Three-dimensional simulation and analysis for heat transfer and flow field on micro-floating zoneof LHPG with asymmetrical perturbation

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题名:	Three-dimensional simulation and analysis for heat transfer and flow field on micro-floating zoneof LHPG with asymmetrical perturbation
作者:	陳平夷;Chen, Peng-Yi;羅家堯;Lo, Chia-Yao;黃恩萍;Huang, En-Ping
贡献者:	民生學院
日期:	2012
上传时间:	2013-09-18T08:05:31Z (UTC)
摘要:	In symmetrical conditions, micro-floating zone showed symmetrical double eddy flow fielddistribution. However when perturbation increases, the double eddy flow field will be symmetrical tothe tilt, and finally presents an unstable flow field vibration. Our purpose is to study the influence of molten zone on shape (vapor-liquid and solid-liquid interfaces) and internal heat flow field caused bythe tilts of CO2 laser heating ring and gravity field with space asymmetrical to the molten zone when the source rod and seed had slight deviation to the growth axis of LHPG system. The asymmetricalsystem frame of three-dimensional simulation is to add the conditions of diameter reduction ratio and laser heating, and modify Lan'sthermocapillary floating numerical mode. In order to enhance the degree of simulation and presentation of a more realistic physical meaning we have completed thecomparison of molten zone shape between the simulation and the experiment. The simulation resultshowed that the double eddy flow field present tilt in x-y plane at z=0. In addition, the flow field vector and equipotential lines of the vertical and horizontal flow field velocities are no longer symmetry at thecentral axial of the molten zone. The flow field mainly affected by the laser heating ring deviation and the influence decrease with the source rod scale and diameter reduction ratio reducing under settingthe deviation parameters of laser heating and gravity field. The influence of gravity to the flow field is extremely not obvious. We also simulate the growth axis and the gravity field perpendicular to eachother under 1000- -diameter source rod. When the surface tension is lowered (~ 500 dyn cm-1) vapor-liquid interface drooped in the direction of gravity field, leading to tilt in the solid-liquidinterface. At this point the appropriate heating ring with reverse angle compensation will enable the solid-liquid interface to maintain symmetry, and help us to develop LHPG crystal fiber growth withgood crystal quality along horizontal direction.
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