A
mechanical fan is an
electricallyElectricity is a general term that encompasses a variety of phenomena resulting from the presence and flow of electric charge...
powered
deviceA machine is any device that uses energy to perform some activity. In common usage, the meaning is that of a device having parts that perform or assist in performing any type of work. A simple machine is a device that transforms the direction or magnitude of a force without consuming any energy...
used to produce an
airflow for the purpose of creature comfort (particularly in the heat),
ventilationVentilation is the intentional movement of air from outside a building to the inside. It is the V in HVAC. With clothes dryers, and combustion equipment such as water heaters, boilers, fireplaces, and wood stoves, their exhausts are often called vents or flues — this should not be confused...
, exhaust,
coolingAn air conditioner is a home appliance, system, or mechanism designed to dehumidify and extract heat from an area, or provide heat to an area. The cooling is done using a simple refrigeration cycle...
or any other gaseous transport.
Mechanically, a fan can be any revolving vane or vanes used for producing
air currentAir currents may be caused by differences in temperature, pressure, or impurity concentration. Temperature differences can cause air currents because warmer air is less dense than cooler air, causing the warmer air to appear "lighter." Thus, if the warm air is under the cool air, air currents will...
s. Fans produce air flows with high volume and low pressure, as opposed to a
gas compressorA gas compressor is a mechanical device that increases the pressure of a gas by reducing its volume.Compressors are similar to pumps: both increase the pressure on a fluid and both can transport the fluid through a pipe. As gases are compressible, the compressor also reduces the volume of a gas...
which produces high pressures at a comparatively low volume. A fan blade will often rotate when exposed to an air stream, and devices that take advantage of this, such as
anemometerAn anemometer is a device that is used for measuring wind speed, and is one instrument used in a weather station. The term is derived from the Greek word anemos, meaning wind...
s and
wind turbineA wind turbine is a rotating machine which converts the kinetic energy of wind into mechanical energy. If the mechanical energy is used directly by machinery, such as a pump or grinding stones, the machine is usually called a windmill...
s often have designs similar to that of a fan.
Typical applications include climate control, cooling systems, personal comfort (e.g., an electric table fan), ventilation (e.g., an exhaust fan), winnowing (e.g., separating chaff of
cerealCereals, grains or cereal grains, {as a collective} are grasses cultivated for the edible components of their fruit seeds - the endocarp, germ and bran...
grains), removing dust (e.g. sucking as in a
vacuum cleanerA vacuum cleaner is a device that uses an air pump to create a partial vacuum to suck up dust and dirt, usually from floors...
), drying (usually in addition to heat) and to provide draft for a
fireFire is the rapid oxidation of a combustible material releasing heat, light, and various reaction products such as carbon dioxide and water. If hot enough, the gases may become ionized to produce plasma. Depending on the substances alight, and any impurities outside, the color of the flame and the...
. It is also common to use electric fans as
air freshenerAir fresheners are consumer products that mitigate unpleasant odors in indoor spaces. They can be in the form of candles, aerosol sprays, potpourri, gels and mechanical or heat release products...
s, by attaching
fabric softenerFabric Softener is used to prevent static cling and make fabric softer. It is available as a liquid or as dryer sheets...
sheets to the protective housing. This causes the fragrance to be carried into the surrounding air.
In addition to their utilitarian function, vintage or antique fans, and in particular electric fans manufactured from the late 19th century through the 1950s, have become a recognized
collectibleA collectable or collectible is typically a manufactured item designed for people to collect. In this respect, they are distinguishable from other subjects of collections, which may also include natural objects and objects manufactured for purposes other than collecting...
category, and in the U.S.A. an active collector club, the Antique Fan Collectors Association, supports the hobby. .
New to the market are sleek portable fans that showcase a modern design sensibility. The New York Times lamented that inexpensive and effective fans abound at drug and discount stores, but they are often eyesores. The writer quoted contemporary ceiling fan designer
Ron RezekRonald John Rezek is a design entrepreneur who started five successful companies and has designed hundreds of contemporary light fixtures and ceiling fans...
as saying: “Portable fans are the ugly ducklings of the fan industry. Not many designers, including myself, have tackled them.” Rezek praised several appealing contemporary fan designs that have found alternatives to the traditional metal cage and have incorporated innovative approaches to safety, such as the Otto fan by Swiss designer Carlo Borer.
