Thermal balance between viscous heating and inlet thermal condition in non stationary polymer flow through a cylindrical die

During the forming of polymer materials under extrusion or injection moulding process conditions, the heat source resulting from the high viscous dissipation within the flow in the die channel plays an important role on the thermal field within the polymer and the experimental device. One difficulty to simulate numerically this kind of flow, besides the accurate knowledge of the actual rheological parameters of the materials, consists in fixing the boundary conditions of the spatial domain of integration. Indeed, for non stationary conditions, they are varying both in space and time. In this paper, experimental data (temperature and flow rate) measured in a specific instrumented die are compared to the solutions predicted by a set of coupled equations which models the heat source release, the heat conduction process and the polymer flow, under non stationary conditions. This analysis leads to evaluate the thermal balance between the viscous heating and the inlet thermal condition.