Here is my single-stage unit from Slovenian builder, LittleDevil. In simple terms, a phase-change unit operates similar to a water cooling system as it uses a fluid to move heat output from one place to another, where it is then radiated or convected out into the atmosphere.
This particular unit was originally supplied with black standard casing, which I’ve since then modified with this carbon style enclosure. It is optimized for around 250 Watt heat dissapation and enables me to run my Intel Core 2 Duo E8600 stable at 5.5 GHz for everyday usage. Using my Intel Core 2 Extreme QX9650 or QX9770 on it will do for around 4.8 GHz continuous operation.
Generally a phase-change system is a bit more complicated than water cooling, and also more effective, because it manipulates the pressure of the fluid and changes it from a liquid to a gas and back. This is called changing the phase of the fluid, hence the name. Its basically the same system used in refrigerators and air conditioners.