Mechanical Engineering
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Item ADVANCED PACKAGING AND THERMAL MANAGEMENT OF DC-DC CONVERTERS AND NOVEL CORRELATIONS FOR MANIFOLD MICROCHANNEL HEATSINKS(2021) Yuruker, Sevket Umut; Ohadi, Michael; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)An advanced packaging configuration of a dual-active-bridge 10 kW DC-DC converter module is introduced in this dissertation. Through utilization of novel heatsinks for the power switches and the transformer assembly, ~20 kW/Lit converter volumetric power density based on numerical and experimental analysis is obtained. Through a unique placement of the high power/high frequency SiC switches on the printed circuit board, many beneficial features such as double-sided cooling, complete elimination of wirebonding, and circumvention of the need for TIM layers between the switches and the heatsinks, and multi functioning heatsinks as electrical busbars is achieved. A Vertically Enhanced Manifold Microchannel System (VEMMS) cooler is developed to address the thermal challenges of a pair of power switches, simultaneously. Both air and liquid cooled versions of VEMMS cooler is presented, thermal resistances of 1.1 K/W and 0.3 K/W for the air and liquid cooled versions, respectively, at reasonable flow rates and pressure drops was obtained. Besides the power switches, thermal management of the transformer assembly is accomplished via Combined Core and Coil (C3) Coolers, where both the magnetic core and coils are liquid cooled simultaneously with electrically insulating but thermally conductive 3D printed Alumina heatsinks, where thermal resistances as low as 0.3 K/W for the magnetic core and 0.09 K/W for the transformer windings is experimentally demonstrated. Furthermore, a system level model was built to investigate the effect of various components in the cooling loop on each other, and what are the limiting factors to prevent a possible thermal runaway failure. Lastly, using a metamodeling approach, closed form pressure drop and heat transfer correlations are developed for thermo-fluidic performance prediction of manifold microchannel heatsinks. Due to complexity and vastness of design variables present in manifold microchannel systems, adequate CFD analysis and optimization require significant computational power. Through utilization of the developed correlations, orders of magnitude reduction in computational time (from days to milliseconds) in prediction of pressure drop and heat transfer coefficient is demonstrated. Extensive mesh independence and residual convergence algorithms are developed to increase accuracy of the created database. Between the correlation and mesh independent CFD results, a mean error of 3.9% and max error of 24% for Nusselt number, and a mean error of 4.6% and max error of 37% for Poiseuille Number predictions are achieved.Item THERMOELECTRIC COOLING OF HIGH FLUX ELECTRONICS(2017) Yuruker, Sevket Umut; Yang, Bao; Bar-Cohen, Avram; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)On-chip thermoelectric cooling is a promising solution for thermal management of next generation integrated circuits. This thesis focuses on three thermoelectric cooling applications for high flux electronics. A micro contact enhanced thin film thermoelectric cooler was designed for remediation of a 5kW/cm2 hotspot and its integration with manifold microchannel system is numerically demonstrated. In addition, thermoelectric cooling was utilized for thermal de-coupling of electronic chips with different operating temperatures, eliminating the need to over-cool the entire package. Furthermore, effect of decreasing contact resistances in thin film thermoelectrics was numerically investigated to effectively remove 100W (~280W/cm2) of heat dissipation from quantum cascade lasers. Finally, a system-level optimization methodology is established with comprehensive mathematical modeling, verified with numerical simulations. Master curves are generated to understand the effect of system-level parasitics on performance and optimal design variables. In conclusion, the advantages of thermoelectric cooling for high flux electronics is demonstrated in this thesis.