In papermaking the pulp and paper treatment processes needs the optimization of various unit operations which require a better knowledge of the pulp of paper behaviour. The Pulp of paper, which is a suspension of cellulose fibers in water, shows several regimes when flowing in pipes. These regimes are experimentally and qualitatively well described in the literature, they are related to the evolution of fibre flocculation characterizing different regimes (called: plug flow, mixed regime and turbulent flow). By against a quantitative descriptions of these regimes are limited and we don't find a model in the literature that describes entirety the behaviour of the pulp of paper flow from a plug flow (high shear friction at low velocities) to identical behaviour that of water at high velocities (turbulent Newtonian flow) going through drag reduction in intermediate velocities.

We propose an experimental analysis of the flow of pulp of paper for several concentrations of fibers in two diameters of pipes (evaluation of confinement effects). These results are compared to a model describing the behaviour of paper in any regimes. The proposed model is based on calculating an average shear stress which takes into account both the elastic moduli of the flocs and the network of fibres (floc agglomerates) and secondly the viscosity of the fluid (water) modified with dispersed fibres..