furnace terminology
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A furnace is a device used for heatHeat
In physics and thermodynamics, heat is any transfer of energy from one body or thermodynamic
system to another due to a difference in temperature....ing. The name derives from Latin
Latin
Latin is an Italic language, historically spoken in Latium and Ancient Rome. Through the Military
history of the Roman Empire, Latin spread throughout the Mediterranean and a large part of Europe.... fornax, ovenOven
An oven is an enclosed compartment for heating, baking or drying. It is most commonly used in
cooking and pottery. Ovens used in pottery are also known as kilns..... The earliest furnace was excavated at Balakot
Balakot
Balakot , is a town in Mansehra District in the North-West Frontier Province of Pakistan. The town
was destroyed during the 2005 earthquake and later rebuilt with the assistance of the Government of
Pakistan and Saudi Public Assistance for Pakistan Earthquake Victims , a Saudi relief organization...., a site of the Indus Valley Civilization
Indus Valley Civilization
The Indus Valley Civilization , abbreviated IVC, was an ancient civilization that flourished in the
Indus River basin. Primarily centered along the Indus river, the civilization encompassed most of
Pakistan, including its Sindh, Punjab and Balochistan provinces, and extending into modern day Indian
states of Gujarat, Haryana, Punjab..., dating back to its mature phase (c. 2500-1900 BC). The furnace was most likely used for the
manufacturing of ceramic
Ceramic
File:Bridge from dental porcelain.jpgFile:Qing vase p1070256.jpgA ceramic is an inorganic, nonmetal
solid prepared by the action of heat and subsequent cooling....objects.
In American English
American English
PhonologyIn many ways, compared to English language in England, North American English is
conservative in its phonology. Some distinctive accents can be found on the East Coast of the UnitedStates , partly because these areas were in contact with England, and imitated prestigious varieties of
English English at a time when those varieties we...and Canadian EnglishCanadian English
Canadian English is the Variety of English language used in Canada. More than 26 million Canadianshave some knowledge of English . Approximately 17 million speak English as their native language....
, the term furnace on its own is generally used to describe house
House
A house generally refers to a or building that is a dwelling or place for habitation by humans. The term
includes many kinds of dwellings ranging from rudimentary huts of nomadic tribes to high-rise
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apartment buildings....hold heating systems based on a central furnace (known either as a boiler
Boiler
A boiler is a closed Pressure vessel in which water or other fluid is heated. The heated or vaporizedfluid exits the boiler for use in various processes or heating applications....
or a heater
Heater
A heater is any object that emits heat or causes another body to achieve a higher temperature. In ahousehold or domestic setting, heaters are commonly used to generate heating ....in British English), and sometimes as a synonym for kiln
Kiln
Kilns are thermally insulated chambers, or ovens, in which controlled temperature regimes are produced. They are used to harden, burn or dry materials....
, a device used in the production of ceramic
Ceramic
File:Bridge from dental porcelain.jpgFile:Qing vase p1070256.jpgA ceramic is an inorganic, nonmetal
solid prepared by the action of heat and subsequent cooling....s. In British English
British English
British English or UK English is the broad term used to distinguish the forms of the English language
used in the United Kingdom from forms used elsewhere....
the term furnace is used exclusively to mean industrial
Industry
An industry is the manufacturing of a Good or Service within a category. Although industry is a broad
term for any kind of economic production, in economics and urban planning industry is a synonym for
the secondary sector, which is a type of economic activity involved in the manufacturing of rawmaterials into goods and products....
furnaces which are used for many things, such as the extractionResource extraction
The related terms resource extraction and resource extraction industry both refer to the practice of
locating, acquiring and selling any resource, but typically a natural resource....of metal
Metal
In chemistry, a metal is a chemical element whose atoms readily lose electrons to form positive ions ,
and form metallic bonds between other metal atoms and ionic bonds between nonmetal atoms....from oreOre
An ore is a type of Rock that contains minerals such as gemstones and metals that can be extractedthrough mining and refined for use. Samples of ore in the form of exceptionally beautiful crystals,
exotic layering visible when sectioned or polished or metallic presentations such as large nuggets or
crystalline formations of metals suc...
(smeltingSmelting
Smelting is a form of extractive metallurgy; its main use is to produce a metal from its ore. This
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includes iron extraction from iron ore, and copper extraction and other base metals from their ores....) or in oil refineries and other chemical plants, for example as the heat source for fractional distillation
Fractional distillation
Fractional distillation is the separation of a mixture into its component parts, or fractions, such as inseparating chemical compound by their boiling point by heating them to a temperature at which several
fractions of the compound will evaporate....
columns.
The term furnace can also refer to a direct fired heater, used in boiler applications in chemicalindustries or for providing heat to chemical reactions for processes like cracking, and is part of thestandard English
English language
English is a West Germanic language that originated in Anglo-Saxon England and has lingua francastatus in many parts of the world as a result of the military, economic, scientific, political and cultural
influence of the British Empire in the 18th, 19th and early 20th centuries and that of the United States
from the mid 20th century onwa...names for many metallurgical furnaces worldwide.
The heat energy to fuel a furnace may be supplied directly by fuel combustionCombustion
Combustion or burning is a complex sequence of exothermic chemical reactions between a fuel andan oxidant accompanied by the production of heat or both heat and light in the form of either a glow or
flames, appearance of light flickering....
