Experimental study and numerical simulation of preform or sheet infra-red radiative heating
Résumé
Forming hollow plastic parts using thermoforming or blow moulding processes requires to heat tube-shaped or sheet-shape preforms above the glass transition temperature. Considering the weak conductivity of polymers, infrared ovens remain the best way to increase rapidly the preforms temperature. As the final thickness distribution of the part is drastically controlled by the initial temperature distribution inside the preform, it is very important to optimise the heating stage. It is more suitable as the efficiency of most industrial infrared ovens is about 20 %. In the present work, we proceed to experiments in order to characterise the interaction between infrared heaters (quartz tube) and semi-transparent PET sheets. An experimental setup has been developed to measure the influence of parameters such as heaters temperature, incidence of the radiation, heat transfer coefficient ,… A 880 LW AGEMA infrared camera is used to evaluate the surface distribution of the transmitted heat flux by measuring the temperature distribution on the surface of the thermoplastic sheet [1]. In addition, a numerical model using a control-volume method has been developed to simulate the heating stage. In particularly, it takes into account the spectral and the directivity properties of both heaters and preforms [2]. Comparisons between experimental data and numerical simulations allow us to validate the numerical model and to emphasise on the main heating parameters.
Origine : Fichiers produits par l'(les) auteur(s)
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