Study on the mechanism of drying uniformity of wet flexible fibers under dynamic coupling of cohesion and entanglement

The dynamic evolution of cohesion and entanglement during drying gives rise to complex mesoscale structural evolution in wet flexible fibers, which hinders the rational optimization of process conditions for improving the drying uniformity and product quality of wet biomass particle. In this study, a Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) approach was employed to investigate the flow, heat and mass transfer processes of wet flexible fibers in a fluidized bed. The evolution of liquid bridge cohesion, mechanical entanglement, agglomeration structures, porosity distribution, and interphase heat transfer was analyzed to reveal the potential causes of drying non-uniformity. The results showed that significant drying non-uniformity developed during the intermediate drying stage, accompanied by the formation of localized high moisture regions. Moisture evaporation continuously weakened liquid bridge cohesion, while mechanical entanglement gradually became the dominant particle interaction. The agglomerate structure evolved from dense clusters to loose networks, with a critical dimensionless time range of t n = 0.4-0.5 identified as the transition threshold. Consequently, drying uniformity was closely associated with the evolution of agglomeration structures driven by the dynamic competition between liquid bridge cohesion and mechanical entanglement. These findings provide a theoretical basis for improving the drying quality of wet flexible biomass particles.