, by electricity such as the electric arc furnace
Electric arc furnace
An is a furnace that heats charged material by means of an electric arc.Arc furnaces range in size from
small units of approximately one ton capacity up to about 400 ton units used for secondary
steelmaking...., or through Induction heating
Induction heating
Induction heating is the process of heating an electrically conducting object by electromagnetic
induction, where eddy currents are generated within the metal and resistance leads to Joule heating of
the metal....in induction furnace
Induction furnace
An induction furnace is an electrical furnace in which the heat is applied by induction heating of a
conductive medium in a crucible placed in a water-cooled alternating current solenoid coil....s.
class="link1" onMouseover='showByLink("m1111821",this)'
onMouseout='hide("m1111821")'href="http://www.absoluteastronomy.com/topics/Household">household
Household
The household is "the basic residential unit in which production , consumption , inheritance, childrearing, and shelter are organized and carried out"; [the household] "may or may not be synonomous
with family"....
furnace is a major appliance
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Major appliance
A major appliance, or domestic appliance, is usually defined as a large machine which accomplishes
some routine housekeeping task, which includes purposes such as cooking, food preservation, or
cleaning, whether in a household, institutional, commercial or industrial setting....that is permanently installed to provide heat to an interior space through intermediary fluid movement,
which may be air
AIR
Air is the part of Earth's atmosphere that humans breath and as such Air .Air may also refer to:..., steamSteam
In physical chemistry, and in engineering, steam refers to vaporized water. It is a pure, completely
invisible gaseous phase . At standard temperature and pressure, pure steam occupies about 1,600 timesthe volume of an equal mass of liquid water....
, or hot water
Water
Water is a common chemical substance that is essential for the survival of all known forms of life. In
typical usage, water refers only to its liquid form or States of matter, but the substance also has a solidstate, ice, and a gaseous state, water vapor or steam....
.
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Encyclopedia
A furnace is a device used for heat
Heat
In physics and thermodynamics, heat is any transfer of energy from one body or thermodynamicsystem to another due to a difference in temperature....
ing. The name derives from Latin
Latin
Latin is an Italic language, historically spoken in Latium and Ancient Rome. Through the Military
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history of the Roman Empire, Latin spread throughout the Mediterranean and a large part of Europe.... fornax, oven
Oven
An oven is an enclosed compartment for heating, baking or drying. It is most commonly used incooking and pottery. Ovens used in pottery are also known as kilns....
. The earliest furnace was excavated at Balakot
Balakot
Balakot , is a town in Mansehra District in the North-West Frontier Province of Pakistan. The townwas destroyed during the 2005 earthquake and later rebuilt with the assistance of the Government of Pakistan and Saudi Public Assistance for Pakistan Earthquake Victims , a Saudi relief organization....
, a site of the Indus Valley Civilization
Indus Valley Civilization
The Indus Valley Civilization , abbreviated IVC, was an ancient civilization that flourished in the
Indus River basin. Primarily centered along the Indus river, the civilization encompassed most of
Pakistan, including its Sindh, Punjab and Balochistan provinces, and extending into modern day Indianstates of Gujarat, Haryana, Punjab...
, dating back to its mature phase (c. 2500-1900 BC). The furnace was most likely used for the
manufacturing of ceramicCeramic
File:Bridge from dental porcelain.jpgFile:Qing vase p1070256.jpgA ceramic is an inorganic, nonmetalsolid prepared by the action of heat and subsequent cooling....
objects.
In American EnglishAmerican English
PhonologyIn many ways, compared to English language in England, North American English is
conservative in its phonology. Some distinctive accents can be found on the East Coast of the UnitedStates , partly because these areas were in contact with England, and imitated prestigious varieties of
English English at a time when those varieties we...and Canadian English
Canadian English
Canadian English is the Variety of English language used in Canada. More than 26 million Canadianshave some knowledge of English . Approximately 17 million speak English as their native language....
, the term furnace on its own is generally used to describe house
House
A house generally refers to a or building that is a dwelling or place for habitation by humans. The termincludes many kinds of dwellings ranging from rudimentary huts of nomadic tribes to high-riseapartment buildings....
hold heating systems based on a central furnace (known either as a boiler
Boiler
A boiler is a closed Pressure vessel in which water or other fluid is heated. The heated or vaporized
fluid exits the boiler for use in various processes or heating applications....
or a heater Heater
A heater is any object that emits heat or causes another body to achieve a higher temperature. In a
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household or domestic setting, heaters are commonly used to generate heating ....in British English), and sometimes as a synonym for kiln
Kiln
Kilns are thermally insulated chambers, or ovens, in which controlled temperature regimes are produced. They are used to harden, burn or dry materials....
, a device used in the production of ceramic
Ceramic
File:Bridge from dental porcelain.jpgFile:Qing vase p1070256.jpgA ceramic is an inorganic, nonmetalsolid prepared by the action of heat and subsequent cooling....s. In British English
British English
British English or UK English is the broad term used to distinguish the forms of the English languageused in the United Kingdom from forms used elsewhere....
the term furnace is used exclusively to mean industrial
Industry
An industry is the manufacturing of a Good or Service within a category. Although industry is a broad
term for any kind of economic production, in economics and urban planning industry is a synonym for the secondary sector, which is a type of economic activity involved in the manufacturing of raw
materials into goods and products....
furnaces which are used for many things, such as the extractionResource extraction
The related terms resource extraction and resource extraction industry both refer to the practice of
locating, acquiring and selling any resource, but typically a natural resource....of metal
Metal
In chemistry, a metal is a chemical element whose atoms readily lose electrons to form positive ions ,and form metallic bonds between other metal atoms and ionic bonds between nonmetal atoms....
from oreOre
An ore is a type of Rock that contains minerals such as gemstones and metals that can be extracted
through mining and refined for use. Samples of ore in the form of exceptionally beautiful crystals,exotic layering visible when sectioned or polished or metallic presentations such as large nuggets or
crystalline formations of metals suc...
(smeltingSmelting
Smelting is a form of extractive metallurgy; its main use is to produce a metal from its ore. Thisincludes iron extraction from iron ore, and copper extraction and other base metals from their ores....
) or in oil refineries and other chemical plants, for example as the heat source for fractional distillation
Fractional distillation
Fractional distillation is the separation of a mixture into its component parts, or fractions, such as in
separating chemical compound by their boiling point by heating them to a temperature at which several
fractions of the compound will evaporate....columns.
The term furnace can also refer to a direct fired heater, used in boiler applications in chemical
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industries or for providing heat to chemical reactions for processes like cracking, and is part of thestandard English
English language
English is a West Germanic language that originated in Anglo-Saxon England and has lingua francastatus in many parts of the world as a result of the military, economic, scientific, political and cultural
influence of the British Empire in the 18th, 19th and early 20th centuries and that of the United States
from the mid 20th century onwa...names for many metallurgical furnaces worldwide.
