{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/101554"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/101554","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Experimental study of flow boiling under subatmospheric pressures in a vertical square channel","abstract":"Experiments have been conducted in a vertical square channel to investigate wall nucleation characteristics and Critical Heat Flux (CHF) in subcooled boiling flows under subatmospheric pressure. Forced convection boiling is a widely used and effective means of heat transfer. An understanding of the mechanisms and limitations involved in forced convection boiling is important for the accurate prediction of the behavior of two phase systems under a wide range of conditions. The objective of this work is to provide a unique dataset to evaluate the scalability of existing models of nucleation characteristics and CHF for flow boiling conditions below atmospheric pressure as the performance of these models has not been investigated under these conditions. The experimental nucleation data are presented as a parametric study of the effects of important dimensionless groups on nucleation characteristics, specifically Boiling number, Jakob number, and density ratio. Bubble departure diameters and departure frequencies are measured via high-speed photography and compared to existing models. CHF data are presented as a parametric study of pressure from 20 kPa to 108 kPa, mass flux from 45 kg/m2s to 190 kg/m2s, and inlet subcooling from 0 to 10 K. Heat flux is gradually increased until an excursion of the wall temperature, signifying CHF, occurs. Several existing models that correlate departure characteristics with the relevant dimensionless groups enumerated above are found to accurately predict departure diameter and frequency. However, at the lowest pressure, departure diameters are of the same length scale as the channel so geometric effects may affect these departures. CHF is shown to vary directly with pressure but is only weakly affected by changes in mass flux and inlet subcooling for the observed conditions. Models of the Boiling number at CHF that incorporate the density ratio and Weber number are found to predict the experimental results well. A new correlation for CHF is developed that incorporates the characteristic bubble diameter into the Weber number and is found to predict CHF with an average error of ±15.62%.","abstract_html":"Experiments have been conducted in a vertical square channel to investigate wall nucleation characteristics and Critical Heat Flux (CHF) in subcooled boiling flows under subatmospheric pressure. Forced convection boiling is a widely used and effective means of heat transfer. An understanding of the mechanisms and limitations involved in forced convection boiling is important for the accurate prediction of the behavior of two phase systems under a wide range of conditions. The objective of this work is to provide a unique dataset to evaluate the scalability of existing models of nucleation characteristics and CHF for flow boiling conditions below atmospheric pressure as the performance of these models has not been investigated under these conditions. The experimental nucleation data are presented as a parametric study of the effects of important dimensionless groups on nucleation characteristics, specifically Boiling number, Jakob number, and density ratio. Bubble departure diameters and departure frequencies are measured via high-speed photography and compared to existing models. CHF data are presented as a parametric study of pressure from 20 kPa to 108 kPa, mass flux from 45 kg/m2s to 190 kg/m2s, and inlet subcooling from 0 to 10 K. Heat flux is gradually increased until an excursion of the wall temperature, signifying CHF, occurs. Several existing models that correlate departure characteristics with the relevant dimensionless groups enumerated above are found to accurately predict departure diameter and frequency. However, at the lowest pressure, departure diameters are of the same length scale as the channel so geometric effects may affect these departures. CHF is shown to vary directly with pressure but is only weakly affected by changes in mass flux and inlet subcooling for the observed conditions. Models of the Boiling number at CHF that incorporate the density ratio and Weber number are found to predict the experimental results well. A new correlation for CHF is developed that incorporates the characteristic bubble diameter into the Weber number and is found to predict CHF with an average error of ±15.62%.","abstract_has_math":false,"creators":["Colgan, Nathan Eamon"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"M.S.","degree_level":"Thesis","degree_discipline":"Nuclear, Plasma, Radiolgc Engr","degree_department":null,"school":null,"contributors":["Brooks, Caleb S.","Kozlowski, Tomasz"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2018,"date_issued":"2018-09-27T16:17:46Z","date_published":"2018-09-27T16:17:46Z","updated_at":"2026-07-22T22:24:40Z","subjects":["critical heat flux","flow boiling","subatmospheric","departure from nucleate boiling"],"languages":["en"],"rights":["Copyright 2018 Nathan Colgan"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/101554","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Brooks, Caleb S.","Kozlowski, Tomasz"]},{"key":"dc:creator","label":"Author","values":["Colgan, Nathan Eamon"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2018-09-27T16:17:46Z","2018-07-11","2018-08"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Nuclear, Plasma, Radiolgc Engr"]},{"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":["critical heat flux","flow boiling","subatmospheric","departure from nucleate boiling"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2018 Nathan Colgan"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/101554"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Experiments have been conducted in a vertical square channel to investigate wall nucleation characteristics and Critical Heat Flux (CHF) in subcooled boiling flows under subatmospheric pressure. Forced convection boiling is a widely used and effective means of heat transfer. An understanding of the mechanisms and limitations involved