The colder the cooling medium (the air), the more effective the cooling. Cooling air temperature can be reduced by 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 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 graphics card designs blow the warm air through the cover of the adjacent slot. There are also some 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 ATX case design can be said to violate this rule, since the power supply gets its "cool" air from the inside of the case, where it has been warmed up already. The BTX case design also violates this rule, since it uses the CPU cooler's exhaust to cool the chipset and often the graphics card.
* 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, helps to keep the intake air cool.
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 However, AMD's (somewhat outdated) system cooling guidelines notes that "A front cooling fan does not seem to be essential.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."[3] 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.
by http://en.wikipedia.org/wiki/Active_cooling
The amount of heat generated by an integrated circuit (e.g., a CPU or GPU), the prime cause of heat build up in modern computers, is a function of the efficiency of its design, the technology used in its construction and the frequency and voltage at which it operates.
The dust on the laptop CPU heat sink after three years of use has made the laptop unusable due to frequent thermal shutdowns.
The dust on the laptop CPU heat sink after three years of use has made the laptop unusable due to frequent thermal shutdowns.
In operation, the temperature levels of a computer's components will rise until the temperature gradient between the computer parts and their surroundings is such that the rate at which heat is lost to the surroundings is equal to the rate at which heat is being produced by the electronic component, and thus the temperature of the component reaches equilibrium.
For reliable operation, the equilibrium temperature must be sufficiently low for the structure of the computer's circuits to survive.
Additionally, the normal operation of cooling methods can be hindered by other causes, such as:
* Dust acting as a thermal insulator and impeding airflow, thereby reducing heat sink and fan performance.
* Poor airflow (including turbulence) due to friction that reduces the amount of air flowing through a case, possibly causing stable whirlpools of hot air in certain areas.[citation needed]
* Poor heat transfer due to a lack or poor application of thermal compounds.