The heat energy to fuel a furnace may be supplied directly by fuel combustionCombustion
Combustion or burning is a complex sequence of exothermic chemical reactions between a fuel and
an oxidant accompanied by the production of heat or both heat and light in the form of either a glow or flames, appearance of light flickering....
, by electricity such as the electric arc furnace
Electric arc furnace
An is a furnace that heats charged material by means of an electric arc.Arc furnaces range in size from
small units of approximately one ton capacity up to about 400 ton units used for secondarysteelmaking....
, or through Induction heating
Induction heating
Induction heating is the process of heating an electrically conducting object by electromagnetic
induction, where eddy currents are generated within the metal and resistance leads to Joule heating of
the metal....in induction furnace
Induction furnace
An induction furnace is an electrical furnace in which the heat is applied by induction heating of aconductive medium in a crucible placed in a water-cooled alternating current solenoid coil....
s.
Household furnaces
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A household
Household
The household is "the basic residential unit in which production , consumption , inheritance, child
rearing, and shelter are organized and carried out"; [the household] "may or may not be synonomous
with family"....
furnace is a major applianceMajor appliance
A major appliance, or domestic appliance, is usually defined as a large machine which accomplishes
some routine housekeeping task, which includes purposes such as cooking, food preservation, or
cleaning, whether in a household, institutional, commercial or industrial setting....
that is permanently installed to provide heat to an interior space through intermediary fluid movement,which may be air
AIR
Air is the part of Earth's atmosphere that humans breath and as such Air .Air may also refer to:...
, steamSteam
In physical chemistry, and in engineering, steam refers to vaporized water. It is a pure, completely
invisible gaseous phase . At standard temperature and pressure, pure steam occupies about 1,600 timesthe volume of an equal mass of liquid water....
, or hot water
Water
Water is a common chemical substance that is essential for the survival of all known forms of life. In
typical usage, water refers only to its liquid form or States of matter, but the substance also has a solid
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state, ice, and a gaseous state, water vapor or steam..... The most common fuel
Fuel
Fuel is any material that is burned or altered in order to obtain energy and to heat or to move an object.Fuel releases its energy either through a chemical reaction means, such as combustion, or nuclear
means, such as nuclear fission or nuclear fusion....
source for modern furnaces in the United StatesUnited States
The United States of America is a Federal government constitutional republic comprising U.S. stateand a federal district. The country is situated mostly in central North America, where its Contiguous
United States and Washington, D.C., the Capital districts and territories, lie between the Pacific Ocean
and Atlantic Oceans, Borders of the U...
is natural gas Natural gas
Natural gas is a gas consisting primarily of methane. It is found associated with fossil fuels, in coal beds, as methane clathrates, and is created by methanogenic organisms in marshes, bogs, and
landfills....
; other common fuel sources include LPG (liquefied petroleum gas), fuel oilFuel oil
Fuel oil is a fractional distillation obtained from petroleum distillation, either as a distillate or aresidue. Broadly speaking, fuel oil is any liquid petroleum product that is burned in a furnace or boiler
for the generation of heat or used in an engine for the generation of power, except oils having a flash
point of approximately and oi...
, coalCoal
Coal is a readily combustion black or brownish-black sedimentary rock. The harder forms, such as
anthracite, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure....
or woodWood
Wood is an organic material; in the strict sense wood is produced as secondary xylem in the stems of
woody plants, notably trees but also shrubs, etc..... In some cases electrical resistance
Electrical resistance
The electrical resistance of an object is a measure of its opposition to the passage of a steady
electrical current. An object of uniform cross section will have a resistance proportional to its lengthand inversely proportional to its cross-sectional area, and proportional to the resistivity of thematerial....
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
Chimney
A chimney is a structure for venting hot flue gases or smoke from a boiler, stove, furnace or fireplace
to the outside Earth's atmosphere. Chimneys are typically vertical, or as near as possible to vertical, to
ensure that the gases flow smoothly, drawing air into the combustion in what is known as the stack
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effect...., which tends to expel heat along with the exhaust
Exhaust
Exhaust or exhaustion may refer to:.... Modern high-efficiency furnaces can be 98% efficient
Thermal efficiency
In thermodynamics, the thermal efficiency is a Dimensionless quantity performance measure of a
thermal device such as an internal combustion engine, a boiler, or a furnace, for example....and operate without a chimney. The small amount of waste gas and heat are mechanically ventilatedthrough a small tube through the side or roof of the house.
• "High-efficiency" in this sense may be misleading, because furnace efficiency is typically
expressed as a "first-law" efficiency
Thermal efficiency
In thermodynamics, the thermal efficiency is a Dimensionless quantity performance measure
of a thermal device such as an internal combustion engine, a boiler, or a furnace, for example...., whereas the energy efficiency of a typical furnace is much lower than the first-law thermalefficiency. By comparison, cogeneration
Cogeneration
Cogeneration is the use of a heat engine or a power station to simultaneously generate both
electricity and useful heat.Conventional power plants emit the heat created as a by-product of electricity generation into the environment through cooling towers, flue gas, or by other
means....
has a higher energy efficiency than is realizable from burning fuel to generate heat directly at amoderate temperature. However, as the vast majority of consumers (as well as many
government regulators) are unfamiliar with exergy efficiency
Exergy efficiency
Exergy efficiency computes the efficiency of a process taking the second law of
thermodynamics into account....
, Carnot efficiency, and the second law of thermodynamics
Second law of thermodynamics
The second law of thermodynamics is an expression of the universal law of increasing
entropy, stating that the entropy of an isolated system which is not in Thermodynamic
equilibrium will tend to increase over time, approaching a maximum value at equilibrium...., the use of first-law efficiencies to rate furnaces is well-entrenched.
