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Title:Developing an active, high-heat-flux thermal management strategy for power electronics via jumping-droplet phase-change cooling
Author(s):Foulkes, Thomas Peter
Advisor(s):Pilawa-Podgurski, Robert C. N.; Miljkovic, Nenad
Department / Program:Electrical & Computer Eng
Discipline:Electrical & Computer Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Hot spot cooling
Electronics hot spot cooling
Jumping-droplet condensation
Electric-field-enhanced jumping-droplet
High power density
Power electronics
Thermal management
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.
Issue Date:2017-04-13
Rights Information:Copyright 2017 Thomas Peter Foulkes
Date Available in IDEALS:2017-08-10
Date Deposited:2017-05

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