There are three ways to heat an object: conductive heating,
convection heating, and radiant heating. Conductive heating occurs when objects of different temperatures come into direct, physical contact. Energy is transferred from the warmer object into the colder object until the temperature of both objects is exactly the same. It's what happens when you drop an egg into a frying pan or accidentally bump your hand against a hot stove.
Convection heating occurs when a warm object is placed in a fluid medium, like water or air. The thin layer of molecules in direct, physical contact with the object heat up through the process of conduction and causes them to expand. As they do, they move up and away from the object, displacing the cooler, denser molecules above them. They're forced to drop down and come into contact with the heat source which warms them up, forcing them to expand and displace more air, which gets heated in turn. This is what is known as a convection current. It's what happens when you heat a pot of water on the stove or turn on a convection heater in a cold room. Because air is a poor heat conductor, convection heaters work slowly, gradually warming the air until it's reached a uniform temperature.
A convector heater is one which relies on the natural expansion and travel of hot air around it to transfer heat throughout the area to be heated. Convector heaters come in many different shapes and sizes, and are based on many different heat sources. Convector heaters, so named for their dependence on convection currents, are one of the earliest forms of heating in homes.
Convector heaters offer a mechanically simple way to heat a home or similar building. Their enclosed design enforces safe operation, and allows for a variety of heating material to be used within it, as no contact with the heating substrate should occur. Furthermore, a convector heater has no fans to force an air current, and as such, they operate much more quietly than forced air heaters.
The two main types of heating elements that can be used in a convection heater are panels or coils. Panel heaters are often mounted on the wall, but coil models can rest on the floor and heat the space from the middle. Coils are often filled with a heat-conducting fluid such as oil, allowing them to remain warm for extended periods of time. The heating elements can be warmed with power from a variety of sources; electricity is the most popular, but natural gas and propane heaters are also available.
Convection heaters can be money-saving devices, but caution should be used with children and pets since some models can be very hot to the touch.