Modern household furnaces are classified as condensing
Condensation
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Condensation is the change of the physical state of aggregation of matter from gaseous phase into
liquid phase. When the transition happens from the gaseous phase into the solid phase directly,
bypassing the liquid phase the change is called Deposition , which is the opposite of sublimation....
or non-condensing based on their efficiency in extracting heat from the exhaust gases. Furnaces withefficiencies greater than approximately 89% extract so much heat from the exhaust that water vapor
Water vapor
Water vapor or water vapour , also aqueous vapor , is the gas phase of water . Water vapor is one
Phase of the water cycle within the hydrosphere....in the exhaust condenses; they are referred to as condensing furnaceCondensing boiler
A condensing boiler is a water heating device designed to recover energy normally discharged to the
atmosphere through the flue. It can do this through the use of a secondary heat exchanger which mostcommonly uses residual heat in the flue gas to heat the cooler returning water stream or by having a
primary heat exchanger with sufficient sur...
s. Such furnaces must be designed to avoid the corrosion that this highly acidic condensate might causeand may need to include a condensate pump
Condensate pump
A condensate pump is a specific type of pump used to pump the Condensation produced in an HVAC
, refrigeration, condensing boiler furnace or steam system....
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
Annual fuel utilization efficiency
The annual fuel utilization efficiency is a thermal efficiency measure of combustion equipment likefurnaces, boilers, and water heaters. The AFUE differs from the true 'thermal efficiency' in that it is not
a steady-state, peak measure of conversion efficiency, but instead attempts to represent the actual,
season-long, average efficiency...
(AFUE) range.
Modern Furnace components
The furnace components can be divided into three categories.
1. The burners, heat exchanger, draft inducer, and venting.
2. The controls and safety devices.
3. The blower and air movement.
The flame originates at the burners and is drawn into the heat exchanger by the negative pressure
produced by the draft inducer. The hot gasses produced by the combustion of the flame pass through
the chambers of the heat exchanger and heat the metal walls of the heat exchanger. The gasses cool asthey transfer the heat to the heat exchanger and are at about 120 degrees as they exit on a high
efficiency furnace. The cooled gasses then enter the draft inducer blower and are pushed into the
venting pipes. The exhaust gasses then are directed out of the house through the vent pipes.
The controls include the gas valve, ignition control, ignitor, flame sensor, transformer, limit control,
blower control board, and flame roll out switch. The transformer provides 24 volts of electricity to
power the controls. 24 volts is applied to the thermostat that is installed in the living space. The
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thermostat is basically an automatic switch that closes and completes the electrical circuit when theroom temperature drops below the heat setting. This then allows 24 volts to the circuit board which
initiates the heat sequence. The circuit board has a relay that closes to power up the motor on the draft
inducer blower. Then the circuit board ignitor relay is energized which sends 120 volts to the hot
surface ignitor and makes it glow bright and get extremely hot. Next the gas valve relay in the circuit board is energized. This allows voltage to the gas valve and energizes a solenoid coil in the gas valve
which opens the valve to allow gas to flow to the burners. The gas flows into the burners and is ignited
by the hot surface ignitor. The ignition control circuit board applies an AC voltage to the flame sensor which is just a stainless steel rod. A interesting thing occurs inside a burning flame called ionization.
That is free electrons are produced which can conduct electricity through the flame itself. The electronswill normally flow from the flame sensor, through the flame when present, and back to ground throughthe grounded burners. The ignition system must prove that a flame is present to continue the gas flow
or if no flame shut off the gas flow through the gas valve to prevent a possible explosion. It also must
not be fooled into thinking there is a flame present by a flame sensor that is touching the ground from
being broken or bent. The way it does this is by a diode effect where the sensor surface area is less than10% of the ground surface area. This produces a half wave of electrical current out of each full wave.
The ignition control circuit detects the half wave to determine if the sensor is merely touching ground.
If the ignition control receives this half wave signal from the flame sensor then combustion willcontinue. Now the circuit board timer counts a determined amount of time and energizes the blower
relay. This relay powers up the blower motor and air is then pushed through the heat exchanger where
it removes the heat from the hot metal and enters the ductwork to go to the various rooms in the house.The limit control is a safety device that will open the electrical circuit to the ignition control and stop
the gas flow if the furnace over heats. The flame roll out switch does the same thing if the flame was
rolling out of the heat exchanger instead of being completely induced into it by the draft inducer.
The blower creates a negative pressure on the intake side which draws air into the ductwork return air
system and blows the air out through the heat exchanger and then into supply air ductwork to distribute
throught the home.
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 ismore commonly termed a boiler
Boiler
A boiler is a closed Pressure vessel in which water or other fluid is heated. The heated or vaporized
fluid exits the boiler for use in various processes or heating applications....
. 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. One disadvantage to this type of application is when the boiler breaks down, both heating and domestic hot water is not available.
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 wasoptimized 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
Fan (mechanical)
A mechanical fan is an electricity powered device used to produce an airflow for the purpose of
creature comfort , Ventilation , exhaust, or any other gaseous transport....
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to circulate air to the rooms of house and pull cooler air back to the furnace for reheating; this is calledforced-air
Forced-air
A forced-air or warm air heating system is one which uses air as its heat transfer medium. Thesesystems use Duct and Diffuser as a means of air distribution....
heat. Because the fan easily overcomes the resistance
Friction
File:Friction alt.svgFriction is the force resisting the relative lateral motion of solid surfaces, fluidlayers, or material elements in contact....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 Heat exchanger
A heat exchanger is a device built for efficient heat transfer from one medium to another, whether themedia are separated by a solid wall so that they never mix, or the media are in direct contact....
of the furnace, whence it is blown throughout the building
Building
In architecture, construction, engineering and Real estate developer the word building may refer to one
of the following:# Any man-made structure used or intended for supporting or sheltering any use or continuous occupancy, or...
. One major advantage of this type of system is that it also enables easy installation of central air
conditioning
Air conditioning
An air conditioner is an appliance, system, or Mechanism designed to extract heat from an area via a
refrigeration cycle. In construction, a complete system of heating, Ventilation , and air conditioning is
referred to as "HVAC." Its purpose, in a building or an automobile, is to provide comfort during either hot or cold...
by simply adding a cooling coil at the exhaust of the furnace.
Air is circulated through ductwork
Duct (HVAC)
Ducts are used in HVAC to deliver and remove air. These needed airflows include, for example,
supply air , return air , and exhaust air ....
