The Fraunhofer ITWM participates in several projects with the URSA International GmbH, under the responsibility of Dr. Roman Rupp and Dipl.-Ing Michael Lieberknecht, for simulation, analysis and optimization of glass fiber spinning process in the production of heat insulation materials. The goal of the current project is to optimize size and distribution of spin nozzles in the fiberization machine. Therefore, we examine the coupled flow processes in the glass reservoir and in the spin nozzles. The main aims of the project are:

• The analysis of deformation of the rotating disk due to mechanical and thermal stresses
• A detailed study of the influence of temperature gradients in the nozzles on the distribution of the temperature in the fibers
• A study on coupled nonisothermal flows through nozzles as well as flows within the glass reservoir
• Optimization of size and distribution of nozzles

The distribution of temperature in liquid glass in a part of the rotating disk

The spin nozzles are small in relation to the rotating disk due to the huge amount of holes. That's why a direct numerical simulation, which contains every detail of the fiberization machine, can't be realized on modern computers. This is the reason why a multi-scale approach is chosen for the solution of this problem. Initially, flows are calculated for a small but representative number of nozzles. All details of the nozzles are represented on the computational grid, so velocity, pressure and temperature distributions are known in detail. These results can be used with the help of an upscaling method to identify effective properties of the rotating disk, which is considered to be a porous medium. These properties are again used to simulate the fiberization machine at the macroscopic level, where it is not possible to resolve single nozzles in detail. This macroscopic simulation is embedded in an optimization algorithm. The goal, i.e. the optimization of size and distribution of the nozzles, is achieved by iteration of the described simulation steps on micro- and macroscales. Critical parameters for the quality of the produced glass fibers are temperature and velocity distribution. The distribution of temperature in liquid glass in a part of the rotating disk is shown in the figure below. The slice material is not shown in the figure for the reason of better visualization.