Vertically Layered Heat Exchanger for the Solid Nitrogen Heat Capacitor Cooling High-Temperature Superconducting Magnet

This study investigates the heat exchanger structure for the solid nitrogen heat capacitor, which slows the warming rate of the superconducting magnet during a power failure. To improve transient heat transfer of the solid nitrogen, the heat exchanger has a vertically layered structure to limit the thickness of the solid nitrogen. Horizontally wide heat transfer fins maintain thermal contact using the weight of the solid nitrogen. The heat exchanger solidified 2000 cm3of liquid nitrogen in one hour and cooled the HTS coil to the operating temperature using just the cryocooler. In the temperature rise test, which stopped the cryocooler for one hour, it was estimated that the heat exchanger utilizes 28.3%-35.1% of the heat capacity of the solid nitrogen.