Numerical investigation of liquid hydrogen production rate in a multi-cryocooler liquefaction system

This study numerically investigates a large liquid hydrogen (LH 2 ) liquefier equipped with one AL630 and two AL330 cryocoolers to evaluate the scalability of cryocooler-based liquefaction systems. A CFD model validated against experimental data from a small-scale liquefier was developed, in which phase change was represented using the Lee model to capture condensation and re-liquefaction behavior. Three configurations with different AL330 cold head lengths (80, 199, and 318 mm) were examined to determine their influence on thermal fields and LH 2 production. The results show that the AL630 unit provides the primary cooling capacity, while the AL330 units enhance re-liquefaction in the vapor region. Increasing the cold head length expands the low temperature zone and promotes vapor mixing, leading to higher overall production rates. The LH 2 production increased from about 14.87 L/h in the baseline case to nearly 18.2 L/h for the longest cold head configuration, with only minor reductions in tank volume. These findings demonstrate that cold head geometry is a key design parameter for improving multi-cryocooler liquefier performance and provide guidance for developing compact LH 2 production systems suitable for fueling and transport applications.