Fiber energy efficiency Part III: Modeling of bar-to-fiber interaction

Journal article, 2014

This paper presents a model for fluid dynamic studies describing the bar-to-fiber interaction in refining processes. The approach is to introduce and validate assumptions for a deeper understanding of physical phenomena between refining bars in a micro-scale perspective. The model is based on Navier-Stokes equations in 2D and special emphasize is put on the pressure dynamics occurring when changing the plate gap, i.e. the distance between refining segments. It is shown that the model can reproduce pressure fluctuations like those obtained in experimentally validated measurements. It is also shown that the pressure varies considerably dependent on the plate gap as well as the position studied along the bar in tangential direction. This is a consequence of varying shear forces between the bars. Moreover, it is stated that the fiber network density variations will be important to describe in more details. Finally, it is shown that the model for the bar-to-fiber interaction can handle different aspects regarding plate pattern design which have significant impact on the fluid dynamics and thereby the final pulp properties in full-scale refiners.