Analyzing the principle of resistance heating with electric heaters in daily life

Analyzing the principle of resistance heating with electric heaters in daily life

The principle of electric heater resistance heating is to use the Joule effect of current to convert electrical energy into thermal energy to heat objects. Usually divided into direct resistance heating and indirect resistance heating.

The power voltage of direct resistance heating is directly applied to the heated object. When there is current flowing through the heated object itself, the object heated by direct resistance must be a conductor, but it must have a high electrical resistivity. Due to the heat generated by the heated object itself, it belongs to internal heating and has high thermal efficiency. For example, an electric heating ironing machine generates heat.

Indirect resistance heating requires heating elements made of specialized alloy or non-metallic materials, which generate heat energy and transmit it to the heated object through radiation, convection, and conduction. Due to the fact that the heated object and heating element are divided into two parts, the type of heated object is generally unrestricted and easy to operate. The materials used for indirect resistance heating heating heating elements generally require high resistivity, low resistance temperature coefficient, small deformation at high temperatures, and are not easily brittle. Commonly used are metal materials such as iron aluminum alloy and nickel chromium alloy, as well as non-metallic materials such as silicon carbide and molybdenum disilicide. The maximum working temperature of metal heating elements can reach 1000-1500 ℃ depending on the type of material; The maximum operating temperature of non-metallic heating elements can reach 1500~1700 ℃. The latter is easy to install and can be replaced by a hot furnace, but it requires a pressure regulating device during operation and has a shorter lifespan than alloy heating elements. It is generally used in high-temperature furnaces, places where the temperature exceeds the maximum allowable working temperature of metal heating elements, and certain special occasions. For example: heating pipes, stainless steel electric heating pipes, ceramic heaters, etc.

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