Numerical Analysis of Cooling Air Systems in Film Blowing

Abstract

Air rings, used today in film blowing systems, have been developed down the years through trial and error experiments. They represent the limiting factor concerning the efficiency of film blowing lines with respect to throughput and take-off speed. Numerical simulation of the cooling process in film blowing provides a tool for the design and optimization of future cooling systems. Individual process and geometric parameters can be changed interactively with the effects on flow and heat transfer processes being analysed and applied to similar situations. The knowledge acquired regarding the physical interactions in the cooling of blown film makes a targeted optimization possible. The purpose of this paper is to present the foundamentals for calculating turbulent air flows in blown film extrusion and, additionally, a model for complete FE-simulation of the flow and heat transfer processes. Furthermore, the achieved simulation results will be discussed.

Heat transfer from plastic film heated by thermal radiation

“…Campbell et al studied the flow field around the film that was estimated using a numerical simulation [6]. Wolf et al employed the finite element method to calculate the turbulent airflows caused by the jets impinging on a blown film [7].…”

Computer simulation of the film blowing process incorporating crystallization and viscoelasticity

“…They followed an approach similar to that developed by Feron et al (1997) and Wolf et al (1997), but with stronger interaction with the viscoelastic behavior of the melt. Sidiropoulos et al (1996Sidiropoulos et al ( , 1997Sidiropoulos et al ( , 1999Sidiropoulos et al ( , 2000 employed Fluent Software ©, which is based on the finite difference method to predict the heat transfer coefficient profiles.…”

“…Discontinuity is expected as the simulation changes the correlation that calculates the heat transfer coefficient in each zone, due to the possible jump in the HTC value. Feron et al (1997) and Wolf et al (1997) considered the turbulence in the flow of the cooling air and developed a numerical simulation to optimize the cooling pro cess by incorporating air flow rate, air temperature, the jet angle, and the location of the air ring.…”

Numerical optimization of a multi-jet cooling system for the blown film extrusion

“…The first one is based on the framework from Pearson and Petrie in combination with a modified Phan-Thien and Tanner rheological material description to calculate the film contour. The other module is a two-dimensional CFD-analysis [12] to compute the temperature profile of the film and the pressure load on the film surface. Both simulation modules act in a loop until a final quasi-stationary film contour is found.…”