in forced convection boiling is important for the accurate prediction of the behavior of two phase systems under a wide range of conditions. The objective of this work is to provide a unique dataset to evaluate the scalability of existing models of nucleation characteristics and CHF for flow boiling conditions below atmospheric pressure as the performance of these models has not been investigated under these conditions. The experimental nucleation data are presented as a parametric study of the effects of important dimensionless groups on nucleation characteristics, specifically Boiling number, Jakob number, and density ratio. Bubble departure diameters and departure frequencies are measured via high-speed photography and compared to existing models. CHF data are presented as a parametric study of pressure from 20 kPa to 108 kPa, mass flux from 45 kg/m2s to 190 kg/m2s, and inlet subcooling from 0 to 10 K. Heat flux is gradually increased until an excursion of the wall temperature, signifying CHF, occurs. Several existing models that correlate departure characteristics with the relevant dimensionless groups enumerated above are found to accurately predict departure diameter and frequency. However, at the lowest pressure, departure diameters are of the same length scale as the channel so geometric effects may affect these departures. CHF is shown to vary directly with pressure but is only weakly affected by changes in mass flux and inlet subcooling for the observed conditions. Models of the Boiling number at CHF that incorporate the density ratio and Weber number are found to predict the experimental results well. A new correlation for CHF is developed that incorporates the characteristic bubble diameter into the Weber number and is found to predict CHF with an average error of ±15.62%.","Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2018-09-27 without embargo terms","The student, Nathan Colgan, accepted the attached license on 2018-07-10 at 12:44.","The student, Nathan Colgan, submitted this Thesis for approval on 2018-07-10 at 12:56.","This Thesis was approved for publication on 2018-07-11 at 13:16.","DSpace SAF Submission Ingestion Package generated from Vireo submission #12796 on 2018-09-27 at 10:47:38","Made available in DSpace on 2018-09-27T16:17:46Z (GMT). No. of bitstreams: 2 COLGAN-THESIS-2018.pdf: 3859479 bytes, checksum: 6851ce6497d46e115afac53f57c7d6a4 (MD5) LICENSE.txt: 4210 bytes, checksum: 2e0ffe7297a936ce17e276db8ed4aefc (MD5) Previous issue date: 2018-07-11"]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Experimental study of flow boiling under subatmospheric pressures in a vertical square channel"]}]}],"canonical_facts":{"dc:contributor":["Brooks, Caleb S.","Kozlowski, Tomasz"],"dc:creator":["Colgan, Nathan Eamon"],"dc:date":["2018-09-27T16:17:46Z","2018-07-11","2018-08"],"dc:description":["Experiments have been conducted in a vertical square channel to investigate wall nucleation characteristics and Critical Heat Flux (CHF) in subcooled boiling flows under subatmospheric pressure. Forced convection boiling is a widely used and effective means of heat transfer. An understanding of the mechanisms and limitations involved in forced convection boiling is important for the accurate prediction of the behavior of two phase systems under a wide range of conditions. The objective of this work is to provide a unique dataset to evaluate the scalability of existing models of nucleation characteristics and CHF for flow boiling conditions below atmospheric pressure as the performance of these models has not been investigated under these conditions. The experimental nucleation data are presented as a parametric study of the effects of important dimensionless groups on nucleation characteristics, specifically Boiling number, Jakob number, and density ratio. Bubble departure diameters and departure frequencies are measured via high-speed photography and compared to existing models. CHF data are presented as a parametric study of pressure from 20 kPa to 108 kPa, mass flux from 45 kg/m2s to 190 kg/m2s, and inlet subcooling from 0 to 10 K. Heat flux is gradually increased until an excursion of the wall temperature, signifying CHF, occurs. Several existing models that correlate departure characteristics with the relevant dimensionless groups enumerated above are found to accurately predict departure diameter and frequency. However, at the lowest pressure, departure diameters are of the same length scale as the channel so geometric effects may affect these departures. CHF is shown to vary directly with pressure but is only weakly affected by changes in mass flux and inlet subcooling for the observed conditions. Models of the Boiling number at CHF that incorporate the density ratio and Weber number are found to predict the experimental results well. A new correlation for CHF is developed that incorporates the characteristic bubble diameter into the Weber number and is found to predict CHF with an average error of ±15.62%.","Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2018-09-27 without embargo terms","The student, Nathan Colgan, accepted the attached license on 2018-07-10 at 12:44.","The student, Nathan Colgan, submitted this Thesis for approval on 2018-07-10 at 12:56.","This Thesis was approved for publication on 2018-07-11 at 13:16.","DSpace SAF Submission Ingestion Package generated from Vireo submission #12796 on 2018-09-27 at 10:47:38","Made available in DSpace on 2018-09-27T16:17:46Z (GMT). No. of bitstreams: 2 COLGAN-THESIS-2018.pdf: 3859479 bytes, checksum: 6851ce6497d46e115afac53f57c7d6a4 (MD5) LICENSE.txt: 4210 bytes, checksum: 2e0ffe7297a936ce17e276db8ed4aefc (MD5) Previous issue date: 2018-07-11"],"dc:format":["application/pdf"],"dc:identifier":["http://hdl.handle.net/2142/101554"],"dc:language":["en"],"dc:rights":["Copyright 2018 Nathan Colgan"],"dc:subject":["critical heat flux","flow boiling","subatmospheric","departure from nucleate boiling"],"dc:title":["Experimental study of flow boiling under subatmospheric pressures in a vertical square channel"],"dc:type":["text"],"thesis:degree_discipline":["Nuclear, Plasma, Radiolgc Engr"],"thesis:degree_level":["Thesis"],"thesis:degree_name":["M.S."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:24:40Z"}