Dynamic Simulation of a Helium Liquefier

Dynamic behavior of a helium liquefier has been studied in detail with a Cryogenic Process REal‐time SimulaTor (C‐PREST) at the National Institute for Fusion Science (NIFS). The C‐PREST is being developed to integrate large‐scale helium cryogenic plant design, operation and maintenance for optimum process establishment. As a first step of simulations of cooldown to 4.5 K with the helium liquefier model is conducted, which provides a plant‐process validation platform. The helium liquefier consists of seven heat exchangers, a liquid‐nitrogen (LN2) precooler, two expansion turbines and a liquid‐helium (LHe) reservoir. Process simulations are fulfilled with sequence programs, which were implemented with C‐PREST based on an existing liquefier operation. The interactions of a JT valve, a JT‐bypass valve and a reservoir‐return valve have been dynamically simulated. The paper discusses various aspects of refrigeration process simulation, including its difficulties such as a balance between complexity of the adopt...