{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/109474"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/109474","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Natural convection of molten salt in laterally heated and top cooled vertical cylinders","abstract":"Molten salt reactors offer a promising reactor technology with higher efficiency, lower pumping power and increased power density. Due to the lower operating pressures, high heat capacities, and the ability to transfer heat through natural circulation, they are especially suitable for passive safety. Unlike the common reactor designs with fuel in the form of solid pellets, molten salt reactors use a liquid fuel form where the fissile materials are dissolved in the molten salt. Natural circulation characteristics within the molten salt FLiNaK (Prandtl number = 16) in a vertical three-dimensional cylindrical geometry are numerically studied. The cylinder is laterally heated with an isothermal cooling at the top and an insulated bottom. The effect of the Rayleigh number is investigated for different aspect ratios (0.5, 1.0, 1.5, 2.0) for a total of nine cases. The spectral element method with high polynomial resolution is used to perform the simulations, using the open-source code Nek5000. The different flow patterns and temperature distributions observed for the nine cases are documented. Validation of the results obtained is done by performing a grid-independent study to ensure all the length scales have been captured appropriately. Spatial variation of azimuthally-averaged Nusselt number is presented across height for the steady state cases. Results show a departure from axisymmetry for higher aspect ratios in the steady cases. For the cases where the flow becomes unsteady, the nature of the flow is characterized by using Fast Fourier Transform on the time evolution of axial velocity. Temporal variation of the average Nusselt number of the configuration is also presented for the unsteady cases.","abstract_html":"Molten salt reactors offer a promising reactor technology with higher efficiency, lower pumping power and increased power density. Due to the lower operating pressures, high heat capacities, and the ability to transfer heat through natural circulation, they are especially suitable for passive safety. Unlike the common reactor designs with fuel in the form of solid pellets, molten salt reactors use a liquid fuel form where the fissile materials are dissolved in the molten salt. Natural circulation characteristics within the molten salt FLiNaK (Prandtl number = 16) in a vertical three-dimensional cylindrical geometry are numerically studied. The cylinder is laterally heated with an isothermal cooling at the top and an insulated bottom. The effect of the Rayleigh number is investigated for different aspect ratios (0.5, 1.0, 1.5, 2.0) for a total of nine cases. The spectral element method with high polynomial resolution is used to perform the simulations, using the open-source code Nek5000. The different flow patterns and temperature distributions observed for the nine cases are documented. Validation of the results obtained is done by performing a grid-independent study to ensure all the length scales have been captured appropriately. Spatial variation of azimuthally-averaged Nusselt number is presented across height for the steady state cases. Results show a departure from axisymmetry for higher aspect ratios in the steady cases. For the cases where the flow becomes unsteady, the nature of the flow is characterized by using Fast Fourier Transform on the time evolution of axial velocity. Temporal variation of the average Nusselt number of the configuration is also presented for the unsteady cases.","abstract_has_math":false,"creators":["Khattak, Divyansh"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"M.S.","degree_level":"Thesis","degree_discipline":"Mechanical Engineering","degree_department":null,"school":null,"contributors":["Brooks, Caleb S.","Vanka, Surya P."],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2021,"date_issued":"2021-03-05T21:40:34Z","date_published":"2021-03-05T21:40:34Z","updated_at":"2026-07-22T22:24:50Z","subjects":["Natural circulation","spectral element method","lateral heating"],"languages":["en"],"rights":["Copyright 2020 Divyansh Khattak"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/109474","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Brooks, Caleb S.","Vanka, Surya P."]},{"key":"dc:creator","label":"Author","values":["Khattak, Divyansh"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2021-03-05T21:40:34Z","2023-03-05T21:43:00Z","2020-09-18","2020-12"]},{"key":"dc:type","label":"Dc Type","values":["text","Thesis"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Mechanical Engineering"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Thesis"]},{"key":"thesis:degree_name","label":"Degree Name","values":["M.S."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Natural circulation","spectral element method","lateral heating"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2020 Divyansh Khattak"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/109474"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Molten salt reactors offer a promising reactor technology with higher efficiency, lower pumping power and increased power density. Due to the lower operating pressures, high heat capacities, and the ability to transfer heat through natural circulation, they are especially suitable for passive safety. Unlike the common reactor designs with fuel in the form of solid pellets, molten salt reactors use a liquid fuel form where the fissile materials are dissolved in the molten salt. Natural circulation characteristics within the molten salt FLiNaK (Prandtl number = 16) in a vertical three-dimensional