Abstract
An experimental investigation of a laminar plug flow of pulp-suspension in a circular pipe was made. The pressure loss was measured by pressure transducers, and the velocity gradient at pipe wall and the local velocity were measured by an electrochemical technique.
From experimental relations between the pressure loss and the flow rate, and between the shear stress and the velocity gradient at pipe wall, the pulp-suspensions should be regarded as Newtonian liquids, though the values of viscosity determined from those relations were undoubtedly different from each other. On the other hand, both the measured velocity profile and the experimental relation between the velocity gradient at pipe wall and the flow rate were not those for a Newtonian liquid.
This inconsistency could be explained by the consideration that the pulp-suspension had a particular average viscosity to the pulp fiber concentration prepared and behaved as a Newtonian liquid at every radial position with different viscosity which was distributed in the radial direction in a circular pipe. Furthermore, an appropriate formula for the radial distribution of viscosity was presented. The calculated velocity profiles based on the formula coincided well with the measured ones.
