{"id":{"repo_id":"ohiolink","oai_identifier":"oai:etd.ohiolink.edu:akron1366033161"},"canonical_url":"https://search.dev.ndltd.org/etd/ohiolink/oai:etd.ohiolink.edu:akron1366033161","repository":{"repo_id":"ohiolink","name":"OhioLINK","base_url":"https://etd.ohiolink.edu/acprod/odb_etd/ws/oai/oai"},"display":{"title":"Numerical Simulation and Experimental Validation of Fluid Flow and Mass Transfer in an Ammonothermal Crystal Growth Reactor","abstract":"Due to their physical properties, gallium nitride crystals are in high demand in applications including light emitting diodes, high power and high frequency devices. One way of growing the crystals is the ammonothermal growth process. The process consists of chemical reactions occurring in reactors under high temperature and high pressure conditions. A basket of gallium nitride nutrient is inserted inside the reactor filled with ammonia and a mineralizer, whereupon gallium nitride is dissolved and transported by natural convection and then deposited onto the seeds. Because the etching and deposition reactions require temperatures in the range of 600 to 1,000 K (620 to 1,340 °F) and pressures in the range of 1,000 to 6,000 bar (14,504 to 87,022 psi), it is impossible to visualize the flow or measure its parameters.This dissertation presents a way to look inside an ammonothermal crystal growth reactor by simulating the process using CFD software. An equivalent reactor and crystal growth environment are created to provide experimental validation. The equivalent reactor respects geometric and dynamic similitude with respect to the actual ammonothermal crystal growth reactor. Experimental temperatures and velocities are recorded and compared with numerical results. Three turbulence models and the laminar model were tested. The laminar and the standard k-omega models performed better compared with experimental results. By simulating an equivalent reactor that allows visualization and measurements, the CFD model was validated.With the validated model, simulations of the actual growth process including mass transfer were performed. The wall temperature profile, the geometry of the nutrient basket, and the baffle were used as parameters to investigate their influence on the deposition rates. The temperatures on the outer walls of the reactor have a great influence on the deposition rate and can lead to etching of the seeds instead of crystal growing. The presence of a baffle inside the reactor also has a great influence on the deposition rates, and the need to find an optimal configurations became obvious. The geometry and the nature of the nutrient basket proved to be a great parameter to improve the deposition rates.","abstract_html":"Due to their physical properties, gallium nitride crystals are in high demand in applications including light emitting diodes, high power and high frequency devices. One way of growing the crystals is the ammonothermal growth process. The process consists of chemical reactions occurring in reactors under high temperature and high pressure conditions. A basket of gallium nitride nutrient is inserted inside the reactor filled with ammonia and a mineralizer, whereupon gallium nitride is dissolved and transported by natural convection and then deposited onto the seeds. Because the etching and deposition reactions require temperatures in the range of 600 to 1,000 K (620 to 1,340 °F) and pressures in the range of 1,000 to 6,000 bar (14,504 to 87,022 psi), it is impossible to visualize the flow or measure its parameters.This dissertation presents a way to look inside an ammonothermal crystal growth reactor by simulating the process using CFD software. An equivalent reactor and crystal growth environment are created to provide experimental validation. The equivalent reactor respects geometric and dynamic similitude with respect to the actual ammonothermal crystal growth reactor. Experimental temperatures and velocities are recorded and compared with numerical results. Three turbulence models and the laminar model were tested. The laminar and the standard k-omega models performed better compared with experimental results. By simulating an equivalent reactor that allows visualization and measurements, the CFD model was validated.With the validated model, simulations of the actual growth process including mass transfer were performed. The wall temperature profile, the geometry of the nutrient basket, and the baffle were used as parameters to investigate their influence on the deposition rates. The temperatures on the outer walls of the reactor have a great influence on the deposition rate and can lead to etching of the seeds instead of crystal growing. The presence of a baffle inside the reactor also has a great influence on the deposition rates, and the need to find an optimal configurations became obvious. The geometry and the nature of the nutrient basket proved to be a great parameter to improve the deposition rates.","abstract_has_math":false,"creators":["Moldovan, Stefan Ilie"],"institution":"University of Akron","degree_name":"Doctor of Philosophy","degree_level":"doctoral","degree_discipline":"Mechanical Engineering","degree_department":null,"school":null,"contributors":["Braun, Minel","Chandy, Abhilash"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2013,"date_issued":"2013-05-09","date_published":"2013-05-09","updated_at":"2026-07-24T03:37:46Z","subjects":["Mechanical Engineering","Ammonothermal crystal growth","natural convection inside cylindrical enclosures","surface reactions","reactions in porous medium","flow in porous medium","turbulent natural convection flow","unsteady laminar flow."],"languages":["English"],"rights":["unrestricted","This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws."],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://rave.ohiolink.edu/etdc/view?acc_num=akron1366033161","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Braun, Minel","Chandy, Abhilash"]},{"key":"dc:creator","label":"Author","values":["Moldovan, Stefan Ilie"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2013-05-09"]},{"key":"dc:publisher","label":"Institution","values":["University of Akron / OhioLINK"]},{"key":"dc:type","label":"Dc Type","values":["Electronic Thesis or Dissertation"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Mechanical Engineering"]},{"key":"thesis:degree_level","label":"Degree Level","values":["doctoral"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Doctor of Philosophy"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Akron"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Mechanical Engineering","Ammonothermal crystal growth","natural convection inside cylindrical enclosures","surface reactions","reactions in porous medium","flow in porous medium","turbulent natural convection flow","unsteady laminar flow."]