NMR imaging of pulp suspension flowing through an abrupt pipe expansion

Nuclear magnetic resonance imaging was used to measure velocity profiles of water and an aqueous, 0.5 wt. % (consistency) wood pulp suspension flowing through a circular pipe in the vicinity of a 1:1.7 tubular expansion. Flow images are provided for various flow rates and axial positions with respect to the expansion plane. For water, both Laminar and turbulent flows were investigated. Pulp suspension flows were investigated upstream and downstream from the expansion plane. The expansion plane imparts shear layer instabilities that disrupt the fiber floc network. The fiber reflocculation length is proportional to the bulk flow rate. We determined a mean reflocculation time of approximately 510 ms for this pulp fiber consistency.