A cooling arrangement for a CPU is known from U.S. Pat. No. 6,549,408 B2, BERCHOWITZ. Disposed on this arrangement is an evaporator, and coolant in this evaporator is evaporated by the heat of the CPU and thereby flows upward in a riser conduit to a condenser that is arranged at a higher geodetic level. The vapor is cooled and liquefied there, and flows in response to gravity through a downpipe back to the evaporator, where it is evaporated again.
The advantage of such an arrangement is that it operates quietly; a disadvantage, however, is that, according to the second law of thermodynamics, it is impossible in this case to achieve a coolant temperature lower than the ambient temperature, since heat flows only from a higher-temperature medium to a lower-temperature medium. What is obtained instead is a coolant temperature that, because of the temperature gradient necessary for heat transfer, is at least 7 to 10° K (=Kelvin) above ambient temperature; this limits heat dissipation from the CPU, especially on hot days. The overall efficiency of such a system is moreover not good.