heating element; heat-generating element
Technical term for a component that produces heat, such as in electric heaters, ovens, or industrial equipment.
The heating element of this heater is made of ceramic.
If the heating element fails, the entire device stops working.
電熱線 is a heating wire, a common type of 発熱体, but 発熱体 can also be a ceramic plate, coil, or other shape.
Compound of 発熱 (heat generation) + 体 (body, element). A straightforward technical coinage.