, which may be made of sheet metal or plastic "flex" duct and insulated or uninsulated. Unless theducts and plenum 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 theinstallation 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 furnaceexceeds a maximum threshold, a safety mechanism with a thermostat
Thermostat
A thermostat is a Measuring instrument for regulating the temperature of a system so that the system'stemperature is maintained near a desired setpoint temperature....
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
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limit switch". This condition commonly occurs if the temperature setting of the high limit thermostat isset 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.
Metallurgical furnaces
In metallurgy
Metallurgy
Metallurgy is a domain of materials science that studies the physical and chemical behavior of metallic Chemical element, their intermetallics, and their mixtures, which are called alloys....
, several specialised furnaces are used. These include:
• Furnaces used in smelters, including:
o The blast furnace
Blast furnace
A blast furnace is a type of metallurgy furnace used for smelting to produce metals,
generally iron.In a blast furnace, fuel and ore are continuously supplied through the top
of the furnace, while air is blown into the bottom of the chamber, so that the chemicalreactions take place throughout the furnace as the material moves downward....
, used to reduce
Redox
Redox describes all chemical reactions in which atoms have their oxidation number
changed.This can be either a simple redox process such as the oxidation of carbon toyield carbon dioxide or the reduction of carbon by hydrogen to yield methane , or it can be a complex process such as the oxidation of sugar in the human body through a ser...
iron ore
Iron ore
Iron ores are Rock and minerals from which metallic iron can be economicallyextracted. The ores are usually rich in iron oxides and vary in colour from dark grey,
bright yellow, deep purple, to rusty red....
to pig iron
Pig iron
Pig iron is the intermediate product of smelting iron ore with coke , usually with
limestone as a flux. Pig iron has a very high carbon content, typically 3.5?4.5%, which
makes it very brittle and not useful directly as a material except for limitedapplications....
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o Steelmaking
Steelmaking
Steelmaking is the second step in producing steel from iron ore. In this stage,
impurities such as sulfur, phosphorus, and excess carbon are removed from the Pig iron,
and alloying elements such as manganese, nickel, chromium and vanadium are added to produce the exact steel required....
furnaces, including:
Puddling furnace
Reverberatory furnace
Reverberatory furnace
A reverberatory furnace is a metallurgy or process furnace that isolates the
material being processed from contact with the fuel, but not from contact withcombustion gases....
Bessemer converter
Open hearth furnace
Open hearth furnace
Open hearth furnaces are one of a number of kinds of furnace where excess
carbon and other impurities are burnt out of the pig iron to Steelmaking....
Basic oxygen furnace
Electric arc furnace
Electric arc furnace
An is a furnace that heats charged material by means of an electric arc.Arc
furnaces range in size from small units of approximately one ton capacity up to
about 400 ton units used for secondary steelmaking....
Electric induction furnace
• Furnaces used to remelt metal in foundries
Foundry
A foundry is a factory which produces metal castings from either ferrous or non-ferrous metals
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alloys. Metals are turned into parts by melting the metal into a liquid, pouring the metal in amold, and then removing the mold material or casting....
.
• Furnaces used to reheat and heat treat
Heat treatment
Heat treatment is a method used to alter the physical property, and sometimes chemical
property, properties of a material. The most common application is metallurgy....
metal for use in:
o Rolling mill
Rolling mill
A rolling mill is a machine or factory for shaping metal by passing it between a pair of work rolls.Rolling mills are often incorporated into integrated steelworks, but also existas separate plants and can be used for other metals, and other materials....
s, including tinplate
Tinplate
Tinplate is sheet carbon steel covered with a thin layer of tin. Before the advent of
cheap mild steel the backing metal was wrought iron. While once more widely used, the
primary use of tinplate now is the manufacture of tin cans....
works and slitting mill
Slitting mill
The slitting mill was a watermill for slitting bars of iron into rods. The rods then were
passed to nailers who made the rods into nail , by giving them a point and head....s.
o Forge
Forge
A forge is the workplace of a smith or a blacksmith. A forge is sometimes referred to asa smithy.The basic smithy contains a forge, also known as a hearth, for heating
metals....
s.
• Vacuum furnace
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Vacuum furnace
A vacuum furnace is a type of furnace that can heat materials, typically metals, to very high
temperatures and carry out processes such as brazing, sintering and heat treatment with high
consistency and low contamination....s
See also
• Extractive metallurgy
Extractive metallurgy
Extractive metallurgy is the practice of extracting metal from ore, purifying it, and recycling
it.Most metals found in the Earth's crust exist as oxide and sulfide compounds....
• Flue gas stacks
• Fire test furnaces
Fire test
A fire test is a means of determining whether or not fire protection products meet minimum performance criteria as set out in a building code or other applicable legislation....
Industrial process furnaces
An industrial furnace or direct fired heater, is an equipment used to provide heat for a process or can
serve as reactor Chemical reactor
In chemical engineering, chemical reactors are vessels designed to contain chemical reactions. Thedesign of a chemical reactor deals with multiple aspects of chemical engineering....
which provides heats of reaction. Furnace designs vary as to its function, heating duty, type of fuel
Fuel
Fuel is any material that is burned or altered in order to obtain energy and to heat or to move an object.
Fuel releases its energy either through a chemical reaction means, such as combustion, or nuclear
means, such as nuclear fission or nuclear fusion....and method of introducing combustion air. However, most process furnaces have some common
features.
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Fuel flows into the burner
Burner
Burner may refer to:Michael Egan aka: Mikey-Mike Device* Gas burner or Oil burner, a mechanicaldevice that burns a gas or liquid fuel into a flame in a controlled manner...
and is burnt with air provided from an air blower. There can be more than one burner in a particular
furnace which can be arranged in cells which heat a particular set of tubes. Burners can also be floor mounted, wall mounted or roof mounted depending on design. The flames heat up the tubes, which in
turn heat the fluid inside in the first part of the furnace known as the radiant section or firebox. In thischamber where combustionCombustion
Combustion or burning is a complex sequence of exothermic chemical reactions between a fuel and
an oxidant accompanied by the production of heat or both heat and light in the form of either a glow or flames, appearance of light flickering....
takes place, the heat is transferred mainly by radiation
Radiant energy
Radiant energy is the energy of electromagnetic waves. The quantity of radiant energy may be
calculated by Integral radiant flux with respect to time and, like all forms of energy, its SI unit is the joule....
to tubes around the fire
Fire
Fire is the oxidation of a combustion material releasing heat, light, and various Chemical reaction
products such as carbon dioxide and water....
in the chamber. The heating fluid passes through the tubes and is thus heated to the desiredtemperature. The gases from the combustion are known as flue gas
Flue gas
Flue gas is gas that exits to the atmosphere via a flue, which is a pipe or channel for conveying exhaustgases from a fireplace, oven, furnace, boiler or steam generator....
