Selecting the minimum complexity for transient thermal-hydraulic modeling of HTS CICC at 20 K

The transition from low-temperature superconductors (LTS) operating at 4.5 K to high-temperature superconductors (HTS) at around 20 K represents a paradigm shift in fusion magnet design. This work investigates the minimum level of thermo-hydraulic model complexity required to accurately capture slow transient behavior in HTS Cable-In-Conduit Conductors (CICC) cooled by forced-flow helium. A complete thermal-hydraulic reference model is compared with progressively simplified advection and advection–diffusion models, where compressibility effects are incorporated through reduced-order formulations. The analysis focuses on energy transport and peak temperature prediction under representative operating conditions. Results show that, for slow transients, reduced-order models reproduce the key thermal features with acceptable accuracy while significantly reducing computational cost. The limits of validity of these simplifications are discussed with respect to compressibility effects and nonlinear material properties.