Experimental investigation and simulation on a small-scale open hydrogen liquefaction system with stepwise cooling

In order to explore the thermodynamic characteristics of the gradual cooling and liquefaction process of hydrogen, a small-scale open hydrogen liquefaction system with stepwise cooling is proposed, designed and experimentally tested. The fabrication and practical cooling operation of the hydrogen liquefaction system are conducted under the premise of pre-test of neon and safety precautions. The cooling capacity required for hydrogen cooling is continuously provided by two Gifford-Mcmahon (G-M) refrigerators and the returned cold hydrogen. The hydrogen gas is gradually cooled to about 21 K through two pre-cooling heat exchangers (PHEX) and three counter-flow heat exchangers (CHEX) and then throttled to about 120 kPa. Hydrogen gas with a mass flow rate of 0.2 kg/h can be liquefied to meet the design requirements in this system and the experimental results are compared with the Hysys simulation. The comparative analysis reveals that the measured data of key nodes are in good agreement with the simulation results, and the maximum deviation is around 8.70%, which proves the effectiveness of the experimental system and provides validation for the simulation. In addition, the design of the heat transfer module including the structure of the PHEX and the cold shield is reasonable and feasible. In conclusion, the designed experimental system and results can provide a technical reference for the corresponding equipment selection and operating experience in hydrogen liquefaction experiments.