CFD modelling and heat transfer in a NNPB process

The metal plunger in an Narrow Neck Press and Blow (NNPB) process serves a dual function of forming the parison and extracting sufficient heat to stabilise the parison when going into the blow stage of producing a glass container. Previous work (1,2,3,4,5) in this area has indicated that there is a need to understand and quantify the heat transferred from the parison to the plunger and subsequently extract sufficient heat without causing "chill" defects in the final product. Preliminary work using computational fluid dynamics (CFD) modelling that has been carried out by others (6,7,8,9) shows that recirculation and choking of the airflow pattern within the bore of the plunger cooling tube system corresponds to the areas of poor cooling. Thus producing areas of ineffective heat extraction from the parison by the air flowing through the plunger cooling tube system. The current work addresses the above problem by examining the cooling tube design using CFD modelling and analyses the heat transfer from the parison to the plunger. These results should prove to be of immense value to designers and manufacturers associated with the glass production industry.