The proposed project was part of the Cleansky Eco-Design activities for the all (or more) electric aircrafts. The main targets of the call were related to improved aircraft weight, improved electronic equipment life cycles & reduced maintenance thanks to the use of highly efficient passive (“green”) thermal control systems (as already used on satellite systems).
The EHP proposal was part of the ECO-Design ITD and addressed the development, and qualification aspects of highly efficient two-phase cooling devices such as heat pipes and loop heat pipes to be used on board of aeronautical aircrafts.
The main objectives were to:
- Qualify two-phase heat transfer devices in accordance with specific aeronautical requirements such as:
- High acceleration loads
- Long duration vibration stresses
- Reduce global aircraft weight at equipment and/or system level => reduce aircraft consumption and increase operating range
- Lower impact on environment through the use of passive and maintenance free thermal equipment
- Increase reliability of controlled equipment (power electronics) => decrease repair and maintenance aspects
The Ammonia HP and LHP products were baselined (with a TRL 9) on all Space satellites or payloads thanks to the reliable capability provided by these “isothermal” lightweight thermal management devices.
Non-space applications were also more and more considered for these two-phases devices to be used on high power electronic (railway applications) or primary flight control actuators.
The AeroL-HP products were developed up to CDR level with qualification of the two-phase hardware. From a technical side, the proposed thermal link had to provide a reliable and competitive (generic, modular and low cost) product (Rejected power/mass). The thermal link was a scalable system able to address payload dissipations from 30W (TBC) up to 900W (or higher).
The developed technology in the Aero-L HP program corresponded to a thermal system for aeronautical applications (business jets) based on two-phase heat transfer phenomenon; it means that the heat is evacuated thanks to vaporization and condensation of a fluid contained in the thermal device.
This device is passive so that no electrical input is necessary to make it function, its activation is only due to the heat dissipation. This device allows carrying heat from equipment located in the inner aircraft side (cabin calculators and wing actuators equipment) to the aircraft structure (cold source) thanks to its flexibility (piping). Indeed, the thermal device is composed of 5 mini-loop heat pipes (mini-LHP) filled with acetone that are distributed on the face of the equipment to be cooled (on their evaporators) and share the total heat to dissipate. The condenser lines of the mini-loop heat pipes are assembled on saddles which are connected to the plane structure.
Such a solution has been selected for the cooling as the best compromise between thermal, hydraulic, mechanical performances, mass, flexibility, cost and modularity criteria.
The integration of such a two-phase thermal device in an aircraft allowed significantly reducing the maximal temperature at equipment using a light and passive thermal device. This led to an increase of equipment’s reliability combined with a fuel consumption reduction.
In addition, a monitoring solution had been proposed to allow managing the AeroL-HP cooling device implemented in an aircraft. The monitoring study had demonstrated the detection of all degraded or failure modes of the LHP’s identified in the risk analysis.
This project had been performed in collaboration with Dassault Aviation (DAv) as topic manager, Fraunhöfer Institute for thermal tests in representative environment of aircraft and Epsilon as partner for the development of the thermal mathematical model (1D modelica model).
After tests in calorimeter (test set-up representing an aircraft fuselage) at Fraunhöfer Institute, EHP thermal device could reach TRL4 (Technology Readiness Level 4) following DAv evaluation; that is to say successful testing in a representative ground test facility.
The potential applications identified by Dassault for such thermal device were the cooling of battery control units, electrical ice protection units, electrical power distribution units, in-flight entertainment systems,...as well as Electromechanical actuators for horizontal tail plane trim and future actuators for flight control surfaces. All these equipment’s corresponded to future high-level business jets.