The fiber spinning process consists of liquefying a polymer and extruding it into several fibers using spinnerettes. The fibers are then solidified and drawn down in a quenching chamber. CFD contributes design guidance to several parts of this process. POLYFLOW, for example, can be used to analyze the balance between viscoelastic die swell effects and winder tension, a determining issue for the shape and size of individual fibers. In addition, fiber quality is strongly influenced by the gas flow field surrounding the fibers, including the rate of convective cooling or heating and the concentration of the gases within the quenching chamber.

" At Hercules Fiber Division, we have employed modeling techniques for many years. As commercial CFD codes have become more flexible and reliable, we have adapted them into our modeling tool chest. Our experience with FLUENT has been quite positive; we have used FLUENT extensively in a variety of problems relating to fiber spinning. This has led to new insights in both polymer flow in spinnerettes and quench airflow dynamics."

Dr. Sanh Le, Hercules Fiber Division

In the past, CFD could not model quenching chambers effectively, as it was difficult to discretize the numerous fibers and include the strong coupling of the heat, mass and momentum between the fibers and the surrounding gas. Now, a new fiber spinning module in FLUENT makes it easy. Developed in collaboration between Bayer Faser GmbH, Professor Ulrich Renz of Aachen University of Technology, and Dr.-Ing. Markus Braun of Fluent Deutschland GmbH, the new model includes numerous fibers in a quenching chamber, with complete coupling between the fibers and gas flow. Gravity effects, friction with the surrounding gas, mass exchange, and exchange of convective and latent heat are included in the module. The effect of fiber motion on the flow field, along with fiber temperatures in the quench box, is calculated by the module.

The new FLUENT fiber spinning model includes multiple fibers, with complete coupling between the fibers and the gas flow field in the quenching chamber. Here, the fibers are colored by temperature.

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