean industrial furnaces which are used for many things, such as the extraction of metal from ore (smelting) or in oil refineries and other chemical plants, for example as the heat source for fractional distillation columns.

The term furnace can also refer to a direct fired heater, used in boiler applications in chemical industries or for providing heat to chemical reactions for processes like cracking, and is part of the standard English names for many metallurgical furnaces worldwide.

Unique furnaces are used to run fire tests to qualify fire protection products for use in construction.

The heat energy to fuel a furnace may be supplied directly by combustion of some fuel, or electric furnaces such as the electric arc furnace or induction furnace use remotely generated electric power.

Household Furnaces
A household furnace is a major appliance that is permanently installed to provide heat to an interior space through intermediary fluid movement, which may be air, steam, or hot water. The most common fuel source for modern furnaces in the United States is natural gas; other common fuel sources include LPG (liquefied petroleum gas), fuel oil, coal or wood. In some cases electrical resistance heating is used as the source of heat, especially where the cost of electricity is low.

Combustion furnaces always need to be vented to the outside. Traditionally, this was through a chimney, which tends to expel heat along with the exhaust. Modern high-efficiency furnaces can be 98% efficient and operate without a chimney. The small amount of waste gas and heat are mechanically ventillated through a small tube through the side or roof of the house.

"High-effiency" in this sense may be misleading, because furnace efficiency is typically expressed as a "first-law" efficiency, whereas the exergy efficiency of a typical furnace is much lower than the first-law thermal efficiency. By comparison, cogeneration has a higher exergy efficiency than is realizable from burning fuel to generate heat directly at a moderate temperature. However, as the vast majority of consumers (as well as many government regulators) are unfamiliar with exergy efficiency, Carnot efficiency, and the Second Law of Thermodynamics, the use of first-law efficiencies to rate furnaces is well-entrenched.
Modern household furnaces are classified as condensing or non-condensing based on their efficiency in extracting heat from the exhaust gases. Furnaces with efficiencies greater than approximately 89% extract so much heat from the exhaust that water vapor in the exhaust condenses. Such furnaces must be designed to avoid the corrosion that this highly acidic condensate might cause and may need to include a condensate pump to remove the accumulated water. Condensing furnaces can typically deliver heating savings of 20%-35% assuming the old furnace was in the 60% Annual Fuel Utilization Efficiency (AFUE) range.


[edit] Heat Distribution
The furnace transfers heat to the living space of the building through an intermediary distribution system. If the distribution is through hot water (or other fluid) or through steam, then the furnace is more commonly termed a boiler. One advantage of a boiler is that the furnace can provide hot water for bathing and washing dishes, rather than requiring a separate water heater.


A condensing furnace.Air convection heating systems have been in use for over a century, but the older systems relied on a passive air circulation system where the greater density of cooler air caused it to sink into the furnace, and the lesser density of the warmed air caused it to rise in the ductwork, the two forces acting together to drive air circulation in a system termed "gravity-feed; the layout of the ducts and furnace was optimized for short, large ducts and caused the furnace to be referred to as an "octopus" furnace.

By comparison, most modern "warm air" furnaces typically use a fan to circulate air to the rooms of house and pull cooler air back to the furnace for reheating; this is called forced-air heat. Because the fan easily overcomes the resistance of the ductwork, the arrangement of ducts can be far more flexible than the octopus of old. In American practice, separate ducts collect cool air to be returned to the furnace. At the furnace, cool air passes into the furnace, usually through an air filter, through the blower, then through the heat exchanger of the furnace, whence it is blown throughout the building. One major advantage of this type of system is that it also enables easy installation of central air conditioning by simply adding a cooling coil at the exhaust of the furnace.

Air is circulated through ductwork, which may be made of sheet metal or plastic "flex" duct and insulated or uninsulated. Unless the ducts and plenums have been sealed using mastic or foil duct tape, the ductwork is likely to have a high leakage of conditioned air, possibly into unconditioned spaces. Another cause of wasted energy is the installation of ductwork in unheated areas, such as attics and crawl spaces; or ductwork of air conditioning systems in attics in warm climates.

The following rare but difficult-to-diagnose failure can occur. If the temperature inside the furnace exceeds a maximum threshold, a safety mechanism with a thermostat will shut the furnace down. A symptom of this failure is that the furnace repeatedly shuts down before the house reaches the desired temperature; this is commonly referred to as the furnace "riding the high limit switch". This condition commonly occurs if the temperature setting of the high limit thermostat is set too close to the normal operating temperature of the furnace. Another situation may occur if a humidifier is incorrectly installed on the furnace and the duct which directs a portion of the humidified air back into the furnace is too large. The solution is to reduce the diameter of the cross-feed tube, or install a baffle that reduces the volume of re-fed air.