History
The first recorded mechanical fan was the punkah fan used in the
Middle EastThe Middle East is a region that spans southwestern Asia, southeastern Europe, and northeastern Africa. It has no clear boundaries, often used as a synonym to Near East, in opposition to Far East...
in the early 19th century. It had a canvas covered frame that was suspended from the ceiling. Servants, known as punkah wallahs, pulled a
ropeA rope is a length of fibers, twisted or braided together to improve strength for pulling and connecting. It has tensile strength but is too flexible to provide compressive strength...
connected to the frame to move the fan back and forth.
The
Industrial RevolutionThe Industrial Revolution was a period from the 18th to the 19th century where major changes in agriculture, manufacturing, mining, and transport had a profound effect on the socioeconomic and cultural conditions in the United Kingdom. The changes subsequently spread throughout Europe, North...
in the late 19th century introduced belt-driven fans powered by factory
water wheelA water wheel is a machine for converting the energy of flowing or falling water into useful forms of power, the development of hydropower. In the Middle Ages, waterwheels were used as tools to power factories throughout different counties. The alternatives were the windmill and human and animal...
s. Attaching wooden or metal blades to shafts overhead that were used to drive the machinery, the first industrial fans were developed. One of the first workable mechanical fans was built by Omar-Rajeen Jumala in 1832. He called his invention, a kind of a centrifugal fan, an Air Pump. Centrifugal fans were successfully tested inside coal mines and factories in 1832-1834. When
Thomas EdisonThomas Alva Edison was an American inventor, scientist and businessman who developed many devices that greatly influenced life around the world, including the phonograph, the motion picture camera, and a long-lasting, practical electric light bulb...
and
Nikola TeslaNikola Tesla was an inventor and a mechanical and electrical engineer. He is frequently cited as one of the most important contributors to the birth of commercial electricity and is best known for his many revolutionary developments in the field of electromagnetism in the late 19th and early 20th...
introduced electrical power in the late 19th and early 20th centuries for the public, the personal electrical fan was introduced. Between 1882 and 1886, Dr.
Schuyler Skaats WheelerSchuyler Skaats Wheeler was an American engineer who invented the two-blade electric fan in 1882 at age 22.Wheeler was born in Massachusetts. His two-bladed electric fan was produced by the Crocker and Curtis Electric Motor Company. He died of angina pectoris at his home in Manhattan. -References:...
developed the two-bladed desk fan, a type of personal electric fan. It was commercially marketed by the American firm Crocker & Curtis electric motor company. In 1882,
Philip DiehlPhilip H. Diehl was a German-American engineer and inventor who held several U.S. patents, including electric incandescent lamps, electric motors for sewing machines and other uses, and ceiling fans. Diehl was a contemporary of Thomas Edison and his inventions caused Edison to reduce the price of...
introduced the electric ceiling fan. Diehl is considered the father of the modern electric fan. In the late 19th century, electric fans were used only in commercial establishments or in well-to-do households. Heat-convection fans fueled by alcohol, oil, or kerosene were common around the turn of the 20th century.
The first American fans were made from around the late 1890s to the early 1920s. They had
brassBrass is any alloy of copper and zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties. In comparison, bronze is principally an alloy of copper and tin. Despite this distinction, some types of brasses are called bronzes. Brass is a...
blades, a lot of them also had brass cages, and though they were built very well internally, they were far from finger safe, as a lot of them had cage openings so big that one could put an entire hand or arm right through it. Many children had hands and fingers severely injured by those fans.
In the 1920s, industrial advances allowed steel to be mass-produced in different shapes, bringing fan prices down and allowing more homeowners to afford them. In the 1930s, the first art deco fan (the "Swan Fan") was designed. In the 1950s, fans were manufactured in colors that were bright and eye catching. Central
air conditioningAn air conditioner is a home appliance, system, or mechanism designed to dehumidify and extract heat from an area, or provide heat to an area. The cooling is done using a simple refrigeration cycle...
in the 1960s brought an end to the golden age of the electric fan. In the 1970s, Victorian-style ceiling fans became popular.
In the 20th century, fans have become utilitarian. During the 2000s, fan aesthetics have become a concern to fan buyers. The fan is part of everyday life in the
Far EastThe Far East is a term used in English mostly equivalent to East Asia and Southeast Asia, sometimes to the inclusion of South Asia for economic and cultural reasons."Far East" came into use in European geopolitical discourse in...
