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 respec t to the expansion plane. For water, both Laminar and turbulent flows were investigated. Pulp suspension flows were investigated upstream and downstre am from the expansion plane. The expansion plane imparts shear layer instab ilities that disrupt the fiber floc network. The fiber reflocculation lengt h is proportional to the bulk flow rate. We determined a mean reflocculatio n time of approximately 510 ms for this pulp fiber consistency.