Heat-dissipation unit
Heat-dissipation units were among the systems of the  starships of the 23rd century. They permitted the ship to dispose of excess , presumably by transferring it to deep space. They were active systems that required power to operate.

In 2267,  constructed a model of the  and dangled it in a candle's flame. Using a science she likened to sympathetic magic, she was able to cause the actual Enterprise to heat by mistreating the model in this fashion. Even with the channeling of bypass power into the heat dissipation units, the Enterprise was not able to shed the heat. ()

See also 
 Thermal deflector unit

Spacecraft components