Overview
New generations of in-flight entertainment (IFE) systems are required to provide more and more services (audio, video, Internet, flight services, multimedia, games, shopping, phone, etc.) at an affordable price. But unlike other avionics systems installed in temperature-controlled bays, most of the IFE equipment and boxes are installed inside the cabin. They may be buried in small enclosed zones, not connected to the aircraft cooling system (ECS), and this situation creates thermal management problems that affect the reliability, safety and cost of the equipment. The most critical piece of equipment is the Seat Electronic Box (SEB) installed under each passenger seat.
To face the increasing power dissipation, fans are used but with the following drawbacks: extra cost, energy consumption when multiplied by the number of seats, reliability and maintenance concern (filters, failures, etc.), risk of blocking by passengers' belongings, and noise, coupled with unpleasant smells creating disturbance in the cabin area.
The main aim of the COSEE project was to develop a new cooling enhanced thermal link dedicated to cabin in-flight entertainment (IFE) equipment based on heat pipe technique with the following characteristics:
- transfer capacity up to 100 W,
- thermal conductivity equivalent or greater than 800 W/m/degrees K (twice that of copper),
- heat transportation distance 500 mm (max),
- resistance to aircraft cabin environment (vibrations, acceleration, shocks, airbus specifications),
- minimum volume and weight,
- easily maintainable, and
- affordable: cost target less than or equal to the cost of a fan system.
The project was structured into individual work packages (WPs) as follows:
WP 1000: System specifications, comparison of existing cooling, system mock up definition, test file definition
The fill charge ratio has a significant effect if the void fraction in the evaporator core varies, leading to a radial heat leak variation. The radial heat leak, as well as the ratio of radial to axial heat leak, is affected by the wick characteristics, and the evaporator and compensation chamber designs. The pore size is an important parameter, which should be as low as possible to increase the capillary and boiling limits. The fluid selection mainly depends on its saturation pressure, which should be sufficiently high at the considered operating temperature. Thus, ammonia and propylene are used for low temperature applications; water, alcohols, acetone and R134a may be used for higher temperature applications. In addition, the compatibility of the fluid with the loop materials should be carefully considered. The gravity effect is important for terrestrial applications: an adverse elevation or tilt decreases the loop heat pipe (LHP) performance, especially at low heat loads. Likewise, a fluid pressure drop increase tends to decrease the performance. The temperature difference between the ambient and the heat sink affects the transition heat load between variable and fixed conductance modes of the LHP operation.
WP 2000: Loop heat pipes studies
The scope of WP2000 was to design a LHP adapted to the specifications defined in WP1000. For the simulation of LHP behaviour, the model should include following parameters:
- capillary structure parameter (porosity, permeability,..),
- fluid type and characteristics,
- thermal operating conditions (heat flux level, cooling fluid temperature, elevation).
When using a low conductivity capillary structure, the LHP performance is sensible to the latent heat of vaporisation, the liquid specific heat and the evaporator thermal resistance RE (which includes container / wick mechanical contact and fluid / wick), particularly when the LHP operates at variable conductance mode. When operating at fixed conductance mode, the LHP performance mainly depends on the heat transfer resistance between the working fluid and the heat sink. The LHP is more sensitive to elevation or acceleration forces when using a high conductivity capillary structure rather than a plastic mesh. A composite wick enables to decrease th
Funding
Results
All the objectives of the COSEE project have been realised. The final testing has shown that the two developed technologies are able to divide by a factor of two the temperature elevation on the critical components or to multiply by two the power dissipated. The heat transportation distance between the box and the structure initially 500 mm has been increased to 700 mm with a good flexibility of the tubes. Software and simulation tools associated with experimental measurement techniques have provided good design optimizations. The quality and excellent cooperation within the consortium has permitted to successfully terminate the project.
The deliverables for this project are:
- D1 Technical report on module specifications,
- D2 Technical report on HP simulations and experimentation,
- D3 Laboratory experimentations,
- D4 Technical report on system integration,
- D5 Technical report on system mock-up definition,
- D6 Technological system mock-up assembly report,
- D7 Test report on thermo-mechanical performance,and
- D8 Final report with synthesis and limits of technologies.
Policy implications
All the companies providing IFE systems today are of American and Japanese ownership and origin. The top four players are supported by huge national companies that have the critical mass to fund research into new generations of products every two or three years. The technological revolution of recent years – moving from analogue systems to integrated digital systems – will continue over the coming years as components evolve in terms of package size and complexity, and because of the convergence of Internet, TV and audio standards; so-called multi-media. Currently the only realistic way for European players to compete in this market is by grouping the experience and knowledge of key partners in a given sector, as in COSEE.