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