As computers became more complex, cooling of the components became a significant issue. [[CPU|central processing unit]]s and [[GPU|graphics processing units]]s generate substantial heat and if they are not cooled properly, performance degradation or even failure can occur. The goal is to keep the temperature gradient between a component and its surroundings equal until they reach thermal equilibrium.

Several methods of cooling are used in modern computers, from the use of simple air cooling fans to more exotic coolers like liquid or phase change cooling. The latter uses a special evaporator that cools a liquid by turning it into a gas. This is done at low pressure and the liquid can be reclaimed and reapplied for another cycle.

Conventional cooling methods involve attaching a heat sink to the CPU package and then using fans to speed up the exchange of hot components for cooler ambient air. The heat sinks have thin metal fins that spread out over a large surface area to maximize the exposure of the heat to the air. Often, the fins are coated with a thermal compound to improve the efficiency of the cooling.

Other cooling methods are used for more demanding computer builds, such as [[liquid]] and [[Peltier effect heatpumps|peltier pumps]]. Liquid systems consist of a water block, pump, radiator, and pipes. The pumped liquid flows through the water block where it transfers the heat to the liquid, which then moves to the radiator, where fans remove the warm liquid. The system may also include a reservoir for additional capacity. Cpu cooling