Overview
ATMOSTAT had been working for a dozen years on the design of two-phase fluid loops for harsh environments with high density puissance dissipated. We had a very innovative and disruptive technology of loop heat pipes based on mechanical pumping with systems including specific evaporators (high performance process). The measured range of heat flux was better than expected for this type of aircraft application (more than 100W/cm²). Our solution met all technical requirements of the CLEANSKY call and we respected the compliance with the expected timetable.
Our Loop Heat Pipes included at least an evaporator, a condenser, a compact mechanical pump, an expansion vessel, an evaporable fluid, connection pipes and an electronic circuit. The purpose of the project was to develop a practical aeronautic application to reduce drastically thermal contraints, weight and dimensions of high dense power electronics modules (PEM with new wide bandgap materials, for example based on SiC or GaN). The reliability of our solution was guaranteed by the method of design used (APASE®) and the experience of ATMOSTAT in this kind of development (Adequacy and quality of resources, management and implementation capabilities).
A lot of applications existed in the future dedicated to the aircraft world but also in the world of renewable energies, rail transport, and more generally carbon-free mobilities. We think the project must contribute to European competitiveness.
ATMOSTAT is a strategic supplier of the French defence. ATMOSTAT is a industrial subsidiary of ALCEN group (Mid-Sized, 1.800 persons, revenues of 250 million euros). This call is a real opportunity to mature our technology and go to market faster.
Funding
Results
Executive Summary:
The purpose of the more electrical aircraft is to reduce the power consumption of the future airplane by decreasing the weight of embedded equipment. To achieve this purpose, it has been shown that mutual use of part of this equipment to reach a general use of on-board electrical power should achieve this purpose. This is the concept of the more electrical aircraft. Naturally, this must significantly increase the amount of electrical power consumed as the power converter efficiency is still fewer than 100%. Therefore, the thermal dissipation will raise levels that are not assumed by the current embedded cooling system design.
The BECOOL project had been planned on a 2 years development program with the aim to provide a complete cooling system able to absorb a specified amount of power, around 1kW, for a nominal working temperature of the future power converter, around 100°C. The equipment involved in the diphasic loop should be constrained to a maximum size and a maximum weight and be able to work in a harsh environment in terms of acceleration and temperature.
ATMOSTAT has developed, thanks to its internal diphasic programs, a new concept of diphasic cooling system to reach more integrated cooling device. Technological bricks required to design a generic diphasic cooling system have already been identified and have reached their own TRL level but the application, coming from the link between all these equipment specifically designed to fit requirements, have to progress also in its own TRL level.
The challenge of this program was to design a complete cooling system to progress significantly in the maturity level of the application and optimise its size and performance to be compliant with the Topic Manager specification.
The most efficient cooling technologies compared to their embedded size and weight are those working in closed circuit. The simplest configuration used was heat pipes, but we can also find heat sinks, capillary-pumped heat pipes (CPL), LHP. In spite of good performances, these technologies keep major constraints, caused by their architecture: the heat flow must be moderate otherwise the hot surface will be dried and then no longer cooled, drying troubles can occurs because of gravity or during acceleration phase due to the insufficient amount of pressure created by the capillarity mesh, power density is limited due to drying risks, distance of heat transportation are limited and finally unexpected unpriming during duty cycle.
The architecture and technology of the 2-phase loop mechanically pumped that ATMOSTAT has proposed can bring answers to the troubles thanks to the embedded pump, forcing the liquid circulation, and its efficiency at high power density thanks to the innovative technology of its evaporator allowing to push away the drying limits.
The current state-of-the-art, diphasic capillary pumped loop technology has welcomed a new concept of diphasic loop: the 2-phase loop mechanically pumped developed by ATMOSTAT. At the end of the project, the advancements of the current state–of-art were coming from the fact that we have moved from the concept of a diphasic loop application, at low TRL level (0 to 1-2) at the beginning of the project, to the level 3 at the end of the project by the experimental proof of the main characteristics and major performance of the loop.
The challenge that might not have been addressed during the program, because of the delay of the project due to the manufacture of the equipment, came from the transitional regime that couldn’t have been designed properly without preliminary tests. Transitional regimes of the power converter were quite difficult to analyse without the Topic Manager expertise. An ideal transitional behaviour should be defined by the Topic Manager and explained to ATMOSTAT to be able to take its behaviour into account in the future design of the ATMOSTAT diphasic loop.
The maturity of our concept has reached a level to let us consider, now, industrial applications and potential commercialisations in different fields such as: defence, civil aeronautics and earth transportation application (train, tram, car), production of renewable energy, telecom (radar), even space application might be considered if we can prove that our pump is reliable enough.