Editing Computer cooling (section)

==Optimization==
Cooling can be improved by several techniques which may involve additional expense or effort. These techniques are often used, in particular, by those who run parts of their computer (such as the CPU and GPU) at higher voltages and frequencies than specified by manufacturer ([[overclocking]]), which increases heat generation.

The installation of higher performance, non-stock cooling may also be considered [[modding]]. Many overclockers simply buy more efficient, and often, more expensive fan and heatsink combinations, while others resort to more exotic ways of computer cooling, such as liquid cooling, Peltier effect heatpumps, heat pipe or phase change cooling.

There are also some related practices that have a positive impact in reducing system temperatures:

===Thermally conductive compounds===
{{Main|thermal compound}}
Often called Thermal Interface Material (TIM).<ref>{{cite web|url=http://www.intel.com/support/processors/sb/CS-030329.htm|title=How to Apply Thermal Interface Material (TIM)|website=Intel|access-date=13 February 2016|archive-url=https://web.archive.org/web/20160112204258/http://www.intel.com/support/processors/sb/CS-030329.htm|archive-date=12 January 2016|url-status=live}}</ref>
[[File:Thermal compound of different brands.jpg|thumb|Thermal compound is commonly used to enhance the thermal conductivity from the CPU, GPU, or any heat-producing components to the heatsink cooler. (Counterclockwise from top left: [[Arctic GmbH|Arctic]] MX-2, [[Arctic GmbH|Arctic]] MX-4, Tuniq TX-4, [[Antec]] Formula 7, Noctua NT-H1).]]
Perfectly flat surfaces in contact give optimal cooling, but perfect flatness and absence of microscopic air gaps is not practically possible, particularly in [[Mass production|mass-produced]] equipment. A very thin skim of [[thermal compound]], which is much more thermally conductive than air, though much less so than metal, can improve thermal contact and cooling by filling in the air gaps. If only a small amount of compound just sufficient to fill the gaps is used, the best temperature reduction will be obtained.

There is much debate about the merits of compounds, and overclockers often consider some compounds to be superior to others. The main consideration is to use the minimal amount of thermal compound required to even out surfaces, as the thermal conductivity of compound is typically 1/3 to 1/400 that of metal, though much better than air. The conductivity of the heatsink compound ranges from about 0.5 to 80W/mK<ref>http://www.tomshardware.com/charts/thermal-compound-charts/-1-Thermal-Conductivity,3361.html {{Dead link|date=February 2022}}</ref> (see articles); that of aluminium is about 200, that of air about 0.02. [[Thermal pad (computing)|Heat-conductive pads]] are also used, often fitted by manufacturers to heatsinks. They are less effective than properly applied thermal compound, but simpler to apply and, if fixed to the heatsink, cannot be omitted by users unaware of the importance of good thermal contact, or replaced by a thick and ineffective layer of compound.

Unlike some techniques discussed here, the use of thermal compound or padding is almost universal when dissipating significant amounts of heat.

===Heat sink lapping===
Mass-produced CPU heat spreaders and heatsink bases are never perfectly flat or smooth; if these surfaces are placed in the best contact possible, there will be air gaps which reduce heat conduction. This can easily be mitigated by the use of thermal compound, but for the best possible results surfaces must be as flat as possible. This can be achieved by a laborious process known as [[lapping]], which can reduce CPU temperature by typically {{convert|2|C-change|0|abbr=on}}.<ref>{{Cite web|url=https://archive.techarp.com/showarticleb086.html?artno=433&pgno=0|title=Tech ARP – The CPU & Heatsink Lapping Guide|website=archive.techarp.com|access-date=7 January 2020|archive-url=https://web.archive.org/web/20180122093901/http://archive.techarp.com/showarticleb086.html?artno=433&pgno=0|archive-date=22 January 2018|url-status=live}}</ref>

===Rounded cables===
Most older PCs use flat [[ribbon cable]]s to connect storage drives ([[AT Attachment|IDE]] or [[SCSI]]). These large flat cables greatly impede airflow by causing drag and turbulence. Overclockers and modders often replace these with rounded cables, with the conductive wires bunched together tightly to reduce surface area. Theoretically, the parallel strands of conductors in a ribbon cable serve to reduce [[crosstalk]] (signal carrying conductors inducing signals in nearby conductors), but there is no empirical evidence of rounding cables reducing performance. This may be because the length of the cable is short enough so that the effect of crosstalk is negligible. Problems usually arise when the cable is not [[Electromagnetic shielding|electromagnetically protected]] and the length is considerable, a more frequent occurrence with older network cables.

