Numerical simulation of external and internal cooling in film blowing

Commercial blown film production is often limited by the rate of cooling that can be achieved in the production line. The flow of the cooling air around the curved bubble is characterized by rather complex aerodynamics. Even for the same air ring design, different set-ups (adjustable air rings) produce significant differences in the air-flow pattern. Internal Bubble Cooling (IBC) designs are also design sensitive, having difficulty keeping the airflow balanced while maximizing the internal air exchange. Numerical simulation suggests that heat transfer rates are affected by all these parameters. Additionally, numerical simulation in the film phase reveals large temperature gradients across the film thickness in the area where the film is emerging from the die.