On the Newtonian Thermal Analysis of Casting: a Critical Aproach

Öz

One of the primary aims of Newtonian thermal analysis (NTA) is the prediction of latent heat and finding solid fraction. When the prediction is made, Newtonian baseline (NBL) is computed, and the difference to experimental cooling rate curve is analyzed. In this study, it was seen that NBL calculations had some contradictions and that latent heat calculations gave high errors. After determining these contradictions, a new method, called one-capacitive-system baseline (OCSBL), was developed by gathering the solution advises to each other. Cooling curve of mold-insulated pure Tin was analyzed by both methods to test them. It was seen that OCSBL predicted the latent heat better than NBL when the results were compared with the literal values.

Anahtar Kelimeler

• Newtonian thermal analysis, solid fraction, latent heat

METAL DÖKÜMLERİNİN NEWTON SALISI ANALİZİ ÜZERİNE: ELEŞTİREL BİR YAKLAŞIM

Öz

Döküm için Newtonsal ısı analizinin başlıca amaçları arasında ergime ısısı tahmini ve katı kesrinin bulunması gelmektedir. Bu tahmin yapılırken Newton taban eğrisi (NTE) hesaplanıp deneysel soğuma eğrisi arasındaki fark analiz edilmektedir. Bu çalışmada, Newton taban eğrisi hesaplamanın bazı çelişkileri barındırdığı ve ergime ısısı hesaplarının yüksek hatalar verdiği görüldü. Bu çelişkiler tespit edildikten sonra, her birine getirilen çözüm önerileri derlenerek, tekli-kapasitif-sistem taban eğrisi (TKSTE) adında yeni bir yöntem geliştirildi. İki yöntemi test etmek için, kaptan yalıtılmış saf kalayın soğuma eğrisi iki yöntemle de analiz edildi. Sonuçlar literatürdeki termal değerler ile kıyaslandığında, TKSTE nin NTE den daha iyi ergime ısısı tahmin ettiği görüldü.

Anahtar Kelimeler

• Termal Analiz, Ergime Isısı, Katı Kesri

Kaynakça

1. K. C. Erbaş. Suggestion of a new model for Newtonian thermal analysis of solidification. PhD Thesis, METU (2013), pp. 49-71.
2. U. Ekpoom and R. W. Heine. Thermal analysis by differential heat analysis (DHA) of cast iron. AFS Trans., Vol. 85, (1981), pp. 27-38
3. C. O’Sullivan. A simple experiment to study cooling by convection and radiation. Department of Physics, National University of Ireland Cork, (2006).
4. P. Marchwica, J.H. Sokolowski and W.T. Kierkus. Fraction solid evolution characteristics of AlSiCu alloys - dynamic baseline approach. Journal of Achievements in Materials and Manufacturing Engineering. Vol. 47, (2011), p.116
5. A. Çetin. Assessment and modelling of particle clustering in cast aluminum matrix composites. PhD Thesis, METU (2008), pp. 13-19
6. L. S. Chao and W. C. Wu. Macro-micro modeling of solidification. Proc. Natl. Counc. ROC (A), Vol. 23, (1999), pp. 622-629
7. D. Emadi, V. Whiting, M. Djurdjevic, Witold T. Kierkus and J. Sokolowski. Comparison of newtonian and fourier thermal analysis techniques for calculation of latent heat and solid fraction of aluminum alloys. Association of metallurgical engineers serbia and montenegro scientific paper. (2004), pp. 91-106.
8. L. A. Dombrovsky and T.N. Dinh. The effect of thermal radiation on the solidification dynamics of metal oxide melt droplets. Nuclear Engineering and Design 238, (2008), pp. 1421–1429.

9. F. Lau, W.B. Lee, S.M. Xiong and B.C. Liu. A study of the interfacial heat transfer between an iron casting and a metallic mould. Journal of Materials Processing Technology 79, (1998), pp. 25–29.
10. J. N. Silva, D. J. Moutinhoa, A. L. Moreirab, I.L. Ferreirac and O.L. Rochaa. Determination of heat transfer coefficients at metal–mold interface during horizontal unsteady-state directional solidification of Sn–Pb alloys. Materials Chemistry and Physics, 130, (2011), pp. 179– 185.
11. W. E. Boyce and R.C. Diprima. Elementary Differential Equations and Boundary Value Problems. 7th ed., Wiley, New York, (2001)
12. R. H. Perry, and D. W. Green. Perry's Chemical Engineers' Handbook. 7th ed. McGrawHill, New York (1999), section 2.