Numerical Study of Internal Bubble Cooling (IBC) in Film Blowing

Abstract Numerical simulation of turbulent airflow emerging from an Internal Bubble Cooling (IBC) stack and directly impinging on the internal surface of a blown film bubble has been carried out. The streamline pattern and heat flux are determined through a finite volume numerical technique using a version of k-∊ turbulence modeling. It is shown that balancing the airflow between the multiple slits of the stack is useful to increase the internal cooling rates, but may require more elaborate designs of the inlet pipe. As the air flows towards the internal bubble surface there is significant deceleration which diminishes the effectiveness of the heat removal mechanisms. Depending on the flow rates and geometrical configurations the airflow may induce compressibility effects at the exhaust pipe. The numerical results suggest that Internal Bubble Cooling (IBC) equipment introduces distinctive design and operation challenges.