GOALI: Fluid Dynamics, Heat Transfer, and Crystal Growth in Solvothermal Reactors: Modeling, Scaling, and Validation

CBET-1336700PI：Chandy这个产学研合作项目将开发并实验验证一个基于计算流体动力学(CFD)的超临界流体中晶体生长模型，目标是：(I)创建一个集成的预测热流体-质量传递方法和工具，用于晶体生长建模，以及(Ii)演示并应用该工具优化氮化镓(GaN)单晶生长的氨热工艺，为将原型和小型反应器放大到批量生产工艺和能力奠定基础。将考虑三个关键领域：晶体生长数值模型、设备放大和强化传质的反应器优化。虽然过去已经对水热和氨热晶体生长过程进行了几次CFD模拟，但它们涉及到限制性的、简化的假设、极其粗糙的晶体生长模型，并且没有得到实验验证。这项研究不仅建议创建一个更现实的增长模型，最重要的是它打算通过实验来验证它。就像在许多混合的数值/实验项目中一样，战略将是利用实验工作为建模提供更多的见解，同时查看数值工作来指导实验工作。这种方法将推进多尺度、多物理现象的模拟，从而晶体生长模型将受益于应用于自由对流环境的三维动量、能量和质量传递三维方程(而不是二维轴对称)的无缝集成。这项研究将首次提供：(A)在晶体种子和多孔养分的真实反应堆结构中联合考虑湍流、传热、质量刻蚀和沉积的溶剂热晶体生长的实验三维计算工具；(B)伴随着集成的多物理程序的实验验证；(C)利用实验工作建立流动和反应堆设计的几何和动态相似尺度的有效规则；以及(D)建立计算的瑞利数与在具有轴对称横向加热的圆柱形几何形状中实验观察到的流型类型之间的分配图。特别是，该模型将应用于具有侧向轴对称加热墙的封闭圆柱形封闭围护结构。这项研究将通过优化流动、传热和传质，自信地扩大大型资本密集型反应堆的工艺，降低氨热工艺反应堆的设计和建造成本，从而实现实质性的工艺开发。Soraa和其他可能的新进入者将从一种经过验证的预测和设计数字工具的可用性中受益匪浅。本课程开发的实验将构成为不同级别的学生举办的流体力学培训讲习班的基础，并有可能为与自由对流相关的其他应用提供一些有用的见解。以实验和模拟为中心的更广泛的影响和外联活动旨在通过加强研究和教育伙伴关系，增加阿克伦大学工程学研究生研究。从这项研究中获得的知识有望对超临界流体中的各种过程产生影响，包括纳米颗粒、沸石和新材料的合成以及废物的热解。

CBET-1336700PI: Chandy This industry-university collaborative project will develop and experimentally validate a computational fluid dynamics (CFD)-based model for crystal growth in supercritical fluids, with the goal of: (i) creating an integrated predictive thermofluid-mass transfer methodological approach and tool for crystal growth modeling, and (ii) demonstrating and applying the tools to optimization of an ammonothermal process for growth of single crystal gallium nitride (GaN), laying the groundwork for scale up of prototype and small scale reactors to a bulk manufacturing process and capability. Three critical areas will be considered: crystal growth numerical model, apparatus scale-up, and reactor optimization for enhanced mass transport. While several CFD simulations of hydrothermal and ammonothermal crystal growth processes have been conducted in the past, they have involved restrictive, simplified assumptions, extremely crude crystal growth models, and have not been validated experimentally. Not only does this research propose to create a more realistic growth model, but most importantly it intends to validate it experimentally. Like in many hybrid numerical/experimental undertakings, the strategy will be to use the experimental work for providing added insight for modeling while at the same time looking at the numerical work to guide the experimental work. This approach will advance a multi-scale, multi-physics phenomena modeling whereby the crystal growth model will benefit from seamless integration of 3-D momentum, energy and mass transfer 3-D equations (rather than 2-D axisymmetric) applied to a free convection environment. This research will for the first time, offer: (a) an experimentally 3-D computational tool for solvothermal crystal growth accounting jointly for turbulence, heat transfer, mass etching and deposition in a realistic reactor architecture of crystal seeds and porous nutrient; (b)concomitant experimental validation of the integrated multiphysics code (c) use experimental work to establish valid rules for geometric and dynamic similitude scaling for flows and reactor design; and (d) establish an assignment map between the calculated Rayleigh numbers and the types of flow regimes experimentally observed in cylindrical geometries with axisymmetric lateral heating.Fundamentally, the integrated experimental and numerical research will make a significant contribution to the general understanding of thermally driven fluid mechanics interacting with porous media as well as the associated surface reaction chemistry. In particular the model will be applied to closed cylindrical enclosures with laterally axisymmetric heated walls. The study will enable substantial process development through optimization of flow, heat and mass transfer, confident scale-up of processes in large, capital-intensive reactors, lower cost of design and construction of ammonothermal process reactors. SORAA and possibly other new entrants will stand to benefit significantly from the availability of a validated predictive and design numerical tool. The experiments developed in this program will form the basis of fluid mechanics training workshops for students at various levels with the added potential of providing some useful insights into other applications related to free convection. The broader impact and outreach activities that are centered on the experiments and simulations are aimed at increasing graduate research in Engineering at University of Akron, through enhancement of research and education partnerships. The knowledge gained from this study are expected to impact diverse processes in supercritical fluids, including synthesis of nanoparticles, zeolites, and novel materials and pyrolysis of waste materials.