Development of an Analytical Model to Describe the Disperse Melting in Wave-Dispersion Screws

Abstract

The progressive development of new screw concepts in single screw extrusion also makes it necessary to develop new models for the correct process description. When looking at wave-dispersion screws, the disperse melting behavior should be mentioned in particular, which has so far been less researched and modeled than the conventional melting behavior, as it occurs in standard screws. Therefore, an analytical model is presented in this paper, which considers the disperse melting under consideration of the melt and solid temperature. The basic assumption is Fourier heat conduction from the melt surrounding the particles into the particles. Furthermore, the melt temperature development by dissipation and the cooling effects were modeled analytically. Additionally, the solid bed temperature was modeled by a 2D-FDM method. By dividing the screw into several calculation sections with constant boundary conditions, it was subsequently possible to calculate the melting process over the screw length. The model developed shows comprehensible results in verification and successfully reproduces the solids content over the screw length with a mean deviation of absolute 11% in validation tests using cooling/pulling-out experiments.

Polymeric field synergy principle: Revealing the intrinsic mechanism of screw channel optimization to enhance thermal management and process efficiency

“…The wavy screw caused periodic strong shear and stretching effects as the flow passed through the screw channels with the periodic variation in the depth because of its eccentric structure. In Dörner et al's work [22], this regular change is considered the fundamental reason for improving the mixing performance of the wavy screw. Besides, the Maddock screw performed strong shear and stretching simultaneously.…”

Method Development for the Prediction of Melt Quality in the Extrusion Process

“…For the investigations in this research work, the thermal homogeneity of the melt was assessed using the standard deviation of the weighted average melt temperature at the screw tip. A high standard deviation indicates low thermal homogeneity [13]. Dead stop tests were performed to determine material homogeneity.…”

Application of Network Analysis to Flow Systems with Alternating Wave Channels: Part B. (Superimposed Drag-Pressure Flows in Extrusion)

“…These developments have also resulted in a variety of high-performance screws being designed to provide excellent melt homogeneity at high output rates and proper discharge temperatures. Despite their importance, only a few studies have examined the performance of wave-dispersion screws [ 2 , 3 , 4 , 5 , 6 ].…”