Browsing by Author "Romera, Francisco"
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Item Development and Characterization of Additive Manufacturing Flat Loop Heat Pipe Evaporator(2023 International Conference on Environmental Systems, 2023-07-16) Corrochano, Javier; Romera, Francisco; Galleguillos, Carlos; Periñán, Antonio; Lasagni, Fernando; Gottero, Marco; Lapensée, StéphaneThis work aims to show the results of the development of a novel ammonia flat Loop Heat Pipe (LHP) stainless steel evaporator manufactured by a combination of Additive Manufacturing (AM) technologies. Firstly, the materials and processes were validated by several tests performed at sample level. The results of this phase revealed that AM technology can manufacture porous stainless steel 316L primary wicks with porosity of 40% and pore diameter of 4.5 µm. Proof and burst tests showed that the flat stainless steel 316L compensation chamber manufactured by selective laser melting technology can withstand up to 200 bar without deformation. In addition, these AM stainless steel 316L materials showed good weldability and excellent chemical compatibility with ammonia. Finally, X-Ray Computed Tomography (CT) has been established as the preferable Non-Destructive Testing (NDT) method for analyzing the manufactured SLM components and flaw detection. For the second phase of the project, the AM flat evaporator was integrated in a technological loop and submitted to a thermal test campaign. The results revealed that the LHP works in a stable way up to 236 W without dry-out in a wide range of temperature sink conditions. The flat AM LHP evaporator combines the advantages of thermal control based on LHPs with the low cost and short production time of AM technologies. Thus, it can be considered as a promising alternative to conventional cylindrical evaporators for cooling applications.Item Integrated Thermal Architecture based on Advanced Control Loop (ACL) with multiple evaporators and condensers(50th International Conference on Environmental Systems, 7/12/2021) Campo, Sa�l; Romera, Francisco; Kulakov, Andrei; Torres, AlejandroA highly-integrated thermal architecture based on Advanced Control Loops (ACLs) has been developed and tested. This architecture consists of a Constant Conductance Heat Pipe (CCHP) network thermally connected to two ACLs. Heat-dissipating units are mounted on the CCHP network. Each ACL has 4 independent evaporators and 4 independent condensers, in the sense that they can be coupled to independent power dissipation sources or sink conditions respectively. The CCHP network has 4 primary CCHPs and 4 spreader CCHPs which serve to equalize the heat load between the primary CCHPs. The CCHP network can be embedded in a honeycomb panel to act as an equipment panel or deck. The ACL cylindrical evaporators, without the thermal interface flanges (saddles), are embedded in dedicated bores as part of the primary CCHP extruded profiles. In this way, the overall thermal gradient between the dissipating units and the condensers is minimized by eliminating the standard bolted interface between evaporator and CCHP flanges. An extensive thermal test campaign was performed on the ACL to validate the novel thermal architecture concept, to characterize the system performance under worst-case operational conditions, and to determine the system performance envelope. The campaign included a number of tests: thermal performance (conductance and heat transfer capability) under various power conditions and with a �split� (ACLs share the thermal sink) and �nonsplit� (each ACL has a dedicated thermal sink) condenser design, minimum and maximum power, start-up, transient input power and heat sink temperature variations, and NCG influence. To cope with transients in the power and thermal boundary conditions, an innovative method of control is also presented. Ammonia is selected as the working fluid for both CCHPs and ACLs taking into account the standard operating and non-operating temperature ranges of most heat-dissipating electronics.Item Loop Heat Pipes for ASTRO-H/SXS(47th International Conference on Environmental Systems, 2017-07-16) Okamoto, Atsushi; Meléndez, Joaquín; Romera, FranciscoIt is becoming increasingly difficult to meet the challenging thermal control requirements of modern spacecraft missions with only existing thermal control devices such as conventional heat pipes. A loop heat pipe (LHP) is an effective method to overcome some of these thermal control constraints. The LHP is a passive two phase heat transfer device that utilizes the evaporation and condensation of a working fluid to transfer heat and capillary force to circulate the fluid. The LHP can transport much heat for a long distance against gravity among many other excellent characteristics, such us the possibility of complex routing or the diode operation. Due to these excellent characteristics, LHPs are used in many space applications. In JAXA’s X-ray astronomy satellite ASTRO-H, mechanical cryocoolers were used in the thermal control system for the Soft X-ray Spectrometer (SXS) which was one of the most important missions in ASTRO-H. The cryocoolers were installed on the dewar and cooled down the dewar to prevent the evaporation of the liquid helium, which keeps the temperature of the SXS sensor at low temperature. 60W of heat dissipated by the cryocloolers as maximum should be transported to the heat sink which is located about 700mm under the dewar. Thus, the heat dissipated by the cryocoolers should be managed by a heat transfer device in top heat mode on ground at the launch pad, as the cryocoolers operated on the launch vehicle until right before launch. It was difficult to manage all the design and testing scenarios with conventional heat pipes whose performances are seriously affected by gravity, so LHPs were chosen for the thermal control of cryocoolers. The overview of the development of LHP (specifications of LHP, development schedule, overview of testing on ground before launch) and the on-orbit performance are presented in this paper.Item Mechanically Pumped Advanced Control Loop: a Solution for High Power Platforms(50th International Conference on Environmental Systems, 7/12/2021) Campo, Sa�l; �lvarez, Jes�s; Kulakov, Andrei; Romera, Francisco; Lara, �scar; Torres, AlejandroTwo-phase mechanically pumped loops have been identified as the potential solution for the heat management of high-powered platforms, such as next generation telecommunications satellites. The proposed concept Mechanically Pumped Advanced Control Loop (M-ACL) combines the advantages of a two-phase modular thermal control system and a mechanically pumped loop. In single-phase fluid loops temperature rise in the fluid and flow rate are directly proportional to the required heat transfer rate. High cooling loads lead to a large temperature rise and high pump power. For more effective thermal transport, the single-phase loop can be replaced by a two-phase one. This allows employing the latent heat of vaporization to significantly reduce flow rates, decrease temperature gradients, and increase heat transfer coefficients. M-ACL concept has been defined after an extensive literature and patents review. It is based on the multi-evaporator, multi-condenser Advanced Control Loop (ACL) concept, which means an integrate solution for the complete thermal control of the platform. The implementation of a mechanical pump in the system means an important increase of the heat transport capability that depends on the pump pressure rise characteristic. A trade-off has been performed to define main mechanical pump and M-ACL features. Additionally, a M-ACL engineering model has been designed based on a NACPA pump from RealTechnologie AG. In this study, the detailed design is presented as well as simulation results using a thermo-hydraulic model developed in EcosimPro simulation tool.