Numerical study on flow characteristic of the KSTAR PF cryogenic loop using supermagnet code

Operation stability study for a large-scale superconducting magnet is of particular importance to protect the magnet from permanent damage. Especially, for a fusion magnet, severe heat load by AC loss needs to be effectively removed during operation to achieve required temperature margin. A unique feature of KSTAR PF (poloidal field) magnet is that all the supercritical helium inlets and outlets of PF1 ∼ 4UL (PF upper and lower) coils are located at high field region. Therefore, major heat loads are localized both at the inlets and outlets, so that a drastically reduced or even no temporal cryogen flow is frequently observed at the inlets of PF1 ∼ 4UL coils. This kind of temporal blockage of cryogenic loop can seriously affect the thermo-hydraulic analysis of a superconducting magnet system. As a preliminary study on this issue, we compared thermos-hydraulic analysis results of a simplified PF1UL model with a semi full scale PF1 ∼ 4UL model by using the SUPERMAGNET code. The numerical simulations were also compared to empirical results.