A study on the Flow Dynamics of Wood Fiber in Dilute Phase Pneumatic Transport

Pneumatic conveying is widely used for transporting bulk powders and granular materials. Dilute-phase systems are preferred for their versatility, but they require precise control of conveying velocity to optimize transport efficiency. While transport characteristics of uniform materials in dilute-phase flow are well-studied, wood fiber poses unique challenges given its unique material characteristics. The morphology of wood fiber appears to consist of loosely bound fiber bundles comprising individual fibers of varying dimensions. This variability leads to inconsistent bulk properties posing difficulties in predicting their aerodynamic behavior and resulting motion. Furthermore, stress applied to a fiber bundle can change its structure and thereby impact its aerodynamics and drag resistance. This study investigates the transport behavior of wood fiber in dilute phase flow using analytical and experimental methods. Analytical methods start with existing empirical correlations for drag coefficients of discrete particles and attempts to define similar ones for a fiber bundle of arbitrary morphology. Experiments focus on understanding bulk behavior of the two-phase flow by measuring limiting gas velocities for fiber transport and furthermore, generating gas velocity field data using particle image velocimetry techniques.