Oil heater
An oil heater, also known as an oil-filled heater, oil-filled radiator, or column heater, is a common form of convection heater used in domestic heating. Although filled with oil, it is electrically heated and does not involve burning any oil fuel; the oil is used as a heat reservoir (buffer), not as a fuel.
Oil heaters consist of metal columns with cavities, inside which silicone oil (mostly siloxanes like polydimethylsiloxane) flows freely around the heater. A heating element at the base of the heater heats up the oil, which then flows around the cavities of the heater by convection. The oil acts as a heat reservoir, with a relatively high specific heat capacity (approximately 2 kJ.kg−1.K−1) and high boiling point (approximately 150–300 degrees Celsius). The high specific heat capacity allows the oil to store a large amount of thermal energy in a small volume, while the high boiling point allows it to remain in the liquid phase for the purpose of heating, so that the heater does not have to be a high pressure vessel.
Using the oil as a heat reservoir, the heating element heats the oil, which remains warm for a long period of time while the heat is transferred to the metal wall through convection, through the walls via conduction, then to the surroundings via convection and radiation. The columns of oil heaters are typically constructed as thin fins, such that the surface area of the metal columns is large relative to the volume of the oil heat reservoir. A large surface area allows more air to be in contact with the heater at any point in time, allowing for the heat to be transferred more rapidly from the heater into the room.
Although oil heaters are more expensive to run and provide far less spatial heating than gas heaters, they are still commonly used in bedrooms and other small-to-medium-sized enclosed areas. This is because gas heaters, especially when unflued, are not suitable for bedroom use - gas heaters cannot be used in confined spaces due to the reduced oxygen, and the emissions produced. This leaves electrically powered heaters, such as oil heaters and fan heaters, as the only alternative.
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