Single screw extruders with barrier screws, grooved feed zones and grooved melting zones were introduced to the European plastics industry in 1999. These extruders have an improved melting and conveying capacity among other advantages, such as a lower melt temperature, less wear, less torque and less energy consumption. The aim of this paper is to present a mathematical model for predicting the melting rate in this type of extrusion system. Based on the classical melting mechanism observed in conventional extruders, it was possible to study the effect of the geometry of the grooved barrel on the melting rate of a polymer. It was shown that the grooves on the barrel notably increase the melting rate, when compared to conventional single screw extruders. A good agreement between theory and experimental data was found.