Feasibility of Heat Pipes for High Performance Components in Airborne Applications: Thermal Integration Challenges and Design Strategies

Abstract

This thesis focused on evaluating passive two-phase heat transfer technologies for potential use in airborne applications. The work included a background study of different heat pipe technologies, wick structures, working fluids and materials to identify suitable concepts for airborne conditions. The concepts were then assessed and compared using a weighted decision matrix based on requirements and constraints. The concept evaluation indicated that wick structure had a major influence on overall heat pipe performance. Sintered wick structures were considered the most favorable due to their reliable performance under varying conditions. The study also highlighted the importance of fluid-material compatibility. Although experiments were only performed on commercially available heat pipes, experimental testing generally confirmed the theoretical expectations. This included that sintered wick structures achieved the best overall performance, particularly in gravity-opposed orientations and that heat pipes with larger cross-sectional diameter demonstrated lower thermal resistance. The results obtained from the experiment also confirmed that higher heat loads and orientation strongly influence thermal performance. Overall, the study showed that passive two-phase cooling systems are promising for airborne applications, but concept selection involves important trade-offs between thermal performance, manufacturability and structural robustness.