Thermo-Hydraulic Analysis of the KSTAR PF Cryogenic Loop Using SUPERMAGNET Code

The KSTAR PF cryogenic circuit is cooled by the supercritical helium in a forced flow. A unique feature of the poloidal field (PF) is that the cryogenic inlets and outlets of the PF1 ~ 4 upper and lower (UL) coils were located inside the coil in a zone with large magnetic field variation. As a result, the major heat load produced by ac losses is localized at both the inlets and outlets, so that a drastically reduced or even no temporal cryogen flow is frequently observed at the inlets of the PF1 ~ 4UL coils. This kind of temporal blockage of the cryogenic loop can seriously affect the thermo-hydraulic analysis of the superconducting magnet system. Understanding the dynamic behavior of the flow affected by ac losses is one of the keys to ensuring operational stability. Therefore, a full KSTAR PF cryogenic loop was developed using the SUPERMAGNET code to investigate dynamic thermo-hydraulic behavior. The numerical simulation results were also compared to the experimental data of the PF1 magnet test, in which the current is applied from 15 to -15 kA.