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Second Thermal and Fluids Engineering  Conference

ISSN: 2379-1748
ISBN: 978-1-56700-430-4

THREE-DIMENSIONAL LARGE EDDY SIMULATIONS OF NATURAL CONVECTION IN LATERALLY HEATED CYLINDRICAL ENCLOSURES WITH RACKS AND SEEDS FOR CRYSTAL GROWTH

Hooman Enayati
University of Akron

Abhilash J. Chandy
Department of Mechanical Engineering, The University of Akron, Akron, Ohio, 44325

Minel J. Braun
Department of Mechanical Engineering, University of Akron, Akron, OH 44325

Abstract

Gallium Nitride (GaN) crystals are widely used in electronic devices such as light emitting diodes (LEDs) or UV detectors. In one of the most effective techniques for growing high-quality GaN crystals, the Ammonothermal crystal growth method, GaN crystals in the nutrient basket are dissolved in the dissolution zone of the autoclave. By virtue of natural convection, the crystals are then transported to the crystallization zone where GaN crystals can be crystalized. The process of crystallization happens on the native seeds that are located in the crystallization zone, and these seeds are mounted on racks within the enclosure. The current study presents large eddy simulations (LES) of turbulent natural convection in a cylindrical enclosure heated laterally, conducted using the commercial CFD code ANSYS FLUENT. The Rayleigh number (Ra) for the numerical simulations, calculated based on a characteristics length scale that is the ratio of volume to its lateral area (R/2) is given by Ra = 8.8×106. Simulations are carried out for three different reactors: one that is empty, another with a rack inside, and the third with a rack and 40 seeds mounted on it. The main objective of these calculations is to understand the effects of the rack and the seeds on the flow patterns and thermal maps inside the reactor. The observations are crucial, as they influence our understanding of the rates of the deposition and etching of GaN crystals inside the reactor. A comprehensive analysis of velocity and temperature across various planes are analyzed, and will be presented.

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