Suggestion of a new model for newtonian thermal analysis of solidification

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Tezin Türü: Doktora

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Fen Edebiyat Fakültesi, Fizik Bölümü, Türkiye

Tezin Onay Tarihi: 2013

Öğrenci: KADİR CAN ERBAŞ

Danışman: EMİNE AYŞE KARASU

Özet:

Newtonian thermal analysis (NTA) of solidification is a widely used tool to understand the solidification kinetics of metals. It depends on cooling curve analysis by using heat equations especially Newton’s law of cooling. Calculation of the latent heat of solidification and solid fraction evolution are one of the primary goals of NTA. Several mathematical models have been proposed in the literature for this purpose. However, there are many discussions on the reliability of these models. In this study, latent heats of pure metals, which are calculated from several models, were compared with their literal values. These methods from the literature include Newtonian baseline (NBL), dynamic baseline (DBL), and logarithmic relative temperature baseline (LRTBL), which produced unreliable results for the latent heat values of four types of pure metals (aluminum, lead, tin, and zinc). The most significant restrictions of NTA were determined as the effect of mold’s thermal capacity and variations in the data analysis process. A new model, which was named “two-capacitive system baseline (TCSBL)”, was developed in order to take thermal capacity of the mold into account. This model also includes the radiative contributions and other temperature dependent effects by considering Taylor expansion approach. At the end of the application of the model to several experiments, it was seen that TCSBL is the most reliable model among other models in the literature.