Resistance heating

The Joule effect of current is used to convert electrical energy into thermal energy to heat objects. Usually divided into direct resistance heating and indirect resistance heating. The power supply voltage of the former is directly applied to the object to be heated, and when current flows, the object to be heated (such as an electric heating ironing machine) generates heat. The object that can be directly heated by resistance 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. 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 heated object through radiation, convection and conduction. Since the heated object and the heating element are divided into two parts, the type of heated object is generally not limited, and the operation is simple.

The materials used for the heating elements of indirect resistance heating generally require high resistivity, small resistance temperature coefficient, small deformation at high temperatures and not easy to embrittlement. Commonly used are metal materials such as iron-aluminum alloy and nickel-chromium alloy and non-metallic materials such as silicon carbide and molybdenum disilicide. Higher metal heating element: working temperature can reach 1000~1500*C according to the type of material;

The higher working temperature of non-metallic heating elements can reach 1500 ~ 1700*C. The latter is easy to install and can be replaced by the heating furnace, but it needs a voltage regulator when working, and has a shorter life than alloy heating elements. It is generally used in high temperature furnaces, places where the temperature exceeds the allowable higher working temperature of metal heating elements and some special occasions .