A transient melting model of polymer balls sliding against the barrel

In the study of solid conveying process in plastics screw extrusion, a part icle element numerical method enables its to simulate behavior of each soli d particle during the process and takes into consideration the parameters o f individual particle in the calculation. The melting of pellets in the solid conveying section is caused predominant ly ky heat from both friction and conduction through close contact. Experim ents showed, melting happened before the solid plug was formed. Hence, when a particle element numerical method is used to simulate the conveying and melting process in the injection bellow, the analysis of melting process ca used by solid particles sliding against wall of bellow should be included. Searching through the recent literature, no valid analysis of the transient close-contact melting process caused by viscous dissipation was found. Thi s paper attempts to present an analysis of the melting process and derive a n expression for describing the transient melting caused by both friction a nd close-contact heating. The melting model of polymer pellets sliding agai nst the barrel was achieved by assuming the friction against the barrel as friction against an isothermal wall given the high heat conductivity of the barrel. To keep the expression simple, a constant temperature boundary con dition is utilized for the wall which concurs with reality.