A computer fan is any fan inside, or attached to, a computer caseused for active cooling, 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 heat sink to cool a particular component.
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[hide]Usage of a cooling fan[edit]
As processors, graphics cards, RAM and other components in computers have increased in speed and power consumption, the amount of heat produced by these components as a side-effect of normal operation has also increased. These components need to be kept within a specified temperature range to prevent overheating, instability, malfunction and damage leading to a shortened component lifespan.
While in earlier personal computers it was possible to cool most components using natural convection (passive cooling), many modern components require more effective active cooling. To cool these components, fans are used to move heated air away from the components and draw cooler air over them. Fans attached to components are usually used in combination with a heatsink to increase the area of heated surface in contact with the air, thereby improving the efficiency of cooling.
In the IBM compatible PC market, the computer's power supply unit (PSU) almost always uses an exhaust fan to expel warm air from the PSU. Active cooling on CPUs started to appear on the Intel 80486, and by 1997 was standard on all desktop processors.[1] Chassis or case fans, usually one exhaust fan to expel heated air from the rear and optionally an intake fan to draw cooler air in through the front, became common with the arrival of the Pentium 4 in late 2000.[1] A third vent fan in the side of the PC, often located over the CPU, is also common. The graphics processing unit (GPU) on many modern graphics cards also requires a heatsink and fan. In some cases, the northbridge chip on the motherboard has another fan and heatsink. Other components such as the hard drives and RAM may also be actively cooled, though as of 2012 this remains relatively unusual. It is not uncommon to find five or more fans in a modern PC.
Cooling fan application[edit]
Case mount[edit]
Used to aerate the case of the computer. The components inside the case cannot dissipate heat efficiently if the surrounding air is too hot. Case fans move air through the case, usually drawing cooler outside air in through the front or bottom (where it may also be drawn over the internal hard drive racks) and expelling it through the top or rear. Some ATX tower cases have one or more vents and mounting points in the left side panel where one or more fans may be installed to blow cool air directly onto the motherboard components and expansions cards, which are ones of the largest heat sources.
Standard case fans are 80 mm, 92 mm, 120 mm, 140 mm, 200 mm and 230 mm in width and length. As case fans are often the most readily visible form of cooling on a PC, decorative fans are widely available and may be lit with LEDs, made of UV-reactive plastic, and covered with decorative grilles. Decorative fans and accessories are popular with case modders. Air filters are often used over intake fans, to prevent dust from entering the case and clogging up the internal components. Heatsinks are especially vulnerable to being clogged up, as the insulating effect of the dust will rapidly degrade the heatsink's ability to dissipate heat.
While the power supply (PSU) contains a fan with few if any exceptions, it is not to be used for case ventilation. The hotter the PSU's intake air is, the hotter the PSU gets. As the PSU temperature rises, the conductivity of its internal components decrease. Decreased conductivity means that the PSU will convert more of the input electric energy into thermal energy (heat). This cycle of increasing temperature and decreased efficiency continues until the PSU either overheats, or its cooling fan is spinning fast enough to keep the PSU adequately supplied with comparatively cool air. The PSU is mainly bottom-mounted in modern PCs, having its own dedicated intake and exhaust vents, preferably with a dust filter in its intake vent.
CPU fan[edit]
Used to cool the CPU (central processing unit) heatsink. Effective cooling of a concentrated heat source such as a large-scale integrated circuit requires a heatsink, which may be cooled by a fan; use of a fan alone will not prevent overheating of the small chip.
- See computer spot cooling.
Graphics card fan[edit]
Used to cool the heatsink of the graphics processing unit or the memory on graphics cards. These fans were not necessary on older cards because of their low power dissipation, but most modern graphics cards designed for 3D graphics and gaming need their own dedicated cooling fans. Some of the higher powered cards can produce more heat than the CPU (dissipating up to 289 watts[2]), so effective cooling is especially important. Since 2010, graphics cards have been released with eitheraxial fans or a centrifugal fan commonly known as a blower or squirrel cage fan.
Chipset fan[edit]
Used to cool the heatsink of the northbridge of a motherboard's chipset; this may be needed where the system bus is significantly overclocked and dissipates more power than as usual, but may otherwise be unnecessary. As more features of the chipset are integrated into the central processing unit, the role of the chipset has been reduced and the heat generation reduced also.
Other purposes[edit]
Fans are, less commonly, used for other purposes such as:
- Expansion slot fan – a fan mounted in one of the PCI or PCI Express slots, usually to supply additional cooling to the graphics cards, or to expansion cards in general.
- Hard disk fan – a fan mounted next to or onto a hard disk drive, for example when a hard disk drive is mounted in a 5.25-inch drive bay. This may be desirable on faster-spinning hard disks with greater heat production. As of 2011 less expensive drives rotated at speeds up to 7,200 RPM; 10,000 and 15,000 RPM drives were available but generated more heat.
- Optical drive fan – some internal CD and/or DVD burners included cooling fans.
- Memory fan – modern computer memory can generate enough heat that active cooling may be necessary, usually in the form of small fans positioned above the memory chips. This applies especially when the memory is overclocked orovervolted,[3] or when the memory modules include active logic, such as when a system uses Fully Buffered DIMMs (FB-
