Browsing by Author "Dehombreux, Emmanuel"
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Item Alkali Metal Loop Heat Pipe Development for Solar Dynamic Energy Conversion(48th International Conference on Environmental Systems, 2018-07-08) Fereres, Sonia; Bonnafous, Bastien; Mohaupt, Mikael; Lagier, Benjamin; Mari, Raphael; Dehombreux, Emmanuel; Guraya, Cristina; Jimenez, Cristina; Azpiroz, Xabier; De La Rosa, SoniaFuture space exploration missions and outposts on the Moon and Mars would benefit from compact, efficient, high temperature energy conversion devices such as nuclear and solar reactors. In the case of solar dynamic systems, extending operation beyond the hours of solar exposure can be achieved by incorporating Thermal Energy Storage (TES) if the concentrated radiation can be decoupled from the power conversion unit and stored. Conventional heat pipes have been previously developed for this purpose in terrestrial solar receivers and dish-Stirling systems, but the low pumping capacity provided by the capillary structure limits their operational range to horizontal configurations and short distances. Here a high temperature Loop Heat Pipe (LHP) is investigated to transport the concentrated solar radiation from a parabolic dish´s focal point to alternative locations. LHP can perform well at high power, transporting heat over large distances and in different orientations. However, the large power transport (> 10 kW) and high temperature (> 600ºC) requirements of dish-Stirling systems are above current state-of-the-art LHP technology, making this a challenge in terms of materials, fluids, and design. A trade-off study is performed taking into account system requirements, performance and cost, developing a numerical model to determine the most promising solution for a future prototype. The working fluids options at these temperatures are limited to liquid metals: mainly sodium, potassium, and cesium. Although sodium might seem like the most promising working fluid candidate, potassium is anticipated to work better within the system requirements. This paper will show through analysis that, in contrast to conventional LHP where working fluids have negligible thermal conductivity, when using a highly conductive liquid metal the parasitic heat fluxes might be extremely important. This is a novel problem, indicating that design parameter optimization has to be performed differently to ensure proper operation.Item Deployable Panel Radiator(47th International Conference on Environmental Systems, 2017-07-16) Lecossais, Anthony; Jacquemart, Francois; Lefort, Georges; Dehombreux, Emmanuel; Beck, Felix; Frard, Valerie"The Deployable Panel Radiator (DPR), a premiere in Europe, is finalizing its development with the extensive support of ESA through the ARTES Large Platform Mission by prime contractor Airbus Defence and Space. A DPR will be incorporated into the Eurostar Neo product line catalog. Eurostar Neo is part of the ARTES14 Next Generation Platform element, the ESA program to develop and qualify satellite product lines in the 3 to 6 tons launch mass range by the end of the decade. Telecommunication operators owing for ever increasing payload capability, thermal dissipation has become one of the most significant challenges for satellite manufacturers. Fixed passive radiators on the north and south panels of telecom spacecraft used to be sufficient to radiate heat into space and prevent the spacecraft from overheating. But for missions such as the new generation of Very High Throughput Satellites, typically generating up to 25kW power, traditional radiators are no longer sufficient. In those instances a DPR offers a significant increase of the thermal heat rejection capability, of the order of 2.4 kW per DPR unit. The DPR’s most innovative aspect is its passive circulation system, which allows efficient cooling of the payload thanks to two-phase loop heat pipes. Heat is transported by gaseous ammonia from LHP evaporators located on the payload heat pipes to condensers embedded within a large radiator panel. After condensation, ammonia returns in liquid state to the evaporators thanks to the capillary mesh acting as a passive pump. During launch, each DPR is stowed against the spacecraft body. Once in orbit, it is deployed thanks to a single axis mechanism which incorporates flexible piping for the cooling fluid. The DPR Qualification Model has successfully undergone extensive thermal, functional and mechanical testing."