Kevin Bennion

A Comparison of Hybrid Electric Vehicle Power Electronics Cooling Options

This study quantifies the heat dissipation potential of three inverter package configurations over a range of control factors. These factors include coolant temperature, number of sides available for cooling, effective heat transfer coefficient, maximum semiconductor junction temperature, and interface material thermal resistance. Heat dissipation potentials are examined in contrast to a research goal to use 105degC coolant and dissipate 200 W/cm2 heat across the insulated gate bipolar transistor and diode silicon area. Advanced double-sided cooling configurations with aggressive heat transfer coefficients show the possibility of meeting these targets for a 125degC maximum junction temperature, but further investigation is needed. Even with maximum tolerable junction temperatures of 200degC, effective heat transfer coefficients of 5,000 to 10,000 W/m2-K will be needed for coolant temperatures of 105degC or higher.

Integrated Vehicle Thermal Management for Advanced Vehicle Propulsion Technologies

Techniques for evaluating and quantifying integrated transient and continuous heat loads of combined systems incorporating electric drive systems operating primarily under transient duty cycles.

Rapid modeling of power electronics thermal management technologies

A methodology was developed to rapidly evaluate trade-offs associated with alternative packaging configurations and thermal management technologies for power electronics packaging. The methodology includes the integration of available experimental correlations, computational fluid dynamics results, parametric 3D finite element analysis (FEA) thermal models, and established heat exchanger analysis techniques. The parametric 3D FEA model enables sensitivity studies related to the power module package configuration and cooling technologies. This paper focuses on the study of alternative cooling technologies as they are applied to a fixed power module package. The methodology is applied to a double-sided power module package for several alternative cooling technologies.

Characterization of Contact and Bulk Thermal Resistance of Laminations for Electric Machines

The ability to remove heat from an electric machine depends on the passive stack thermal resistances within the machine and the convective cooling performance of the selected cooling technology. This report focuses on the passive thermal design, specifically properties of the stator and rotor lamination stacks. Orthotropic thermal conductivity, specific heat, and density are reported. Four materials commonly used in electric machines were tested, including M19 (29 and 26 gauge), HF10, and Arnon 7 materials.

Design of light-weight, single-phase liquid-cooled heat exchanger for automotive power electronics

Efficient thermal management is critical to increasing power density, improving reliability, and reducing the cost of automotive power electronics. In this paper, we present a heat exchanger design based on impinging jets (with 50%-50% mixture by volume of water-ethylene glycol as coolant) on the copper base plate with and without microfinned/enhanced surfaces, and a plastic fluid manifold. Finite-element analyses as well as computational fluid dynamics (CFD) modeling were utilized for the design. The performance of the jet-based heat exchanger is compared to the baseline channel-flow heat exchanger via CFD modeling. We also characterized the thermal performance of the channel-flow-based heat exchanger experimentally to validate the CFD predictions. CFD results indicate that the jet-based heat exchanger can provide up to 45% lower thermal resistance, 79% increase in power density, and 118% increase in specific power with respect to the baseline channel-flow heat exchanger. We also initiated experimental characterization of the reliability of jet impingement on a plain surface as well as on microfinned/enhanced surfaces. Results to date suggest that jet impingement does not degrade the thermal performance of the enhanced surfaces after six months of near-continuous impingement on the surface.

Microstructured Surfaces for Single-Phase Jet Impingement Heat Transfer Enhancement

An experimental investigation was conducted to examine the use of microstructured surfaces to enhance jet impingement heat transfer. Three microstructured surfaces were evaluated: a microfinned surface, a microporous coating, and a spray pyrolysis coating. The performance of these surface coatings/structures was compared to the performance of simple surface roughening techniques and millimeter-scale finned surfaces. Experiments were conducted using water in both the free- and submerged-jet configurations at Reynolds numbers ranging from 3300 to 18,700. At higher Reynolds numbers, the microstructured surfaces were found to increase Nusselt numbers by 130% and 100% in the free- and submerged-jet configurations, respectively. Potential enhancement mechanisms due to the microstructured surfaces are discussed for each configuration. Finally, an analysis was conducted to assess the impacts of cooling a power electronic module via a jet impingement scheme utilizing microfinned surfaces.

Sensitivity analysis of traction drive motor cooling

Electric motor cooling affects the power capability of electric motors, which has direct impacts on power density and cost. In this paper we present a sensitivity study of factors associated with electric motor thermal management specific to electrified vehicle propulsion applications. Thermal models of two electric motor configurations were developed and validated against available test data. Once confidence was established in the thermal models, a sensitivity analysis was performed over a range of thermal management control factors. These factors included heat transfer coefficients, cooling locations, material orthotropic thermal conductivity properties, heat distributions, and interface contact resistances. The work helps prioritize future research efforts to improve motor thermal management.

Fuel Savings from Hybrid Electric Vehicles

National Renewable Energy Laboratorys study shows that hybrid electric vehicles can significantly reduce oil imports for use in light-duty vehicles, particularly if drivers switch to smaller, more fuel-efficient vehicles overall.

Advanced liquid cooling for a traction drive inverter using jet impingement and microfinned enhanced surfaces

This study evaluates a jet impingement based cooling strategy combined with microfinned enhanced surfaces as a means of improving thermal management for power electronic devices. For comparison, a baseline channel flow heat exchanger and jet impingement on plain surfaces are characterized. The jets, augmented with enhanced microfinned surfaces, provide localized cooling to areas heated by the insulated-gate bipolar transistors and diode devices. Lighter materials and simpler manufacturing while managing required pumping power increase the overall performance while reducing weight, volume, and cost. Computational fluid dynamics modeling validated by experiments was used to characterize the baseline as well as jet-impingement-based heat exchangers at typical automotive flow rates using a 50%-50% mixture by volume of water and ethylene glycol. The three cooling configurations were tested at full inverter power (40 to 100 kW output power) on a dynamometer. An increased thermal performance was observed for the jet-impingement configurations. Experiments were also performed to investigate the long-term reliability of the jets impinging on enhanced surfaces.

Gaining Traction: Thermal Management and Reliability of Automotive Electric Traction-Drive Systems

Increasing the number of electric-drive vehicles (EDVs) on America?s roads has been identified by the U.S. Department of Energy (DOE), the federal cross-agency electric vehicle (EV)-Everywhere Challenge, and the automotive industry as a strategy with near-term potential for dramatically decreasing the nation?s dependence on oil. Mass-market deployment will rely on meeting aggressive technical targets, including improved efficiency and reduced size, weight, and cost. Many of these advances will depend on the optimization of thermal management.