{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/97344"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/97344","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Developing an active, high-heat-flux thermal management strategy for power electronics via jumping-droplet phase-change cooling","abstract":"Mitigating heat generated by hot spots inside of power electronic devices is a formidable obstacle to further increases in power density. This work presents the first demonstration of active cooling for hot spots in compact electronics via electric-field-enhanced (EFE) jumping-droplet condensation. To test the viability of EFE condensation for electronic hot spot cooling, an experimental setup was developed to remove heat via droplet evaporation from single and multiple high-power gallium nitride (GaN) transistors acting as local hot spots (4.6 mm x 2.6 mm). An externally powered circuit was developed to direct jumping droplets from a copper oxide (CuO) nanostructured superhydrophobic surface to the transistor hot spots by applying electric fields between the condensing surface and an electrically floated circuit (directly to the transistor) or a guard ring (surrounding the transistor). Heat transfer measurements were performed in ambient air (22-25 degrees Celsius air temperature, 20-45% relative humidity) to determine the effect of gap spacing (1-5 mm) between the GaN transistor and superhydrophobic surface, strength of the electric field (50-250 V/cm), and the cooling performance at different applied heat flux conditions (demonstrated to 13 W/cm^2) along with power dissipation levels (approximately 1.57 W). EFE condensation was shown to enhance the heat transfer from the local hot spot by approximately 200% compared to cooling without jumping and by 20% compared to non-EFE jumping. Dynamic switching of the electric field for a two-GaN system reveals the potential for active cooling of mobile hot spots. The opportunity for further cooling enhancement by the removal of non-condensable gases (NCGs) is discussed, promising local hot spot heat dissipation rates approaching 120 W/cm^2. This work not only demonstrates EFE-condensation-based electronics cooling for the first time, but also provides a framework for the development of active jumping-droplet-based vapor chambers and heat pipes capable of spatial and temporal thermal dissipation control.","abstract_html":"Mitigating heat generated by hot spots inside of power electronic devices is a formidable obstacle to further increases in power density. This work presents the first demonstration of active cooling for hot spots in compact electronics via electric-field-enhanced (EFE) jumping-droplet condensation. To test the viability of EFE condensation for electronic hot spot cooling, an experimental setup was developed to remove heat via droplet evaporation from single and multiple high-power gallium nitride (GaN) transistors acting as local hot spots (4.6 mm x 2.6 mm). An externally powered circuit was developed to direct jumping droplets from a copper oxide (CuO) nanostructured superhydrophobic surface to the transistor hot spots by applying electric fields between the condensing surface and an electrically floated circuit (directly to the transistor) or a guard ring (surrounding the transistor). Heat transfer measurements were performed in ambient air (22-25 degrees Celsius air temperature, 20-45% relative humidity) to determine the effect of gap spacing (1-5 mm) between the GaN transistor and superhydrophobic surface, strength of the electric field (50-250 V/cm), and the cooling performance at different applied heat flux conditions (demonstrated to 13 W/cm^2) along with power dissipation levels (approximately 1.57 W). EFE condensation was shown to enhance the heat transfer from the local hot spot by approximately 200% compared to cooling without jumping and by 20% compared to non-EFE jumping. Dynamic switching of the electric field for a two-GaN system reveals the potential for active cooling of mobile hot spots. The opportunity for further cooling enhancement by the removal of non-condensable gases (NCGs) is discussed, promising local hot spot heat dissipation rates approaching 120 W/cm^2. This work not only demonstrates EFE-condensation-based electronics cooling for the first time, but also provides a framework for the development of active jumping-droplet-based vapor chambers and heat pipes capable of spatial and temporal thermal dissipation control.","abstract_has_math":false,"creators":["Foulkes, Thomas Peter"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"M.S.","degree_level":"Thesis","degree_discipline":"Electrical & Computer Engr","degree_department":null,"school":null,"contributors":["Pilawa-Podgurski, Robert C. N.","Miljkovic, Nenad"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2017,"date_issued":"2017-08-10T19:14:57Z","date_published":"2017-08-10T19:14:57Z","updated_at":"2026-07-22T22:24:32Z","subjects":["Electronics hot spot cooling","Jumping-droplet condensation","Electric-field-enhanced jumping-droplet","High-heat-flux","High power density","Power electronics","Thermal management","Hot spot cooling"],"languages":["en"],"rights":["Copyright 2017 Thomas Peter Foulkes"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/97344","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Pilawa-Podgurski, Robert C. 