Developing an active, high-heat-flux thermal management strategy for power electronics via jumping-droplet phase-change cooling

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.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Electrical & Computer Engr

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2017

Author dc:creator

• Foulkes, Thomas Peter

Contributors dc:contributor

• Pilawa-Podgurski, Robert C. N.
• Miljkovic, Nenad

• 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

Statement dc:rights

• Copyright 2017 Thomas Peter Foulkes

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/97344

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/97344