Thermodynamic and Sensitivity Analysis of a 5 t/d Claude-Cycle Hydrogen Liquefaction System

Due to its high storage density, liquid hydrogen is regarded as a key medium for large-scale hydrogen storage and long-distance transportation. As one of the widely adopted hydrogen liquefaction processes, the Claude cycle achieves a reduction in liquefaction energy consumption through turboexpander refrigeration. However, under process feasibility constraints, the system’s response to simultaneous changes in the high-pressure side pressure of circulating hydrogen and the expander inlet pressure has not yet been fully quantified. A 5 t/d hydrogen liquefaction system model based on the Claude cycle is established using Aspen Plus. The model comprehensively incorporates liquid nitrogen precooling, circulating hydrogen refrigeration, hydrogen turbine expansion, and ortho–para hydrogen conversion processes. The high-pressure side pressure of circulating hydrogen and the expander inlet pressure are selected as two operating variables. A constraint is applied whereby the expander inlet pressure does not exceed the upstream pressure. The specific energy consumption (SEC) and component-level exergy destruction are used to evaluate their effects on the system. The established Claude-cycle system can produce liquid hydrogen at 21.65 K and 150 kPa, with a para-hydrogen mole fraction of 99.41%. Under baseline conditions, the total system SEC reaches 10.35 kWh·kg−1 LH2 when the equivalent power consumption of liquid nitrogen precooling is considered. Constrained two-pressure analysis is performed to investigate the combined effects of the high-pressure side pressure of circulating hydrogen and expander inlet pressure on system SEC. Combined with the exergy destruction of major components, the thermodynamic mechanisms underlying variations in energy consumption are identified. The findings provide a basis for the coordinated selection of operating pressures and the reduction in energy consumption and irreversible losses in Claude-cycle hydrogen liquefaction systems.