Numerical simulation of the flow in a disc refiner

• Main Author: Kohkar, Gohar
• Format: Others
• Language: English
• Published: KTH, Mekanik 2011
• Subjects: Engineering and Technology; Teknik och teknologier
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-65518

The thesis work is carried out in Innventia AB and Royal Institute of Technology (KTH). The objective of the study was to numerically simulate the flow inside the disc refiner and to determine the factors influencing the development of flow in the rotor and the stator of the disc refiner. Simplified single groove model is used to analyze the flow in the rotor and stator of the refiner. Fluid is assumed to be Newtonian and single phase with dynamic viscosity 100 times higher than water. Model and mesh used for the rotor and stator are identical with different wall boundary conditions and fluid zone conditions. Simulations were performed with different pressure gradients and angular speed of the refiner. The study shows that the flow in the rotor depends on the pressure difference and the speed of the refiner. Flow in the stator depends on the pressure difference; speed has little effect on the flow in the stator. In the rotor fluid flows towards the periphery while in the stator direction of flow is towards origin. Rotational motion is observed both in the rotor and the stator groove. This rotational motion carries the fluid into the gap, fibres present in the fluid form flocs and got stapled at the bar edge. They get treated every time a rotating bar crosses a stationary bar. To study the intensity of refining, strain rate and shear force is determined. Shear force is due to the rotation of the rotor and due to the motion of the fluid down into the groove along its wall i.e. fluid that is carried along with the rotating plate.