AbstractThe first quantitative description of melting in single‐screw extruders was given by Tadmor around 1965. A simple analytical theory was developed for Newtonian fluids assuming the fluid viscosity to be unaffected by changes in temperature. Also, an approximate analytical theory was developed for a power‐law fluid assuming the power‐law constants to be independent of temperature and viscous dissipation to be negligible. Later workers extended the theory; however, most of these extensions did not allow closed‐form analytical solutions, thus requiring numerical techniques to obtain solutions. One of the most crucial assumptions in the analytical melting theory is the assumption that the viscosity of the polymer melt in the melt film is not affected by temperature differences in the melt film. This assumption has been eliminated in the improved melting theory by deriving and exact solution of the temperature and velocity profile in pure drag flow of a temperature‐dependent power‐law fluid between two parallel plates. It will be shown that the inclusion of the temperature dependence of the viscosity dramatically affects the predictions of the melting rate. It will further be shown how the new theory can be used to predict the optimum barrel temperature