Assessing the Sensitivity of the Heat Transfer Coefficient at the Polymer-Calibrator Interface in Profile Extrusion

One of the major challenges in modeling the cooling stage of the thermoplastic profile extrusion process is defining the heat transfer coefficient at the polymer-calibrator interface (h(int)), which significantly affects the cooling rate. Accurate values for the h(int) are essential for improving process efficiency using numerical modeling codes. In the existing literature, values of h(int) are only available for a limited number of cases, and there are no systematic studies regarding the influence of processing conditions on this parameter. This study focuses on the determination of accurate values for h(int) and on the influence of processing parameters, namely: cooling fluid temperature, pulling velocity, and vacuum pressure. To accomplish this, a previously developed calibrator prototype, and associated methodology, targeting the measurement of h(int) for thermoplastic materials, is utilized in a conventional profile extrusion line. The results obtained show h(int) values in the range of 200-1500 W.m(-2).K-1, which is in accordance with the results published in the available literature. The results also reveal that the cooling fluid temperature and the pulling velocity have the most substantial influence on h(int), while vacuum pressure has minimal impact within the range of the experiments conducted.