화학공학소재연구정보센터
Polymer Engineering and Science, Vol.41, No.12, 2095-2107, 2001
Converging flow analysis, entrance pressure drops, and vortex sizes: Measurements and calculated values
The use of converging flows for the determination of the elongational behavior of polymer melts is interesting provided that the solving of the inverse problem is fast. For this purpose, this paper shows that the entrance pressure drops that occur during the axisymmetric flow of a polymer melt from the reservoir of a capillary rheometer into a cylindrical die with flat entry can be rapidly calculated using a Wagner constitutive equation and Protean coordinates. This calculation technique performs particle tracking, which is absolutely necessary when using integral constitutive equations. In turn, the method also enables the determination of the particle path in the entrance zone and gives the boundary of the vortex. The appropriate solution is obtained through the minimization of the power consumption in the entrance zone. Calculation results are compared with experimental pressure drops and vortex pictures using two well-characterized polyethylenes and show good agreement.