Modeling of the plasticating process in a single-screw extruder: A fast-track approach

A new mathematical model has been developed to analyze the entire flow fiel d of a single screw extruder under steady-state conditions. Intended as a r ational design tool for practising engineers in the polymer processing indu stry, the model contains no partial differential equations and hence does n ot require the use of numerical solution techniques. To achieve generality, a generic approach is proposed and has been adopted in the derivation of g overning algebraic equations from general conservation laws covering channe l geometry, polymer flow speed, equivalent radius in a pipe, material prope rties, power consumption and heat transfer. The model makes no use of empir ical factors or correlation. The validity of the new model has been assesse d by comparison with published experimental results. Good agreement was ach ieved with respect to its ability to predict (a) the solid-bed width profil e; (b) the axial pressure profile and (c) the temperature and pressure of t he melt pool at the extruder exit. Furthermore, the model can predict other information including the solid-bed velocity in the axial direction and th e power consumption. The work has demonstrated the potential of a fast trac k approach to designing helical extruder screws, while maintaining a level of accuracy comparable with more complex 3D models but without the penalty of computational efforts.