Theoretical Study of the Three-Dimensional Flow Field in the Calender Bank

Abstract

The three-dimensional flow field in the calender gap is calculated with consideration of the free surface of the bank. Calender units with rotating rolls are used to produce foils or sheets from polymer material with viscous or elastometric flow properties. The flow field and the adjusting form of the bank determine the properties of the product. The results of the calculations include the determiniation of vortex patterns inside the bank for fluids with viscous non-Newtonian and Newtonian flow behaviour as well as the determination of the influence of gap height and speed ratio on the coordinates of the free surface and the flow field. Additionally the influence of the flow field on the product quality is presented. Due to the requirement of a good product quality the influencing parameters are subject to boundaries. Such boundaries of the parameters are discussed and a schematic processing window for a specific product geometry is given. Analysed product properties are thickness, surface appearance, air inclusions, mixing and temperature. The numerical calculation is based on a decoupled calculation method for the free surface. The transport equation for mass and impulse are solved with the fluid dynamics analysis package Polyflow. The coordinates of the free surface are shifted until the free surface becomes a stream line. To analyse the flow behaviour polymeric fluids the power-law model of Ostwald-de-Waele is used.