2026-09-22T02:22:43Z https://www.ideals.illinois.edu/oai-pmh

oai:www.ideals.illinois.edu:2142/97344 2023-07-11 col_2142_5131 col_2142_8888 com_2142_5130 com_2142_8887 com_2142_234

Electronics hot spot cooling Jumping-droplet condensation Electric-field-enhanced jumping-droplet High-heat-flux High power density Power electronics Thermal management 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. 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. Pilawa-Podgurski, Robert C. N. Miljkovic, Nenad Foulkes, Thomas Peter 2017-08-10T19:14:57Z 2017-08-10T19:14:57Z 2017-04-13 2017-05 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). No. of bitstreams: 2 FOULKES-THESIS-2017.pdf: 6016241 bytes, checksum: 337b6fdf22f946d504d10f03a0fadc3b (MD5) LICENSE.txt: 4211 bytes, checksum: 08d0bf3568dbdd73dcab13092b8494d8 (MD5) Previous issue date: 2017-04-13 application/pdf http://hdl.handle.net/2142/97344 en Copyright 2017 Thomas Peter Foulkes Hot spot cooling Developing an active, high-heat-flux thermal management strategy for power electronics via jumping-droplet phase-change cooling text text Electrical & Computer Eng Electrical & Computer Engr University of Illinois at Urbana-Champaign Thesis M.S.