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["English"]},{"key":"dc:rights","label":"Dc Rights","values":["unrestricted","This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws."]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://rave.ohiolink.edu/etdc/view?acc_num=akron1366033161"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Due to their physical properties, gallium nitride crystals are in high demand in applications including light emitting diodes, high power and high frequency devices. One way of growing the crystals is the ammonothermal growth process. The process consists of chemical reactions occurring in reactors under high temperature and high pressure conditions. A basket of gallium nitride nutrient is inserted inside the reactor filled with ammonia and a mineralizer, whereupon gallium nitride is dissolved and transported by natural convection and then deposited onto the seeds. Because the etching and deposition reactions require temperatures in the range of 600 to 1,000 K (620 to 1,340 °F) and pressures in the range of 1,000 to 6,000 bar (14,504 to 87,022 psi), it is impossible to visualize the flow or measure its parameters.This dissertation presents a way to look inside an ammonothermal crystal growth reactor by simulating the process using CFD software. An equivalent reactor and crystal growth environment are created to provide experimental validation. The equivalent reactor respects geometric and dynamic similitude with respect to the actual ammonothermal crystal growth reactor. Experimental temperatures and velocities are recorded and compared with numerical results. Three turbulence models and the laminar model were tested. The laminar and the standard k-omega models performed better compared with experimental results. By simulating an equivalent reactor that allows visualization and measurements, the CFD model was validated.With the validated model, simulations of the actual growth process including mass transfer were performed. The wall temperature profile, the geometry of the nutrient basket, and the baffle were used as parameters to investigate their influence on the deposition rates. The temperatures on the outer walls of the reactor have a great influence on the deposition rate and can lead to etching of the seeds instead of crystal growing. The presence of a baffle inside the reactor also has a great influence on the deposition rates, and the need to find an optimal configurations became obvious. The geometry and the nature of the nutrient basket proved to be a great parameter to improve the deposition rates."]},{"key":"dc:format","label":"Dc Format","values":["application/pdf","p.355","13.84 MB"]},{"key":"dc:title","label":"Title","values":["Numerical Simulation and Experimental Validation of Fluid Flow and Mass Transfer in an Ammonothermal Crystal Growth Reactor"]}]}],"canonical_facts":{"dc:contributor":["Braun, Minel","Chandy, Abhilash"],"dc:creator":["Moldovan, Stefan Ilie"],"dc:date":["2013-05-09"],"dc:description":["Due to their physical properties, gallium nitride crystals are in high demand in applications including light emitting diodes, high power and high frequency devices. One way of growing the crystals is the ammonothermal growth process. The process consists of chemical reactions occurring in reactors under high temperature and high pressure conditions. A basket of gallium nitride nutrient is inserted inside the reactor filled with ammonia and a mineralizer, whereupon gallium nitride is dissolved and transported by natural convection and then deposited onto the seeds. Because the etching and deposition reactions require temperatures in the range of 600 to 1,000 K (620 to 1,340 °F) and pressures in the range of 1,000 to 6,000 bar (14,504 to 87,022 psi), it is impossible to visualize the flow or measure its parameters.This dissertation presents a way to look inside an ammonothermal crystal growth reactor by simulating the process using CFD software. An equivalent reactor and crystal growth environment are created to provide experimental validation. The equivalent reactor respects geometric and dynamic similitude with respect to the actual ammonothermal crystal growth reactor. Experimental temperatures and velocities are recorded and compared with numerical results. Three turbulence models and the laminar model were tested. The laminar and the standard k-omega models performed better compared with experimental results. By simulating an equivalent reactor that allows visualization and measurements, the CFD model was validated.With the validated model, simulations of the actual growth process including mass transfer were performed. The wall temperature profile, the geometry of the nutrient basket, and the baffle were used as parameters to investigate their influence on the deposition rates. The temperatures on the outer walls of the reactor have a great influence on the deposition rate and can lead to etching of the seeds instead of crystal growing. The presence of a baffle inside the reactor also has a great influence on the deposition rates, and the need to find an optimal configurations became obvious. The geometry and the nature of the nutrient basket proved to be a great parameter to improve the deposition rates."],"dc:format":["application/pdf","p.355","13.84 MB"],"dc:identifier":["http://rave.ohiolink.edu/etdc/view?acc_num=akron1366033161"],"dc:language":["English"],"dc:publisher":["University of Akron / OhioLINK"],"dc:rights":["unrestricted","This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws."],"dc:subject":["Mechanical Engineering","Ammonothermal crystal growth","natural convection inside cylindrical enclosures","surface reactions","reactions in porous medium","flow in porous medium","turbulent natural convection flow","unsteady laminar flow."],"dc:title":["Numerical Simulation and Experimental Validation of Fluid Flow and Mass Transfer in an Ammonothermal Crystal Growth Reactor"],"dc:type":["Electronic Thesis or Dissertation"],"thesis:degree_discipline":["Mechanical Engineering"],"thesis:degree_level":["doctoral"],"thesis:degree_name":["Doctor of Philosophy"],"thesis:institution_name":["University of Akron"]},"updated_at":"2026-07-24T03:37:46Z"}