Numerical Modelling of the Fiber Breakage in the Glass Spinning Process for Mineral Wool Manufacturing

Discontinuous glass fibers, used in thermal insulation panels, are manufactured by centrifugal spinning, akin to cotton candy. In this process, continuous fibers exiting the spinner holes are first kept above the liquidus temperature by a burner flow, then cooled and chopped further downstream by a cold, high-speed vertical jet. The resulting small discontinuous glass fibers are simultaneously propelled downwards and collected by a conveyor belt. The insulation properties of the final product strongly depend on the fiber geometry, highlighting the need to understand fiber formation and breakage.

A one-dimensional fiber model, originally developed for polymer nanofibers by Noroozi (2021), is extended to account for the specificities and challenges of glass wool manufacturing. The model includes three spatial dimensions, internal and surface heat transfer, and drag due to high-speed flows. Initially, comparison with a three-dimensional model confirms that the one-dimensional model accurately represents the fiber. Next, the breakage process is analyzed by introducing a numerical, yet physically plausible, breaking criterion. It is shown that the break induces a significant stress relaxation in the fiber remaining attached to the spinner, leading to a substantial alteration in its trajectory. After the transient phase following the initial cut, the process exhibits a limit cycle of growth and break. Finally, the dependence of the fiber length and radius on the process parameters is discussed.