, Japan, and
SpainSpain , officially the Kingdom of Spain , is a country located in southwestern Europe on the Iberian Peninsula.
[The Spanish constitution does not establish any official denomination of the country, even though España , Estado español and Nación española are used interchangeably...]
(among other places). Electric fans have been largely replaced by air conditioners in offices, but they are still a common household appliance.
Types of fans
Mechanical revolving blade fans are made in a wide range of designs. In a home you can find fans that can be put on the floor or a table, or hung from the ceiling, or are built into a window, wall, roof, chimney, etc. They can be found in electronic systems such as
computerA computer is a machine that manipulates data according to a set of instructions.Although mechanical examples of computers have existed through much of recorded human history, the first electronic computers were developed in the mid-20th century . These were the size of a large room, consuming as...
s where they cool the circuits inside, and in appliances such as hair dryers and space heaters. They are also used for cooling in air-conditioning systems, and in automotive engines, where they are driven by belts or by direct motor. Fans create a
wind chillWind chill is the apparent temperature felt on exposed skin due to wind. The degree of this phenomenon depends on both air temperature and wind speed. The wind chill temperature is always lower than the air temperature for values where the wind chill formula is valid...
but do not lower temperatures directly.
There are three main types of fans used for moving air,
axial,
centrifugal (also called
radial) and
cross flow (also called
tangential).
Axial fans
The axial-flow fans have blades that force air to move
parallelParallelism is a term in geometry and in everyday life that refers to a property in Euclidean space of two or more lines or planes, or a combination of these. The existence and properties of parallel lines are the basis of Euclid's parallel postulate. Two lines in a plane that do not intersect or...
to the shaft about which the blades rotate. Axial fans blow air across the axis of the fan, linearly, hence their name. This type of fan is used in a wide variety of applications, ranging from small cooling fans for electronics to the giant fans used in
wind tunnelA wind tunnel is a research tool used in aerodynamic research. It is used to study the effects of air moving past solid objects.-Theory of operation:Wind tunnels were first proposed as a means of studying vehicles in free flight...
s.
Examples of axial fans are:
- Table fan - Basic elements of a typical table fan include the fan blade, base, armature and lead wire
A wire is a single, usually cylindrical, string of metal. Wires are used to bear mechanical loads and to carry electricity and telecommunications signals. Wire is commonly formed by drawing the metal through a hole in a die or draw plate. Standard sizes are determined by various wire gauges...
s, motor, blade guard, motor housing, oscillator gearbox, and oscillator shaft. The oscillator is a mechanism that motions the fan from side to side. The axle comes out on both ends of the motor, one end of the axle is attached to the blade and the other is attached to the oscillator gearbox. The motor case joins to the gearbox to contain the rotor and stator. The oscillator shaft combines to the weighted base and the gearbox. A motor housing covers the oscillator mechanism. The blade guard joins to the motor case for safety.
- Electro-mechanical fans, among collectors, are rated according to their condition, size, age, and number of blades. Four-blade designs are the most common. Five-blade or six-blade designs are rare. The materials from which the components are made, such as brass, are important factors in fan desirability.
- Ceiling fan
A ceiling fan is a device suspended from the ceiling of a room, which employs hub-mounted rotating paddles to circulate air in order to move air.- History :...
- A fan suspended from the ceiling of a room is a ceiling fan.
- In automobile
An automobile, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...
s, a mechanical fan provides engine coolingInternal combustion engine cooling refers to the cooling of an internal combustion engine, typically using either air or a liquid.-History:The change of air cooling to liquid cooling occurred at the start of World War II when the US military needed reliable vehicles. The subject of boiling engines...
and prevents the engine from overheating by blowing or sucking air through a coolantA coolant is a fluid which flows through a device to prevent its overheating, transferring the heat produced by the device to other devices that use or dissipate it. An ideal coolant has high thermal capacity, low viscosity, is low-cost, non-toxic, and chemically inert, neither causing nor...
-filled radiatorRadiators are heat exchangers used to transfer thermal energy from one medium to another for the purpose of cooling and heating. The majority of radiators are constructed to function in automobiles, buildings, and electronics...
. It can be driven with a belt and pulley off the engineThe internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine the expansion of the high temperature and pressure gases, which are produced by the combustion, directly applies force to a movable...
