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Proceedings of CHT-12. ICHMT International Symposium on Advances in Computational Heat Transfer.
July, 1-6, 2012, Bath, England

DOI: 10.1615/ICHMT.2012.CHT-12


ISBN: 978-1-56700-303-1

ISSN: 2578-5486

COMPLEX HEAT TRANSFER AT DIRECTED CRYSTALLIZATION OF SEMITRANSPARENT MATERIALS

pages 755-770
DOI: 10.1615/ICHMT.2012.CHT-12.470
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RÉSUMÉ

The present paper deals with use of numerical simulation of complex heat transfer at semitransparent crystal growth. The sensibility of thermal regimes at crystal-melt system to a number of inner of outer process parameters was explored. This allows justification of several possible simplifying approaches at development of numerical models of crystal growth furnaces, including on-line models for operative control of growth process.
For this research a numerical model of radiation-convective and radiation-conductive heat transfer was developed with commercially available CFD software. Several advanced features of the model, such as dynamic evolution of the semitransparent crystallization front, were realized by implementation of user-defined functions. The 2D axisymmetric model is limited geometrically to cylindrical crystal-melt system since heat regimes and temperature gradients in the area near crystallization front are the most important.
We examine the combined effect of radiation, convective and conductive heat transfer mechanisms on the formation of temperature fields and heat flows, position and shape of the crystallization front, and distribution of temperature gradients in the crystal-melt system. Numerical simulations are carried out for the oxide and alkali-halide classes of semitransparent materials at different growth conditions, considering selectivity of their absorptivity. Analysis of the results allowed developing the recommendations for approximation the effects of radiation and convection heat transfer and their interaction.

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