Blow molding is a widely used process for making plastic bottles or containers. The cooling processes during the blow molding operation offer unique opportunities for thermal designing and optimization. While at the external surface it is reasonable to assume a perfect thermal contract with a chilled mold, it is the internal heat removal that needs special attention. Pressured air is used to enhance internal cooling which then governs the mold resident time and the mold resident time dictates the cycle time. In order to carry out meaningful thermal simulations, estimation of internal local heat transfer coefficient (perhaps as a function of the employed air pressure) is needed. Such coefficients have not been reported in the open literature and will be hard to determine experimentally. Here a computational fluid dynamics (CFD) program can offer some assistance. There are programs that are commercially available that can do thermal simulation across a solid-fluid interface without needing the convective heat transfr coefficients. The authors have advantageously utilized this feature to back-out the convective heat transfer coefficients from the temperature profile though the thermal boundary layer. Details of our methodology and preliminary verifiction results towards this goal are presented.
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