's crankshaftThe crankshaft, sometimes casually abbreviated to crank, is the part of an engine which translates reciprocating linear piston motion into rotation...
or an electric fan switched on/off by a thermostaticA thermostat is a device for regulating the temperature of a system so that the system's temperature is maintained near a desired setpoint temperature. The name is derived from the Greek words thermos "hot" and statos "a standing"...
switchIn electronics, a switch is an electrical component that can break an electrical circuit, interrupting the current or diverting it from one conductor to another. The most familiar form of switch is a manually operated electromechanical device with one or more sets of electrical contacts...
.
- Computer fan
A computer fan is any fan inside a computer case used for cooling purposes, and may refer to fans that draw cooler air into the case from the outside, expel warm air from inside, or move air across a heatsink to cool a particular component...
- Variable Pitch Fan A variable pitch fan is used where precise control of static pressure within supply ducts is required. The fan wheel will spin at a constant RPM (1780 in this case). The blades follow the control pitch hub. As the hub moves toward the rotor the blades increase their angle of attack and an increase in flow results.
Centrifugal fan
Often called a "squirrel cage" (due to its similarity in appearance to
exercise wheelsMost wheels are constructed of steel or plastic, both with advantages and problems. Solid plastic wheels are safer for some types of pets, such as hamsters, because the space between rungs is solid and the animal's feet or legs cannot get stuck between rungs, an injury risk in steel wheels...
for pet rodents), the centrifugal fan has a moving component (called an impeller) that consists of a central shaft about which a set of blades, or ribs, are positioned. Centrifugal fans blow air at right angles to the intake of the fan, and spin the air outwards to the outlet (by deflection and
centrifugal forceIn classical mechanics, centrifugal force is an outward force associated with curved motion, that is, rotation about some center...
). The impeller rotates, causing air to enter the fan near the shaft and move
perpendicularIn geometry, two lines or planes , are considered perpendicular to each other if they form congruent adjacent angles . The term may be used as a noun or adjective. Thus, referring to Figure 1, the line AB is the perpendicular to CD through the point B...
ly from the shaft to the opening in the scroll-shaped fan casing. A centrifugal fan produces more pressure for a given air volume, and is used where this is desirable such as in
leaf blowerA leaf blower is a gardening tool that propels air out of a nozzle to move yard debris such as leaves. Leaf blowers are usually powered by two-stroke engine or an electric motor, but four-stroke engines were recently introduced to partially address air pollution concerns. Leaf blowers are...
s,
blowdryerA blowdryer or hairdryer is an electromechanical device designed to blow cool or hot air over wet or damp hair, in order to accelerate the evaporation of water particles and dry the hair. Blowdryers allow to better control the shape and style of hair, by accelerating and controlling the formation...
s, air mattress inflators,
inflatable structureInflatable structures are structures made of a flexible outer membrane or fabric that is filled with gas, such as air or helium. The gas gives shape and strength to the structure....
s, and various industrial purposes. They are typically noisier than comparable axial fans.
Cross flow fan
A cross flow fan, is a centrifugal fan in which the air flows through the fan, rather than through an inlet. The rotor of a cross flow fan is covered to create a pressure differential. When used in household fans, cross flow fans have a smaller opening on one side and a larger opening on the other. The resultant pressure difference allows air to flow straight through the fan, even though the fan blades counter the flow of air on one side of the rotation. Cross flow fans give airflow along the entire width of the fan. Cross flow fans are noisier than ordinary centrifugal fans presumedly because the fan blades fight the flow of air on one side of the rotation unlike normal squirrel cage fans. Cross flow fans are often used in air conditioners, automobile ventilation systems, and for cooling in medium-sized equipment such as
photocopierA photocopier is a machine that makes paper copies of documents and other visual images quickly and cheaply. Most current photocopiers use a technology called xerography, a dry process using heat...
s.
The action of a fan or blower causes pressures slightly above atmospheric, which are called
plenumPlenum may refer to:* Plenum chamber, a chamber intended to contain air, gas, or liquid at positive pressure* Plenism, or Horror vacui...
s.
