Transversal thermal conductivity of HTS tapes
Lammintaus, Patrik (2024)
2024
Sähkötekniikan DI-ohjelma - Master's Programme in Electrical Engineering
Informaatioteknologian ja viestinnän tiedekunta - Faculty of Information Technology and Communication Sciences
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Hyväksymispäivämäärä
2024-05-29
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202405266311
https://urn.fi/URN:NBN:fi:tuni-202405266311
Tiivistelmä
Superconductivity refers to the ability of certain materials to conduct electricity without any resistance. This phenomenon is only possible below a specific critical temperature threshold, usually extremely low temperature. When designing superconducting devices, such as superconducting magnets, ensuring constant low-enough-temperature is essential to maintain the desired superconducting state.
The thermal conductivity of a superconducting magnet significantly affects its thermal stability concerns. Reliable thermal conductivity data for the materials used allows for precise simulations of the magnet's thermal behavior. Literature-based thermal conductivity data for materials may not always align perfectly with the actual properties of the magnet. Therefore, conducting specific thermal conductivity measurements directly on the magnet could offer valuable insights.
In this thesis, transversal thermal conductivity measurements were conducted on two superconductor tape stacks, representing segments of two different superconducting magnets. The tape stacks consisted of yttrium barium copper oxide (YBCO) high-temperature superconductor tapes, which were layered on top of each other and bonded together with adhesive. The first stack used insulated tapes, whereas the second stack employed non-insulated tapes. The thermal conductivity measurements were conducted in the vacuum of a conduction-cooled cryostat.
Two different complexity simulation models were built to simulate the thermal conductivity of the tape stacks. The results from these simulation models were then compared with the measurement results. The measured thermal conductivity of the insulated tape stack was 100% to 150% higher than what was predicted by the simulation, while for the non-insulated tape stack, it was 45% to 55% lower than predicted. The discrepancy between the measurement and simulation results necessitates further inspection of both the measurement setup and the simulation models, particularly if the simulation model is intended for practical use. However, with an adequate safety margin, it is already usable.
The thermal conductivity of a superconducting magnet significantly affects its thermal stability concerns. Reliable thermal conductivity data for the materials used allows for precise simulations of the magnet's thermal behavior. Literature-based thermal conductivity data for materials may not always align perfectly with the actual properties of the magnet. Therefore, conducting specific thermal conductivity measurements directly on the magnet could offer valuable insights.
In this thesis, transversal thermal conductivity measurements were conducted on two superconductor tape stacks, representing segments of two different superconducting magnets. The tape stacks consisted of yttrium barium copper oxide (YBCO) high-temperature superconductor tapes, which were layered on top of each other and bonded together with adhesive. The first stack used insulated tapes, whereas the second stack employed non-insulated tapes. The thermal conductivity measurements were conducted in the vacuum of a conduction-cooled cryostat.
Two different complexity simulation models were built to simulate the thermal conductivity of the tape stacks. The results from these simulation models were then compared with the measurement results. The measured thermal conductivity of the insulated tape stack was 100% to 150% higher than what was predicted by the simulation, while for the non-insulated tape stack, it was 45% to 55% lower than predicted. The discrepancy between the measurement and simulation results necessitates further inspection of both the measurement setup and the simulation models, particularly if the simulation model is intended for practical use. However, with an adequate safety margin, it is already usable.