Parameter sensitivity analysis of 2 K helium refrigerator in China Spallation Neutron Source
In the second phase of China Spallation Neutron Source project(CSNS),a 2 K helium refrigerator will be con-structed to provide a superfluid helium cooling environment for the newly added superconducting accelerator in the H-linear ac-celerator section.According to the equipment layout,the 4.5 K and 2 K cold boxes of the 2 K helium refrigerator will be con-nected by a 100-meter multi-channel low-temperature pipeline,which significantly affects the throttling stage and subcooling stage of the refrigerator.Based on parameter sensitivity analysis,It was examined for the impacts of the supercritical helium outlet temperature of the first stage subcooler in the 4.5 K cold box,the type of expansion element for the first throttling stage and the outlet pressure of the first throttling stage on the system.The results indicate that adding a first stage subcooler in the 4.5 K cold box and lowering the supercritical helium outlet temperature to 4.5 K can significantly reduce the mass flow rate of the helium,thereby decreasing the manufacturing cost and installation difficulty of the multi-channel low-temperature pipeline.Additional-ly,when designing the first stage subcooler,the turbine should be considered as the expansion element for the first throttling stage;for the second stage subcooler,the design should be based on the throttling valve.
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