| Air cooling While any method used to move air | | | | baseplates or are entirely made of copper, |
| around or to computer enclosures would count | | | | and mount fans of considerable size and |
| as air cooling, fans are by far the most | | | | power. |
| commonly used implement for accomplishing | | | | |
| that task. The term 'computer fan' usually | | | | Heat sinks tend to get less effective with |
| refers to fans attached to computer | | | | time due to the build up of dust between |
| enclosures, but may also be intended to | | | | their metal fins, which reduces the |
| signify any other computer fan, such as a CPU | | | | efficiency with which the heat sink transfers |
| fan, GPU fan, a chipset fan, PSU fan, HDD | | | | heat to the ambient air. Dust build up is |
| fan, or PCI slot fans. Common fan sizes | | | | commonly countered with canned air, which are |
| include 60, 80, 92 and 120 mm. | | | | used to blow away the dust along with any |
| | | | other unwanted excess material. |
| Air cooling in desktops Desktop computers | | | | |
| typically use one or more fans for heat | | | | Passive heat sinks are commonly found on |
| management. Almost all desktop power supplies | | | | older CPUs, parts that do not get very hot |
| have at least one fan to exhaust air from the | | | | (such as the chipset), and low-power |
| case. Most manufacturers recommend bringing | | | | computers. |
| cool, fresh air in at the bottom front of the | | | | |
| case, and exhausting warm air from the top | | | | Active heat sink cooling This uses the same |
| rear. | | | | principle as a passive heat sink cooler, with |
| | | | the only difference being that a fan is |
| If there is more air being forced into the | | | | directed to blow over or through the heat |
| system than being pumped out (due to an | | | | sink. |
| imbalance in the number of fans), this is | | | | |
| referred to as a "positive" airflow, as the | | | | This results in more air being blown through |
| pressure inside the unit would be higher than | | | | the heat sink, increasing the rate at which |
| outside. A balanced or neutral airflow is the | | | | the heat sink can exchange heat with the |
| most efficient, although a slightly positive | | | | ambient air. Active heat sinks are the |
| airflow results in less dust build up if dust | | | | primary method of cooling a modern day |
| filters are used.[citation needed] Air | | | | processor or graphics card. |
| cooling in high density computing Data | | | | |
| centers typically contain many racks of flat | | | | Peltier cooling or TEC In 1821, J. T. Seebeck |
| 1U servers. Air is drawn in at the front of | | | | discovered that Different metals that are |
| the rack and exhausted at the rear. Because | | | | connected at two different Junctions will |
| datacenters typically contain such large | | | | develop a micro-voltage if the two junctions |
| amounts of computers and other | | | | are held at different temperatures. This |
| power-consuming devices, they risk | | | | effect is known as the "Seebeck effect"; it |
| overheating of the various components if no | | | | is the basic theory behind the TEC In 1834, a |
| additional measures are taken. Thus, | | | | scientist by the name of Leonard Peltier |
| extensive HVAC systems are used. Often a | | | | discovered the inverse of the Seebeck effect, |
| raised floor is used so the area under the | | | | now known as the "Peltier effect". He found |
| floor may be used as a large plenum for | | | | that if you take a thermocouple and apply a |
| cooled air and power cabling. | | | | voltage, this causes a temperature difference |
| | | | between the junctions. This results in an |
| Liquid submersion cooling An uncommon | | | | effective, albeit extremely unefficient Heat |
| practice is to submerse the computer's | | | | pump Modern TECs use several stacked |
| components in a thermally conductive liquid. | | | | thermocouples, which allows for a substantial |
| Personal computers that are cooled in this | | | | amount of heat transfer. A combination of |
| manner do not generally require any fans or | | | | Bismuth and Telluride is most commonly used |
| pumps, and may be cooled exclusively by | | | | for thermocouples. |
| passive heat exchange between the computer's | | | | |
| parts, the cooling fluid and the ambient air. | | | | Since TEC's are active heat pumps, they are |
| | | | capable of cooling PC components below |
| Extreme density computers such as the Cray-2 | | | | ambient temperatures, which is impossible |
| may use additional radiators in order to | | | | with common radiator cooled Watercooling |
| facilitate heat exchange. | | | | systems and heatpipe HSF's Watercooling While |
| | | | originally limited to mainframe computers, |
| The liquid used must have sufficiently low | | | | computer watercooling has become a practice |
| electrical conductivity in order for it not | | | | largely associated with overclocking in the |
| to interfere with the normal operation of the | | | | form of either manufactured "kits" or in the |
| computer's components. | | | | form of DIY setups assembled from |
| | | | individually gathered parts. Lately |
| If the liquid is somewhat electrically | | | | watercooling has seen increasing use in |
| conductive, it may be necessary to insulate | | | | pre-assembled desktop computers, most notably |
| certain parts of components susceptible to | | | | Apple's Power Mac G5. |
| electromagnetic interference, such as the | | | | |
| CPU.[1][2] For these reasons, it is preferred | | | | Heat pipe A heat pipe is a hollow tube |
| that the liquid be dielectric. | | | | containing a heat transfer liquid. As the |
| | | | liquid evaporates, it carries heat to the |
| Liquids commonly used in this manner include | | | | cool end, where it condenses to the hot end |
