Development and Characterization of Additive Manufacturing Flat Loop Heat Pipe Evaporator

This 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.