How Does a Radiator Heat a Room?
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Steam Radiators
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Traditional radiators are powered by steam or hot water. A boiler in the basement of a building heats pressurized water to an extremely high temperature, turning it into steam. As the water turns into a gas, it expands and becomes less dense, which causes it to flow up through steam tubes into radiators in the building. As the water flows through tubes inside the metal radiators, some of its heat is transferred into the metal. This gives the radiator the heat it needs to warm the room and cools the water, which then flows back to the boiler to be heated again.
Electric Radiators
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Electric radiators are powered by a heating element. Heating elements are actually specialized resistors--devices that resist the flow of electricity. When electric energy flows into a resistor, it is turned into heat. The heating element in a radiator is usually suspended in oil, which conducts the heat away from the element. The heat then flows out into the metal body of the radiator and from there, into the room.
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Convection Currents
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Heat gets into the room in two ways: convection and infrared radiation. The fins of a radiator heat the air molecules around it, causing them to expand. As the hot air expands, it rises, creating a vacuum behind it. This vacuum pulls in cold air from near the ground, which also gets heated and rises. After a little while, the radiator creates a continuous stream of air called a convection current. This stream heats up, rises, spreads and out into the room and cools, dispersing the heat throughout.
Infrared Radiation
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Pretty much everything emits infrared radiation, including you. The warmer an object is, the more infrared it emits. When infrared radiation comes into contact with a solid object, it gets absorbed and turned into heat. That is why it feels hot to stand next to a fire. The heat from the fire is actually flowing up with the air currents, but some of the infrared radiation strikes your body, turning into heat. Although infrared radiation is not the primary way a radiator works, it does help heat the room.
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