. After the flue gas leaves the firebox, most furnace designs include a convectionConvection
Convection in the most general terms refers to the movement of molecules within fluids . Convection
is one of the major modes of heat transfer and mass transfer....section where more heat is recovered before venting to the atmosphere
Earth's atmosphere
The Earth's atmosphere is a layer of gases surrounding the planet Earth that is retained by the Earth's
gravity. Dry air contains roughly 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.038% Carbondioxide in the Earth's atmosphere, and trace amounts of other gases....through the flue gas stack
Flue gas stack
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 to the outside air....
. (HTF=Heat Transfer Fluid. Industries commonly use their furnaces to heat a secondary fluid with
special additives like anti-rustRust
Rust is a general term for a series of iron oxides, usually red oxides, formed by the reaction of iron and
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oxygen in the presence of water or air moisture....and high heat transfer efficiency. This heated fluid is then circulated round the whole plant to heat
exchangers to be used wherever heat is needed instead of directly heating the product line as the
product or material may be volatile or prone to cracking
Cracking (chemistry)
In petroleum geology and chemistry, cracking is the process whereby complex organic compound
molecules such as kerogens or heavy hydrocarbons are broken down into simpler molecules by the breaking of carbon-carbon chemical bond in the precursors....
at the furnace temperature.)
Radiant section
The radiant section is where the tubes receive almost all its heat by radiation
Thermal radiation
Thermal radiation is electromagnetic radiation emitted from the surface of an object which is due tothe object's temperature. Infrared radiation from a common household radiator or electric heater is an
example of thermal radiation, as is the light emitted by a glowing incandescent light bulb....
from the flame. In a vertical, cylindrical furnace, the tubes are vertical. Tubes can be vertical or horizontal, placed along the refractory
Refractory
A refractory material is one that retains its strength at high temperatures. ASTM International C71
defines refractories as "non-metallic materials having those chemical and physical properties that made
them applicable for structures, or as components of systems, that are exposed to environments above
1000 ?F "....wall, in the middle, etc., or arranged in cells. Studs are used to hold the insulation
Thermal insulation
The term thermal insulation can refer to materials used to reduce the rate of heat transfer, or themethods and processes used to reduce heat transfer....
together and on the wall of the furnace. They are placed about 1 ft (300 mm) apart in this picture of the inside of a furnace. The tubes, shown below, which are reddish brown from corrosion
Corrosion
Corrosion means the breaking down of essential properties in a material due to chemical reactions
with its surroundings. In the most common use of the word, this means a loss of electrons of metals
reacting with water and oxygen....
, are carbon steel tubes and run the height of the radiant section. The tubes are a distance away fromthe insulation so radiation can be reflected to the back of the tubes to maintain a uniform tube wall
temperature. Tube guides at the top, middle and bottom hold the tubes in place.
Convection section
The convection
Convection
Convection in the most general terms refers to the movement of molecules within fluids . Convection
is one of the major modes of heat transfer and mass transfer....
section is located above the radiant section where it is cooler to recover additional heat. Heat transfer
Heat transfer
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Heat transfer is the transition of thermal energy or simply heat from a hotter object to a cooler object .
When an object or fluid is at a different temperature than its thermodynamic system or another object,
transfer of thermal energy, also known as heat transfer, or heat exchange, occurs in such a way that the
body and the surround...takes place by convection here, and the tubes are finned to increase heat transfer. The first two tube
rows in the bottom of the convection section and at the top of the radiant section is an area of bare
tubes (without fins) and are known as the shield section, so named because they are still exposed to plenty of radiation
Radiant energy
Radiant energy is the energy of electromagnetic waves. The quantity of radiant energy may be
calculated by Integral radiant flux with respect to time and, like all forms of energy, its SI unit is the
joule....
from the firebox and they also act to shield the convection section tubes, which are normally of lessresistant material from the high temperatures in the firebox. The area of the radiant section just before
flue gas
Flue gas
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 or steam generator....enters the shield section and into the convection section called the bridgezone. Crossover is the term
used to describe the tube that connects from the convection section outlet to the radiant section inlet.
The crossover piping is normally located outside so that the temperature can be monitored and theefficiency of the convection section can be calculated. The sightglass at the top allows personnel to see
the flame
Fire
Fire is the oxidation of a combustion material releasing heat, light, and various Chemical reaction
products such as carbon dioxide and water....
shape and pattern from above and visually inspect if flame impingement is occurring. Flame
impingement happens when the flame touches the tubes and causes small isolated spots of very hightemperature.
Burner
The burner
Burner
Burner may refer to:Michael Egan aka: Mikey-Mike Device* Gas burner or Oil burner, a mechanicaldevice that burns a gas or liquid fuel into a flame in a controlled manner...
in the vertical, cylindrical furnace as above, is located in the floor and fires upward. Some furnaceshave side fired burners, eg: train locomotive. The burner tileTile
A tile is a manufactured piece of hard-wearing material such as ceramic, Rock , metal, or even glass.Tiles are generally used for covering roofs, floors, and walls, showers, or other objects such as
tabletops....
is made of high temperature refractory
Refractory
A refractory material is one that retains its strength at high temperatures. ASTM International C71
defines refractories as "non-metallic materials having those chemical and physical properties that made
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them applicable for structures, or as components of systems, that are exposed to environments above1000 ?F "....
and is where the flame is contained in. Air registers located below the burner and at the outlet of the
air blower are devices with movable flaps or vanes that control the shape and pattern of the flame,
whether it spreads out or even swirls around. Flames should not spread out too much, as this will causeflame impingement. Air registers can be classified as primary, secondary and if applicable, tertiary,
depending on when their air is introduced. The primary air register supplies primary air, which is the
first to be introduced in the burner. Secondary air is added to supplement primary air. Burners mayinclude a premixer to mix the air and fuel
Fuel
Fuel is any material that is burned or altered in order to obtain energy and to heat or to move an object.