These computer cables can then be cable tied to the chassis or other cables to further increase airflow.

This is less of a problem with new computers that use [[serial ATA]] which has a much narrower cable.

===Airflow===

The colder the cooling medium (the air), the more effective the [[Heat Transfer|cooling]]. Cooling air temperature can be improved with these guidelines:
* Supply cool air to the hot components as directly as possible. Examples are air snorkels and tunnels that feed outside air directly and exclusively to the CPU or GPU cooler. For example, the [[BTX (form factor)|BTX]] case design prescribes a CPU air tunnel.
* Expel warm air as directly as possible. Examples are: Conventional PC ([[ATX]]) power supplies blow the warm air out the back of the case. Many dual-slot [[Video card|graphics card]] designs blow the warm air through the cover of the adjacent slot. There are also some [[Aftermarket (merchandise)|aftermarket]] coolers that do this. Some CPU cooling designs blow the warm air directly towards the back of the case, where it can be ejected by a case fan.
* Air that has already been used to spot-cool a component should not be reused to spot-cool a different component (this follows from the previous items). The BTX case design violates this rule, since it uses the CPU cooler's exhaust to cool the chipset and often the graphics card. One may come across old or ultra-low-budget ATX cases which feature a PSU mount in the top. Most modern ATX cases do however have a PSU mount in the bottom of the case with a filtered air vent directly beneath the PSU.
* Prefer cool intake air, avoid inhaling exhaust air (outside air above or near the exhausts). For example, a CPU cooling air duct at the back of a tower case would inhale warm air from a graphics card exhaust. Moving all exhausts to one side of the case, conventionally the back/top, helps to keep the intake air cool.
* Hiding cables behind motherboard tray or simply apply ziptie and tucking cables away to provide unhindered airflow.

Fewer fans strategically placed will improve the airflow internally within the PC and thus lower the overall internal case temperature in relation to ambient conditions. The use of larger fans also improves efficiency and lowers the amount of waste heat along with the amount of noise generated by the fans while in operation.

There is little agreement on the effectiveness of different fan placement configurations, and little in the way of systematic testing has been done. For a rectangular PC (ATX) case, a fan in the front with a fan in the rear and one in the top has been found to be a suitable configuration. However, AMD's (somewhat outdated) system cooling guidelines notes that "A front cooling fan does not seem to be essential. In fact, in some extreme situations, testing showed these fans to be recirculating hot air rather than introducing cool air."<ref>[http://support.amd.com/us/Processor_TechDocs/23794.pdf AMD Thermal, Mechanical, and Chassis Cooling Design Guide] {{Webarchive|url=https://web.archive.org/web/20110515181129/http://support.amd.com/us/Processor_TechDocs/23794.pdf |date=15 May 2011 }} – Although somewhat out of date, it appears to be backed up by some amount of systematic testing which is lacking in many other guides.</ref> It may be that fans in the side panels could have a similar detrimental effect – possibly through disrupting the normal air flow through the case. However, this is unconfirmed and probably varies with the configuration.

==== Air pressure ====
[[File:Computer cooling.svg|thumb|300px|1) Negative pressure &nbsp; &nbsp; 2) Positive pressure]]
Loosely speaking, positive pressure means intake into the case is stronger than exhaust from the case. This configuration results in pressure inside of the case being higher than in its environment. Negative pressure means exhaust is stronger than intake. This results in internal air pressure being lower than in the environment. Both configurations have benefits and drawbacks, with positive pressure being the more popular of the two configurations. Negative pressure results in the case pulling air through holes and vents separate from the fans, as the internal gases will attempt to reach an equilibrium pressure with the environment. Consequently, this results in dust entering the computer in all locations. Positive pressure in combination with filtered intake solves this issue, as air will only incline to be exhausted through these holes and vents in order to reach an equilibrium with its environment. Dust is then unable to enter the case except through the intake fans, which need to possess dust filters.