As part of Europe’s sustainable energy strategy, the aircraft industry aims at gradually shifting to electrical power. The appearance of new silicon carbide and gallium nitride (SiC/GaN) power modules with better behaviour in terms of dissipation level and temperature limits has allowed revisiting air-cooled solutions. The EU-funded ICOPE project designed innovative and efficient air-cooled heat sinks to cool the power electronics modules. The project was coordinated by Joaquim Rigola from the Polytechnic University of Catalonia, with partners AAVID (Boyd Corporation), Schunk Carbon Technology, and with THALES Avionics as Topic Manager.
Improved performance and lightweight design
The innovation lays in the integration and combination of two new advanced thermal materials: annealed pyrolytic graphite (APG) and metal matrix composites (MMCs). APG is integrated into the heat spreader, intended to reduce the temperature gradients in the base plate of the heat sink. Moreover, the selected MMCs are a composition of aluminium and graphite, which improves the aluminium features (thermal conductivity, thermal diffusivity and thermal expansion coefficient). In addition to the project’s heat sink research activities, their integration into a power management bay has also been an important objective. “The improvement of air-cooled solutions implies a potential reduction of weight in the thermal management system because the related equipment for liquid or two-phase units (pumps, piping, additional heat exchangers, etc.) can be avoided. This simplification of the system also impacts in an increase of its reliability and a reduction of maintenance,” says project technical coordinator, Carles Oliet.
A demanding manufacturing process
The inherent challenges of the project have been confirmed in its execution. “The first difficulties were related to the design of a heat sink that at the same time should achieve exigent thermal requirements with air as a cooling medium, while keeping the air pressure drop and heat sink weight below specified thresholds. On top of this, the final solution should be feasible in terms of manufacturing limits,” Oliet explains. To fulfil these prerequisites, the ICOPE consortium intensified the design efforts and finally achieved a successful result, as confirmed by the tests done. The second block of difficulties is linked to the fact that it was the first time that APG and MMCs were combined in a single component. “The preliminary task of developing and characterising different coupon samples of material combinations has been important to address the challenge,” points out Oliet. Aiming to reduce the risk of possible manufacturing or performance limitations, the consortium has designed, manufactured and tested three different heat sinks with different combinations of APG/MMC materials and manufacturing processes.
Towards a vast implementation
The ICOPE team’s next steps include the consolidation and optimisation of the manufacturing processes for the heat sinks. There will be a focus on both a novel implementation of a heat spreader as a finned heat sink base and an innovative new combination of heat spreading materials. “We expect to develop these further steps within the context of new projects, implementing the concept to new electric/hybrid aircrafts, transport vehicles or other energy conversion applications,” adds Oliet.
ICOPE, heat, heat sink, thermal, power, aircraft, manufacturing, air-cooled, power electronics modules, SiC/GaN