Radiator is a set of pipes or tubes that gives off heat to its surroundings. Steam or hot-water radiators in homes transfer heat to the air in a room. When warmed, the air next to the pipes expands, becomes lighter, and rises. Cooler air from the room streams in to take its place, creating a constant circulation of air. This process is called convection, and certain types of radiators are called convectors. Radiators also heat room air by direct radiation. See Heat (How heat travels) .
An automobile radiator works in the same way. Water carries heat from the engine to tubes at the front of the radiator. Air rushing past the tubes absorbs heat from the water and cools it. An engine-driven or electric fan helps move air through the radiator when the car is stopped or moving at low speed.
