Most cars use a radiator to cool the engine. To produce power, engines must burn a fuel. This creates a lot of heat. If the heat is not removed, the engine will overheat and stop running. The radiator is connected to the engine with hoses.
A liquid flows into the engine. Heat is moved from the engine to the liquid. The heat moves because of Newton's Law of Cooling. This law says that heat will move from something hot to something cooler.
The liquid then moved into the radiator. The radiator has many small tubes for the liquid to flow through. Air moves around to the tubes to cool them. This cools the liquid. The liquid then return to the engine. This is a closed loop.
Many houses are located in areas that get cold. Heat needs to be added to the house so the people are comfortable. A radiator is placed in a room to add heat to the room. The heat is created by a furnace. A heating radiator works just like a cooling radiator. The heat from the furnace moves to the radiator. The room is cooler than the radiator. The heat moves from the radiator into the room to warm the room.