Turbo-Brayton Refrigerator for High Temperature Superconducting Device

Abstract

　High temperature superconducting (HTS) cable is kept below the material specific critical temperature utilizing sub-cooled liquid nitrogen. Sub-cooled liquid nitrogen to flow in a HTS cable is cooled and circulated by a refrigerator and a pump. The high efficiency refrigerator is important in order to reduce the transmission loss of HTS cable including the power consumption of refrigerator. Then we have developed the high efficiency and reliability refrigerator.We set a goal of developing a refrigerator with a COP of 0.1, a maintenance interval of 30,000 hours and a cooling capacity of 5kW. Our goal was achieved by using the reverse Brayton cycle and turbo-compressor and expander. A year-long performance test had verified that our cooling system of sub-cooled liquid nitrogen using this refrigerator is stable for long operation.