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Numerical simulation of wire‐coating low‐density polyethylene: Theory and experiments
Author(s) -
Mitsoulis E.,
Wagner R.,
Heng F. L.
Publication year - 1988
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760280505
Subject(s) - materials science , mechanics , finite element method , die (integrated circuit) , isothermal process , biot number , low density polyethylene , heat transfer , thermodynamics , composite material , polyethylene , physics , nanotechnology
The wire‐coating process was analyzed numerically making use of a particular die design employed in highspeed industrial operations. Both the lubrication approximation theory and a fully two‐dimensional finite element analysis were applied under isothermal and nonisothermal conditions, respectively. Particular emphasis has been given to the heat transfer effects between the melt arid the solid and free boundaries. A variety of thermal boundary conditions was studied, ranging from adiabatic to constant temperature walls. The influence of dimension less groups such as Peclet, Nahme, and Biot numbers is examined. Oscillation‐free solutions are obtained for the temperature field by using a standard finite element Streamline‐Upwind/Petrov‐Galerkin technique. Rheological data for a wire‐coating low‐density polyethylene (LDPE) resin (Alathon‐3535) were used in the analysis. The predictions include pressure and temperature distributions, shear stresses and shear rates both at the die wall and the wire, and wire tension for different wire speeds. The numerical results are compared with a set of experimental data for LDPE in a typical die used by Du Pont Co. It is found that the isothermal lubrication approximation for power‐law fluids overestimates pressure distributions when applied at die operating temperature. The nonisothermal finite element analysis gives better predictions, especially when realistic thermal boundary conditions are imposed, with the experimental results lying between those found from simulations assuming isothermal walls (upper limit) and adiabatic walls (lower limit).