AbstractsPhysical Sciences

The pulp and paper industry consumes high amount of energy when producing paper. Large flows of pulp suspensions are handled during the process. There is still a lack of knowledge of the flow and fluid properties of pulp suspensions which is important in the design and operation of more efficient process equip- ment. The boundary layer growth and near wall flow over a flat plate in pulp suspensions were investigated in this thesis usung Computational Fluid Dynamics (CFD) simulations. The numeric results were compared with experimental results obtained by Claesson et al (2013). The pulp suspension flow was simulated as a Bingham plastic fluid using different values of the yield stress. A variation of the inlet flow velocity was also conducted. Both the velocity profiles and the pres- sure drops were studied. A comparison of the boundary layer growth in the CFD simluations and the experiments showed that the velocity profile was established faster in the experiments and that the boundary layer thickness was thinner. An increased value of the yield stress gave a more similar velocity profile. The exper- imental values of the pressure drops were lower than the ones obtained in the CFD simulations. A lower value of the yield stress gave a more realistic pressure drop. This is a contradiction since lower values of the yield stress gave a worse agree- ment of the velocity profiles. Therefore, the wall treatment for the pulp suspension is suggested to be revised as well as the rheology of the fluid model.