Heat and Impurity Transfer Mechanisms of Czochralski and Directional Solidification Processes

2019 ◽  
Vol 18 (1) ◽  
pp. 925-933 ◽  
Author(s):  
Koichi Kakimoto ◽  
Xuejiang Chen ◽  
L. J. Liu ◽  
H. Miyazawa ◽  
Hitoshi Matsuo ◽  
...  
Keyword(s):  
Directional Solidification ◽  
Impurity Transfer ◽  
Solidification Processes ◽  
Transfer Mechanisms

Application of the Meshless Element-Free Galerkin Method to Freckle Formation in Directional Solidification

2009 ◽  
Author(s):  
Udaya K. Sajja ◽  
Sergio D. Felicelli
Keyword(s):  
Finite Element ◽  
Directional Solidification ◽  
Turbine Blades ◽  
Solidification Process ◽  
Solute Concentration ◽  
Momentum Equation ◽  
Thermosolutal Convection ◽  
Element Free Galerkin ◽  
Solidification Processes ◽  
Element Free

Freckles or channel segregates are the most severe form of the macrosegregation that can occur in unidirectionally solidified superalloy castings used in the manufacturing of gas turbine blades. These defects are formed due to thermosolutal convection during solidification. Mathematical modeling of the solidification process involves the simultaneous solution of the conservation equations of momentum, energy and solute concentration in all regions (liquid, mush and solid). Most numerical simulations of dendritic solidification processes have been performed using finite element or the finite volume techniques. The dependence of these methods on the mesh is not always advantageous for problems in which discontinuities or regions of sharp gradients do not coincide with the original mesh lines. In the present work, the meshless element free Galerkin (EFG) method has been investigated to simulate directional solidification processes in which sharp gradients in the field variables can occur as a result of the formation of channels. Simulations of a multicomponent Ni-Al-Ta-W alloy have been performed in a two dimensional domain. The calculations are started with the alloy in all-liquid state and the growth of the mushy zone is followed in time. A projection method is used to solve the momentum equation which makes the computation more efficient than the previously used penalty method. The accuracy of the EFG results is compared with that of the finite element calculations and the potential advantages of the meshless methods for this type of problems are discussed.

Complex banded structures in directional solidification processes

2015 ◽  
Vol 28 (3) ◽  
pp. 035001
Author(s):  
A L Korzhenevskii ◽  
R E Rozas ◽  
J Horbach
Keyword(s):  
Directional Solidification ◽  
Solidification Processes

Effects of Geometrical Parameters in the DS Method for the Growth of Large Sized Polycrystal Silicon

2007 ◽  
Author(s):  
Jung-Hoon Hwang ◽  
Youn-Jea Kim ◽  
Joong-Won Shur ◽  
Dae-Ho Yoon
Keyword(s):  
Directional Solidification ◽  
Polycrystalline Silicon ◽  
Crystalline Silicon ◽  
Thermal Characteristics ◽  
Geometrical Parameters ◽  
Dynamics Model ◽  
Heat Transfer Characteristics ◽  
Short Cycle ◽  
Market Growth ◽  
Solidification Processes

Polycrystalline silicon (Si) wafers share more than 60% of the photovoltaic market due to its cost advantage compared to the mono-crystalline silicon wafers. Several solidification processes have been developed by industries, including casting, heat exchanger method and electromagnetic casting. However, the market growth using mono- and polycrystalline Si wafers might be saturated due to the shortage of Si feedstock. One of the methods to solve this issue is to make higher quality polycrystalline Si wafers which are capable of producing higher efficiency solar cells. In this work, the effects of changing several geometrical parameters were evaluated to improve the directional solidification (DS) method and to satisfy the above-mentioned main targets. The developed DS method has the advantages of the small heat loss, short cycle time and efficient directional solidification. Based on the fluid dynamics model, the numerical simulation was performed on the thermal characteristics during the DS process. Using a commercial CFD code, Fluent, the heat transfer characteristics in the DS system are calculated, and the results are graphically depicted.

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