| various liquids invented and manufactured for | | | | (under capillary force). Heat pipes thus have |
| this purpose by 3M, such as Fluorinert. | | | | a much higher effective thermal conductivity |
| Various oils, including but not limited to | | | | than solid materials. In computers, the heat |
| cooking, motor and silicone oils have all | | | | sink on the CPU is attached to a larger |
| been successfully used for cooling personal | | | | radiator heat sink. |
| computers. | | | | |
| | | | Both heat sinks are hollow as is the |
| Evaporation can pose a problem, and the | | | | attachment between them, creating one large |
| liquid may require either to be regularly | | | | heat pipe that transfers heat from the CPU to |
| refilled or sealed inside the computer's | | | | the radiator, which is then cooled using some |
| enclosure. | | | | conventional method. |
| | | | |
| Waste heat reduction Where full-power, | | | | This method is expensive and usually used |
| full-featured modern computers are not | | | | when space is tight (as in small form-factor |
| required, some companies opt to use less | | | | PC's), or absolute quiet is needed (such as |
| powerful computers or computers with fewer | | | | in computers used in audio production studios |
| features. E.g. in an office setting, the IT | | | | during live recording). |
| department may opt for a thin client or a | | | | |
| diskless workstation thus cutting out the | | | | Phase-change cooling The simplest approach, |
| heat of components such as hard drives and | | | | and somewhat similar to a heat pipe, is to |
| optical disks. These devices are also often | | | | boil a fluid in a vessel (evaporator) |
| powered with direct current from an external | | | | attached to the hot CPU die. This vapor is |
| power supply brick (which still wastes heat, | | | | condensed in the tubes of an air cooled |
| but not inside the computer). | | | | heat-exchanger. The condensed vapor drains by |
| | | | gravity back to the boiling vessel. This is |
| The components used can greatly affect the | | | | known as a "thermo-syphon". A key limitation |
| power consumption and hence waste heat. A VIA | | | | is that the condenser must be positioned |
| EPIA motherboard with CPU typically radiates | | | | above the boiling vessel. This system is |
| approximately 25 watts of heat whereas a | | | | totally passive and requires no pumps or |
| Pentium 4 motherboard typically radiates | | | | compressors. |
| around 140 watts. | | | | |
| | | | A more extreme way to cool the processor. A |
| While the former has considerably less | | | | phase-change cooler is a unit which usually |
| computing power, both types are adequate and | | | | sits underneath the PC, with a tube leading |
| responsive for tasks such as word processing | | | | to the processor. |
| and spreadsheets. Opting for a LCD monitor | | | | |
| rather than a CRT can also reduce power | | | | Inside the unit is a compressor, the same |
| consumption and excess room heat. | | | | type that cools a freezer. The compressor |
| | | | compresses a gas which is cooled (usually |
| Conductive and radiative cooling Some laptop | | | | with fans and air) condensing it to a liquid. |
| components, such as hard drives and optical | | | | Then, the liquid is pumped up to the |
| drives, are commonly cooled by having them | | | | processor, which heats it, causing the liquid |
| make contact with the computer's frame, | | | | to evaporate, and absorb the heat from the |
| increasing the surface area which can radiate | | | | processor. This evaporation can produce |
| and otherwise exchange heat. | | | | temperatures reaching around -30 degrees |
| | | | Celsius. The gas flows down to the compressor |
| Spot cooling In addition to system cooling, | | | | and the cycle begins over again. This way, |
| various individual components usually have | | | | the processor can be cooled to temperatures |
| their own cooling systems in place. | | | | ranging from -15 to -30 degrees Celsius, |
| Components which are individually cooled | | | | depending on the load, type and speed of the |
| include, but are not limited to, the CPU, | | | | processor. |
| GPU, hard disk and the Northbridge chip. | | | | |
| | | | Liquid nitrogen By welding an open pipe onto |
| Passive heat sink cooling This involves | | | | a heat sink, and insulating the pipe, it is |
| attaching a block of machined metal to the | | | | possible to cool the processor either with |
| part that needs cooling. An adhesive may be | | | | liquid nitrogen, which has a temperature |
| used, or more commonly for a home-user PC | | | | below -196° C, or dry ice. |
| laptop/Mac CPU, a clamp is used to affix the | | | | |
| heat sink tight over the chip, with a | | | | However, after the nitrogen evaporates, it |
| thermally conductive pad or gel spread | | | | has to be refilled. In the realm of personal |
| in-between. This block usually has fins and | | | | computers, this method of cooling is only |
| ridges to increase its surface area. | | | | used for extreme overclocking trial runs and |
| | | | record-setting attempts (since the CPU will |
| The heat conductivity of metal is much better | | | | usually expire within a relatively short |
| than that of air, and its ability to radiate | | | | period of time). |
| heat is better than that of the component | | | | |
| part it is protecting (usually an integrated | | | | Softcooling Softcooling uses software to take |
| circuit/CPU). | | | | advantage of CPU power saving technology to |
| | | | minimize energy use. This is done using halt |
| Until recently, fan cooled aluminium heat | | | | instructions to turn off or put in standby |
| sinks were the norm for desktop computers. | | | | state CPU subparts that aren't being used or |
| Today many heat sinks feature copper | | | | by underclocking the CPU. |