Keep fuel cells cool

Operating without moving parts, heat pipes are a thermal management technology used in military/aerospace and commercial applications because of their thermal efficiency, simplicity and reliability. The Therma-Base is a flat, ultra-thin heat pipe developed by Thermacore with the NASA Glenn Research Center under a Small Business Innovative Research (SBIR) contract. The titanium-water vapor chamber Therma-Base is for cooling proton exchange membrane (PEM) fuel cells used for primary and backup power for mission—critical space—based applications.

As passive thermal management devices, heat pipes use the evaporation and condensation cycle of a working fluid (in this case water) within an evacuated, vacuum-tight containment shell to transfer heat to an area where it can be rejected. At 1.2 mm thick, this design is among the thinnest vapor chambers in the industry. It uses a titanium shell and a sintered titanium powder wick structure for high heat flux capability (greater than
60 W/cm2) and thermal conductivity (greater than 5,000 W/m·K) — an order of magnitude greater than typical solid copper solutions.

“For PEM fuel cells, the Therma-Base vapor chamber can simplify and improve the reliability of the bulky and complex pumped liquid cooling solutions that typically consume 10 to 20% of the parasitic power,” said Nelson J. Gernert, Thermacore Vice President, Engineering and Technology. “It can be used for direct die attachment to the electronics, improving thermal spreading, which allows for further miniaturization of the electronics for both military/aerospace and commercial applications.”

More specifically, when the Therma-Base is constructed with materials that match the coefficient of thermal expansion (CTE) of the electronic materials, it can be used in applications for direct die attachment, assuring reliability of the electronics while increasing performance.

A CTE-matched Therma-Base vapor chamber that uses a copper/moly/copper system was applied to transmit/receive modules used in radar applications. Initial modules made with this technology demonstrated a 40% reduction in junction-to-case temperature difference. Other applications for direct die attachment with CTE-matching Therma-Base include light emitting diodes (LEDs), batteries, power amplifiers, monolithic microwave integrated circuits (MMIC), insulated-gate bipolar transistors (IGBTs), metal–oxide–semiconductor field-effect transistors (MOSFETs), traveling wave tubes (TWTs), and spin-filter transistors (SFTs), among others.

Thermacore
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