Electric heater resistance heating principle principle: use the Joule effect of electric current to convert electrical energy into heat energy to heat the object. Usually divided into direct resistance heating and indirect resistance heating.
The power supply voltage of direct resistance heating is directly applied to the object to be heated. When a current flows, the object itself is heated. The object heated by direct resistance heating must be a conductor, but it must have a higher resistivity. Since the heat is generated by the heated object itself, it belongs to internal heating, and the thermal efficiency is very high. For example: the electric heating ironing machine generates heat.
Indirect resistance heating requires special alloy materials or non-metallic materials to make heating elements. The heating elements generate heat, which is transmitted to the object to be heated by means of radiation, convection and conduction. Since the heated object and the heating element are divided into two parts, the type of the heated object is generally not limited, and the operation is simple. The materials used for indirect resistance heating heating elements generally require high resistivity, low temperature coefficient of resistance, small deformation at high temperatures and not easy to embrittlement. Commonly used are metal materials such as iron-aluminum alloy, nickel-chromium alloy and non-metallic materials such as silicon carbide and molybdenum disilicide. The maximum working temperature of metal heating elements can reach 1000～1500℃ according to the type of material; the highest working temperature of non-metal heating components can reach 1500～1700℃. The latter is easy to install and can be replaced by the heating furnace, but it needs a voltage regulator when it works, and has a shorter life than the alloy heating element. It is generally used in high temperature furnaces, places where the temperature exceeds the maximum working temperature of the metal heating element and some special occasions. For example: heating tube, stainless steel electric heating tube, ceramic heater, etc.
