Temperature fields in extruder dies with circular, annular, or slit cross‐section

Viscous dissipation causes significant temperature increases in polymers while they are flowing through extruder dies. The development of the temperature field has been studied numerically using the dimensionless parameters Na and Gz. With the annular geometry (parameter: ratio of radii κ) the well known developing temperature fields in capillaries could be compared with the developing temperature fields in an annulus and in a plane slit. The shear dependence of the viscosity is described by a “power law” and the temperature dependence by an exponential function. A simple graphical method is suggested for estimating temperature fields in extruder dies, making use of the fully‐developed temperature field for very long dies as a reference state. For the demonstration of results, a power law exponent n = 0.4 has been chosen.