cylindrical geometry are numerically studied. The cylinder is laterally heated with an isothermal cooling at the top and an insulated bottom. The effect of the Rayleigh number is investigated for different aspect ratios (0.5, 1.0, 1.5, 2.0) for a total of nine cases. The spectral element method with high polynomial resolution is used to perform the simulations, using the open-source code Nek5000. The different flow patterns and temperature distributions observed for the nine cases are documented. Validation of the results obtained is done by performing a grid-independent study to ensure all the length scales have been captured appropriately. Spatial variation of azimuthally-averaged Nusselt number is presented across height for the steady state cases. Results show a departure from axisymmetry for higher aspect ratios in the steady cases. For the cases where the flow becomes unsteady, the nature of the flow is characterized by using Fast Fourier Transform on the time evolution of axial velocity. Temporal variation of the average Nusselt number of the configuration is also presented for the unsteady cases.","Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2022-12-01","The student, Divyansh Khattak, accepted the attached license on 2020-09-14 at 17:39.","The student, Divyansh Khattak, submitted this Thesis for approval on 2020-09-14 at 17:50.","This Thesis was approved for publication on 2020-09-18 at 16:47.","DSpace SAF Submission Ingestion Package generated from Vireo submission #15811 on 2021-03-04 at 16:18:47","Made available in DSpace on 2021-03-05T21:40:34Z (GMT). No. of bitstreams: 2 KHATTAK-THESIS-2020.pdf: 5329200 bytes, checksum: f3e00504c3c0b9cf771f4fa21cda9221 (MD5) LICENSE.txt: 4213 bytes, checksum: e0109c8fcfa3558db36f6ce3796a9c1d (MD5) Previous issue date: 2020-09-18","Embargo set by: Seth Robbins for item 117178 Lift date: 2023-03-05T21:40:52Z Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD system","Embargo set by: Seth Robbins for item 117178 Lift date: 2023-03-05T21:43:00Z Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD system","Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD system","U of I Only"]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Natural convection of molten salt in laterally heated and top cooled vertical cylinders"]}]}],"canonical_facts":{"dc:contributor":["Brooks, Caleb S.","Vanka, Surya P."],"dc:creator":["Khattak, Divyansh"],"dc:date":["2021-03-05T21:40:34Z","2023-03-05T21:43:00Z","2020-09-18","2020-12"],"dc:description":["Molten salt reactors offer a promising reactor technology with higher efficiency, lower pumping power and increased power density. Due to the lower operating pressures, high heat capacities, and the ability to transfer heat through natural circulation, they are especially suitable for passive safety. Unlike the common reactor designs with fuel in the form of solid pellets, molten salt reactors use a liquid fuel form where the fissile materials are dissolved in the molten salt. Natural circulation characteristics within the molten salt FLiNaK (Prandtl number = 16) in a vertical three-dimensional cylindrical geometry are numerically studied. The cylinder is laterally heated with an isothermal cooling at the top and an insulated bottom. The effect of the Rayleigh number is investigated for different aspect ratios (0.5, 1.0, 1.5, 2.0) for a total of nine cases. The spectral element method with high polynomial resolution is used to perform the simulations, using the open-source code Nek5000. The different flow patterns and temperature distributions observed for the nine cases are documented. Validation of the results obtained is done by performing a grid-independent study to ensure all the length scales have been captured appropriately. Spatial variation of azimuthally-averaged Nusselt number is presented across height for the steady state cases. Results show a departure from axisymmetry for higher aspect ratios in the steady cases. For the cases where the flow becomes unsteady, the nature of the flow is characterized by using Fast Fourier Transform on the time evolution of axial velocity. Temporal variation of the average Nusselt number of the configuration is also presented for the unsteady cases.","Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2022-12-01","The student, Divyansh Khattak, accepted the attached license on 2020-09-14 at 17:39.","The student, Divyansh Khattak, submitted this Thesis for approval on 2020-09-14 at 17:50.","This Thesis was approved for publication on 2020-09-18 at 16:47.","DSpace SAF Submission Ingestion Package generated from Vireo submission #15811 on 2021-03-04 at 16:18:47","Made available in DSpace on 2021-03-05T21:40:34Z (GMT). No. of bitstreams: 2 KHATTAK-THESIS-2020.pdf: 5329200 bytes, checksum: f3e00504c3c0b9cf771f4fa21cda9221 (MD5) LICENSE.txt: 4213 bytes, checksum: e0109c8fcfa3558db36f6ce3796a9c1d (MD5) Previous issue date: 2020-09-18","Embargo set by: Seth Robbins for item 117178 Lift date: 2023-03-05T21:40:52Z Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD system","Embargo set by: Seth Robbins for item 117178 Lift date: 2023-03-05T21:43:00Z Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD system","Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD system","U of I Only"],"dc:format":["application/pdf"],"dc:identifier":["http://hdl.handle.net/2142/109474"],"dc:language":["en"],"dc:rights":["Copyright 2020 Divyansh Khattak"],"dc:subject":["Natural circulation","spectral element method","lateral heating"],"dc:title":["Natural convection of molten salt in laterally heated and top cooled vertical cylinders"],"dc:type":["text","Thesis"],"thesis:degree_discipline":["Mechanical Engineering"],"thesis:degree_level":["Thesis"],"thesis:degree_name":["M.S."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:24:50Z"}