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首页> 外文会议>ASME international mechanical engineering congress and exposition >Modeling of fluid flow and heat transfer in a hydrothermal crystal growth system: Usr of fluid-superposed porous layer theory
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Modeling of fluid flow and heat transfer in a hydrothermal crystal growth system: Usr of fluid-superposed porous layer theory

机译：水热晶体生长系统中流体流动和热传递的建模：流体叠加多孔层理论的USR

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Hydrothermal synthesis, which uses aqueous solvents under high pressure and relatively low temperature, is an important technique for the growth of crystalline materials such as quartz, bismuth silicate and various kinds of oxides all of which are difficult to grow. A hydrothermal growth system usually consists of finely divided particles of the nutrient, predetermined volume of a solvent and a suitably oriented crystal seed (Fig. 1) under very high pressures, generally several thousand psi. Thenutrient dissolves at a higher temperature in the lower region, moves to the upper region due to buoyancy-induced convective flows and deposits on the seed due to lower solubility if the seed region is maintained at a lower temperature. The system can bemodeled as a composite fluid and porous layer using the Darcy-Brinkman-Forchheimer flow model in the porous bed. Since the growth process is very slow, the process can be considered quasi-steady and the effect of dissolution and growth can be neglected.This first study on transport phenomena in a hydrothermal system therefore focuses on the flow and temperature fields without the presence of the seed and mass transfer. A three-dimensional algorithm based on the curvilinear finite volume technique and anon-staggered grid layout has been developed to simulate the flow and heat transfer in a typical autoclave system. An axisymmetric flow pattern at low Grashof numbers and three dimensional flow pattern at high Grashof numbers are predicted. The study isalso extended to study the onset of oscillatory flow with a variation in the porous bed height. These results, for the first time, depict the possible flow patterns in a hydrothermal system, that can have far reaching consequences on the growth processand crystal quality.
机译：在高压和相对低温下使用含水溶剂的水热合成是用于生长晶体材料的重要技术，例如石英，铋硅酸盐和各种氧化物难以生长。水热生长系统通常由营养素的细碎颗粒组成，溶剂的预定体积和适当化的晶体种子（图1）在非常高的压力下，通常是几千psi。当种子区域保持在较低温度下，在下部区域的较高温度下溶解于下部区域的较高温度下，由于较低的溶解度，由于较低的溶解度，在种子上沉积在种子上，沉积物。使用多孔床中的Darcy-Brinkman-Forchheimer流程模型，该系统可以作为复合流体和多孔层。由于生长过程非常缓慢，因此可以被认为可以被认为是准稳态的，并且可以忽略溶解和生长的效果。这首先研究了水热系统中的运输现象，因此在没有存在的情况下聚焦在流动和温度场上种子和传质。已经开发了一种基于曲线有限体积技术和ANON交错电网布局的三维算法，用于模拟典型的高压灭菌系统中的流量和传热。预测了在高格雷什数下的低格雷什数和三维流动模式下的轴对称流动模式。研究中的研究延伸以研究振荡流动的发作，在多孔床高度的变化下变化。这些结果首次描绘了水热系统中可能的流动模式，这可能对生长处理和晶体质量具有深远的影响。

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