Fuel releases its energy either through a chemical reaction means, such as combustion, or nuclear
means, such as nuclear fission or nuclear fusion....
for better combustionCombustion
Combustion or burning is a complex sequence of exothermic chemical reactions between a fuel andan oxidant accompanied by the production of heat or both heat and light in the form of either a glow or
flames, appearance of light flickering....
before introducing into the burner. Some burners even use steam as premix to preheat the air andcreate better mixing of the fuel and heated air. The floor of the furnace is mostly made of a different
material from that of the wall, typically hard castable refractory to allow technicians to walk on its
floor during maintenance.
A furnace can be lit by a small pilot flame
Pilot light
A pilot light is a small gas flame, usually natural gas or liquefied petroleum gas, which is kept alight in
order to serve as an ignition source for a more powerful gas burner....
or in some older models, by hand. Most pilot flames nowadays are lit by an ignition transformer
(much like a car's spark plugs). The pilot flame in turn lights up the main flame. The pilot flame usesnatural gas
Natural gas
Natural gas is a gas consisting primarily of methane. It is found associated with fossil fuels, in coal
beds, as methane clathrates, and is created by methanogenic organisms in marshes, bogs, and
landfills....while the main flame can use both diesel
Diesel
Diesel or diesel fuel in general is any fuel used in diesel engines. The most common is a specific
fractional distillation of petroleum fuel oil, but alternatives that are not derived from petroleum, suchas biodiesel, biomass to liquid or gas to liquid diesel, are increasingly being developed and adopted....and natural gas. When using liquid fuels, an atomizer is used, otherwise, the liquid fuel will simply
pour onto the furnace floor and become a hazard. Using a pilot flame for lighting the furnace increases
safety and ease compared to using a manual ignition method (like a match).
Sootblower
Sootblowers are found in the convection section. As this section is above the radiant section and air movement is slower because of the fins, soot
Soot
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Soot is a general term that refers to impure carbon particles resulting from the incomplete combustion
of a hydrocarbon. It is more properly restricted to the product of the gas-phase combustion process but
is commonly extended to include the residual pyrolyzed fuel particles such as cenospheres, charred
wood, petroleum coke, etc....tends to accumulate here. Sootblowing is normally done when the efficiency of the convection section
is decreased. This can be calculated by looking at the temperature change from the crossover piping
and at the convection section exit. Sootblowers utilize flowing media such as water, air or steam toremove deposits from the tubes. This is typically done during maintenance with the air blower turned
on. There are several different types of sootblowers used. Wall blowers of the rotary type are mountedon furnace walls protruding between the convection tubes. The lanceLance
The term lance has become a catchall for a variety of different pole weapons based on the spear. The
name is derived from lancea, Ancient Rome auxiliaries' javelin, although according to the OxfordEnglish Dictionary, the word may be of Iberian language origin....
s are connected to a steam source with holes drilled into it at intervals along its length. When it is
turned on, it rotates and blows the soot off the tubes and out through the stack.
Stack
The flue gas stack
Flue gas stack
A flue gas stack is a type of chimney, a vertical pipe, channel or similar structure through whichcombustion product gases called flue gases are exhausted to the outside air....
is a cylindrical structure at the top of all the heat transfer chambers. The breeching
Flue
A flue is a Duct , pipe, or chimney for conveying exhaust gases from a fireplace, furnace, water heater,
boiler, or Electrical generator to the outdoors....directly below it collects the flue gas
Flue gas
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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 or steam generator....
and brings it up high into the atmosphere
Earth's atmosphere
The Earth's atmosphere is a layer of gases surrounding the planet Earth that is retained by the Earth's
gravity. Dry air contains roughly 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.038% Carbondioxide in the Earth's atmosphere, and trace amounts of other gases....
where it will not endanger personnel.
The stack damper
Damper (architecture)
A damper is a valve or plate that stops or regulates the flow of air inside a Duct , chimney, Variable air volume, air handler, or other air handling equipment....
contained within works like a butterfly valve
Butterfly valve
A butterfly valve is a type of flow control device, typically used to regulate a fluid flowing through a
section of pipe. The valve is similar in operation to a ball valve....and regulates draft
Stack effect
Stack effect is the movement of air into and out of buildings, chimneys, flue gas stacks, or other
containers, and is driven by buoyancy. Buoyancy occurs due to a difference in indoor-to-outdoor air
density resulting from temperature and moisture differences....
(pressure difference between air intake and air exit)in the furnace, which is what pulls the flue gasthrough the convection
Convection
Convection in the most general terms refers to the movement of molecules within fluids . Convectionis one of the major modes of heat transfer and mass transfer....
section. The stack damper also regulates the heat lost through the stack. As the damper closes, theamount of heat escaping the furnace through the stack decreases, but the pressure
Pressure
Pressure is the force per unit area applied to an object in a direction surface normal to the surface.
Gauge pressure is the pressure relative to the local atmospheric or ambient pressure....
or draft in the furnace increases which poses risks to those working around it if there are air leakages
in the furnace, the flames can then escape out of the firebox or even explode if the pressure is too great.
Insulation
Insulation
Thermal insulation
The term thermal insulation can refer to materials used to reduce the rate of heat transfer, or the
methods and processes used to reduce heat transfer....
is an important part of the furnace because it prevents excessive heat loss. Refractory
Refractory
A refractory material is one that retains its strength at high temperatures. ASTM International C71
defines refractories as "non-metallic materials having those chemical and physical properties that made
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them applicable for structures, or as components of systems, that are exposed to environments above1000 ?F "....
materials such as firebrick, castable refractories
Refractory
A refractory material is one that retains its strength at high temperatures. ASTM International C71
defines refractories as "non-metallic materials having those chemical and physical properties that made
them applicable for structures, or as components of systems, that are exposed to environments above1000 ?F "....
and ceramic fibreHigh temperature insulation wool
High temperature insulation wool is a material manufactured from alumino silicate glass which is
used for thermal insulation in high temperature applications and processes up to 700 ?Celsius....
