Simulation-based thermodynamic analysis of hydrogen liquefaction processes: Design implications and limitations

This study evaluates hydrogen (H₂) liquefaction systems using several thermodynamic models to better understand how property predictions affect process performance. Simulations were conducted in Aspen HYSYS® and Aspen Plus® using four equations of state: Peng-Robinson (PR), Soave-Redlich-Kwong (SRK), Modified Benedict-Webb-Rubin (MBWR), and RefProp (RF). The analysis focused on key parameters such as enthalpy, entropy, exergy, and heat capacity across cryogenic temperatures. Results show that model selection significantly impacts energy efficiency and heat integration. Additionally, the risk of refrigerant freezing at extremely low temperatures is evaluated, which can cause operational issues, and the most stable compositions are identified. The analysis of heat exchanger behavior shows that variations in fluid properties can change energy recovery by up to 45%. Results reveal that MBWR and RF models provide more accurate predictions in cryogenic conditions, thereby may potentially improve process efficiency by approximately 20% compared to other models. The findings underscore the criticality of accurate thermodynamic modeling in designing efficient and commercially viable liquid H₂ production processes.