Abstract:

A geometric model was first established based on the current twin⁃screw barrel and coil distribution， and then the barrel flux variation and temperature uniformity of the electromagnetic heating process were studied using the COMSOL finite element software. Furthermore， a mathematical model was established according to the theoretical basis of electromagnetic heat and heat conduction. A specific experiment was conducted under the guidance of numerical simulation to verify and compare the temperature uniformity on the internal wall and flange of the twin⁃screw barrel， electricity consumption， and electromagnetic radiation safety under electromagnetic and cast copper heating. The results indicated that the temperature uniformity， electricity consumption， and electromagnetic radiation safety were not affected at the same heating time. In the same period of heating time， electromagnetic heating could realize simultaneous barrel and flange heating， resulting in faster barrel heating to the set temperature and reducing the screw torque and host current. This leads to a 40 % saving in the preheating time as well as a higher temperature control accuracy， ensuring temperature uniformity within ± 1 ℃. This is consistent with the simulation results and improves the extrusion performance of molten raw materials. Compared to cast copper heating， electromagnetic heating has less heat loss and heat stress and a lower surface temperature of equipment. Such a new heating mode improves the workshop environment， gains energy saving more than 50 %， and improves the product quality and production efficiency. In addition， electromagnetic radiation conforms to the national safety standard GB 8702—2014， ensuring the personal safety of workers in workshop.

Key words: electromagnetic heating, twin?screw extruder barrel, cast copper heating, plasticizing system, electromagnetic heat and conduction heat theory, comsol numerical simulation