There have been applications of cross flow fan in aircraft propulsion systems, in close coupling with wings. For a wing
leading edgeThe leading edge is the part of the wing that first contacts the air.During a tailslide, from an aerodynamic point-of-view, the trailing edge becomes the leading edge and vice-versa.The leading edge may be equipped with one or more of the following:...
application, see the
FanWingFanWing or fan wing is a concept for a type of aircraft. It is distinct from existing types of aircraft such as airplanes and helicopters in that it uses a fixed wing with a forced airflow produced by cylindrical fans mounted above the wing....
, for a
trailing edgeThe trailing edge of a wing is the rear edge of the wing, where the airflow separated by the leading edge rejoins after passing over and under the top and bottom surfaces of the wing....
application see external links section
http://images.google.co.in/images?hl=en&source=hp&q=cross+flow+fan&btnG=Search+Images&gbv=2&aq=f&oq=
Fan motor
A stand alone fan is typically powered with an
electric motorAn electric motor uses electrical energy to produce mechanical energy, usually through the interaction of magnetic fields and current-carrying conductors. The reverse process, producing electrical energy from mechanical energy, is accomplished by a generator or dynamo. Traction motors used on...
. Fans are often attached directly to the motor's output, with no need for gears or belts. The electric motor is either hidden in the fan's center hub or extends behind it. For big industrial fans, 3-phase asynchronous motors are commonly used, placed near the fan and driving it through a belt and pulleys. Smaller fans are often powered by
shaded pole AC motorsA shaded-pole motor is a type of AC single-phase induction motor. As in other induction motors the rotating part is a squirrel-cage rotor. All single-phase motors require a means of producing a rotating magnetic field for starting. In the shaded-pole type, a part of the face of each field pole...
, or
brushedA brushed DC motor is an internally commutated electric motor designed to be run from a DC power source.-Simple two-pole DC motor:The following graphics illustrate a two-pole DC motor....
or
brushless DC motorsA brushless DC motor is a synchronous electric motor which is powered by direct-current electricity and which has an electronically controlled commutation system, instead of a mechanical commutation system based on brushes...
. AC-powered fans usually use mains voltage, while DC-powered fans use low voltage, typically 24 V, 12 V or 5 V. Cooling fans for computer equipment exclusively use brushless DC motors, which produce much less
electromagnetic interferenceElectromagnetic interference is a disturbance that affects an electrical circuit due to either electromagnetic conduction or electromagnetic radiation emitted from an external source. The disturbance may interrupt, obstruct, or otherwise degrade or limit the effective performance of the circuit...
.
In machines which already have a motor, the fan is often connected to this rather than being powered independently. This is commonly seen in cars, boats, large cooling systems and winnowing machines, where the fan is connected either directly to the drive shaft or through a belt and pulleys. Another common configuration is a dual-shaft motor, where one end of the shaft drives a mechanism, while the other has a fan mounted on it to cool the motor itself.
See also
- Affinity laws
The affinity laws are used in hydraulics and HVAC to express the relationship between several variables involved in pump or fan performance . They apply to pumps, fans, and hydraulic turbines...
- Balancing machine
A balancing machine is a measuring tool used for balancing rotating machine parts such as rotors for electric motors, fans, turbines, disc brakes, disc drives, propellers and pumps. The machine usually consists of two rigid pedestals, with suspension and bearings on top supporting a mounting...
- Fan death
Fan death is a South Korean urban legend which states that an electric fan, if left running overnight in a closed room, can cause the death of those inside...
- Turbine
A turbine is a rotary engine that extracts energy from a fluid or air flow and converts it into useful work.The simplest turbines have one moving part, a rotor assembly, which is a shaft or drum, with blades attached. Moving fluid acts on the blades, or the blades react to the flow, so that they...
- Whole-house fan
- Wind turbine
A wind turbine is a rotating machine which converts the kinetic energy of wind into mechanical energy. If the mechanical energy is used directly by machinery, such as a pump or grinding stones, the machine is usually called a windmill...
- Window fan
A window fan is a fan designed to be placed inside the frame of a window. Window fans have been used for many decades to maintain comfortable temperatures and ventilation within one's home, and operate at a tiny fraction of the cost of central air conditioning.-Design and operation:Window fans are...
- Impeller
An impeller is a rotor inside a tube or conduit to increase the pressure and flow of a fluid.- Impellers in pumps :An impeller is a rotating component of a centrifugal pump, usually made of iron, steel, bronze, brass, aluminum or plastic, which transfers energy from the motor that drives the pump...
External links