The principle used in a typical liquid cooling system for computers is identical to that used in an automobile's internal combustion engine, with the water being circulated by a water pump through a waterblock mounted on the CPU (and sometimes additional components as GPU and northbridge)and out to a heat exchanger, typically a radiator. The radiator is itself sometimes cooled additionally by means of a fan. Besides a fan, it could possibly also be cooled by other means, such as by means of a Peltier cooler (although Peltier elements are most commonly placed directly on top of the hardware to be cooled, and the coolant is used to conduct the heat away from the hot side of the Peltier element).Also, a coolant reservoir is often also connected to the system.