Fan (machine)

A fan consists of rotating vanes or blades, generally made of wood, plastic, or metal, which act on the air.

Typical applications include climate control and personal thermal comfort (e.g., an electric table or floor fan), vehicle engine cooling systems (e.g., in front of a radiator), machinery cooling systems (e.g., inside computers and audio power amplifiers), ventilation, fume extraction, winnowing (e.g., separating chaff from cereal grains), removing dust (e.g. sucking as in a vacuum cleaner), drying (usually in combination with a heat source) and providing draft for a fire.

Instead, they work by evaporative cooling of sweat and increased heat convection into the surrounding air due to the airflow from the fans.

During British rule, the word came to be used by Anglo-Indians to mean a large swinging flat fan, fixed to the ceiling and pulled by a servant called the punkawallah.

The English architect Sir Christopher Wren applied an early ventilation system in the Houses of Parliament that used bellows to circulate air.

In 1849 a 6m radius steam-driven fan, designed by William Brunton, was made operational in the Gelly Gaer Colliery of South Wales.

In 1885 a desktop direct drive electric fan was commercially available by Stout, Meadowcraft & Co. in New York.

During this intense period of innovation, fans powered by alcohol, oil, or kerosene were common around the turn of the 20th century.

Window and central air conditioning in the 1960s caused many companies to discontinue production of fans,[12] but in the mid-1970s, with an increasing awareness of the cost of electricity and the amount of energy used to heat and cool homes, turn-of-the-century styled ceiling fans became popular again as both decorative and energy-efficient.

In 1998 William Fairbank and Walter K. Boyd invented the high-volume low-speed (HVLS) ceiling fan, designed to reduce energy consumption by using long fan blades rotating at low speed to move a relatively large volume of air.

Fans used for comfort inside a room create a wind chill by increasing the heat transfer coefficient but do not lower temperatures directly.

Both the vortex and paddling regions are dissipative, and as a result, only a portion of the impeller imparts usable work on the flow.

The popularity of the crossflow fan in HVAC comes from its compactness, shape, quiet operation, and ability to provide a high-pressure coefficient.

Effectively a rectangular fan in terms of inlet and outlet geometry, the diameter readily scales to fit the available space, and the length is adjustable to meet flow rate requirements for the particular application.

[20] Much of the early work focused on developing the cross-flow fan for both high- and low-flow-rate conditions and resulted in numerous patents.

One interesting phenomenon particular to the cross-flow fan is that, as the blades rotate, the local air incidence angle changes.

Since the flow enters and exits the impeller radially, the crossflow fan has been studied and prototyped for potential aircraft applications.

[21] Due to the two-dimensional nature of the flow, the fan can be integrated into a wing for use in both thrust production and boundary-layer control.

This design creates lift by deflecting the wake downward due to the rotational direction of the fan, causing a large Magnus force, similar to a spinning leading-edge cylinder.

Another configuration utilizing a crossflow fan for thrust and flow control is the propulsive wing, another experimental concept prototype initially developed in the 1990s and 2000s.

[23] A relatively small quantity of air from a high-pressure-bladed impeller fan, which is contained inside the base rather than exposed, induces the slower flow of a larger airmass through a circular or oval-shaped opening via a low-pressure area created by an airfoil surface shape (the Coandă effect).

The airflow is typically generated by a mechanical fan of any type, as described in this article, and is hidden in the base of the display cabinet.

HVAC linear slot diffusers also utilize this effect to increase airflow evenly in rooms compared to registers while reducing the energy used by the air handling unit blower.

[26] Fans generate noise from the rapid flow of air around blades and obstacles causing vortexes, and from the motor.

While fans are commonly used to lower body temperature through evaporative cooling, there is a point at which the convection effect of moving air can counteract this benefit.

This is commonly seen in motor vehicles with internal combustion engines, large cooling systems, locomotives, and winnowing machines, where the fan is connected to the drive shaft or through a belt and pulleys.

Because of the wide availability of 12 V brushless DC electric motors and the convenience of wiring such a low voltage, such fans usually operate on 12 volts.

The detached solar panel is typically installed in the spot that gets most of the sunlight and then connected to the fan mounted as far as 25 feet (8 m) away.

Other permanently mounted and small portable fans include an integrated (non-detachable) solar panel.