In devices generating heat, such as gasoline-engine motor vehicles, the cooling of the device by increasing its radiating surface by means of ribs or radiators, and placing it so that it is exposed to a current of air. Cf. Water cooling.
Alternative method of engine cooling in which no water is used. An engine-driven fan forces air at high speed over the surfaces of the engine.
Cooling that involves using a heatsink and/or fan. Heat generated by the CPU (or whatever is being cooled) is transfered to the heatsink. The heatsink is cooled by the surrounding air, in most modern computers, a fan is used to increase the efficiency of this process. In all cases, the surrounding air has to be cooler than the object or surface from which the heat is being removed.