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This work presents the first demonstration of active cooling for hot spots in compact electronics via electric-field-enhanced (EFE) jumping-droplet condensation. To test the viability of EFE condensation for electronic hot spot cooling, an experimental setup was developed to remove heat via droplet evaporation from single and multiple high-power gallium nitride (GaN) transistors acting as local hot spots (4.6 mm x 2.6 mm). An externally powered circuit was developed to direct jumping droplets from a copper oxide (CuO) nanostructured superhydrophobic surface to the transistor hot spots by applying electric fields between the condensing surface and an electrically floated circuit (directly to the transistor) or a guard ring (surrounding the transistor). Heat transfer measurements were performed in ambient air (22-25 degrees Celsius air temperature, 20-45% relative humidity) to determine the effect of gap spacing (1-5 mm) between the GaN transistor and superhydrophobic surface, strength of the electric field (50-250 V/cm), and the cooling performance at different applied heat flux conditions (demonstrated to 13 W/cm^2) along with power dissipation levels (approximately 1.57 W). EFE condensation was shown to enhance the heat transfer from the local hot spot by approximately 200% compared to cooling without jumping and by 20% compared to non-EFE jumping. Dynamic switching of the electric field for a two-GaN system reveals the potential for active cooling of mobile hot spots. The opportunity for further cooling enhancement by the removal of non-condensable gases (NCGs) is discussed, promising local hot spot heat dissipation rates approaching 120 W/cm^2. This work not only demonstrates EFE-condensation-based electronics cooling for the first time, but also provides a framework for the development of active jumping-droplet-based vapor chambers and heat pipes capable of spatial and temporal thermal dissipation control.","Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2017-08-10 without embargo terms","The student, Thomas Foulkes, accepted the attached license on 2017-04-12 at 16:42.","The student, Thomas Foulkes, submitted this Thesis for approval on 2017-04-12 at 17:53.","This Thesis was approved for publication on 2017-04-13 at 14:08.","DSpace SAF Submission Ingestion Package generated from Vireo submission #10729 on 2017-08-10 at 13:39:35","Made available in DSpace on 2017-08-10T19:14:57Z (GMT). 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To test the viability of EFE condensation for electronic hot spot cooling, an experimental setup was developed to remove heat via droplet evaporation from single and multiple high-power gallium nitride (GaN) transistors acting as local hot spots (4.6 mm x 2.6 mm). An externally powered circuit was developed to direct jumping droplets from a copper oxide (CuO) nanostructured superhydrophobic surface to the transistor hot spots by applying electric fields between the condensing surface and an electrically floated circuit (directly to the transistor) or a guard ring (surrounding the transistor). Heat transfer measurements were performed in ambient air (22-25 degrees Celsius air temperature, 20-45% relative humidity) to determine the effect of gap spacing (1-5 mm) between the GaN transistor and superhydrophobic surface, strength of the electric field (50-250 V/cm), and the cooling performance at different applied heat flux conditions (demonstrated to 13 W/cm^2) along with power dissipation levels (approximately 1.57 W). EFE condensation was shown to enhance the heat transfer from the local hot spot by approximately 200% compared to cooling without jumping and by 20% compared to non-EFE jumping. Dynamic switching of the electric field for a two-GaN system reveals the potential for active cooling of mobile hot spots. The opportunity for further cooling enhancement by the removal of non-condensable gases (NCGs) is discussed, promising local hot spot heat dissipation rates approaching 120 W/cm^2. This work not only demonstrates EFE-condensation-based electronics cooling for the first time, but also provides a framework for the development of active jumping-droplet-based vapor chambers and heat pipes capable of spatial and temporal thermal dissipation control.","Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2017-08-10 without embargo terms","The student, Thomas Foulkes, accepted the attached license on 2017-04-12 at 16:42.","The student, Thomas Foulkes, submitted this Thesis for approval on 2017-04-12 at 17:53.","This Thesis was approved for publication on 2017-04-13 at 14:08.","DSpace SAF Submission Ingestion Package generated from Vireo submission #10729 on 2017-08-10 at 13:39:35","Made available in DSpace on 2017-08-10T19:14:57Z (GMT). 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