In polymer blown film extrusion, inhomogeneous die temperature distributions lead to an inhomogeneous temperature and cause film thickness variations. To avoid an inhomogeneous film thickness and to achieve good film qualities, thermal homogenisation of the melt is necessary. Therefore, a new approach for cooling hot spots with heat pipes is investigated. CFD Simulations in OpenFOAM show that heat pipes can be used to influence melt temperatures locally in the places in which a temperature reduction is required. Since the outlets interact in a pre-distribution die, one heat pipe is not sufficient to homogenise the temperature at every outlet to similar temperatures. Two heat pipes show much better results with lower average temperature deviations between the distributor outlets. In order to equalise the temperature at all outlets, at least one heat pipe per outlet will be required.
Keywords: CFD; blown film extrusion; heat pipe; pre-distribution; thermal homogenisation.