The aviation industry is undergoing an important shift towards net-zero emissions, with hydrogen-electric aircraft (HEA) emerging as a leading solution. To enable megawatt scale power distribution on these platforms, superconducting (SC) DC systems are essential for their high efficiency and low weight. However, these systems possess a critical limitation: the termination where the cryogenic superconducting cable must connect to a current lead (CL) which in turn exits the cold environment and leads to the fuel cell. This generates a significant thermal load from both Joule heating and thermal conduction. If the heat generated here is not managed, it will cause the local temperature of the superconductor to exceed its critical limit, causing a ”quench” and a system power failure. This thesis directly addresses this issue by detailing the design, multi-physics analysis, and experimental validation of an optimized heat sink. The component is designed to be integrated into the superconducting DC link for the Airbus UpNext Cryoprop demonstrator.
The research methodology followed a structured progression from analytical modeling to high-fidelity simulation and experimental validation. First some 1D analytical models based on the McFee optimization method and general heat transfer equations were developed to get a preliminary idea on the feasibility of the design. These 1D codes provided the length to area ratio for an optimized geometry for a 1.5 kA Copper (RRR-10) current lead and specified the primary thermal load that the heat sink must dissipate: 80 W per current lead. With this heat load defined, a 3D-printed copper heat sink was designed and iterated using COMSOL Multiphysics simulations. This iterative process showed that the simple axial fin designs were not able to meet the project requirements, creating thermal bottlenecks and fluid stagnation at the current lead base. The key design innovation of this work was the development of a novel concentric fin topology. This design, which arranges the cooling fins radially outward from the CL base, creates a highly efficient, short thermal path to the 42 K supercritical helium. In simulation, this topology successfully met all project constraints, maintaining the HTS termination temperature below the 50 K critical limit with a predicted pressure drop of 90 Pa.
The design’s performance was then validated through an experimental campaign on a 3D-printed copper prototype at the University of Bath’s cryogenic test facility. The results provided two important yet contrasting outcomes that form the core conclusion of this work. The thermal model was proven to be accurate. Under the nominal 80 W load, the sensors measured a peak HTS termination temperature of 49.6 K. This result successfully meets the primary project requirement, validating the concentric fin topology as a viable solution for the Cryoprop demonstrator. However, a significant discrepancy was found in the pressure drop. The experiment measured 187 Pa across the heat sink assembly. This resulted in an underestimation of 45% compared to the 129 Pa predicted by the COMSOL simulation. This under prediction is attributed to real-world factors that were not captured in the ”perfect” CAD model such as the complex, non-uniform flow in the headers, a higher than estimated surface roughness (> 120 _m) from the additive manufacturing process, and minor losses from the silver brazing assembly.
In conclusion, this thesis provides an important component for the operation of a superconducting powertrain for a hydrogen electric aircraft. More importantly, it quantitatively demonstrates that for high performance cryogenic hardware, the manufacturing and assembly are not just secondary concerns but primary performance drivers that must be taken into account in the design process. iii