Design of 20 K Cold Helium Circulation System Based on Liquid Nitrogen Precooling

In the design of cold helium circulation system, there are generally two ways to provide power for the circulation: compressors at normal temperature and centrifugal fans at cryogenic temperature. When cryogenic temperature centrifugal fans provide power for the circulation, the working condition is difficult to predict. The heat transfer loss is large when the compressor provides circulating power at normal temperature. In this paper, a cold helium circulation system based on liquid nitrogen precooling was designed, and the regenerator and cold head heat exchanger were designed in detail. The effects of heating load and circulation mass flow rate on the system performance under stable operation were tested. The test results showed that when the electric power was 19.7 kW, the cryogenic circulating helium gas with mass flow rate of 0.84 g/s and cooling capacity of 50 W @19.3 K can be provided, which have certain engineering practicability and provide certain reference significance for the design of cryogenic helium circulating system.