CFD modelling of Retention Aids Dosage Nozzles
Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesisAlternative title
Numeriska flödesberäkningar av retetionsmedel i doseringsmunstycken (Swedish)
The objective of this project is to design, using computational fluid dynamics (CFD), a set of retention aid dosage nozzles that minimize shear levels during their operation. This includes the effect of dosage nozzle size, contour and dosage velocity - absolute and relative to the stock flow. As a starting point, the three different dosage nozzles currently implemented on the Innventia FEX paper-machine have been studied using CFD. Problem areas, defined as regions of high viscous and/or turbulent shear, with these designs should be identified, and solutions to their improvement have been realized. The computational models considered here include non Newtonian models of the retention aid solution, as well as turbulent modeling of the stock flow. Novel configurations have been implemented which attempt to minimize the strain rate and shear stress during dosage and at the same time improve the mixing quality of the retention aid polymers. While the velocity of the side jet is determined to be the main cause of high strain rates and shear stresses, a good mixing can be reached by varying the position of the nozzles and the diameter penetrating the stock flow. The best compromise of mixing and shear stress has been reached with a triple side-wall nozzles configuration.
Place, publisher, year, edition, pages
Engineering and Technology
IdentifiersURN: urn:nbn:se:kth:diva-98660OAI: oai:DiVA.org:kth-98660DiVA: diva2:538302
Prahl Wittberg, Lisa, PhD