It typically consists of a cylindrical metal sheath, usually made of materials like stainless steel. Inside the sheath, there is a coiled resistance wire which is the key component for generating heat. The wire is often made of high – resistance alloys such as Nichrome. The space between the wire and the sheath is filled with magnesium oxide powder. This powder serves multiple purposes. It provides good electrical insulation to prevent short – circuits between the wire and the sheath. En même temps, it has excellent thermal conductivity, allowing efficient transfer of heat from the wire to the sheath.
Working Principle

When an electrical current passes through the resistance wire, according to the Joule heating effect (P = I²R, where P is power, I is current, and R is resistance), the wire heats up rapidly. The heat is then transferred through the magnesium oxide powder to the metal sheath. The sheath, in turn, transfers the heat to the surrounding medium, whether it’s a liquid, gas, or solid that the cartridge heater is in contact with.
Applications

Cartridge heaters are widely used in various industrial and commercial applications. In the plastics industry, they are used in injection molding machines to heat the barrels to melt the plastic materials. In the food processing industry, they can be found in heating chambers for sterilization and cooking processes. They are also commonly used in packaging machinery to heat sealing elements, and in many other applications where precise and efficient heating of a small to medium – sized area is required.