Analysis and Optimization of Polymer Spin Packs

Spin packs are widely used for the production of synthetic fibers and nonwoven materials. In a typical spin pack polymer melt enters through a small inflow tube. Within a cavity the polymer is distributed over the whole cross-sectional area of the device before it passes several layers of filters. Finally, the material is pressed through small capillaries and spun into fibers. Spin packs are heated to keep the polymer melt flowing which may lead to degradation if residence times are too long.

Fraunhofer ITWM uses modeling, simulation and optimization to improve the geometric design of spin packs. This goes back to ProFil funded by the German Federal Ministry of Education and Research which was a joint project with TU Kaiserslautern, FAU Erlangen-Nürnberg and University of Kassel. Within ProFil shape optimization methods were developed which are used to design distributor cavities with a uniform level of wall shear stress. This is based on the idea that a low level of wall shear stress indicates a stagnation zone because flow velocities rise slowly in proximity to the wall. Therefore, we can prevent stagnation zones by designing cavities with a sufficiently high level of wall shear stress.

The bridge from academia to an industrial application was taken in the subsequent project AUTOPOS funded by the German Federal Ministry for Economic Affairs and Energy in cooperation with the Institute of Textile Technology (ITA, Aachen) and 11 partners from industry. Since the end of AUTOPOS Fraunhofer ITWM is successfully offering the analysis and optimization of polymer spin packs as a consulting service. A typical project usually starts with a flow simulation of the original design. An analysis based on the simulation data then reveals potential problems with respect to residence time, pressure drop or other important quantities. Finally, the geometric design is optimized and another analysis of the new design is performed to validate the improvements.

For more information contact Dr. Christian Leithäuser (christian.leithaeuser@itwm.fraunhofer.de)