Simulation and Analysis of a Novel Hydrogen Liquefaction Process Based on the Liquid Nitrogen and Helium Joule–Brayton Cycle

To facilitate the design, analysis, and optimization of the hydrogen liquefaction system, this study developed a MATLAB-based independent simulation program encompassing unit equipment models and exergy analysis models. The program incorporated REFPROP software to accurately calculate fluid physical properties and the heat of conversion between ortho- and parahydrogen. The proposed hydrogen liquefaction process utilized LN₂ precooling, the helium Joule-Brayton cryogenic cycle, and a throttle valve to efficiently produce liquid hydrogen. The simulation results were rigorously validated using the industry standard Unisim Design software. For the 0.5 t/d hydrogen liquefaction system, the exergy efficiency stood at 28.82%, accompanied by a specific energy consumption of 9.82 kW h/kg_LH2. Notably, the compressor contributed the highest exergy loss ratio, accounting for 38.79% of the total. Increasing the compressor efficiency could significantly improve the exergy efficiency and reduce energy consumption. A comparative analysis revealed that at a larger scale of 50 t/d, the exergy losses of both the compressor and expander decreased, whereas the heat exchanger accounted for 36.29% of the total. In conclusion, the independent simulation program established in this study served as a valuable tool for simulating and analyzing the hydrogen liquefaction system, providing a crucial reference for design improvements and optimization efforts.