Passive cooling is the cooling of machines, electrical and electronic devices and components solely on the basis of "free" convection and thermal radiation . The waste heat is given off or radiated into the surrounding air via cooling fins , radiators or the like.
The heat sinks are usually made of metal that conducts heat well, such as copper or aluminum, and have a large surface on which the heat from the heated cooling medium is released into the air, which expands as a result of the heating and flows away upwards (convection). Heat pipes are sometimes used as part of the heat sink to conduct heat between the part to be cooled and the cooling fins .
Combinations of this technology with elements of active cooling , which accelerate the heat dissipation, are also possible.