Radiators are
heat exchangers used to transfer
thermal energy from one medium to another for the purpose of cooling and heating. The majority of radiators are constructed to function in
automobiles,
buildings, and
electronics. The radiator is always a source of heat to its environment, although this may be for either the purpose of heating this environment, or for cooling the fluid or
coolant supplied to it, as for engine cooling. Despite the name, most radiators transfer the bulk of their heat via
convection instead of
thermal radiation (the main exception to this rule being the radiators on spacecraft, see spacecraft radiators below), though the term "convector" is used more narrowly; see radiation and convection, below.