, are used for insulation. The floor of the furnace are normally castable type refractories while those onthe walls are nailed or glued in place. Ceramic fibre is commonly used for the roof and wall of the
furnace and is graded by its density
Density
The density of a material is defined as its mass per unit volume. The symbol of density is ....
and then its maximum temperature rating. For eg: 8# 2,300°F means 8 lb/ft 3 density with a maximumtemperature rating of 2,300°F. An example of a castable composition is kastolite.
Outdoor wood-fired boilers
Description
An outdoor wood-fired boiler (OWB) also known as a waterstove or outdoor wood furnace or simply a
wood boiler, is a heating technology that has grown in popularity in the Northern United States. OWBs
in most cases look like a small shack with metal siding. They are self-contained, and are onlyconnected to the building they heat through underground insulated water pipes. OWBs contain a metal
combustion chamber for a wood fire, which is surrounded by a water tank or water jacket. The fire
heats the water, which is then circulated through the insulated water pipes into the heated building.Once the hot water from the boiler reaches the building, the heat from the hot water can be transferred
to most existing heating systems and the building's hot water supply.
A damper and fan on the boiler interacts with a thermostat inside the building. If the building's
temperature falls, the thermostat will trigger the damper to open, letting oxygen enter the combustion
chamber, which causes the fire to burn more intensely. The fire will then raise the temperature of thewater which increases the heat supplied to the home.
Benefits
OWBs have several benefits that increase their popularity. Their large combustion chamber
accommodates more fuel than many other forms of wood heat, decreasing the number of times an
owner has to add fuel to the fire. Home insurance may cost more for people who heat with an indoor form of wood heat than with an OWB. Finally, for people with a large supply of free wood and willing
to invest the time to prepare the wood and stock the OWB, an OWB can be less expensive than heating
with gas, oil, or electricity (*).
Controversy
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OWBs are not without controversy, as their emissions sometimes bother neighbors. Some states and
municipalities have regulated the devices (*). They are not currently regulated by the United States
Environmental Protection Agency (EPA), unlike other forms of wood heat. (However, recently the EPA
has worked with manufacturers to develop a method for manufacturers to identify OWBs that meet avoluntary emissions standard (*).) Studies conducted on OWBs suggest that these devices may
produce more emissions, most notably particulate
Particulate
Particulates, alternatively referred to as particulate matter or fine particles, are tiny particles of
solid or liquid suspended in a gas or liquid....matter under 2.5 micrometers (PM2.5) than other heating technologies, though manufacturers dispute
these assessments (*). Exposure to elevated levels of PM2.5 has been associated with
cardiopulmonary health effects and premature death (*)
As of July 2006, the HPBA, along with many of the major OWB manufactures, have requested users
of their products follow the "Outdoor Wood Furnace Best Burn Practices" (*) These guidelines have
been set up by the HPBA to help cut down on problems associated with OWBs.
Early in January 2007, the United States Environmental Protection Agency (EPA) initiated a voluntary program (*) for manufacturers of outdoor wood furnaces. The EPA's primary intent is to encourage
manufacturers to produce cleaner Outdoor Wood-fired Hydronic Heaters (OWHH) models. The EPAalso wants those who buy an OWHH / OWB to buy the cleanest models available, which are those thatmeet EPA performance verified levels. To participate in this program, manufacturers commit their best
efforts to develop cleaner models with goals of distributing their units starting in April 2007. (*)
The EPA now publishes a list of all OWHH / OWB units that pass the new voluntary program. (*)
These furances come with the 'orange EPA OWHH tag' to notify the customer of the units particular
emission level output.
See also
• Russian Oven
Russian oven
A Russian oven is a unique type of oven/furnace, invented in Ancient Rus and used for both
cooking and house heating. The Russian oven burns firewood or wood manufacturing waste....
• Boiler
Boiler
A boiler is a closed Pressure vessel in which water or other fluid is heated. The heated or vaporized fluid exits the boiler for use in various processes or heating applications....
• Shell boiler
Shell boiler
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A shell or flued boiler is an early, and relatively simple, form of boiler used to make steam,
usually for the purpose of driving a steam engine....
• Jetstream furnace
Jetstream furnace
Jetstream furnaces , were an advanced design of wood-fired water heaters conceived by Dr.
Richard Hill of the University of Maine in Orono, Maine, Maine, USA....
• HVAC
HVAC
HVAC is an initialism or acronym that stands for "heating, Ventilation , and air
conditioning". HVAC is sometimes referred to as climate control and is particularly importantin the design of medium to large industrial and office buildings such as skyscrapers and in
marine environments such as aquariums, where humidity and tem...
• Flue gas stacks
• Humidifier
Humidifier
A humidifier is a household appliance that increases humidity in a single room or in the entirehome. There are point-of-use humidifiers, which are commonly used to humidify a singleroom, and whole-house or furnace humidifiers, which connect to a home's HVAC system to
provide humidity to the entire house....
• Solar power
Solar power
Solar energy is the radiant light and heat from the Sun that has been harnessed by humanssince ancient history using a range of ever-evolving technologies....
• Cremation
Cremation
Cremation is the process of reducing human remains to basic Chemical element in the form of
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bone fragments through flame, heat, and vaporization....
• Fan heater
Fan heater
A fan heater is a heater that works by using a fan to pass air over a heating element. This heats
up the air, which then leaves the heater, warming up the surrounding area....
• Geothermal Systems
Geothermal Systems
A geothermal heat pump system is a HVAC and/or cooling system that uses the earth?s abilityto store heat in the shallow ground or water thermal masses....
• Fire test
Fire test
A fire test is a means of determining whether or not fire protection products meet minimum
performance criteria as set out in a building code or other applicable legislation....
External links
•
Industrial Fired Heaters
• Castable refractories