Analysis of influent parameters during infrared radiative heating of PET preform
Abstract
The processing parameters during radiative heating of PET preform are: The number of infrared heaters N h , The temperature T i of each infrared heater L i=1, N h The heating time t h , The cooling time t c , The coordinate vector x i=1,N h of each infrared heater L i=1, N h , The heat transfer coefficient h c between cooling air and PET preform. In previous papers [1,2], the spectral emissivity and directivity of different halogen lamps (Philips 300-700W electric nominal power made of a coiled tungsten filament, contained in a quartz tubular enclosure and a diffuse reflector made of a ceramic coating) have been reported. Recent measurements using a 0.6-25 m thermopile sensor on similar halogen lamps of 1000W (used in an industrial oven of injection-blow moulding machine) have been processed. The maximum temperature of the tungsten filament is 2400 K. As shown in fig. 1, these infrared heaters exhibit a slightly different behaviour from a lambertian source (diffuse radiation) due to the reflector. The average discrepancy is about 8 %. In order to take into account the participation of the diffuse reflector in the amount of the incident radiation, a coefficient of efficacy k rf is introduced. Fig. 2 shows the experimental setup that has been developed in order to measure the surface temperature distribution (front face and back face), when a PET sheet is heating using previous infrared heaters. An 880 LW AGEMA infrared camera (8-12 m bandwidth) is used to measure the spatial and transient temperature distribution. The surface dimension of the PET sheet is 20cm 20cm cm and the thickness is 1.5 mm. A 3D control-volume model has been developed for computing radiative heat transfer during the infrared heating stage. The sheet-shape domain sketched in fig. 3 is discretised into cubic elements, called control-volumes [3]. The energy equation including radiative transfer integrated over each control volume V e x y z and over the time from t to t t leads to:
Origin : Files produced by the author(s)
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