| A computer fan can be any fan inside a computer | | | | removing warm air from inside the case. Many modern |
| case used for cooling purposes, and may refer to fans | | | | PSUs expel the air from the rear, but only from the |
| that draw cooler air into the case from the outside, | | | | PSU itself. PSUs with two fans are also available, |
| expel warm air from inside, or move air across a | | | | which have a large fan on the bottom for removing |
| heatsink to cool a particular component. The use of | | | | case air and a smaller one on the back for expelling |
| fans and/or other hardware to cool a computer is | | | | the warm air at a faster rate. |
| sometimes referred to as active cooling. | | | | Graphics card fan Used to cool the GPU and/or |
| Usage As processors, graphics cards, RAM and other | | | | memory on graphics cards. These fans were not |
| components in computers have increased in clock | | | | necessary on older cards because of their low heat |
| speed and power consumption, the amount of heat | | | | dissipation, but most modern graphics cards, especially |
| produced by these components as a side-effect of | | | | those designed for 3D graphics and gaming, need their |
| normal operation has also increased. The | | | | own dedicated cooling fans. Some of the higher |
| temperatures of these components need to be kept | | | | powered cards can produce as much or more heat |
| within a reasonable range to prevent overheating, | | | | than even the CPU (over 140 watts[2]), so efficient |
| malfunction and possible damage. | | | | cooling is especially important. |
| While in earlier personal computers it was possible to | | | | Chipset fan Used to cool the northbridge of a |
| cool most components using convection (passive | | | | motherboard's chipset or for system bus overclocking. |
| cooling), more efficient cooling has become a | | | | Other fans Other less commonly encountered fans |
| necessity on many components. To cool these | | | | may include: PCI slot fan: A fan mounted in one of the |
| components, fans are used to move heated air away | | | | PCI slots, usually to supply additional cooling to the PCI |
| from the components and draw cooler air over them. | | | | and/or graphics cards. |
| Fans attached to components are usually used in | | | | Hard disk fan: A fan mounted next to or on a hard |
| combination with a heatsink to increase the surface | | | | disk drive. This may be desirable on faster-spinning (e.g. |
| area available for heat conduction, thereby improving | | | | 10,400 RPM) hard disks where heat production is |
| the efficiency of cooling. | | | | higher. |
| In the IBM compatible PC market, the computer's PSU | | | | Physical characteristics The width and height of these |
| (power supply unit) has always used an exhaust fan | | | | usually square fans are measured in millimeters, with |
| to expel warm air from the PSU. Active cooling on | | | | common sizes including 60 mm, 80 mm, 92 mm and |
| CPUs started to appear on the retail Intel Pentium, and | | | | 120 mm. The amount of airflow which these fans |
| by 1997 was standard on all desktop processors[1]. | | | | generate is measured in cubic-feet per minute (CFM), |
| Chassis or case fans, usually one exhaust fan to expel | | | | and the speed of rotation is measured in revolutions |
| heated air from the rear and optionally an intake fan to | | | | per minute (RPM). Often, computer enthusiasts choose |
| draw cooler air in through the front, became common | | | | fans which have a higher CFM rating, but produce less |
| with the arrival of the Pentium 4 in late 2000[1]. A third | | | | noise (measured in decibels, or dB), and some fans |
| vent fan in the side of the PC, often located over the | | | | come with an adjustable RPM rating to produce less |
| CPU, is also common. The GPU (graphics processing | | | | noise if the computer does not need much airflow. Fan |
| unit) on many modern graphics cards requires a | | | | speeds may be controlled manually (a simple |
| heatsink and fan. In some cases, the northbridge chip | | | | potentiometer control, for example), by the computer |
| on the motherboard requires a fan and heatsink. | | | | hardware or by software. |
| Other components such as the RAM and hard drives | | | | The type of bearing used in a fan can affect its |
| may also be actively cooled, though as of 2006 this | | | | performance and noise output. |
| remains relatively unusual. It is not uncommon to find | | | | Most computer fans use one of the following bearing |
| five or more fans in a modern PC. | | | | types: Sleeve bearing fans use two surfaces |
| Case fan Used to aerate the case of the computer. | | | | lubricated with oil or grease as a friction contact. |
| The components inside the case which use active | | | | Sleeve bearings are less durable as the contact |
| cooling cannot remove heat efficiently if the | | | | surfaces can become rough and/or the lubricant dry |
| surrounding air is too hot. Case fans move air through | | | | up, eventually leading to failure. Sleeve bearings can fail |
| the case, usually drawing cooler outside air in through | | | | at higher temperatures, and may perform poorly when |
| the front (where it may also be drawn over the | | | | mounted in any orientation other than horizontally. |
| internal hard drive racks) and expelling it through the | | | | The lifespan of a sleeve bearing fan may be around |
| rear. | | | | 40,000 hours at 50°C. Fans that use sleeve |
| There may be a third fan in the side or top of the | | | | bearings are generally cheaper than fans that use ball |
| case to draw outside air into the vicinity of the CPU, | | | | bearings.[3] Ball bearing' fans use a sealed bearing |
| which is usually the largest single generator of heat. | | | | containing steel balls against which the axle rotates. |
| Case fans are usually 80mm or 120mm along each | | | | Though more generally more expensive, ball bearing |
| side. Because case fans are often the most readily | | | | fans do not suffer the same orientation limitations as |
| visible form of cooling on a PC, decorative fans are | | | | sleeve bearing fans, can endure higher temperatures, |
| widely available and may be lit with LEDs or made of | | | | produce less noise and are more durable. The lifespan |
| UV-reactive plastic. Decorative grilles are also | | | | of a ball bearing fan may be around 63,000 hours at |
| common. Decorative fans and accessories are | | | | 50°C.[3] Fluid bearing fans have the advantages |
| popular with case modders. | | | | of silent operation and high life expectency |
| PSU fan PSU fans often play a double role, not only | | | | (comparable to ball bearing fans). |
| keeping the PSU itself from overheating, but also | | | | |