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NREL Tests New Structure for Jet Impingement Cooling of Power Electronics

November 25, 2008

Researchers in the Center for Transportation Technologies and Systems at the National Renewable Energy Laboratory (NREL) recently tested a novel prototype heat exchanger that uses jet impingement cooling and does not require materials that restrict heat flow in the power electronic components of advanced vehicles.

The power electronics module and electric motor are critical systems for advanced vehicles such as plug-in hybrid electric and electric vehicles. Most of these vehicles have electric powertrains and accessories. Power electronics control the flow of electricity between the electric motors and the energy storage system. They can generate excessive heat, which degrades their performance, reliability, and life. NREL's research focuses on developing thermal management technologies that help to increase power density and lower system costs. To do this, NREL uses state-of-the-art equipment and cutting-edge computer models.

Advanced thermal control technologies are critical to enabling higher power densities and lower system costs. Tests at NREL showed that the new jet impingement cooling design reduces thermal resistance by 37% in comparison to results for a baseline pin-fin heat exchanger. The design also achieves a more uniform temperature distribution across the electronic devices.

Semikron, a leader in the power electronics industry, provided the inverter module and baseline heat exchanger. NREL researchers applied their expertise in computational fluid dynamics and fundamental test results from single-jet experiments as they worked with Semikron engineers to optimize the technology and demonstrate it in an inverter package. This technology will help to eliminate a dedicated power electronics cooling loop by lowering the package thermal resistance and enabling the use of high-temperature coolants.

The technology also eliminates the need for thermal grease, a major obstacle to heat removal, by incorporating a seal that allows cooling directly on the back of the direct-bonded copper layer. In addition, the design reduces temperature distributions between chips by directing impinging-jet coolant at a uniform temperature to all devices simultaneously.

This work is part of important transportation-related research carried out at NREL and supported by the U.S. Department of Energy, often in partnership with U.S. industry.

For more information, please contact Ken Kelly.