Convective Transport in an Optical Fiber Coating Applicator for a Non-Newtonian Fluid

Convective transport in an optical fiber coating applicator and die system has been simulated for a non-Newtonian fluid. Low density Polyethylene (LDPE) is employed for the numerical analysis, though ultraviolet (UV) curable acrylates are commonly used, because of lack of property information for acrylates and similar behavior of these two materials. The equations governing fluid flow and heat transfer are transformed to obtain flow in a cylindrical domain. A SIMPLE-based algorithm is used with a non-uniform grid. In contrast to the isothermal case, streamlines for the non-Newtonian fluid are found to be quite different for various fiber speeds. The temperature level in the applicator is much higher for the Newtonian case, due to the larger fluid viscosity and associated viscous dissipation. The shear near the fiber is found to be lower for the Newtonian fluid. As expected, the effects become larger with increasing fiber speed. A very high temperature rise is observed in the die, regardless of fiber speed. This study focuses on the non-Newtonian effects during the coating process, and several interesting and important features, as compared to the Newtonian case, are observed.