Effect of Targeted Porosity in Additively Manufactured Heat Pipes

Heat pipes are highly efficient passive thermal conductors in which heat is transported by evaporation and condensation of a working fluid. The main applications for heat pipes result from their basic properties: Cooling of electronics due to the high thermal conductivity (with small size), thermal management in satellites due to the robustness and the passive, maintenance-free operating principle, and the creation of isothermal conditions, e.g. in accurate furnaces. The manufacturing of heat pipes and the required porous wick structures by Laser Powder Bed Fusion (PBF-LB/M) can be highly advantageous. The goal of this study is to gain a better understanding of the manufacture of additively produced heat pipes. In particular, the interactions in the generation of targeted porosity by a) varying the PBF-LB/M process parameters and b) using lattice structures will be investigated and both approaches will be evaluated. In systematic experiments, porous test specimens are fabricated according to both approaches and characterized using the statistical design of experiments method. The properties relevant for heat pipes can be predicted by the derived regression models. Heat pipes are fabricated with selected parameter sets and the transferred heat flow is measured. The functionality of the additively manufactured heat pipes using PBF-LB/M is demonstrated.