Heat exchangers transfer heat energy from one fluid or gas to another without mixing the two. Heat from hot engine water is pumped through a radiator while air is blown through the radiator tins. The heat energy from the hot engine water is transferred into the air, keeping the water at the right temperature and preventing the engine from overheating. Automotive radiators are one example of heat exchangers that are liquid-to-air heat exchangers. Other types of heat exchangers include boilers, furnaces, refrigerators, and air conditioning systems.