Steady MHD flow and heat transfer of a third grade fluid in wire coating analysis with temperature dependent viscosity

Wire coating is an important industrial process as it provides insulation and mechanical strength. The most important plastic resins used in coating of wires are plasticized polyvinyl chloride (PVC) and low/high density polyethylene (LDPE/HDPE), nylon and polysulfone. The designs of wire coating die are of fundamental importance as these affect the final product after processing. In the present study wire coating is performed using melt polymer satisfying third grade fluid model. The novelty of this study is to analyze the effect of a radial magnetic field and varying temperature dependent viscosity on the wire coating. In our discussion we have considered (i) Reynolds model (ii) Vogel's model to account for temperature dependent viscosity. We have investigated the flow in a pressure type die. The equations characterizing the flow and heat transfer phenomena are solved numerically and the effects of emerging parameters are shown with the help of graphs. It is interesting to remark that an increase in non-Newtonian parameter increases the velocity in the absence of magnetic field which coincides with the results reported earlier but in the presence of magnetic field the velocity decreases in the entire span of the flow domain. Further, the flow instability in the flows of extrusion die is well marked in case of Vogel's model as pointed out by Nhan-Phan-Thien. (C) 2014 Elsevier Ltd. All rights reserved.